U.S. patent application number 11/530298 was filed with the patent office on 2007-05-24 for catalytic adsorbents obtained from municipal sludges, industrial sludges, compost and tobacco waste and process for their production.
This patent application is currently assigned to Research Foundation of the City University of New York. Invention is credited to Teresa J. Bandosz.
Application Number | 20070113736 11/530298 |
Document ID | / |
Family ID | 37836495 |
Filed Date | 2007-05-24 |
United States Patent
Application |
20070113736 |
Kind Code |
A1 |
Bandosz; Teresa J. |
May 24, 2007 |
CATALYTIC ADSORBENTS OBTAINED FROM MUNICIPAL SLUDGES, INDUSTRIAL
SLUDGES, COMPOST AND TOBACCO WASTE AND PROCESS FOR THEIR
PRODUCTION
Abstract
Industrial waste derived adsorbents were obtained by pyrolysis
of sewage sludge, metal sludge, waste oil sludge and tobacco waste
in some combination. The materials were used as media to remove
hydrogen sulfide at room temperature in the presence of moisture.
The initial and exhausted adsorbents after the breakthrough tests
were characterized using sorption of nitrogen, thermal analysis,
XRD, ICP, and surface pH measurements. Mixing tobacco and sludges
result in a strong synergy enhancing the catalytic properties of
adsorbents. During pyrolysis new mineral phases are formed as a
result of solid state reaction between the components of the
sludges. High temperature of pyrolysis is beneficial for the
adsorbents due to the enhanced activation of carbonaceous phase and
chemical stabilization of inorganic phase. Samples obtained at low
temperature are sensitive to water, which deactivates their
catalytic centers.
Inventors: |
Bandosz; Teresa J.;
(Teaneck, NJ) |
Correspondence
Address: |
DARBY & DARBY P.C.
P. O. BOX 5257
NEW YORK
NY
10150-5257
US
|
Assignee: |
Research Foundation of the City
University of New York
New York
NY
|
Family ID: |
37836495 |
Appl. No.: |
11/530298 |
Filed: |
September 8, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60715788 |
Sep 8, 2005 |
|
|
|
60782593 |
Mar 14, 2006 |
|
|
|
60801545 |
May 17, 2006 |
|
|
|
Current U.S.
Class: |
95/136 ;
95/139 |
Current CPC
Class: |
B01D 2253/112 20130101;
B01J 20/28059 20130101; B01J 20/0244 20130101; B01J 20/103
20130101; B01J 20/3483 20130101; B01J 21/02 20130101; B01J 31/26
20130101; B01D 2257/304 20130101; B01J 20/3433 20130101; B01J 23/06
20130101; B01D 53/565 20130101; B01D 2255/2092 20130101; B01J
20/0229 20130101; B01J 20/0237 20130101; B01J 20/06 20130101; B01D
53/508 20130101; B01D 2255/405 20130101; B01J 20/28069 20130101;
B01D 2259/40088 20130101; B01J 23/005 20130101; B01J 20/041
20130101; B01J 20/3425 20130101; B01D 53/8612 20130101; B01D 53/04
20130101; B01D 2255/20761 20130101; B01J 20/08 20130101; B01J 20/20
20130101; B01D 2255/20792 20130101; B01J 20/2808 20130101; B01D
2257/408 20130101; B01D 2253/308 20130101; B01J 20/24 20130101;
B01J 23/72 20130101; B01D 53/52 20130101; B01D 53/54 20130101; B01J
2220/42 20130101; B01D 2255/20738 20130101; B01D 2257/302 20130101;
B01J 20/3078 20130101; B01J 20/28061 20130101; B01J 23/745
20130101; B01D 53/02 20130101; B01D 2253/311 20130101; B01J 20/3416
20130101; B01J 2220/4887 20130101; B01D 2253/102 20130101; B01D
2253/104 20130101; B01J 20/22 20130101 |
Class at
Publication: |
095/136 ;
095/139 |
International
Class: |
B01D 53/02 20060101
B01D053/02 |
Claims
1. An adsorbent derived from one of compost or compost materials
and sludge comprising: a) 20-30% porous carbon with incorporated
organic nitrogen species; and b) 70-80% inorganic matter, wherein
the sludge is a at least one of industrial or municipal sludge.
2. The adsorbent of claim 1, wherein the inorganic matter includes
highly dispersed catalytic oxides.
3. The adsorbent of claim 2, wherein the catalytic oxides are one
or more of copper oxide, zinc oxide, iron oxide, calcium oxide,
silica and alumina.
4. The adsorbent of claim 1, wherein the nitrogen species comprises
amine or pyridine groups.
5. The adsorbent of claim 1, wherein the surface area of the
adsorbent is 100-500 m2/g.
6. The adsorbent of claim 5, wherein the surface area of the
adsorbent is 100-200 m2/g.
7. The adsorbent of claim 1, wherein the adsorbent contains
micropores and the volume of the micropores are at least 0.03 cm
3/g.
8. The adsorbent of claim 1, wherein the pH of the adsorbent is
greater than 10.
9. The adsorbent of claim 1, wherein the pH of the adsorbent is
between 7 and 10.
10. The adsorbent of claim 1, wherein the pH of the adsorbent is
between 4 and 7.
11. A method of making an adsorbent which comprises the steps of:
a) composting compost materials; b) thermally drying dewatered
sewage sludge to form granulated organic fertilizer; c) mixing the
organic fertilizer and the compost; and b) pyrolyzing the mixture
at temperatures between 600.degree. C. and 1000.degree. C.
12. The method of claim 11, wherein the heating rate is between 5
and 10.degree. C./minute and the hold time is between 60 and 90
minutes.
13. The method of claim 11, wherein the temperature of pyrolysis is
between 800 and 1000.degree. C.
14. The method of claim 13, wherein the temperature of pyrolysis is
between 900 and 1000.degree. C.
15. The method of claim 11, wherein the temperature of pyrolysis is
between 600 and 900.degree. C. and the adsorbent is further treated
with 15-20% HCl.
16. The method of claim 15, wherein the temperature of pyrolysis is
between 800 and 900.degree. C.
17. The method of claim 11, further comprising the step of treating
the mixture with between about 5 and about 30 wt % mineral oil, and
wherein the mineral oil is selected from light mineral oil, heavy
mineral oil, natural mineral oil, synthetic mineral oil, spent
motor oil, and combinations thereof.
18. The process of removing acidic gases from wet air streams
comprising putting an adsorbent comprising 20-30% porous carbon
with incorporated organic nitrogen species and 70-80% inorganic
matter derived from sewage sludge in contact with the wet air
stream and allowing the adsorbent to adsorb the acidic gases.
19. The process of claim 18, wherein the acidic gases are one or
more of hydrogen sulfide, sulfur dioxide, hydrogen cyanide, and
nitrogen dioxide.
20. The process of claim 18, wherein the acidic gas is hydrogen
sulfide which reacts with inorganic matter to be oxidized to sulfur
dioxide or elemental sulfur and salt forms thereof.
21. The process of claim 18, wherein the wet air stream is effluent
from a sewage treatment plant, gaseous fuel, or gases from
hydrothermal vents.
22. The process of removing acidic gases from wet air streams
comprising: composting compost materials; forming an adsorbent by
thermally drying dewatered sewage sludge to form granulated organic
fertilizer; mixing the compost with the organic fertilizer; and
pyrolyzing said mixture at temperatures between 600-1000.degree.
C., putting said adsorbent in contact with the wet air stream, and
allowing the adsorbent to adsorb the acidic gases.
23. The process of claim 22, wherein the acidic gases are one or
more of hydrogen sulfide, sulfur dioxide, hydrogen cyanide, and
nitrogen dioxide.
24. The process of claim 22, wherein the temperature of pyrolysis
is between 800 and 1000.degree. C.
25. The process of claim 24, wherein the temperature of pyrolysis
is between 900 and 1000.degree. C.
26. The process of claim 22, wherein the temperature of pyrolysis
is between 600 and 900.degree. C. and the adsorbent is further
treated with 15-20% HCl.
27. The process of claim 26, wherein the temperature of pyrolysis
is between 800 and 900.degree. C.
28. The process of claim 22, wherein the adsorbent may be
regenerated by heating to 300-500.degree. C. to remove elemental
sulfur and sulfur dioxide.
29. A method for producing an adsorbent, comprising the steps of:
combining a first sludge and at least one of a second sludge and a
compost material to form a mixture; thermally drying the mixture;
pyrolizing the mixture at a temperature between about 600.degree.
C. and 1,100.degree. C.; and forming at least one of wurtzite,
ferroan, chalcocite, spinel, feroxyhite, bornite, hibonite,
zincite, ankerite, pyrope, perrohotite, chalocopyrite, triolite,
fersilicite, sapphirine, maghemite, cohenite, lawsonite,
smithsonite, sphalerite, goethite, huntite, anorthite, diaspore,
vaterite, lepidirocite, bayerite, moghemite, pyrohotite, hematite,
sphalerite, almandine, and hematite during the pyrolizing step.
30. The method of claim 29, wherein the compost material is at
least one of tobacco waste, waste paper and wood char, or a
combination thereof, wherein the first sludge is a municipal sludge
or an industrial sludge, and wherein the second sludge is a
municipal sludge or an industrial sludge and different from the
first sludge.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Patent Application Nos. 60/715,788 filed Sep. 8, 2005; 60/782,593
filed Mar. 14, 2006; and 60/801,545 filed May 17, 2006. The
entireties of the applications are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to the formation of catalytic
adsorbents formed from the pyrolysis of different types of sludges
alone or in combination with composting materials. The sludges
include municipal, industrial, waste oil and metal based sludges.
The composting materials can include tobacco waste.
[0004] 2. Discussion of the Related Art
[0005] Growing concerns about the environment has resulted in the
development of new environmentally friendly technologies, new
materials, and new ways to reduce and minimize wastes. One of the
wastes produced by contemporary society in abundant quantity is
municipal sewage sludge, often referred to as biosolids. Biosolids
are a mixture of exhausted biomass generated in the aerobic and
anaerobic digestion of the organic constituents of municipal sewage
along with inorganic materials such as sand and metal oxides. Other
sludges include wastes from such industry as shipyards, foundry, or
paper mills. It is estimated that about 10 million dry tons of
sewage sludge is produced in the United States. Moreover, Sweden
alone contributes 220,000 dry tons of sludge to the 8-10 million
tons of dry sludge produced by European Union.
[0006] Various methods have been used to dispose of or utilize
municipal sewage sludge, including incineration, landfilling, road
surfacing, conversion to fertilizer, compression into building
blocks, and carbonization. Since 1976, several patents have been
issued on carbonization of sewage sludge and various applications
of the final materials. Carbonization of sludge in the presence of
chemical activating agents such as zinc chloride and sulfuric acid
produces new sorbents, with patented applications in processes such
as removal of organics in the final stages of water cleaning and
removal of chlorinated organics. Industrial sludges after
dewatering processes/drying are ether used as landfills or disposed
mainly as hazardous wastes.
[0007] Carbonization of sludge to remove pollutants either from gas
of liquid phase, is based on the fact that typically activated
carbons are chosen. This is owing to their large surface area and
high volume of pores. Often, these characteristics of activated
carbons are not potent enough to retain certain molecules,
especially small ones, for which the dispersive interactions with
the carbon surface are rather weak. In such cases, the carbon
surface has to be modified to impose the specific interactions.
These interactions include hydrogen bonding, complexation,
acid/base reactions or redox processes. Fortunately, in the case of
carbons, various technologies leading to modified surfaces exist
and are relatively easy to achieve. Examples are oxidations with
various oxidants such as strong acids, ozone, or air, impregnation
with catalytic metals or reducing/oxidizing compounds, heat
treatment in the presence of heteroatom sources such as chlorine or
nitrogen compounds, and others.
[0008] As a result of the treatments mentioned above, new
functional groups/chemical species are introduced to the surface.
They impose the specific and/or chemical interactions with the
species to be removed. To have the removal process efficient, the
chemical state of these species and their dispersion on the surface
are important issues. Another important challenge is preservation
of carbon porosity which is a crucial asset for the
retention/storage of pollutants. Thus, the surface modifications
can be done in such a way in which a minimal decrease in the
surface area/pore occur.
[0009] Taking into account the above requirements, in some cases
modifications of a carbon surface, besides being a challenge, can
also be associated with high expenses, especially when noble or
catalytic metals are involved. Industrial sludges, as those coming
from shipyards or other heavy metal industries, are rich in
catalytic transition metals. By pyrolysis of these materials, not
only the volume of waste is reduced but those environmentally
detrimental wastes can be recycled and converted into valuable
products. These products, when used, can be safely disposed since
the leaching of materials is significantly reduced by
mineralization of those metals via high temperature solid state
reactions.
[0010] The process of carbonization of sewage sludges has been
studied in detail previously and it is described in the literature.
Materials obtained as a result of the treatment have surface areas
between 100 and 500 m.sup.2/g. Their performance as adsorbents of
hydrogen sulfides, sulfur dioxide, basic or acidic dyes, phenol or
mercury has been reported as comparable or better that that of
activated carbons. In many process the excellent sorption ability
of these materials is linked to the catalytic action of metals
present in various forms in the final products. Their chemical
forms along with the location on the surface were reported as
important factors governing the pollutant removal capacities. In
some case the wastes were mingled and, owing to the synergy between
the components, more efficient adsorbents were obtained.
[0011] Adsorbents obtained by pyrolysis of sludge can be considered
as complex pseudocomposite materials. However, the process of
carbonization of biosolids has been studied in detail previously
and it is described in the literature. It has been recently shown
that by simple pyrolysis of municipal sewage sludge derived
fertilizer, Terrene.RTM., exceptionally good adsorbents for removal
of sulfur containing gases can be obtained. The removal capacity is
twice that of coconut shell based activated carbon. Although, it
was attributed to the specific combination of inorganic oxides of
such metals as iron, copper, zinc or calcium. The predominant
influence of inorganic phase or combination of oxides, which are
also quite commonly used as catalysts for hydrogen sulfide
oxidation or sulfur dioxide adsorption, was ruled out on the bases
of the performance of a pure inorganic phase in the removal of
sulfur containing gases. The capacity of pure inorganic phase
heated at 950.degree. C. was negligible. The data also showed that
the oxidation of hydrogen sulfide occurs until all micropores
(mainly about 6 .ANG. in size), likely within carbonaceous deposit
or on the carbon/oxide interface, are filled with the reaction
products. The form of that carbonaceous deposit is important and
that deposit may play a role in adsorption capacity.
[0012] The products of oxidation immobilized on the surface are
stored there. Table 1 shows the capacity of sewage sludge derived
materials as adsorbents of sulfur containing gases. For removal of
a toxic gas containing reduced sulfur the capacity is much greater
than that of activated carbons. It happens in spite of the fact
that the carbon content is small (about 20%) and pore volume much
smaller than that of carbons. TABLE-US-00001 TABLE 1 H.sub.2S and
SO.sub.2 breakthrough capacities for sludge derived adsorbents (SC
series) and activated carbon (S208). The number after SC refers to
the temperature of heat treatment in Centigrade. H.sub.2S
breakthrough capacity SO.sub.2 breakthrough capacity Sample [mg/g]
[mg/g] SC-400 8.2 5.1 SC-600 14.9 9.5 SC-800 23.6 22.2 SC-950 82.6
29.8 S208 48.8 48.2
[0013] Since pore volume seems to be a limiting factor for the
capacity of sewage sludge derived materials, an increase in the
content of carbonaceous deposit and pore volume with maintaining
the desired content of a catalytically active phase seems to be the
desired direction of feature research. Resent studies showed that
the pore volume active in the removal of such compounds as hydrogen
sulfide does not need to be in pores similar in size to adsorbent
molecule. Since the catalytic oxidation is the predominant
mechanism of adsorption, the larger pores, (meso- and macropores)
where the product of oxidation is stored were found to be
beneficial.
[0014] Another important factor is the chemistry of a catalytic
phase, its dispersion, location on the surface, compatibility with
the carbon phase and the effects of both phases on the removal
process (adsorption/catalytic oxidation/storage). It was found that
excellent capacity of an expensive desulfurization catalyst, US
Filter carbon Midas.RTM., is linked to the presence of calcium and
magnesium oxides dispersed within the microporous activated carbon.
On this catalyst, hydrogen sulfide is oxidized on basic centers of
alkali earth metal oxides and sulfur is formed. The fact that this
carbon is able retain up to 60 wt % sulfur is linked to a limited
reactivity of MgO and CaO. On their surface, due to the basic pH
and the presence of moisture, sulfur is formed and owing to the
close proximity of the carbon phase, that sulfur migrates to the
high-energy adsorption centers, small pores. In this way the
catalytic centers are renewed and the adsorbents works until all
small pores are filled by sulfur.
[0015] Sewage sludge based materials were also found as efficient
adsorbents for removal of mercury from waste water and copper.
Other common industrial pollutants which can be efficiently removed
using those materials are basic and acidic dyes. In the case of
these adsorbates the high capacity is linked to surface chemical
nature (acidic and basic sites) and relatively large pores which
are similar in size to the molecules of organic dyes.
[0016] At high temperature, the organic matter vaporizes,
dehydrogenation occurs and carbon can be deposited back on the
surface of an inorganic support as carbon nanotubes of filaments.
This may happen due to the presence of highly dispersed
catalytically active metals. Since this process resembles the
chemical vapor deposition (CVD), it is referred to as the
self-imposed chemical vapor deposition (SICVD). The process of
carbon nanotube growth on the catalysts containing nickel or cobalt
is well-known and described in the literature. The nanotubes and
carbon filaments grow on metal "seeds" and their effective size
depends on the sizes of the seeds. Introduction of more carbon
phase can increase the porosity leading to more space for storing
of oxidation products and also can lead to the formation of greater
quantity of novel carbon entities in the process of CVD. FIG. 1
shows an SEM image of carbon nanotubes grown on the surface of
sewage sludge-derived materials.
[0017] The carbon and nitrogen content of the sludge plays a role
in the formation and properties of the adsorbent. While municipal
sewage sludge is a promising material to use as a base with other
waste sludges, other carbon or nitrogen based wastes can also be
used. Besides formation of new carbon entities in the presence of
catalytic metals as a result of heat treatment the new
spinel-like/mineral like active components can be formed. Recently,
for some sewage sludges containing iron and calcium the
catalytically important entities were identified as dicalcium
ferrite (Ca.sub.2Fe.sub.2O.sub.5).
SUMMARY OF THE INVENTION
Definitions
[0018] The term "adsorption" refers to the phenomenon wherein the
surface of a solid accumulates a concentration of molecules from
its gaseous or liquid environment.
[0019] The term "adsorbent" refers to a material that is able to
adsorb gases or vapors under certain conditions.
[0020] The term "pyrolysis" refers to heat treatment (e.g., at a
temperature over 400.degree. C.) in inert atmosphere of materials
having organic origin.
[0021] The term "chemical activation" refers to the treatment of
organic precursors with certain chemicals during pyrolysis.
[0022] The term "activated carbon" refers to a carbonaceous
material obtained by pyrolysis of organic precursors (e.g., coal,
wood, peat, etc.) at elevated temperatures followed by their
activation using various physical or chemical agents (e.g., at a
temperature between about 600.degree. C. and 1,000.degree. C.).
[0023] The term "caustic-impregnated carbon" refers to activated
carbons impregnated with KOH and NaOH in order to increase their pH
and adsorption capacity for acidic gases.
[0024] The term "breakthrough capacity" refers to the amount of
substance adsorbed on the sorbent surface until the substance is
detected in effluent air at a certain concentration level.
[0025] The term "acidic gases" refers to gases that are able to
transform into acids, or gases that are able to interact as acid
(e.g., electron acceptors).
[0026] The term "specific surface area" refers to the surface area
of adsorbent considered as an area where adsorption of various
molecules could occur.
[0027] The term "pore volume" refers to the volume of pores in an
adsorbent calculated as available for nitrogen molecules at its
boiling point.
[0028] The term "oxidation" refers to the change in the chemical
stage of a substance associated with an electron loss. The charge
on the species becomes more positive.
[0029] The term "residence time" refers to the average time taken
by reagent molecules to pass through a reactor.
[0030] The term "compost material" refers to the individual
materials that are composted.
[0031] The term "compost" can refer to either a mixture that
consists largely of decayed organic matter or the act of converting
compost materials into compost.
[0032] Waste oil sludge, waste metal sludge (both from a shipyard,
but the origin of the sludges can be from any heavy industry
facilities where transition metals such as iron, zinc, copper,
nickel, chromium are used) were mixed with municipal sewage sludge
at different proportions then pyrolyzed in the nitrogen atmosphere
at 650.degree. C. and 950.degree. C. for two different time periods
(half an hour and an hour). Additional samples were pyrolyzed in
the nitrogen atmosphere at a low temperature, e.g., about
600.degree. C., 625.degree. C., 650.degree. C., 675.degree. C., or
700.degree. C. or less, and at a high temperature, e.g., about
900.degree. C., 925.degree. C., 950.degree. C., or 975.degree. C.,
1,000.degree. C., 1,100.degree. C. or higher. As used herein, the
term "industrial sludge" includes any sludge that is not domestic
wastewater sludge. This includes wastewater sludge from
manufacturing or processing of raw materials, intermediate
products, final products or other activities that include
pollutants from non-domestic wastewater sources. "Municipal" or
"domestic" wastewater sludge can be generated at plants servicing
the general population and may conform to the "10 State
Standards."
[0033] Combinations of compost/compost materials and
municipal/industrial sludge, along with pyrolyzation in a nitrogen
atmosphere, can lead to formation of new adsorbents. The new
adsorbents can consist of an inorganic phase (70-95% and 80-98%)
and a carbonaceous phase (5-30% and 10-30%). The inorganic phase
can contain highly dispersed catalytic metals such as iron, nickel,
copper, zinc, chromium, and calcium and magnesium oxides, alumina,
silica, etc.
[0034] As a result of synergy, a ceramics/mineral-like phase is
formed. This phase reacts with nitrogen gas when exposed to
elevated temperatures. The specific surface areas are about 10
m.sup.2/g to about 200 m.sup.2/g. For example, the specific surface
areas may be about 10 m.sup.2/g, 20 m.sup.2/g, 30 m.sup.2/g, 40
m.sup.2/g, 50 m.sup.2/g, 60 m.sup.2/g, 70 m.sup.2/g, 80 m.sup.2/g,
90 m.sup.2/g, 100 m.sup.2/g, 110 m.sup.2/g, 120 m.sup.2/g, 130
m.sup.2/g, 140 m.sup.2/g, 150 m.sup.2/g, 160 m.sup.2/g, 170
m.sup.2/g, 180 m.sup.2/g, 190 m.sup.2/g, 200 m.sup.2/g, or greater.
The specific pore volumes are about 0.002 cm.sup.3/g to about 0.074
m.sup.2/g. For example, the specific pore volumes are about 0.002
cm.sup.3/g, 0.005 m.sup.2/g, 0.015 m.sup.2/g, 0.025 m.sup.2/g,
0.035 m.sup.2/g, 0.045 m.sup.2/g, 0.055 m.sup.2/g, 0.065 m.sup.2/g,
0.074 m.sup.2/g, or greater. An important aspect of the texture is
a significant volume of mesopores reaching about 0.8 cm.sup.3/g.
All materials have basic pH, e.g., a pH over 9. They are capable of
adsorbing up to about 10, 15, 20, 25, or 30 wt % of hydrogen
sulfide, mainly as elemental sulfur.
[0035] The discovered solid state reactions form ceramics/mineral
like crystallographic phases. Spinel-like compounds can form when
municipal/industrial sludge is pyrolized at 950.degree. C., such as
wurtzite (ZnS), ferroan (Ca.sub.2(Mg,
Fe).sub.5(SiAl).sub.8O.sub.22(OH).sub.2), chalcocite
(Cu.sub.1.96S), spinel (MgAl.sub.2O.sub.4), and feroxyhite
(FeO(OH)) were found. In waste oil-based materials besides metallic
iron, bornite (Cu.sub.5FeS.sub.4), hibonite (CaAl.sub.12O.sub.19),
zincite (ZnO), ankerite (Ca(Fe, Mg)(CO.sub.3).sub.2) are present.
In metal sludge based adsorbent aluminum, metallic iron, copper,
zinc, pyrope (Mg.sub.3Al.sub.2(SiO.sub.4).sub.3), perrohotite
(Fe.sub.7S.sub.8), Chalocopyrite (CuFeS.sub.2), Triolite (FeS) and
Fersilicite, (FeSi) exist. Mixing industrial sludges with compost
or compost materials can result in synergy enhancing the catalytic
properties which can be linked to formation of new entities such as
sapphirine (Mg.sub.3.5Al.sub.9Si.sub.1.5O.sub.20), maghemite
(Fe.sub.2O.sub.3), cohenite (Fe.sub.3C), lawsonite
(CaAl.sub.2Si.sub.2O.sub.7(OH)2H.sub.2O), smithsonite (ZnCO.sub.3),
sphalerite (ZnS), and hematite (Fe.sub.2O.sub.3).
[0036] The new entities can be formed during pyrolysis that react
with nitrogen gas when exposed to elevated temperatures
(200-600.degree. C.). This can result in an increase in weight
between 0-3%. Some of these entities can be nitrides. The specific
surface areas and total pore volumes of the adsorbents are between
10-210 m.sup.2/g and 0.15-0.85 cm.sup.3/g, respectively. An
important aspect of the texture can be a significant volume of
mesopores reaching 0.8 cm.sup.3/g (between 0.14-0.77 cm.sup.3/g).
All materials have basic pH between 7-12. They are capable to
adsorb up to 30 wt % of hydrogen sulfide mainly as elemental
sulfur. Exposure to hydrogen sulfide and deposition of sulfur
results in an increase in the volume of mesopores up to 25% as a
result of formation of new pore space in-between deposited sulfur
in large pores. The important components besides alkaline earth
metals and transition metals are iron oxides and hydoxyoxides (but
not only) since they contribute to oxidation of hydrogen sulfide to
elemental sulfur. The developed materials are also good adsorbents
of cationic or ionic dyes and heavy metals (up to 80 mg/g copper
and up to 130 mg/g dyes). The spinel-like phase formed during
pyrolysis contributes to cation exchange, complexations and
precipitation reactions. During these reactions only small quantity
of calcium and zinc is released to the solution as a result of a
cation exchange process.
[0037] The present invention uses the combination of compost and/or
compost materials and municipal and/or industrial waste sludge to
form adsorbents. Successful results used fertilizer and municipal
sludge to create adsorbents, because they contain, in part, large
amounts of carbon and nitrogen. Other wastes are available that are
rich in carbon and nitrogen to use as a base material. One waste is
compost and compost materials. Compost materials can be divided
into two categories, "brown"--high in carbon, and "green"--high in
nitrogen.
[0038] Brown compost materials can be fall leaves, spent plants,
straw and hay, pine needles, small twigs and wood chips, sawdust
and woodshavings, shredded newspaper, egg shells, corncobs, bread
and grains, wood ashes, old potting soil, food-soiled paper towels
and napkins, dried flowers, brewery waste, hops, and pomace,
food-soiled cardboard (recycle if clean, but compost if dirty),
stale flour, cereal, spices, beans, nutshells, meat and fish
scraps.
[0039] Green compost materials can be fruit and vegetable scraps,
coffee grounds and filters, tea bags, fresh leaves, green plants,
prunings and hedge trimmings, grass clippings, weeds, flower
bouquets, seaweed, feathers, horse manure, manure and bedding from
small pets such as hamsters and rabbits, cornstarch and other
organic packing materials, and spoiled juice.
[0040] Additionally, over 70,000 tons of tobacco waste is generated
every year during the production of cigarettes. In India alone,
over 20 years ago, almost 100,000 tons of tobacco waste was
generated, and more is generated every year. Tobacco waste is
currently used as a compost material and fertilizer. Tobacco waste
spans the entire cigarette making process from growing and
harvesting to final production. The types of wastes generated
during pre- and post- harvest practice of tobacco include suckers,
stems, mid ribs, leaf waste and dust. For example, green trimmings
are generated as the either the stalks and/or leaves are harvested
and separated from their stalks for curing. After curing, certain
varieties of tobacco are threshed (by separating the midrib of the
leaf) generating particle waste and stalks can also be removed at
this stage, depending on the type of tobacco. Stems are removed
from the cured and aged tobacco and the leaves and stems are
chopped and blended. Tobacco dust can be formed during the chopping
and blending stages. Further dust can be generated as the chopped
tobacco is formed into tobacco rods and finally wrapped into paper.
Some chemical characteristics of tobacco waste are listed in Table
2. TABLE-US-00002 TABLE 2 Some Chemical Characteristics of Tobacco
pH EC(1/5) Ca Mg N K P Na Fe Cu Zn Mn O.M. % (1/5) (.mu.m/cm)
(.mu.g/g) (.mu.g/g) (%) (%) (.mu.g/g) (.mu.g/g) (.mu.g/g) (.mu.g/g)
(.mu.g/g) (.mu.g/g) 41 5.80 10700 8050 9400 2.35 1.95 973 572 3150
84 90 279
[0041] The use of compost and/or compost material was determined
from studies using combinations of municipal sewage sludge and
industrial sludge and municipal sludge and waste paper. The waste
paper is used for its high carbon content. The paper was ground
fine and added to the sludge. Compost materials can be ground like
the paper and tobacco dust is in particulate/powder form. Sawdust
is another compost material that is already in particulate/powder
form. Sawdust is a brown compost material that is high in carbon.
Wood char/ash can also be used based on its carbon content.
[0042] The invention can combine the compost/compost materials with
industrial sludge or with a mixture of municipal and industrial
sludge. The compost/compost materials can be wetted as it is mixed,
or may contain enough natural moisture to be mixed directly. The
ratios of compost to sludge can range between 25% and 75%.
Additionally, calcium hydroxide may be added to help influence the
dissociation of hydrogen sulfide.
BRIEF DESCRIPTION OF THE FIGURES
[0043] The above and still further objects, features and advantages
of the present invention will become apparent upon consideration of
the following detailed description of a specific embodiment
thereof, especially when taken in conjunction with the accompanying
drawings wherein like reference numerals in the various figures are
utilized to designate like components, and wherein:
[0044] FIG. 1 is a SEM image of the carbon nanotubes on the surface
of sewage sludge-derived adsorbent of the prior art;
[0045] FIGS. 2A and 2B are graphs depicting the predicted and
measured volume of meso- and micro-pores, respectively, for the
adsorbents derived from mixtures of industrial and municipal
sludges;
[0046] FIG. 3 is a graph depicting dependence of H.sub.2S removal
capacity on the volume of mesopores in industrial and municipal
sludge-derived adsorbents;
[0047] FIG. 4 is a graph depicting a comparison of the predicted
and measured H.sub.2S breakthrough capacity for sewage and
industrial sludge-based adsorbents;
[0048] FIG. 5 is a graph depicting DTG curves in nitrogen for
selected adsorbants for initial and H.sub.2S exposed samples
(E);
[0049] FIG. 6 is a graph depicting DTG curves in nitrogen for
selected adsorbants for initial and H.sub.2S exposed samples
(E);
[0050] FIGS. 7A and 7B illustrate X-ray diffraction patterns at
650.degree. C. and 950.degree. C., respectively;
[0051] FIG. 8 illustrates changes in pore size distribution after
H.sub.2S adsorption;
[0052] FIG. 9 illustrates DTG curves in nitrogen for initial and
exhausted samples;
[0053] FIG. 10 shows X-ray diffraction patterns for samples
obtained at 650.degree. C.;
[0054] FIG. 11 illustrates a comparison of the measured and
predicted mesopores volume for WOSS samples obtained at various
conditions;
[0055] FIG. 12 illustrates a comparison of the measured and
predicted H.sub.2S breakthrough capacities for samples obtained at
various conditions;
[0056] FIG. 13 illustrates the H.sub.2S breakthrough capacity
curves for adsorbents obtained at 650.degree. C.;
[0057] FIG. 14 illustrates the H.sub.2S breakthrough curves for
adsorbents obtained at 950.degree. C.;
[0058] FIG. 15 illustrates the dependence of the H.sub.2S
breakthrough capacity on the amount of preadsorbed water;
[0059] FIG. 16 illustrates a comparison of measured and calculated
(assuming the physical mixture of components) H.sub.2S breakthrough
capacities;
[0060] FIG. 17 illustrates XRD patterns for tobacco derived
samples;
[0061] FIG. 18 illustrates XRD patterns for metal and waste oil
sludge derived adsorbents;
[0062] FIG. 19 illustrate a XRD diffraction pattern for composite
tobacco/metal sludge based adsorbents;
[0063] FIG. 20 illustrates nitrogen adsorption isotherms for
samples pyrolyzed at 650.degree. C.;
[0064] FIG. 21 illustrates nitrogen adsorption isotherms for
samples pyrolyzed at 950.degree. C.;
[0065] FIG. 22 illustrates pore size distributions for single
component samples;
[0066] FIGS. 23A and 23B illustrate pore size distributions for
samples pyrolyzed at 650.degree. C.;
[0067] FIGS. 24A and 24B illustrate pore size distributions for
samples pyrolyzed at 950.degree. C.;
[0068] FIG. 25 shows a comparison of the volume of micropores
measured and calculated assuming physical mixture of the
components;
[0069] FIG. 26 shows a comparison of the volume of mesopores
measured and calculated assuming physical mixture of the
components;
[0070] FIG. 27 illustrates the dependence of H.sub.2S breakthrough
capacity on the volume of pores (micropores and mesopores for
samples pyrolyzed at two temperatures);
[0071] FIG. 28 illustrates DTG curves in nitrogen for single
component samples;
[0072] FIGS. 29A and 29B illustrate DTG curves in nitrogen for
samples pyrolyzed at 650.degree. C.; and
[0073] FIGS. 30A and 30B illustrate DTG curves in nitrogen for
samples pyrolyzed at 950.degree. C.
DETAILED DESCRIPTION OF THE INVENTION
[0074] Industrial sludges such as waste oil sludge and metal sludge
can be utilized using pyrolysis to produce new catalytic
adsorbents. An important result of mixing is an enhancement in the
properties of the above-mentioned sewage sludge-based adsorbents.
Although only waste oil sludge can lead to adsorbents with an
exceptional ability for desulfurization with 30 wt % removal
capacity, the presence of sewage sludge is an economically feasible
method of utilizing this abundant material.
[0075] Mixing the sludge and their pyrolysis resulted in the
enhanced properties compared to the physical mixture of pyrolized
single components. FIGS. 2A and 2B show the comparison of the
volumes of pores measured and predicted for the physical mixture of
waste oil sludge (WO), sewage sludge (SS) and metal sludge (MS).
The generally observed trend indicates that mixing sludges results
in the development of an additional pore volume. That pore volume,
especially mesopores, was identified as one of the factors
governing the adsorption capacity. FIG. 3 shows the dependence of
the H.sub.2S removal capacity on the volume of mesopores. Since the
analysis of materials pH and thermodesorption indicated elemental
sulfur as an oxidation product, only mesopores can store such
amount of sulfur as found from H.sub.2S breakthrough capacity tests
(up to 30 wt %).
[0076] Besides porosity, surface chemistry is also altered during
pyrolysis of the sludge mixture as compared to the single
components. FIG. 4 shows the comparison of the measured and
predicted capacity based on the performance of the individual
components assuming the physical mixture. The huge enhancement
found, reaching 100%, is the result of changes in the composition
and the surface distribution of an inorganic phase. The sludges
studied contain iron, copper, nickel, zinc, calcium, chromium and
other metals in significant quantities. Their high temperature
reaction in the presence of carbon phase can lead to unique
spinel/mineral-like components active in the oxidation
reactions.
[0077] FIG. 5 illustrates an increase in the mass of the sample
obtained by high temperature pyrolysis. FIG. 5 shows DTG curves in
nitrogen for selected adsorbants for initial and H.sub.2S exposed
samples (E). The phenomenon was not observed for the samples
pyrolized at low temperature. While not intending to be bound by
theory, the increase may be a result of nitride formation. It was
found the certain ceramic materials, when exposed to nitrogen in
the presence of char, are able to form nitrides. Formation of these
ceramics can be crucial for catalytic performance.
[0078] Although the best adsorbents are obtained at about
650.degree. C., the synergy is the most predominant at about
950.degree. C. when a mineral like/ceramic phase is formed.
Moreover, an increase in the mass of samples under nitrogen at
about 600.degree. C. indicates that ceramic components of
adsorbents form nitrides in the presence of carbon. FIG. 6
illustrates DTG curves in nitrogen for selected adsorbants for
initial and H.sub.2S exposed samples (E). Those ceramics must be
active in the process of H.sub.2S adsorbents since an increase in
mass significantly decreased after exposure to hydrogen sulfide and
water. The surface of adsorbents treated at about 950.degree. C.
has very low affinity to retain water (hydrophobic). Temperature
has also an effect on the density of the final products, which
varies from about 0.25 at 650.degree. C. to about 0.50 at
950.degree. C.
[0079] As mentioned above, unique compounds exist as
crystallographic phases and they consist of metals such as calcium,
magnesium, alumina, copper, iron, zinc and nonmetals such as oxygen
sulfur, carbon and silica. The level of mineralization increases
with an increase in the pyrolysis temperature and time. Higher
temperature results in formation of two component metal-nonmetal
crystallographic compounds with metals at low oxidation states.
FIGS. 7A and 7B show the changes in the X-ray diffraction pattern
for samples obtained at different temperatures. FIG. 7A illustrates
the X-ray diffraction pattern at 650.degree. C. and FIG. 7B is at
950.degree. C.
[0080] Advantages of the present invention include the fact that
the sorbents obtained from industrial sludge have five times higher
capacity for hydrogen sulfide removal than unmodified carbons.
Their capacity is comparable to that of caustics impregnated carbon
used worldwide as hydrogen sulfide adsorbents in sewage treatment
plants. Furthermore, the kinetics of the removal process are very
fast and no heat is released. Moreover, during adsorption, H.sub.2S
reacts with inorganic matter and is oxidized to elemental sulfur.
The product is environmentally inert. Importantly, the pH of the
spent material is basic, so it can be safely discarded. Only small
amounts of SO.sub.2 are released. Another advantage of the
invention is that, since the sorbents are obtained from waste
sludge, the significant amount of industrial and municipal waste
can be recycled and reused in sewage treatment plants. The sorbents
can be also used in desulfurization of gaseous fuels (for fuel cell
applications) and in hydrothermal vents. The sorbents find another
environmental application in removal of mercury from waste water.
Furthermore, there is the possibility of regeneration of spent
materials using heating to about 300.degree. C. to remove elemental
sulfur.
EXAMPLE 1
[0081] The homogeneous mixtures of waste sludges were prepared as
listed in Table 3 and dried at 120.degree. C. The dried samples
were then crushed and pyrolized in a horizontal furnace at
950.degree. C. for 30 min. The temperature ramp was 10
degrees/minute. An inert atmosphere was provided by 10 ml/min. flow
of nitrogen. The yields, ash content and densities of materials are
listed in Table 3. TABLE-US-00003 TABLE 3 Adsorbents' composition,
yields, ash content and densities. Wet Dry Yield compo- Solid
compo- (dry Ash .gamma. Sample sition content sition mass) content*
[g/cm.sup.3] WO WO: 23.6 WO: 29 92 0.48 100% 100% SS SS: 100% 24.6
SS: 100% 45 80 0.46 MS MS: 100% 23.4 MS: 100% 47 @ 0.85 WOSS WO:
50% -- WO: 49% 34 @ 0.46 SS: 50% SS: 51% WOMS WO: 50% -- WO: 50% 50
@ 0.47 MS: 50% MS: 50% WOSSMS WO: 40% -- WO: 46% 41 @ 0.46 SS: 40%
SS: 31% MS 10% MS 23% *Determined as mass left at 950.degree. C.
after in TA run in air. @ - not determined due to reaction with air
during burning
[0082] The performance of materials as sorbents for hydrogen
sulfide was evaluated using lab developed breakthrough tests.
Adsorbent samples were packed into a column (length 60 mm, diameter
9 mm, bed volume 6 cm.sup.3) and pre-humidified with moist air
(relative humidity 80% at 25.degree. C.) for an hour. The amount of
adsorbed water was estimated from the increase in the sample weight
after pre-humidification (the sorbents were removed from the column
and weighted). Moist air containing 0.3% (3,000 ppm) H.sub.2S was
then passed through the column of adsorbent at 1.4 L/min. The
breakthrough of H.sub.2S was monitored using an Interscan LD-17
H.sub.2S continuous monitor system interfaced with a computer data
acquisition program. The test was stopped at the breakthrough
concentration of 350 ppm. The adsorption capacities of each sorbent
in terms of grams of H.sub.2S per gram of material were calculated
by integration of the area above the breakthrough curves, and from
the H.sub.2S concentration in the inlet gas, flow rate,
breakthrough time, and mass of sorbent. The obtained results are
collected in Table 4. TABLE-US-00004 TABLE 4 H.sub.2S breakthrough
capacities, adsorption of water and surface pH before and after
H.sub.2S adsorption Brth Bth Water capacity capacity adsorbed
Sample [mg/g] [mg/cm.sup.3] [mg/g] pH pHE WO 109 52 0 9.9 9.4 SS 45
21 26 10.9 10.0 MS 2.8 2.4 0 10.67 10.04 WOSS 108 50 11 10.8 9.1
WOMS 86 40 3 9.9 8.8 WOSSMS 121 56 4 10.5 9.4 E - after exposure to
H.sub.2S
[0083] Characterization of pore sizes and adsorption capacity of
materials prepared was accomplished using physical sorption
measurement. The equilibrium adsorption isotherms of N.sub.2 were
measured by volumetric techniques. From the isotherms, the pore
size distribution (PSD) was evaluated using the Density Functional
Theory (DFT). The surface area was calculated using BET approach
and micropore volumes using Dubinin-Radushkevich equation (DR). The
results are presented in Table 5. The symbol ".DELTA." represents
the difference in the specific pore volume before and after
deposition of sulfur. For all samples but MS an increase in the
volume of mesopores was found as a result of deposition of
elemental sulfur and formation of new pores within that deposit.
The examples of PSDs are presented in FIG. 8. TABLE-US-00005 TABLE
5 Parameters of porous structure S.sub.BET V.sub.mic [m.sup.2/
[cm.sup.3/ .DELTA.V.sub.mic V.sub.mes .DELTA.V.sub.mes V.sub.t
V.sub.mic/ Sample g] g] [cm.sup.3/g] [cm.sup.3/g] [cm.sup.3/g]
[cm.sup.3/g] V.sub.t WO 132 0.050 0.314 0.364 14 WO-E 96 0.034
-0.16 0.355 0.041 0.389 8 SS 141 0.058 0.151 0.209 28 SS-E 121
0.032 -0.26 0.190 0.039 0.222 17 MS 10 0.002 0.015 0.017 12 MS-E 4
0.001 -0.01 0.005 -0.010 0.006 17 WOSS 150 0.061 0.163 0.224 41
WOSS-E 89 0.030 -0.31 0.258 0.096 0.288 31 WOMS 70 0.022 0.144
0.166 13 WOMS-E 60 0.017 -0.05 0.154 0.010 0.171 11 WOSSMS 144
0.053 0.267 0.320 20 WOSSMS-E 59 0.022 -0.21 0.183 -0.085 0.205 11
WO--waste oil origin; SS--sewage sludge origin; MS--metal sludge
origin; E--after exposure to H.sub.2S.
[0084] Thermal analysis was carried out to identify the oxidation
products and to balance the amount of sulfur deposited on the
surface and the results are below in Table 6. The peaks between
200-450.degree. C., illustrated in FIG. 9, represent the removal of
elemental sulfur. TABLE-US-00006 TABLE 6 Weight losses in various
temperature ranges and amount of sulfur adsorbed from H.sub.2S
breakthrough capacity test. Weight loss is corrected for amount
adsorbed in H.sub.2S breakthrough test (Bth. Cap.) S Bth Sample
20-150.degree. C. .DELTA. 150-450.degree. C. .DELTA.
450-700.degree. C. .DELTA. 800-1000.degree. C. .DELTA. Total
.DELTA. Capacity WO 3.02 0.84 0.05 2.3 WO-E 2.31 0 9.20 8.36 1.0
0.95 1.9 0.0 9.31 10.2 SS 2.40 1.15 0.12 4.96 6.22 SS-E 3.45 1.0
1.15 0 0.03 0 2.7 6.8 4.23 WOSS 3.48 0.21 0.43 2.67 WOSS-E 3.15 0
5.85 5.64 0.53 0.1 2.67 0 5.64 10.1 WOMS 0.58 +1.88 +0.80 2.64
WOMS-E 0.81 0.23 2.56 4.44 +0.59 0.21 2.12 0 4.88 8.08 WOSSMS 1.77
0.06 0.55 2.83 WOSSMS-E 3.30 1.53 2.34 2.28 0.58 0.03 4.11 1.28
5.12 11.4 E - after exposure to H.sub.2S.
[0085] X-Ray fluorescence was used to evaluate the content of iron,
and sulfur after exhaustion. The results are presented in Table 7.
Although the total amount is not given the intensities of the peaks
in arbitrary units are related to the amount of specific species.
TABLE-US-00007 TABLE 7 XRF results. Sample Fe S(E) WO 139.6 2496.86
SS 8584.02 ND MS 12844.08 ND WOSS 7321.80 ND WOMS 12574.54 732.85
WOSSMS 12173.98 1352.93
EXAMPLE 2
[0086] The homogeneous mixtures of waste sludges were prepared as
listed in Table 8 and dried at 120.degree. C. The dried samples
were then crushed and pyrolized in a horizontal furnace at
650.degree. C. for 30 min. The temperature ramp was 10
degrees/minute. An inert atmosphere was provided by 10 ml/min flow
of nitrogen. The yields, ash content and densities of materials are
listed in Table 8. TABLE-US-00008 TABLE 8 Adsorbents' composition,
yield, and densities Yield Wet Solid Dry (dry .gamma. Sample
composition content composition mass) [g/cm.sup.3] WOLT WO: 100%
23.6 WO: 100% 32 0.26 SSLT SS: 100% 24.6 SS: 100% 47 0.52 MSLT MS:
100% 23.4 MS: 100% 0.47 WOSSLT WO: 50% -- WO: 49% 0.36 SS: 50% SS:
51% WOMSLT WO: 50% -- WO: 50% 58 0.38 MS: 50% MS: 50% WOSSMSLT WO:
40% -- WO: 46% 46 0.38 SS: 40% SS: 31% MS 10% MS 23% *Determined as
mass left at 950.degree. C. after thermol analyses run in air.
LT--low temperature, 650.degree. C.
[0087] The performance of materials as sorbents for hydrogen
sulfide was evaluated using lab developed breakthrough tests.
Adsorbent samples were packed into a column (length 60 mm, diameter
9 mm, bed volume 6 cm.sup.3) and pre-humidified with moist air
(relative humidity 80% at 25.degree. C.) for an hour. The amount of
adsorbed water was estimated from the increase in the sample weight
after pre-humidification (the sorbents were removed from the column
and weighted). Moist air containing 0.3% (3,000 ppm) H.sub.2S was
then passed through the column of adsorbent at 1.4 L/min. The
breakthrough of H.sub.2S was monitored using an Interscan LD-17
H.sub.2S continuous monitor system interfaced with a computer data
acquisition program. The test was stopped at the breakthrough
concentration of 350 ppm. The adsorption capacities of each sorbent
in terms of grams of H.sub.2S per gram of material were calculated
by integration of the area above the breakthrough curves, and from
the H.sub.2S concentration in the inlet gas, flow rate,
breakthrough time, and mass of sorbent. The obtained results are
collected in Table 9. TABLE-US-00009 TABLE 9 H.sub.2S breakthrough
capacities, adsorption of water and surface pH before and after
H.sub.2S adsorption Bth Brth capacity capacity Water adsorbed
Sample [mg/g] [mg/cm.sup.3] [mg/g] pH pH-E WOLT 315 82 48 9.3 9.3
SSLT 9 5 18 10.9 11.1 MSLT 79 37 0 7.8 7.1 WOSSLT 146 53 21 9.2 9.1
WOMSLT 130 49 14 9.8 9.4 WOSSMSLT 73 33 20 9.7 9.2 LT--low
temperature, 650.degree. C.; E - after exposure to H.sub.2S.
[0088] Characterization of pore sizes and adsorption capacity of
materials prepared was accomplished using physical sorption
measurement. Equilibrium adsorption isotherms of N.sub.2 will be
measured by volumetric techniques. From the isotherms the pore size
distribution was evaluated using the Density Functional Theory
(DFT). The surface area was calculated using BET approach and
micropore volumes using Dubinin-Radushkevich equation (DR). The
results are presented in Table 10. The symbol ".DELTA." represents
the difference in the specific pore volume before and after
deposition of sulfur. TABLE-US-00010 TABLE 10 Parameters of porous
structure S.sub.BET V.sub.mic V.sub.mes [m.sup.2/ [cm.sup.3/
.DELTA.V.sub.mic [cm.sup.3/ .DELTA.V.sub.mes V.sub.t V.sub.mic/
Sample g] g] [cm.sup.3/g] g] [cm.sup.3/g] [cm.sup.3/g] V.sub.t WOLT
202 0.074 0.765 0.839 10 WOLT-E 83 0.032 -0.42 0.434 -0.321 0.517 6
SSLT 92 0.037 0.113 0.150 25 SSLT-E 79 0.029 -0.008 0.106 -0.007
0.135 27 MSLT 34 0.014 0.122 0.136 11 MSLT-E 25 0.011 -0.003 0.160
0.038 0.171 6 WOSSLT 154 0.058 0.459 0.517 12 WOSSLT-E 72 0.027
-0.031 0.281 -0.178 0.308 10 WOMSLT 92 0.036 0.270 0.306 12
WOMSLT-E 65 0.026 -0.010 0.265 -0.005 0.291 9 WOSSMSLT 110 0.042
0.372 0.415 10 WOSSMSLT-E 59 0.023 -0.011 0.250 -0.122 0.273 8
LT--low temperature, 650.degree. C.; E - after exposure to
H.sub.2S
Thermal analysis was carried out to identify the oxidation products
and to balance the amount of sulfur deposited on the surface is
listed in Tables 11A and 11B, noting two different temperature
ranges.
[0089] Tables 11A and 11B--Weight losses [in %] in various
temperature ranges and amount of sulfur adsorbed from H.sub.2S
breakthrough capacity test [in %]. Weight loss is corrected for
amount adsorbed in H.sub.2S breakthrough test (Bth. Cap.); (LT--low
temperature, 650.degree. C.; E--after exposure to H.sub.2S).
TABLE-US-00011 TABLE 11A S brth Sample 20-150.degree. C. .DELTA.
150-450.degree. C. .DELTA. 450-700.degree. C. .DELTA.
800-1000.degree. C. .DELTA. Total .DELTA. capacity WOLT 4.70 1.85
1.00 6.69 WOLT-E 7.21 2.51 34.6 32.75 4.88 3.88 7.28 0.59 39.7 29.6
SSLT 1.86 0.59 0.97 9.18 SSLT-E 3.34 1.48 1.40 0.81 1.93 0.96 9.53
0.35 3.6 8.4 WOSSLT 3.56 1.49 1.04 10.46 WOSSLT-E 5.20 1.64 15.9
14.41 2.87 1.83 12.17 1.71 19.59 13.7
[0090] TABLE-US-00012 TABLE 11B S brth Sample 20-150.degree. C.
.DELTA. 150-400.degree. C. .DELTA. 400-650.degree. C.
.DELTA.150-650.degree. C. Total .DELTA. capacity WOLT 4.70 1.71
0.77 WOLT-E 5.42 0.72 23.35 21.64 3.41 2.64 31.6 31 SSLT 1.86 0.46
0.68 SSLT-E 3.08 1.22 1.03 0.57 1.48 0.80 1.38 0.9 MSLT 3.66 1.37
0.78 MSLT-E 4.48 0.82 13.3 11.93 2.28 1.5 15.2 14.3 WOSSLT 1.01 0
2.49 WOSSLT-E 1.16 0.15 6.62 6.62 2.13 0 7.14 7.7 WOMSLT 3.31 0
0.93 WOMSLT-E 2.86 0 6.13 6.13 2.78 1.85 9.00 12.7 WOSSMSLT 1.52 0
3.23 WOSSMSLT-E 4.65 3.13 8.2 8.2 3.16 0 9.20 12.0
EXAMPLE 3
[0091] The homogeneous mixtures of waste sludges were prepared as
listed in Table 12 and dried at 120.degree. C. The dried samples
were then crushed and pyrolyzed in a horizontal furnace at
950.degree. C. for 60 min. The temperature ramp was 10 deg/min. An
inert atmosphere was provided by 10 ml/min flow of nitrogen. The
yields and densities of the materials are listed in Table 12.
TABLE-US-00013 TABLE 12 Adsorbents' composition and their densities
Wet Solid Dry .gamma. Sample composition content composition
[g/cm.sup.3] WO60 WO: 100% 23.6 WO: 100% 0.47 SS60 SS: 100% 24.6
SS: 100% 0.46 MS60 MS: 100% 23.4 MS: 100% 0.84 WOSS60 WO: 50% --
WO: 49% 0.41 SS: 50% SS: 51% WOMS60 WO: 50% -- WO: 50% 0.46 MS: 50%
MS: 50% WOSSMS60 WO: 40% -- WO: 46% 0.45 SS: 40% SS: 31% MS 10% MS
23%
[0092] The performance of materials as sorbents for hydrogen
sulfide was evaluated using lab developed breakthrough tests.
Adsorbent samples were packed into a column (length 60 mm, diameter
9 mm, bed volume 6 cm.sup.3) and prehumidified with moist air
(relative humidity 80% at 25.degree. C.) for an hour. The amount of
adsorbed water was estimated from the increase in the sample weight
after pre-humidification (the sorbents were removed from the column
and weighted). Moist air containing 0.3% (3,000 ppm) H.sub.2S was
then passed through the column of adsorbent at 1.4 L/min. The
breakthrough of H.sub.2S was monitored using an Interscan LD-17
H.sub.2S continuous monitor system interfaced with a computer data
acquisition program. The test was stopped at the breakthrough
concentration of 350 ppm. The adsorption capacities of each sorbent
in terms of grams of H.sub.2S per gram of material were calculated
by integration of the area above the breakthrough curves, and from
the H.sub.2S concentration in the inlet gas, flow rate,
breakthrough time, and mass of sorbent. The obtained results are
collected in Table 13. TABLE-US-00014 TABLE 13 H.sub.2S
breakthrough capacities, adsorption of water and surface pH before
and after H.sub.2S adsorption (E - after exposure to H.sub.2S) Brth
Bth Water capacity capacity adsorbed Sample [mg/g] [mg/cm.sup.3]
[mg/g] pH pH-E WO60 61 29 11 10.7 10.2 SS60 78 36 26 10.5 9.3 MS60
2 1.7 0 9.8 9.6 WOSS60 78 32 36 11.8 9.8 WOMS60 9.4 WOSSMS60 73 33
20 10.7 10.2
EXAMPLE 4
[0093] X-ray diffraction measurements were conducted on WO, SS, MS,
WOSS and WOSSMS adsorbent samples using standard powder diffraction
procedure. Adsorbents were ground with methanol in a small agate
mortar. Grinding of the adsorbents by hand ensures particle sizes
between 5-10 .mu.m, which prevents line broadening in diffraction
peaks. The mixture was smear-mounted onto the zero-background
quartz window of a Philips specimen holder and allow to air dry.
Samples were analyzed by Cu K.quadrature. radiation generated in a
Phillips XRG 300 X-ray diffractometer. A quartz standard slide was
run to check for instrument wander and to obtain accurate location
of 2.THETA. peaks.
[0094] In the waste oil based sludge sample heated at 650.degree.
C. (WO650) only metallic copper was detected as a separate
crystallographic phase. See, FIG. 10. In the case of SS650, quartz
(SiO.sub.2), cristobalite (SiO.sub.2), truscottite
(Ca.sub.14Si.sub.24)O.sub.58(OH).sub.82 H.sub.2O), and metallic
iron are present. After mixing two components and heating at
650.degree. C., besides quartz, cristobalite and metallic iron and
copper, anorthite (CaAl.sub.2Si.sub.2O.sub.8) and diaspore
(AlO(OH)) are detected.
[0095] Comparison of the diffraction patterns presented in FIG. 10
clearly shows the synergetic effect in the chemical composition of
materials. New components formed having their origin on addition of
silica (coming from sewage sludge), and iron and zinc from waste
oil sludge. These results indicated formation of new phases with an
increase in the pyrolysis temperature and time. FIG. 10 shows the
changes in chemistry after pyrolysis for half an hour at
650.degree. C. while FIGS. 7A and 7B compare the sample pyrolyzed
at 950.degree. C.
[0096] The examples of crystallographic phases found for samples
pyrolyzed at various conditions are presented in Tables 14 and 15.
The headings indicate the composition of the sample, the
temperature it was pyrolyzed at and the duration of the pyrolysis.
For example, SS650-0.5 is sewage sludge pyrolyzed at 650.degree. C.
for 30 minutes. TABLE-US-00015 TABLE 14 Crystallographic phases
identified based on XRD analysis WOSS650- WO950- SS650-0.5
WO650-0.5 0.5 SS950-0.5 0.5 WOSS950-0.5 Aluminum Aluminum Anorthite
Al Al CaAl.sub.2Si.sub.2O.sub.8 Iron, Fe Iron, Fe Iron, Fe Bayerite
Al(OH).sub.3 Bornite Bornite Bornite Cu.sub.5FeS.sub.4
Cu.sub.5FeS.sub.4 Cu.sub.5FeS.sub.4 Maghemite Fe.sub.2O.sub.3
Cohenite Fe.sub.3C Lawsonite
CaAl.sub.2Si.sub.2O.sub.7(OH).sub.2H.sub.2O Hibonite
CaAl.sub.12O.sub.19 Diaspore Ankerite AlO(OH)
Ca(Fe,Mg)CO.sub.3).sub.2 Calcite Huntite Vaterite Vaterite
magnesium Mg.sub.3Ca(CO.sub.3).sub.4 CaCO.sub.3 CaCO.sub.3
Sapphirine Sapphirine Sapphirine
(Mg.sub.4Al.sub.4)Al.sub.4Si.sub.2O.sub.20
(Mg.sub.4Al.sub.4)Al.sub.4Si.sub.2O.sub.20
(Mg.sub.4Al.sub.4)Al.sub.4Si.sub.2O.sub.20 Spinel Spinel
MgAl.sub.2O.sub.4 MgAl.sub.2O.sub.4 Barringerite Zincite Zincite
Fe.sub.2P ZnO ZnO Wurtizite Wurtzite ZnS ZnS Goethite Ferroxyhite,
goethite Lepidicrocite, FeO(OH) FeO(OH) FeO(OH) Almandine
Smithsonite Fe.sub.3Al.sub.2(SiO.sub.4).sub.3 ZnCO.sub.3 Quartz,
Quartz Quartz Cristobalite SiO.sub.2 SiO.sub.2 SiO.sub.2
[0097] TABLE-US-00016 TABLE 15 Crystallographic phases identified
based on XRD analysis MS650 MS950 WOSSMS650 WOSSMS950 Aluminum
Aluminum Al Iron, Fe Iron, Fe Iron Fe Copper, Cu Copper, Cu Zinc,
Zn Huntite Mg.sub.5Ca(CO.sub.3) Hematite, Fe.sub.2O.sub.3
Fersilicite, FeSi Moisanite, SiC Margarite,
CaAl(Si.sub.2Al.sub.2)O.sub.10(OH).sub.2 Almandine Sphalerite, ZnS
Fe.sub.3Al.sub.2(SiO.sub.4).sub.3 Pyrrhotite, Fe.sub.1-xS
Pyrrhotite, Fe.sub.1-xS Pyrrhotite, Fe.sub.1-xS Trioilite, FeS
Trioilite, FeS Trioilite, FeS Pyrope,
Mg.sub.3Al.sub.2(SiO.sub.4).sub.3 Spinel MgAl.sub.2O.sub.4
Chalocopyrite CuFeS.sub.2 Pyrrohotite Sphalerite Fe.sub.7S.sub.8
ZnS Zhanghengite, CuZn Quartz, SiO.sub.2 Quartz, Cristobalite
Moganite, SiO.sub.2 SiO.sub.2
[0098] Thus, in sewage sludge origin materials obtained at
950.degree. C. such spinel-like compounds as wurtzite (ZnS),
ferroan (Ca.sub.2(Mg,Fe).sub.5(SiAl).sub.8O.sub.22(OH).sub.2),
chalcocite (Cu.sub.1.96S), spinel (MgAl.sub.2O.sub.4), and
feroxyhite (FeO(OH)) were found. In waste oil-based materials
besides metallic iron, bornite (Cu.sub.5FeS.sub.4), hibonite
(CaAl.sub.12O.sub.19), zincite (ZnO), ankerite (Ca(Fe,
Mg)(CO.sub.3).sub.2) are present. In metal sludge based adsorbent
aluminum, metallic iron, copper, zinc, pyrope
(Mg.sub.3Al.sub.2(SiO.sub.4).sub.3), perrohotite (Fe.sub.7S.sub.8),
Chalocopyrite (CuFeS.sub.2), Triolite (FeS) and Fersilicite, (FeSi)
exist. Mixing sludges results in synergy enhancing the catalytic
properties which is linked to formation of new entities such as
sapphirine (Mg.sub.3.5Al.sub.9Si.sub.1.5O.sub.20), maghemite
(Fe.sub.2O.sub.3), cohenite (Fe.sub.3C), lawsonite
(CaAl.sub.2Si.sub.2O.sub.7(OH)2H.sub.2O), smithsonite (ZnCO.sub.3),
sphalerite (ZnS), and hematite (Fe.sub.2O.sub.3).
[0099] The materials obtained at 650.degree. C. differ
significantly from those obtained at 950.degree. C. In the latter,
more double-component crystallographic phases (metal-nonmetal) are
present with metals at lower oxidation states. The samples
pyrolyzed at 650.degree. C. contain more aluminosilicates with
calcium, magnesium and iron cations.
EXAMPLE 5
[0100] The performance of adsorbents obtained at 650.degree. C. and
950.degree. C. for 0.5 hour or 1 hour as H.sub.2S removal media was
compared. The results are presented in Tables 16-18. TABLE-US-00017
TABLE 16 H.sub.2S breakthrough capacities, amount of water
pre-adsorbed, and pH values for the initial and exhausted
adsorbents. H.sub.2S Brth. H.sub.2S Brth. Water Cap. Cap. adsorbed
Sample [mg/g] [mg/cm.sup.3] [mg/g] pH pH-E WO650-0.5 315 82 48 9.3
9.3 WO950-0.5 109 52 0 9.9 9.4 WO950-1 62 29 11 10.7 10.2 SS650-0.5
9 5 18 10.9 11.1 SS950-0.5 42 21 26 10.9 10.0 SS950-1 78 36 26 10.5
9.3 WOSS950-0.5 146 53 21 9.2 9.1 WOSS950-0.5 108 50 11 10.8 9.1
WOSS950-1 78 32 36 11.8 9.4
[0101] TABLE-US-00018 TABLE 17 Shift in the pH - .DELTA.pH between
initial and exhausted samples, amount of sulfur expected based on
the H.sub.2S breakthrough capacity -SBT, weight loss between
150-400.degree. C., .quadrature.W, and selectivity for oxidation to
elemental sulfur, S.sub.el S.sub.BT .DELTA.W S.sub.el Sample
.DELTA.pH [%] [%] [%] WO650-0.5 0 30.8 22.52 73 WO950-0.5 0.5 10.7
6.04 56 WO950-1 0.5 6.1 4.39 72 SS650-0.5 0 0.8 0.15 19 SS950-0.5
0.9 4.1 2.02 47 SS950-1 0.8 7.7 4.32 56 WOSS650-0.5 0.1 14.2 11.91
83 WOSS950-0.5 1.7 10.6 4.58 42 WOSS950-1 2.4 7.7 6.32 82
[0102] TABLE-US-00019 TABLE 18 Structural parameters calculated
from nitrogen adsorption isotherms S.sub.BET V.sub.mic V.sub.mes
V.sub.t Sample [m.sup.2/g] [cm.sup.3/g] [cm.sup.3/g] [cm.sup.3/g]
V.sub.mes/V.sub.t WO650-0.5 202 0.074 0.765 0.839 0.92 WO650-0.5E
83 0.032 0.434 0.517 0.84 WO950-0.5 132 0.050 0.314 0.364 0.86
WO950-0.5E 96 0.054 0.355 0.389 0.91 WO950-1 92 0.037 0.303 0.340
0.89 WO950-1E 64 0.024 0.275 0.299 0.92 SS650-0.5 92 0.037 0.113
0.150 0.75 SS650-0.5E 79 0.029 0.106 0.135 0.78 SS950-0.5 141 0.058
0.151 0.209 0.72 SS950-0.5E 121 0.032 0.190 0.222 0.85 SS950-1 125
0.049 0.138 0.187 0.74 SS950-1E 47 0.018 0.124 0.132 0.94
WOSS650-0.5 154 0.058 0.459 0.517 0.89 WOSS650-0.5E 72 0.027 0.281
0.308 0.91 WOSS950-0.5 150 0.061 0.163 0.224 0.73 WOSS950-0.5E 89
0.030 0.258 0.288 0.89 WOSS950-1 199 0.075 0.377 0.447 0.84
WOSS950-1E 79 0.031 0.269 0.300 0.90
[0103] The results demonstrate the possibility of obtaining the
valuable desulfurization catalysts from mixture of waste oil sludge
and sewage sludge. Up to 30 wt % hydrogen sulfide can be retained
on their surface. The surface properties, such as porosity,
selectivity, or catalytic activity can be modified by changing the
pyrolysis conditions. The catalytic activity and hydrogen sulfide
removal capacity are directly related to the new surface chemistry
formed by solid-state reactions during pyrolysis. This chemistry
can also be controlled to certain degree by varying the composition
of the precursor mixture. As a result of the synergy between the
sludge components new chemistry and porosity is formed which
enhances both the physicochemical properties of the materials and
their performance. FIG. 11 shows the comparison of the predicted
(based on the composition and yield of the individual components)
and measured volume of mesopores while FIG. 12 compares the
predicted and measured H.sub.2S breakthrough capacities.
EXAMPLE 6
[0104] Equilibrium studies for adsorption of acid red and basic
fuchsin were conducted in a series of 100 ml Erlenmeyer flasks at
293 K. Each flask was filled with 10 ml of dye solution with
concentrations between 10-1000 mg/l. After equilibration, the
samples were filtrated, analyzed for their dyes content and the
equilibrium adsorption capacity was calculated. The equilibrium
data was fitted to the so-called Langmuir-Freundlich single solute
isotherm. The results are presented in Table 19. The variable
q.sub.m is the adsorption capacity per unit gram of adsorbent, K is
the Langmuir-type equilibrium constant, and the exponential term n
is the heterogeneity parameter of the site energy. TABLE-US-00020
TABLE 19 Fitting parameters to Langmuir-Freundlich isotherm q.sub.m
K ample [mg dye/g] [l/mg] n R.sup.2 Acid Red1 SS 45.00 0.10 0.44
0.9706 WO 46.35 0.14 0.23 0.9757 WOSSO 71.19 0.17 0.75 0.9610
WOSS650 68.40 0.15 0.74 0.9325 WVA 71.42 0.029 0.76 0.9919 Basic
Fuchsin SS 70.36 0.03 0.36 0.9969 WO 94.21 0.18 0.65 0.9851 WOSS
126.89 0.29 0.59 0.9929 WOSS650 105.94 0.15 0.57 0.9804
[0105] The adsorption capacity is much higher than that for
commercial activated carbon and it is attributed to the high volume
of mesopores and the presence of mineral-like structures, which can
participate in ion exchange reactions and precipitation
reactions.
EXAMPLE 7
[0106] To check the effect of water exposure on the porosity of
samples, the materials were dispersed in water and shake in room
temperature for 24 hours. After drying the surface area, pore
volumes and the average pore sizes were determined. The results
indicted an increase in the volume of mesopores are as a result of
the reaction of inorganic oxides/salts with water. The results are
presented in Table 20. .DELTA. is the average pore size.
TABLE-US-00021 TABLE 20 Structural parameters S.sub.BET V.sub.mic
V.sub.mes V.sub.t .DELTA. Sample (m.sup.2/g) (cm.sup.3/g)
(cm.sup.3/g) (cm.sup.3/g) V.sub.mic/V.sub.t (.ANG.) SS 950 103
0.043 0.100 0.143 0.301 56 SS950-H.sub.2O 100 0.041 0.095 0.136
0.302 55 W950 128 0.047 0.363 0.414 0.114 130 WO950-H.sub.2O 109
0.040 0.390 0.431 0.093 158 WOSS950 192 0.077 0.279 0.356 0.216 74
WOSS950-H.sub.2O 174 0.068 0.301 0.369 0.184 85 WOSS650 108 0.043
0.317 0.356 0.121 132 WOSSO650-H.sub.2O 199 0.077 0.253 0.332 0.232
67
EXAMPLE 8
[0107] Equilibrium studies for adsorption of copper were conducted
in a series of 100 ml Erlenmeyer flasks at 20.degree. C. Each flask
was filled with 10 ml of copper chloride solution with
concentrations between 10-1000 mg/l. After equilibration, the
samples were filtrated, analyzed for their coppers content and the
equilibrium adsorption capacity was calculated. The equilibrium
data was fitted to the so-called Langmuir-Freundlich single solute
isotherm. The results are presented in Table 21. The variable
q.sub.m is the adsorption capacity per unit gram of adsorbent, K is
the Langmuir-type equilibrium constant, and the exponential term n
is the heterogeneity parameter of the site energy. The adsorption
capacity, especially for samples obtained at 650.degree. C. is much
higher than that on activated carbon. TABLE-US-00022 TABLE 21
Fitting parameters of copper (Cu.sup.2+) adsorption isotherms to
Langmuir-Freundlich Equation q.sub.m K Sample [mg Cu.sup.2+/g]
[l/mg] n R.sup.2 SS650 63.48 0.009 0.65 0.9985 WO650 74.28 0.025
0.72 0.9964 WOSS650 69.72 0.018 0.78 0.9978 SS950 34.01 0.001 0.51
0.9970 WO950 15.88 0.006 0.92 0.9834 WOSS950 47.08 0.001 0.43
0.9957
EXAMPLE 9
[0108] The content of Fe, Ca, Cu, Zn, and Mg was determined in the
single component samples, and based on the composition of the mixed
samples, the content of these elements was evaluated. The results
are presented in Table 22. TABLE-US-00023 TABLE 22 Cr Sample Fe [%]
Ca [%] Mg [%] Cu [%] Zn [%] [ppm] SS650 4.9 4.8 1.3 0.13 0.19 58
SS950 6.1 5.1 1.1 0.17 0.09 90 WO650 3.2 4.0 11.0 0.20 0.54 140
WO950 3.7 5.1 8.4 0.25 0.51 280 MS950 2.2 14 0.46 0.77 0.16 6700
WOSS650* 4.0 4.4 6.15 0.16 0.36 99 WOSS950* 4.9 5.1 4.75 0.21 0.3
185 WOSSMS950* 4.4 6.9 3.89 0.32 0.27 1488 *evaluated assuming the
same yield of each component (50%).
EXAMPLE 10
Materials
[0109] Two industrial sludges, waste oil sludge (WO) and metal
sludge (M) from Newport News Shipyard were mixed with dry tobacco
compost, homogenized, dried at 120.degree. C. for 48 hours and then
carbonized at 650.degree. C. and 950.degree. C. in nitrogen in a
horizontal furnace. The heating rate was 10 deg/min with a one hour
holding time. The weight of the wet industrial sludges (they
contain 75% water) was adjusted to have 10% and 50% industrial
sludge component based on the dry mass. The names of the adsorbents
obtained, their compositions along with the yield, ash content and
bulk density are collected in Table 23. Tobacco waste is referred
to as TC.
[0110] The waste oil sludge was treated with CaCl.sub.2,
Na.sub.3PO.sub.4, NaOH and alum. Metal sludge treatment history
includes addition of sulfuric acid and sodium hydroxide for pH
adjustments, Al.sub.2SO.sub.4 for coagulation, anionic and cationic
polymers, sodium bisulfide for chromium reduction, lime and
CaCl.sub.2. Thus, besides alkaline or alkaline earth
element-containing compounds and iron, the waste oil sludge also
contains 0.4% Cu, 2% Zn and between 200 and 1000 ppm of chromium,
lead and nickel. In metal sludge there are less than 1% each of
cadmium, chromium, copper, lead, manganese, selenium, vanadium and
zinc. The content of volatile compounds in both waste oil sludge
and metal sludge reaches 40% their dry mass, while the content of
water in as-received materials is about 75%. TABLE-US-00024 TABLE
23 Names of the adsorbents, their compositions, pyrolysis
temperature, yield, bulk density an ash content Pyrolysis Bulk Dry
Temper- Yield Density Ash Sample waste composition ature [.degree.
C.] [%] [g/cm.sup.3] [%] CTCA TC: 100% 650 52 0.63 67 CTCB TC: 100%
950 51 0.52 76 CWOB WO: 100% 950 30 0.48 92 CMB M: 100% 950 47 0.58
ND CTCWO-1A TC 90%; WO 10% 650 52 0.42 72 CTCWO-2A TC 50%; WO 50%
650 53 0.41 67 CTCWO-1B TC 90%; WO10% 950 45 0.40 78 CTCWO-2B TC:
50%; WO 50% 950 38 0.40 86 CTCM-1A TC 90%; M 10% 650 0.55 63
CTCM-2A TC 50%; M 50% 650 65 0.52 86 CTCM-1B TC 90%; M 10% 950 0.58
95 CTCM-2B TC 50%; M 50% 950 57 0.30 96
Evaluation of H.sub.2S Sorption Capacity
[0111] A custom-designed dynamic test was used to evaluate the
performance of adsorbents for H.sub.2S adsorption from gas streams
as described above. Adsorbent samples were ground (1-2 mm particle
size) and packed into a glass column (length 370 mm, internal
diameter 9 mm, bed volume 6 cm.sup.3), and pre-humidified with
moist air (relative humidity 80% at 25.degree. C.) for one hour.
The amount of water adsorbed was estimated from an increase in the
sample weight. Moist air (relative humidity 80% at 25.degree. C.)
containing 0.3% (3,000 ppm) of H.sub.2S was passed through the
column of adsorbent at 0.5 L/min. The flow rate was controlled
using Cole Parmer flow meters. The breakthrough of H.sub.2S was
monitored using MultiRae photoionization sensor. The test was
stopped at the breakthrough concentration of 100 ppm. The
adsorption capacities of each adsorbent in terms of mg of hydrogen
sulfide per g of adsorbent were calculated by integration of the
area above the breakthrough curves, and from the H.sub.2S
concentration in the inlet gas, flow rate, breakthrough time, and
mass of sorbent. For each sample the test was repeated at least
twice. Besides H.sub.2S the content of SO.sub.2 in the outlet gas
was also monitored using MultiRae photoionization sensor. The
adsorbents exhausted after H.sub.2S adsorption are designated by
adding an additional letter E to their names.
Characterization of Pore Structure of Adsorbents
[0112] On the materials obtained sorption of nitrogen at its
boiling point was carried out using ASAP 2010 (Micromeritics).
Before the experiments, the samples were outgassed at 120.degree.
C. to constant vacuum (10-4 torr). From the isotherms, the surface
areas (BET method), total pore volumes, V.sub.t, (from the last
point of isotherm at relative pressure equal to 0.99), volumes of
micropores, V.sub.mic (DR), mesopore volume V.sub.mes, total pore
volume, V.sub.t, along with pore size distributions were calculated
(DFT).
pH
[0113] The pH of a carbonaceous sample suspension provides
information about the acidity and basicity of the surface. A sample
of 0.4 g of dry carbon powder was added to 20 mL of distilled water
and the suspension was stirred overnight to reach equilibrium. Then
the pH of suspension was measured.
Thermal Analysis
[0114] Thermal analysis was carried out using TA Instrument Thermal
Analyzer. The instrument settings were: heating rate 10.degree.
C./min and a nitrogen atmosphere with 100 mL/min flow rate. For
each measurement about 25 mg of a ground adsorbent sample were
used. For analysis of the results the derivative thermogravimetric
curves (DTG curves) are used. Ash content was determined from the
residue left at 800.degree. C. after heating the samples in
air.
Elemental Analysis
[0115] Metal content in the adsorbents was determined using ICP in
LSL labs, Syracuse, N.Y.
XRD
[0116] X-ray diffraction measurements were conducted using standard
powder diffraction procedure. Adsorbents were ground with methanol
in a small agate mortar. Grinding of the adsorbents by hand ensures
particle sizes between 5-10 .mu.m, which prevents line broadening
in diffraction peaks. The mixture was smear-mounted onto the
zero-background quartz window of a Phillips specimen holder and
allow to air dry. Samples were analyzed by Cu K.sub..alpha.
radiation generated in a Phillips XRG 300 X-ray diffractometer. A
quartz standard slide was run to check for instrument wander and to
obtain accurate location of 20 peaks.
[0117] The H.sub.2S breakthrough curves are presented in FIG. 13
and 14. As seen based on the steep rise in the breakthrough curves
all tobacco based materials have short diffusion zone and almost
immediately after H.sub.2S is detected in the outlet gas, the
adsorbents stop to work allowing the challenge gas to pass
chemically undisturbed through the bed. No SO.sub.2 concentration
was detected which indicates that all H.sub.2S is converted to
sulfur. In the case of metal and oil sludge derived materials small
concentrations of sulfur dioxide, up to few ppm were measured at
the same time when hydrogen sulfide appeared in the outlet gas.
Even after mixing 50% tobacco waste and 50% waste oil, the kinetics
of hydrogen sulfide retention characteristic to tobacco were still
predominant since the shape of the slope of the curve does not
resemble the one obtained for waste oil derived adsorbent.
[0118] The results of the H.sub.2S breakthrough capacity
measurements are summarized in Table 24 where besides the capacity
expressed unit mass per gram of the adsorbents and per unit volume
of the bed, the amount of water adsorbed during the
prehumidification and the pH of the surface before and after
adsorption process are reported.
[0119] As seen from Table 24, the highest capacity is found for
tobacco waste oil sludge compositions pyrolyzed at 950.degree. C.
Although higher content of oil sludge is beneficial for the
performance, even only 10% waste oil sludge increases the
performance about 100% compared to pure tobacco waste based
material. For CTC. material the high temperature of pyrolysis also
significantly enhances the capacity. The results suggest the
predominant influence of the tobacco waste on the performance since
the waste oil sludge derived materials were reported to have best
capacity at low temperature. In fact comparison of the capacity
obtained for both tobacco and waste oils sludge based materials
obtained at 950.degree. C. clearly shows the synergetic effect; the
capacity obtained for the mixture is much higher than for either
one of its components. TABLE-US-00025 TABLE 24 H.sub.2S
breakthrough capacity, amount of water adsorbed and the pH values
of adsorbent surfaces. H.sub.2S breakthrough water capacity
adsorbed pH Sample [mg/g] [mg/cm.sup.3] [mg/g] initial exhausted
CWOB 40.2 21.1 11 10.7 10.2 CMB 5.0 2.9 0 11.2 11.2 CTC-A 6.6 4.2
51.8 11.2 10.7 CTC-B 23.1 12.1 38.2 11.3 11.3 CTCWO-1A 16.1 6.7
45.4 10.6 9.6 CTCWO-2A 0.9 0.4 82.0 9.2 9.2 CTCWO-1B 42.6 17.8 35.4
10.0 9.8 CTCWO-2B 90.2 36.4 43.3 10.3 9.3 CTCM-1A 13.0 7.2 29.6
10.6 10.5 CTCM-2A 22.5 11.7 11.2 9.4 9.3 CTCM-1B 23.1 13.5 21.5
11.2 11.1 CTCM-2B 18.9 5.7 10.8 10.8 10.6
[0120] As seen from Table 24, the highest capacity is found for
tobacco waste oil sludge mixtures pyrolyzed at 950.degree. C.
Although higher content of oil sludge is beneficial for the
performance, even only 10% waste oil sludge increases the
performance about 100% compared to pure tobacco waste based
material. For CTC. material, the high temperature of pyrolysis also
significantly enhances the capacity. These results suggest the
predominant influence of the tobacco waste on the performance since
the waste oil sludge derived materials were reported to have best
capacity at low temperature. In fact comparison of the capacity
obtained for both tobacco and waste oils sludge-based materials
obtained at 950.degree. C. clearly shows the synergetic effect; the
capacity obtained for the mixture is much higher than for either
one of its components.
[0121] Pyrolysis of waste oil sludge/tobacco mixture at 650.degree.
C. with a high content of waste oil sludge component has a
detrimental effect on the capacity. Although on the surface of this
sample the high amount of water is adsorbed, the capacity is
negligible. Since the materials from waste oil sludge pyrolized at
650.degree. C. had a very high capacity (reaching 30% wt.), the
tobacco component hinders the capacity when low temperature
treatment is applied. On the other hand, when metal sludge is used
and mixture is pyrolyzed at low temperature, the capacity is
enhanced compared to pure tobacco or pure metal sludge. Pyrolyzing
those two mixtures at high temperature enhances capacity for low
sludge content indicating once again the importance of the tobacco
phase for hydrogen sulfide removal on composite adsorbents.
[0122] Taking into account variations in the behavior of the
samples within their pyrolysis temperature, the relationship
between the amount of water preadsorbed and the H.sub.2S
breakthrough capacity was analyzed. As seen from FIG. 15, for the
samples pyrolyzed at low temperature have a detrimental effect on
the H.sub.2S breakthrough capacity. This may be linked to the low
degree of mineralization and reactivity of the surface. It is
likely that exposure to water causes its reaction with metal oxides
and formation of hydroxides, which was observed previously. If the
small pores are present, those hydroxides may block their entrances
and thus decrease the available space for H.sub.2S adsorption and
sulfur storage. This problem is readdressed below were the porosity
is discussed.
[0123] In the case of samples pyrolyzed at 950.degree. C., water
apparently enhances the capacity. This might be linked to its
physical retention on the surface and formation of water film, in
which the basic pH exists. This enables high concentration of
HS.sup.- ions and thus their oxidation to elemental sulfur.
[0124] All samples have basic pH, which helps with in hydrogen
sulfide removal. The lowest pH is found for the CTCWO-2A sample,
which has also the very low H.sub.2S removal capacity. That pH is
much lower than the pH of its components. The reason for this might
be either in oxidation of the carbon phase or specific chemistry
formed as a result of synergetic effect between the composite
components.
[0125] Checking the synergetic effect on the H.sub.2S breakthrough
capacity, the measured values were compared to those calculated
assuming the physical mixtures of the components, and taking into
account their yields. The results presented in FIG. 16. While in
the case of metal sludge only slight enhancement in the capacity is
observed as a result of mixing, for the waste oil sludge/tobacco
composites a significant synergetic effect is found with four fold
increase in the capacity for CTCWO-2B.
[0126] That synergetic effect might be the result of either new
catalytic phases formed when the materials are mixed and exposed to
high temperature, formation of new pores enhancing physical
adsorption and storage of oxidation products, an increased
dispersion of catalytic phase, or more likely, the combination of
all of these factors.
[0127] Using X-ray diffraction one may see both, the changes in the
degree of crystallinity of the adsorbents and the formation of new
phases as a result of solid state reaction. FIG. 17 shows the
comparison of XRD patterns for CTC adsorbents obtained at 650 and
950.degree. C. As seen from the analysis of the ash content (Table
23) all adsorbents, even those derived from only tobacco waste have
the majority of the inorganic phase. In the case of CTCA only
quartz, and magnesian of ferrosilite ((Fe,Mg)SiO.sub.3) are
identified. Heating at 950.degree. C. results in formation of more
crystalline phases identified as bayerite (Al(OH).sub.3), ordered
anorthite (CaAl.sub.2Si.sub.2O.sub.8),anthophyllite ((Mg,
Fe).sub.7Si.sub.8O.sub.22(OH).sub.2), and barrigerite (Fe.sub.2P).
Some of these minerals such as barrigerite, were also identfied in
sewage sludge derived materials in which enhanced H.sub.2S
adsorption was found. Magnesium, calcium and iron from these
minerals can contribute to catalytic oxidation of hydrogen sulfide
to sulfur. In the case of CWOB metallic iron, bornite
(Cu.sub.5FeS.sub.4), hibonite (CaAl.sub.12O.sub.19), zincite (ZnO)
and ankerite (Ca(Fe Mg)(CO.sub.3).sub.2) are detected (FIG. 18).
Heating metal sludge to 950.degree. C. resulted in formation of
numerous crystalline phases (multipeak pattern) from which
pyrrohotite (Fe.sub.1-xS), troilite (FeS), pyrope
(Mg.sub.3Al.sub.2(SiO.sub.4).sub.3), and metallic copper, zinc and
iron have high probability to exist.
[0128] A multipeak pattern is also observed for the mixtures of
tobacco with metal sludge of various compositions and pyrolyzed at
two different temperatures. Comparison of FIGS. 17, 18 and 19
clearly shows that new phases are detected. Examples of these new
phases for CTCM-1A are spinel (MgAl.sub.2O.sub.4), margarite
(CaAl.sub.2(Si.sub.2Al.sub.2)O.sub.10(OH).sub.2), malachite
(Cu.sub.2CO.sub.3(OH).sub.2, calcite (CaCO.sub.3), cordierite
(Mg.sub.2Al.sub.4Si.sub.5O.sub.18), pigeonite (Fe,Mg,Ca)SiO.sub.3),
corundum (Al.sub.2O.sub.3), tenorite (CuO), magnesioferrite
(MgFe.sub.2O.sub.4), moissanite (SiC) and metallic iron. By
pyrolyzing at 950.degree. C., the mixture containing more metal
sludge derived phase results in even more complex chemistry with
predominant structures of mixed calcium iron and magnesium
silicates and aluminosilicates. Some of them, as ferrocilite,
anorthite were present in CTC-A. Examples are fosterite
(Mg.sub.2SiO.sub.4), huntite (Mg.sub.3Ca(CO.sub.3).sub.4),
aragonite (CaCO.sub.3), wollastonite (CaSiO.sub.3), dolomite
(CaMg(CO.sub.3).sub.2, cohenite, (Fe.sub.3C) fersilicite (FeSi),
covelite (CuS), bornite (Cu.sub.5FeS.sub.4), grunerite
(Fe.sub.7Si.sub.8O.sub.22(OH).sub.2), hardystonite
(Ca.sub.2ZnSi.sub.2O.sub.7) or akermanite
(Ca.sub.2MgSi.sub.2O.sub.7). In this case, compared to the sample
pyrolized at 650.degree. C., more carbonates are present, likely
the result of gasification of carbon, less aluminum is involved in
crystalline phase, and more two element-compounds appear.
[0129] Very complex and different form parent compound structure is
obtained for CTCWO-2B (FIG. 19). In this case, besides significant
amount of quartz, over 50 new compounds were detected. They are
mainly aluminoslicate with magnesium, calcium, iron, sodium, copper
and lead. Examples include: sodian of anorthite ((Ca, Na) (Al,
Si).sub.2Si.sub.2O.sub.8), forsterite (Mg.sub.2SiO.sub.4), albite
(CaAl.sub.2Si.sub.2O.sub.8), richterite
(KNaCaMg.sub.5Si.sub.8O.sub.22(OH).sub.2), renhahnite
(Ca.sub.3(Si.sub.3O.sub.8(OH).sub.2), Dahlite
(Ca.sub.9.35Na.sub.1.07(PO.sub.4).sub.5.46CO.sub.3), rockbridgeite
(Fe.sub.5 (PO.sub.4).sub.3(OH).sub.5).
[0130] Although surface chemistry can play a crucial role in the
process of hydrogen sulfide oxidation on the surface of materials
studied, its effects cannot be discussed in isolation from the
description of porous structure. The nitrogen adsorption isotherms
are collected in FIGS. 20 and 21. Their shapes and nitrogen uptakes
indicate differences in the sizes and volume of pores. While
tobacco derived adsorbents are both very microporous, addition of
waste oil sludge and metals sludge component contributes to the
development of mesoporosity. The structural parameters calculated
from nitrogen adsorption isotherms are collected in Table 25.
Either waste oil sludge or metal sludge addition increase the
surface areas of samples obtained at 950.degree. C. in spite of the
fact that the surface areas of both components pysolyzed separately
are much smaller. This indicates the beneficial synergetic effect.
That development of porosity can be caused by gasification of
carbon phase by alkaline earth metals present in the sludges, which
can be considered as self-activation. Adding more waste oil sludge
increases surface area, volume of micropores and volume of
mesopores. Although the latter are present in much higher volume in
the CWOB adsorbent, the new volume of micropores is the result of
activation during pyrolysis. On the other hand, addition of metal
sludge, even in only small quantity seems to be most beneficial for
tobacco/metal sludge mixtures. These materials have a new volume of
mesopores formed, which do not exist in either tobacco or metal
sludge only based materials. Gasification can be important here.
Much more alkaline earth metals than in waste oil sludge results
(Table 26) in formation of larger pores in the carbonaceous
deposit. It is interesting that the smallest surface area and pore
volume are obtained for metal sludge tobacco mixture with 50/50
ratio of composition pyrolyzed at 650.degree. C. This is consistent
with this sample low capacity for hydrogen sulfide removal. Since
both tobacco derived samples have almost identical structural
parameters the differences in their performance as hydrogen sulfide
adsorbents must be attributed to differences in surface chemistry
mentioned above. TABLE-US-00026 TABLE 25 Structural parameters
calculated from nitrogen adsorption S.sub.BET V.sub.mic V.sub.meso
V.sub.t D.sub.BJH D.sub.DA E.sub.o Sample [m.sup.2/g] [cm.sup.3/g]
[m.sup.2/g] [cm.sup.3/g] V.sub.mic/V.sub.t [.ANG.] [.ANG.] [kJ/mol]
CTCA 73 0.037 0.016 0.053 0.698 69 15 25.06 CTCAE 0 0 0 0 0 0 0 0
CTCB 78 0.039 0.020 0.059 0.661 41 16 21.82 CTCB-E 42 0.017 0.039
0.056 0.304 44 17 19.28 CTCWO-1A 71 0.041 0.051 0.092 0.446 95 16
23.80 CTCWO-1AE 33 0.014 0.088 0.102 0.137 100 17 17.62 CTCWO-2A 35
0.015 0.165 0.180 0.083 123 21 10.09 CTCWO-2AE 13 0.009 0.127 0.136
0.066 144 21 9.61 CTCWO-1B 120 0.055 0.096 0.151 0.364 56 16 20.65
CTCWO-1BE 37 0.019 0.072 0.091 0.209 68 17 17.55 CTCWO-2B 162 0.069
0.180 0.249 0.277 61 17 20.01 CTCWO-2BE 59 0.026 0.163 0.189 0.138
85 18 15.45 CTCM-1A 77 0.035 0.071 0.106 0.330 63 15 23.94 CTCM-1AE
8 0.006 0.047 0.053 0.113 138 17 18.79 CTCM-2A 74 0.031 0.144 0.175
0.177 79 17 18.67 CTCM-2AE 24 0.013 0.115 0.128 0.102 124 18 16.36
CTCM-1B 96 0.043 0.113 0.156 0.276 62 16 20.53 CTCM-1BE 46 0.018
0.097 0.115 0.157 99 18 15.62 CTCM-2B 59 0.031 0.061 0.092 0.337 82
16 20.19 CTCM-2BE 49 0.022 0.109 0.131 0.168 107 18 16.67
[0131] After H.sub.2S removal the surface area and volumes of
micropores significantly decrease. For the majority of samples, but
CTC-BE, CTCWO-1AE and CTCM-2BE the volume of mesopores increases.
This phenomenon was observed before and was attributed to formation
of new pores within either sulfur deposit in large pores, if
capacity was high, or/and formation of hydroxides on the surface as
a result of exposure to water during prehumidification. Although in
the case of CTCM-2BE only small amount of water was adsorbed with
relatively high amount of H.sub.2S, taking into account the small
surface area of the samples, a significant, almost 100% increase in
the volume of mesopores can be attributed to that sulfur deposit.
The surface in large pores of the materials must be active since
extensive gasification helped in high dispersion on the catalysts
on the surface. For CTCWO-1AE, that increase can be attributed to
the formation of hydroxides, since the surface is active and large
amounts of water are adsorbed, and also to sulfur deposit. These
hydroxides can totally block the porosity in the carbon deposit
when more sludge derived phase is present and sample is exposed to
moisture from the atmosphere. This likely happens in the case of
CTCWO-2A, which was totally inactive in the process of H.sub.2S
adsorption, contrary to only waste oil sludge based sample whose
capacity was found significant previously and it was attributed to
the high volume of mesopores, which, owing to their large sizes,
cannot be blocked by hydroxides. As seen from Table 25 the average
pore sizes calculated using Dubinin-Astakhov method are related to
the values of the characteristic energy of adsorption, which is the
highest for CTC-A, CTCWO-1A, and CTCM-1A. These materials are
obtained at low temperature so they can be considered as chars or
"underactivated" carbons. TABLE-US-00027 TABLE 26 Content of
catalytic metals Sample Fe [%] Ca [%] Mg [%] Cu [%] Zn[%] Cr [ppm]
CWOB 3.7 5.1 8.4 0.25 0.51 280 CMB 22 14 0.46 0.77 0.16 6700 CTCB
1.45 .times. 0.0115 0.00255 1.55 .times. 2 .times. ND 10 - 4
10.sup.-5 10.sup.-5
[0132] Details about the differences in the porosity of our samples
are presented in FIGS. 22, 23A & B and 24A & B as pore size
distributions. For all samples on the distributions two regions can
be seen. One consists of micropores which are much more
heterogeneous in their sizes for CTC. and CTWO series of samples
than for CTCM. On the other hand, the heterogeneity of mesopores is
much greater for the latter group of samples. After H.sub.2S
adsorption the smallest pores are not seen anymore indicating that
sulfur is deposited either there, or at their entrances, and the
new pores appears, especially with the range of sizes between
50-200 .ANG.. In same cases it happens with the expense of
macropores. This shows importance of large porosity with
catalytically active surface to the process of hydrogen sulfide
oxidation. If only physical adsorption were predominant those pores
would not play any role and would have a negative effect on the
performance of materials based on the unit volume of the bed. Thus
in the case of this groups of materials very light adsorbents can
be used which may increase the cost effectiveness of the removal
process.
[0133] The synergetic effect of the porosity development in our
materials is presented in FIGS. 25 and 26 where the measured
volumes of micro and mesopores are compared to those calculated
assuming the physical mixture of the components and taking into
account the yield of materials. As dissussed above, the synergetic
effects of the sludge components on activation of the final
products is clearly seen with the most pronounced effects of waste
oil sludge on the volume of micropores and metal sludge--on the
volume of mesopores.
[0134] To check the role of porosity for H.sub.2S adsorption, the
dependence of the capacity on the volume of pores was analyzed. The
results are presented in FIG. 27. As seen, a good relationship is
found for the volume of micropores. They have they origin likely in
the tobacco derived carbon phase thus this component of the
H.sub.2S adsorption process has to have similar mechanism on all
tobacco containing samples. Linear trend is also noticed for the
volume of mesopores but only for materials obtained at 950.degree.
C. As it was shown above, water has a detrimental effect on the
chemistry of low temperature pyrolyzed samples, thus the linear
trend in his case is not expected. The linear relationship between
the capacity and volume of mesopores indicates the activity of
large pores in the process of hydrogen sulfide catalytic
oxidation.
[0135] The comparison of DTG curves before and after adsorption of
hydrogen sulfide is presented in FIGS. 28, 29, and 30. The peaks on
the curves represent weight loss due to the
decomposition/desorption of surface species. For some initial
samples as CTCB, CTCM-1A, CTCM-1B an increase in weight (negative
peaks) is observed between 150 and 400.degree. C. and between 600
and 800.degree. C. The latter negative peak is also found for
CTCWO-2B. This strange behavior was noticed previously for some
metal sludge, waste oil sludge and even sewage sludge-based
adsorbents. Since only nitrogen was present formation of nitrides
was given as the only plausible explanation. After H.sub.2S
adsorption a negative peak is present only at high temperature
range for CTCM-2BE. For other samples it is compensated by weight
loss caused by removal of deposited sulfur between 200-400.degree.
C. Although this weight loss/peak intensity should be proportional
to the amount of hydrogen sulfide deposited on the surface in the
case of material pyrolyzed at 650.degree. C. addition to the weight
loss occurs as a result of dehydroxylation of surface at
temperature smaller than 600.degree. C. The hydroxides were formed
when samples were exposed to water during prehumidification and
H.sub.2S adsorption.
[0136] Pyrolysis of waste tobacco compost and industrial sludges
from heavy industries leads to the development of effective
catalyst for desulfurization of air. An important role of
carbonaceous phase derived from waste tobacco is in its relatively
high carbon content. That carbon contributes to the development of
porosity in both, micro and mesopore ranges. This happens via
self-activation of carbon material by alkaline earth metals and
water released from the decomposition of inorganic matter during
heat treatment. As a result of solid state reactions at high
temperature new catalytic species are formed on the surface of
adsorbent as a result of synergy between the components of sludges.
Location of these species in mesopores is beneficial for the
desulfurization process. The surface of those pores retain water
film where hydrogen sulfide can dissociate in the basic
environment, Sulfur formed in oxidation reaction can be stored
there in large quantity without rapid deactivation of the catalytic
centers by sterical hindrances. High temperature of pyrolysis is
beneficial for the adsorbents due to the enhanced activation of
carbonaceous phase and chemical stabilization of inorganic phase.
Samples obtained at low temperature are sensitive to water, which
deactivates their catalytic centers.
[0137] The present invention is not to be limited in scope by the
specific embodiments described herein. Indeed, various
modifications of the invention in addition to those described
herein will become apparent to those skilled in the art from the
foregoing description and the accompanying figures. Such
modifications are intended to fall within the scope of the appended
claims.
[0138] It is further to be understood that all values are
approximate, and are provided for description.
[0139] Patents, patent applications, publications, product
descriptions, and protocols are cited throughout this application,
the disclosures of which are expressly incorporated herein by
reference in their entireties for all purposes.
* * * * *