U.S. patent application number 12/781965 was filed with the patent office on 2010-09-09 for method and composition for sorbing toxic substances.
This patent application is currently assigned to J.I. Enterprises, Inc.. Invention is credited to Joseph Iannicelli.
Application Number | 20100224576 12/781965 |
Document ID | / |
Family ID | 38236486 |
Filed Date | 2010-09-09 |
United States Patent
Application |
20100224576 |
Kind Code |
A1 |
Iannicelli; Joseph |
September 9, 2010 |
Method and Composition for Sorbing Toxic Substances
Abstract
Toxic substances such as heavy metals are extracted from a
medium using a sorbent composition. The sorbent composition is
derived by sulfidation of red mud, which contains hydrated ferric
oxides derived from the Bayer processing of bauxite ores. Exemplary
sulfidizing compounds are H.sub.2S, Na.sub.2S, K.sub.2S,
(NH.sub.4).sub.2S, and CaS.sub.x. The sulfur content typically is
from about 0.2 to about 10% above the residual sulfur in the red
mud. Sulfidized red mud is an improved sorbent compared to red mud
for most of the heavy metals tested (Hg, Cr, Pb, Cu, Zn, Cd, Se,
Th, and U). Unlike red mud, sulfidized red mud does not leach
naturally contained metals. Sulfidized red mud also prevents
leaching of metals when mixed with red mud. Mixtures of sulfidized
red mud and red mud are more effective for sorbing other ions, such
as As, Co, Mn, and Sr, than sulfidized red mud alone.
Inventors: |
Iannicelli; Joseph;
(Brunswick, GA) |
Correspondence
Address: |
BANNER & WITCOFF, LTD.
1100 13th STREET, N.W., SUITE 1200
WASHINGTON
DC
20005-4051
US
|
Assignee: |
J.I. Enterprises, Inc.
Brunswick
GA
|
Family ID: |
38236486 |
Appl. No.: |
12/781965 |
Filed: |
May 18, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12537907 |
Aug 7, 2009 |
|
|
|
12781965 |
|
|
|
|
11277282 |
Mar 23, 2006 |
7763566 |
|
|
12537907 |
|
|
|
|
Current U.S.
Class: |
210/800 |
Current CPC
Class: |
C02F 1/281 20130101;
B01J 20/3078 20130101; B01J 20/0285 20130101; Y10S 210/914
20130101; Y10S 95/90 20130101; C02F 2101/22 20130101; Y10S 210/913
20130101; B01J 20/0259 20130101; B01J 20/045 20130101; C02F 2101/20
20130101; C02F 2103/06 20130101; C02F 2103/10 20130101; B01J
20/0229 20130101; Y10S 210/912 20130101; B01J 20/06 20130101; B01J
2220/4887 20130101; B01J 20/08 20130101; C10G 25/003 20130101; B01J
20/3085 20130101 |
Class at
Publication: |
210/800 |
International
Class: |
C02F 11/12 20060101
C02F011/12 |
Claims
1. A process of dewatering red mud, the process comprising
preparing a dispersion of sulfidized red mud in water, and allowing
the dispersion to stand for a sufficient time to form a sedimentary
layer and supernatant layer.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a division of U.S. application Ser. No.
12/537,907, filed Aug. 7, 2009, which is a division of U.S.
application Ser. No. 11/277,282, filed Mar. 23, 2006, the
disclosures of which are hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention is directed to sorbents for heavy
metals and their use for facile extraction of heavy metals from
liquid and gaseous streams, as well as removal of the sorbed heavy
metals by solids/fluid separation means.
DESCRIPTION OF RELATED ART
[0003] Heavy metal contaminated flue gases and liquids from various
sources (ground, stream, runoff, mines, petroleum, industrial
waste) are among the most dangerous and difficult environmental
problems facing the world today. An especially serious problem is
posed by toxic metals in such streams. Among these metals are
mercury, chromium, cobalt, nickel, copper; zinc, silver, gold,
cadmium, lead, selenium, and transuranic elements.
[0004] Mercury contamination of the environment is the subject of
increasing attention because it eventually accumulates at very high
levels in the bodies of large predatory fish such as tuna,
swordfish, and sharks. A major concern is the atmospheric release
of mercury from coal fired power plants, currently estimated at 46
tons per year in the United States. The Environmental Protection
Agency (EPA) has identified women of childbearing age as especially
threatened because of possible neurological damage to unborn
children. It is estimated that 8% of women in this category have a
methyl mercury blood level above 5.8 ppb.
[0005] On Dec. 14, 2000, the EPA issued a determination that their
agency must propose new regulations under the Clean Air Act to
control mercury emissions from coal and oil fined power plants by
Dec. 15, 2003. One proposal was to reduce mercury emissions from
power plants by 90% by 2007. According to an article in Forbes
(Apr. 14, 2003, page 104) such regulation "could cost the power
industry at least 8.8 billion dollars per year." Other, more recent
proposals such as the Clear Skies Act call for a 70% reduction in
mercury emissions over 15 years.
[0006] At present, a major control technology for mercury is the
use of activated carbon treatment of flue gases from power plants.
Activated carbon currently sells for about 45 cents per pound ($
900 per ton) but the disposal or possible regeneration of
mercury-sorbed activated carbon presents unresolved problems at
this time.
[0007] Red mud is an undesirable by-product and major pollutant
from the Bayer Process. Bayer caustic leaching of bauxite is the
principal process for production of alumina. This process relies on
the solubility of aluminous minerals in hot (e.g., 125-250.degree.
C.) sodium hydroxide solution and the insolubility of most of the
remaining minerals (iron, titanium compounds and silica), which are
either insoluble or react and re-precipitate. The insoluble, iron
rich residue byproduct is known as "red mud." Red mud can contain
from about 17.4 to 37.5% iron (Fe) (Bauxite Residue Fractionation
with Magnetic Separators, D. William Tedder, chapter 33, Bauxite
symposium, 1984, AIME 1984). Red mud is a complex mixture of finely
divided hydrated iron oxides with a wide variety of lesser minerals
(Al, Na, Ti, Si, Ca, Mg) and traces of over a score of other
elements (Cr, Ni, Zn, Pb, As, etc). These hydrous iron oxides have
extraordinary sorptive and complexing properties.
[0008] Red mud is a very hydrophilic, high pH slime which is
extremely difficult to dewater by filtration or sedimentation
means. This complicates and limits its utility as a sorbent in
aqueous systems.
[0009] Red mud has been proposed as a sorbent for heavy metals,
cyanides, phosphates, and the like (David McConchie, Virotec
website: virotec.com/global.htm). However, the sorptive and release
properties of red mud are not always complementary. Depending on
the source of a particular red mud, it can also leach out
significant amounts of toxic pollutants such as radioactive
thorium, uranium, chromium, barium, arsenic, copper, zinc, cobalt,
as well as lead, cadmium, beryllium, and fluorides.
[0010] The potential problems involved with use of red mud to
control pollution are highlighted in an e-newsletter article
entitled "The Great Red Mud Experiment that Went
Radioactive"--Gerard Ryle, May 7, 2002
(smh.com.au/articles/2002/05/06/1019441476548.html). This
experiment conducted by the Western Australian Agricultural
Department involved placing 20 tonnes of Alcoa red mud per hectare
on farmland in order to stop unwanted phosphorous from entering
waterways. An unintended result of this application was that runoff
waters showed excessive quantities of copper, lead, mercury,
arsenic, and selenium. Emaciated cattle grazing on such land
exhibited high chromium, cadmium, and fluoride levels. Each hectare
contained up to 30 kilograms of radioactive thorium. The disastrous
red mud application test was abruptly terminated after five
years.
[0011] It is therefore evident that extreme caution must be
exercised in selecting and testing red mud before attempting to use
it to sorb toxic compounds.
[0012] Furthermore, the capacity of red mud to capture and hold
toxic substances such as mercury and related metals is not adequate
to eliminate traces of these metals in leachate. The possibility
also exists that sorption of one toxic pollutant may release other
pollutants. As a result, use of red mud as a sorbent to achieve
drinking water standards can be problematic.
[0013] There remains a need for improved sorbents for extracting
toxic compounds such as mercury and other heavy metals.
SUMMARY OF THE INVENTION
[0014] The present invention, according to one aspect, is directed
to a sorbent comprising the reaction product of a sulfidizing
compound and red mud. Red mud contains hydrated ferric oxides
derived from Bayer processing of bauxitic ores. The sorbent is
particularly useful for sorbing toxic substances from a medium,
such as heavy metals present in a liquid or gaseous stream.
Exemplary sulfidizing compounds include H.sub.2S, Na.sub.2S,
K.sub.2S, (NH.sub.4).sub.2S, and CaS.sub.x. The sulfur content of
the reaction product typically is from about 0.2 to about 10% above
the residual sulfur in the red mud.
[0015] According to one aspect of the invention, potable water
(e.g., meeting drinking water standards) is prepared by treating
contaminated water with a sulfidized red mud sorbent.
[0016] According to another aspect of the invention, heavy metals
such as mercury are sorbed from flue gases of coal- or oil-fired
power plants by treating the flue gases with a sulfidized red mud
sorbent.
[0017] According to another aspect of the invention, heavy metals
are sorbed from mine drainage waters by treating the mine drainage
waters with a sulfidized red mud sorbent.
[0018] According to yet another aspect of the invention, heavy
metals are sorbed from a hydrocarbon stream, such as a petroleum
stream, by treating the stream with a sulfidized red mud
sorbent.
[0019] The sorbent of the present invention is effective for
sorbing various contaminants, such as mercury, which are not
effectively sorbed by red mud. Conversely, red mud is effective for
sorbing other contaminants, such as arsenic, which are not
effectively sorbed by the sulfidized red mud sorbent. Thus, some
treatments can benefit by using both red mud and sulfidized red
mud, either in the same sorbent composition or in separate
treatment stages. Such sorbent combinations potentially can allow
for the extraction of a wider range of contaminants.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The present invention has applicability in removing
contaminants from a wide variety of mediums, non-limiting examples
of which include flue gases and liquids from various sources such
as groundwater, water streams, runoff, mines, petroleum streams,
and industrial waste streams. Of particular interest is sorbing
heavy metals, such as mercury (Hg), chromium (Cr), lead (Pb),
copper (Cu), zinc (Zn), silver (Ag), gold (Au), cadmium (Cd),
selenium (Se), thorium (Th), and uranium (U), from such mediums.
The metal(s) may be present as ions, as free elements, or in
compounds with other elements.
[0021] The sorbents of the present invention can be used for the
preparation of potable water, e.g., meeting drinking water
standards. Other exemplary applications include sorbing heavy
metals, such as mercury, from flue gases of coal- or oil-fired
power plants, mine drainage waters, or hydrocarbon streams such as
petroleum streams.
[0022] The sorbent can be prepared by the sulfidation of red mud,
which contains hydrated ferric oxides derived from the Bayer
processing of bauxitic ores. Sulfidation can be achieved by
reacting the red mud with one or more sulfidizing compounds such as
H.sub.2S, Na.sub.2S, K.sub.2S, (NH.sub.4).sub.2S, and CaS.sub.x.
Unlike red mud, which is very hydrophilic, the sulfidized red mud
is lyophobic and more readily dewatered. As a result, sulfidized
red mud exhibits significantly faster filtration rates than those
exhibited by red mud.
[0023] The relative amount of the sulfidizing compound preferably
is selected so that the sulfur content of the reaction product is
from about 0.2 to about 10% above the residual sulfur content of
the red mud. The weight ratio of sulfidizing compound to red mud
will vary on the type of sulfidizing compound used and the desired
level of sulfidation for a particular end use. Most often, the
sulfidizing compound and red mud are combined at a weight ratio of
from about 1:40 to about 1:4, more usually from about 1:25 to about
1:6, and even more usually from about 1:20 to about 1:8.
[0024] The conditions under which the red mud can be sulfidized
depend on such factors as the identity of the sulfidizing
compound(s) and the intended use of the resulting sorbent. In some
cases, sulfidation can be accomplished by mixing red mud and the
sulfidizing compound at ambient temperature and atmospheric
pressure. In general, higher sulfur contents can be obtained when
the reaction is carried out at elevated temperatures and/or
elevated pressures. Sulfur content in the reaction product also can
be influenced by factors such as the sulfur content of the
sulfidizing agent. For example, compounds with higher sulfur
contents, such as calcium polysulfide, typically yield products
having higher sulfur contents.
[0025] When using gaseous sulfidizing compounds, such as hydrogen
sulfide (H.sub.2S), it is often preferable to conduct the reaction
at elevated temperature and/or elevated pressure to increase the
rate of reaction and the sulfur content of the resulting sorbent.
Suitable exemplary reaction temperatures range from about 40 to
about 200.degree. C., often from about 80 to about 120.degree. C.
The reaction pressure typically ranges from about 1 to about 225
psi, often from about 30 to about 70 psi (absolute).
[0026] In one embodiment of the present invention, the sorbent is
slurried together with the medium containing the contaminant(s) to
be extracted. Suitable mixing equipment can be used to provide
sufficient contact between the sorbent and the contaminant(s). The
sorbent, which forms a complex with the contaminant(s), can then be
separated from the slurry using one or more conventional techniques
such as filtration, sedimentation, or centrifugation.
[0027] In an alternative embodiment of the present invention, the
sulfidized red mud sorbent is processed into pellets or the like
using conventional pelletizing or extrusion equipment. Preparing
the sorbent in pellet form can simplify its handling and/or use.
The pellets may be incorporated into filters of conventional
construction for use in a variety of industrial or consumer
filtration applications, such as filters usable for preparing
potable water.
[0028] It has been found that the sulfidized red mud sorbent is
effective for sorbing various contaminants, such as mercury, which
are not effectively sorbed by red mud. On the other hand, red mud
is effective for sorbing other contaminants, such as arsenic, which
are not effectively sorbed by sulfidized red mud. For the treatment
of mediums having contaminants in both of these categories, the use
of red mud and sulfidized red mud in tandem, either in the same
sorbent composition or in sequential treatment stages (e.g., red
mud followed by sulfidized red mud) can be more effective than
using either sorbent alone.
EXAMPLES
Example 1
[0029] This example shows the preparation of red mud. A 1 kg sample
of red mud received from Sherwin Alumina Company of Corpus Christi,
Texas was slurried at 15% solids in demineralized water and
filtered on a Buchner funnel. The resulting filter cake was
re-slurried with demineralized water, re-filtered, and used as the
starting material in Example 2.
Example 2
[0030] This example illustrates the preparation of sulfidized red
mud using hydrogen sulfide (H.sub.2S). Washed red mud (100 g) from
Example 1 was slurried in demineralized water at 15% solids and the
stirred slurry was saturated with hydrogen sulfide for 30 minutes
at ambient temperature. The sample was dried overnight at
100.degree. C. and the resulting cake was pulverized.
Example 3
[0031] This example shows the preparation of sulfidized red mud
using H.sub.2S under pressure in a Parr Bomb. The sulfidation
procedure of Example 2 was repeated using a Laboratory Parr Bomb.
After saturation of the slurry with hydrogen sulfide gas, the bomb
was sealed and heated four hours at 100.degree. C. while stirred.
The bomb was then cooled, depressurized and the contents filtered,
dried, and pulverized.
Example 4
[0032] This example illustrates the preparation of sulfidized red
mud using ammonium sulfide (NH.sub.4).sub.2S. Red mud (200 g) was
dispersed in 600 grams of deionized (DI) water in a Waring Blender
for 5 minutes. Ammonium sulfide (10 g) was added and the slurry was
heated with stirring on a hot plate for 1 hr. at 60.degree. C. It
was then filtered and dried at 90.degree. C.
Example 5
[0033] This example shows the preparation of sulfidized red mud
using sodium sulfide
[0034] (Na.sub.2S). The procedure of Example 2 was repeated using
sodium sulfide instead of ammonium sulfide.
Example 6
[0035] This example illustrates the preparation of sulfidized red
mud using calcium polysulfide (CaS.sub.x). The procedure of Example
2 was repeated using 33.5 g of 30% solution of Cascade calcium
polysulfide.
Example 7
[0036] The following table summaries the sulfur content of the red
mud (RM) of Example 1 and the sulfidized red mud (SRM) of Examples
2, 3, 4, 5, and 6.
TABLE-US-00001 Code Description Example S (wt %) RM Red Mud 1 0.19
SRM-2 Sulfidized Red Mud H.sub.2S 2 0.48 SRM-3 Sulfidized Red Mud
H.sub.2S w/Pressure 3 0.90 SRM-4 Sulfidized Red Mud
(NH.sub.4).sub.2S 4 0.46 SRM-5 Sulfidized Red Mud Na.sub.2S 5 0.62
SRM-6 Sulfidized Red Mud CaS.sub.x 6 1.19
[0037] A complete analysis of RM, SRM-3, SRM-4, SRM-5, SRM-6 is
given in Table A below. The analysis reveals that filtration and
washing during preparation of sulfidized red mud extracts sodium
chloride (except for SRM-5) and reduces bound water in the red mud.
It is notable that very small amounts of reacted sulfur have such a
profound effect on the chemical and physical properties of red
mud.
TABLE-US-00002 TABLE A Weight % Code Description Na.sub.2O MgO
Al.sub.2O.sub.3 SiO.sub.2 P.sub.2O.sub.5 S Cl K.sub.2O CoO
TiO.sub.2 MnO Fe.sub.2O.sub.3 BaO RM Control 4.73 0.12 17.1 8.23
1.14 0.19 0.20 0.06 6.79 6.12 0.73 39.9 0.02 SRM-3 H.sub.2S (b)
3.94 0.14 14.6 9.14 1.38 0.90 0.11 0.05 6.36 6.79 0.90 46.2 0.02
SRM-4 (NH.sub.4).sub.2S 4.39 0.13 17.9 9.24 1.26 0.46 0.15 0.04
8.82 6.95 0.85 42.3 0.02 SRM-5 Na.sub.2S 5.20 0.11 17.2 8.56 1.15
0.62 0.15 0.03 7.53 6.22 0.75 41.5 0.02 SRM-6 CaS.sub.x 4.44 0.09
16.2 8.41 1.29 1.19 0.14 0.04 9.32 6.60 0.81 41.2 0.02 PPM Code
Description V Cr Co Ni W Cu Zn As Sn Pb Mo Sr U RM Control 1100
1258 99 680 16 119 416 47 247 144 <10 424 65 SRM-3 H.sub.2S (b)
1252 1506 121 860 23 138 458 44 177 180 <10 498 57 SRM-4
(NH.sub.4).sub.2S 1093 1379 120 762 30 146 648 46 155 176 13 447 36
SRM-5 Na.sub.2S 942 1272 103 695 24 130 504 31 181 159 11 387 39
SRM-6 CaS.sub.x 1054 1364 113 780 29 138 471 49 155 165 13 431 50
PPM Code Description Th Nb Zr Rb Y RM Control 186 188 1757 24 673
SRM-3 H.sub.2S (b) 199 207 1503 21 831 SRM-4 (NH.sub.4).sub.2S 159
153 1888 <10 748 SRM-5 Na.sub.2S 123 148 1659 <10 695 SRM-6
CaS.sub.x 146 146 1767 <10 745
Example 8
[0038] This example illustrates leaching of red mud and sulfidized
red mud. In part (a), a slurry of red mud (50 g) and demineralized
water (450 ml) was prepared, mixed for 30 minutes, and filtered.
The filtrate was acidified with 2 ml concentrated nitric acid and
analyzed by ICP using EPA3050 and EPA6010 methods.
[0039] In part (b), the procedure of part (a) was repeated using
sulfidized red mud from Example 2.
[0040] Results are given in Table I and show that leachate from
sulfidized red mud (SRM) gave a lower content of heavy metals (low
parts per billion) than leachate from the red mud (RM) in every
case except Cd, where the difference was insignificant.
TABLE-US-00003 TABLE I Metal Concentration in Leachate (ppm) Hg As
Cd Cr Pb Se SRM 0.0026 ND* 0.0013 0.0044 ND ND RM 0.0032 0.096 ND
0.0510 0.0064 0.017 *ND--Not detectable, below limits
Example 9
[0041] This example shows mercuric ion (3.5 ppm) sorption by
sulfidized red mud. Ten grams of sulfidized red mud from Example 3
was slurried 30 minutes with 1 kg demineralized water containing
3.5 ppm mercury (5.66 ppm mercuric nitrate). The slurry was
filtered and analyzed for mercury (Hg.sup.++) by ICP (Method EOA
245.1).
Example 10
[0042] This example illustrates mercuric ion (3.5 ppm) sorption by
red mud. Example 9 was repeated using red mud.
Example 11
[0043] This example shows mercuric ion (22 ppm) sorption by
sulfidized red mud. Example 9 was repeated using 22 ppm mercury
(Hg.sup.++).
Example 12
[0044] This example illustrates mercuric ion (22 ppm) sorption by
red mud. Example 11 was repeated using red mud.
Example 13
[0045] This example shows mercuric ion (41 ppm) sorption by
sulfidized red mud. Example 9 was repeated using 41 ppm mercury
(Hg.sup.++).
Example 14
[0046] This example illustrates mercuric ion (41 ppm) sorption by
red mud. Example 13 was repeated using red mud.
[0047] Results of Examples 9-14 are summarized in Table II and
demonstrate the superior performance of sulfidized red mud compared
to red mud for sorption of mercuric ion from aqueous solutions.
TABLE-US-00004 TABLE II Mercuric Concentration Example In Filtrate
Sorbent Control 3.5 ppm none 9 0.56 ppm red mud 10 0.2 ppm
sulfidized red mud Control 22.0 ppm none 11 8.0 ppm red mud 12 0.22
ppm sulfidized red mud Control 41.0 ppm none 13 23.4 ppm red mud 14
0.04 ppm sulfidized red mud
Example 15
[0048] This example shows mercury (metal) sorption from vapor phase
by sulfidized red mud and by red mud (spray absorbed). In part (a),
one gram of mercury metal was placed in a two necked round bottom
(RB) flask on a supported heating mantle. One neck of the flask was
open and the second neck was connected with a Teflon.RTM. tube to
an aperture in the inlet duct of a spray dryer. The mercury was
heated to 300.degree. C. while hot air was aspirated through the
vessel. Mercury vapor was entrained in the air as it was drawn into
the inlet air duct of the spray dryer heated to 300.degree. C. A
slurry of 50 g SRM (Example 3) in 450 ml demineralized water was
sprayed by a rotary atomizer operating at 30,000 rpm. The feed rate
of SRM was regulated to produce an outlet temperature of
100.degree. C. from the dryer.
[0049] In part (b), the procedure of part (a) was repeated using RM
(Example 1) instead of SRM.
[0050] The mercury content of the spray dried SRM from part (a) and
the RM from part (b) are tabulated in Table III and demonstrate
that the SRM had a significantly improved sorption of mercury.
TABLE-US-00005 TABLE III Hg Concentration (ppm) 15(a) SRM-3 61.0
15(b) RM-1 8.1
[0051] SRM-3 absorbed 7.5 times as much mercury as RM-1 when spray
dried at 300.degree. C. inlet and 100.degree. C. outlet in the
presence of an air stream contacted by mercury heated to
250.degree. C. Sulfidized red mud is significantly superior to red
mud as a sorbent for elemental mercury metal vapor.
Example 16
[0052] This example shows mercury (metal) sorption from vapor phase
by sulfidized red mud and by red mud (spray absorbed). Example 15
was repeated except that a slurry of 100 g SRM in 900 ml
demineralized water was used. On completion of drying, a 50 g
sample (a) was set aside for analysis and 50 g was re-slurried in
450 ml demineralized water and re-dried (b). Samples 16a and 16b
were analyzed for mercury.
[0053] This experiment was then repeated using 100 g RM to furnish
samples 16c and 16d, which were analyzed. The results of parts
(a)-(d) are shown in Table IV below.
TABLE-US-00006 TABLE IV Hg Concentration (ppm) 16(a) SRM-3 1.sup.st
pass 95 16(b) SRM-3 2.sup.nd pass 340 16(c) RM-1 1.sup.st pass 43
16(d) RM-1 2.sup.nd pass 48
[0054] As evident from Table IV, SRM-3 was about twice as efficient
as RM-1 on the 1.sup.st pass and about seven times as efficient as
RM-1 on the second pass. The results show that the affinity of
SRM-3 for mercury improves with increased exposure to mercury,
indicating an induction effect.
Example 17
[0055] This example illustrates mercury (metal) sorption from vapor
phase by sulfidized red mud (a) and red mud (b) using a column. In
part (a), one gram of mercury was placed in a two necked RB flask
supported on a heating mantle. One neck of the flask was open
(vented) and the second neck was connected to a vertical tube 20 cm
long and 2.5 cm diameter half filled with spray dried sulfidized
red mud. A slight vacuum was applied to the open end of the packed
tube and regulated to fluidize the spray dried sulfidized red mud
while the mercury in the flask was heated to 300.degree. C. The
aspiration was continued for 20 minutes, the tube was disconnected
from the RB flask and the sulfidized red mud contents analyzed for
mercury by ICP.
[0056] In part (b), the procedure of part (a) was repeated using
spray dried red mud, after which the red mud was also submitted for
mercury analysis by ICP.
[0057] Results of the above experiment are tabulated in Table V and
demonstrate increased sorption of mercury vapor by sulfidized red
mud (SRM-3) compared to red mud (RM-1).
TABLE-US-00007 TABLE V Hg Concentration (ppm) 17(a) SRM-3 72 17(b)
RM-1 25
Example 18
[0058] This example shows sorption of mercury (metal) from naphtha
by sulfidized red mud (a) and red mud (b). In part (a), a solution
of 500 ml naphtha containing 100 ppb of mercury was slurried with
10 grams of spray dried sulfidized red mud (SRM) for 30 minutes.
The resulting slurry was filtered, and the SRM filter cake was
dried for 1 hour at room temperature and analyzed for mercury by
ICP.
[0059] In part (b), the procedure of part (a) was repeated using
red mud (RM).
[0060] Results of parts (a) and (b) are shown in Table VI and
reveal the increased capture of mercury from naphtha by sulfidized
red mud (SRM-3).
TABLE-US-00008 TABLE VI Mercury (ppb) 18(a) SRM-3 filtrate 46 18(b)
RM-1 filtrate 21
Example 19
[0061] This example shows sorption of chromium (III) by sulfidized
red mud (SRM) and red mud (RM). In part (a), ten grams of SRM was
slurried 30 minutes with 1 kg demineralized water containing 2.240
ppm chromium III. The slurry was filtered and the filtrate analyzed
for chromium by EPA 200.9 method.
[0062] In part (b), the procedure of part (a) was repeated using
2.240 ppm chromium III and red mud (RM). The results are shown in
Table VII below.
TABLE-US-00009 TABLE VII Chromium III (ppm) Control 2.240 19(a)
SRM-3 filtrate 0.005 19(b) RM-1 filtrate 0.018
[0063] Results shown in Table VII demonstrate improved sorption of
Chromium III by SRM-3 compared to RM-1.
Example 20
[0064] This example illustrates sorption of cobalt (II) by
sulfidized red mud (SRM) and by red mud (RM). The procedures of
Examples 19 (a) and (b) were repeated using 2.75 ppm of cobalt II.
The results are shown in Table VIII below.
TABLE-US-00010 TABLE VIII Cobalt II (ppm) Control 2.75 20(a) SRM-3
filtrate 0.013 20(b) RM-1 filtrate 0.046
[0065] Results in Table VIII show that SRM-3 has greater affinity
for cobalt II than RM-1, with the filtrate from SRM-3 containing
less than 1/3 of cobalt II than that contained in the filtrate from
RM-1.
Example 21
[0066] This example shows sorption of nickel (II) by sulfidized Red
Mud (SRM) and by red mud (RM). The procedures of Examples 15(a) and
(b) were repeated using 1.13 ppm nickel (II). The results are shown
in Table IX below.
TABLE-US-00011 TABLE IX Nickel II (ppm) Control 1.13 21(a) SRM-3
filtrate 0.056 21(b) RM-1 filtrate 0.009
[0067] The results show nickel removal by SRM-3 was less efficient
than by RM-1.
Example 22
[0068] This example illustrates sorption of copper (II) by
sulfidized red mud (SRM-3) and by red mud (RM-1). The procedures of
Examples 19 (a) and (b) were repeated using 1.550 ppm, 6.250 ppm,
and 30.500 ppm copper (II). The results are shown in Table X
below.
TABLE-US-00012 TABLE X Copper II (ppm) Control A 1.550 22(a) SRM-3
filtrate <0.004 22(b) RM-1 filtrate 0.028 Control B 6.250 22(c)
SRM-3 filtrate 0.038 22(d) RM-1 filtrate 0.054 Control C 30.500
22(e) SRM-3 filtrate 0.040 22(f) RM-1 filtrate 0.073
[0069] The results show a clear advantage of SRM-3 over RM-1 for
copper removal over a 15-fold range of copper concentrations.
Example 23
[0070] This example shows sorption of zinc (II) by sulfidized red
mud (SRM) and by red mud (RM). The procedures for Examples 15(a)
and (b) were repeated using 1.850 ppm zinc (II) and 2.380 ppm zinc
(II). The results are shown in Table XI below.
TABLE-US-00013 TABLE XI Zinc II (ppm) Control A 1.850 23(a) SRM-3
filtrate 0.009 23(b) RM-1 filtrate 0.035 Control B 2.380 23(c)
SRM-3 filtrate 0.022 23(d) RM-1 filtrate 0.103
[0071] The results show SRM-3 is superior to RM-1 for zinc removal
and yields filtrates with about one-fourth the concentration of
zinc.
Example 24
[0072] This example illustrates sorption of silver (I) by
sulfidized red mud (SRM). The procedure of Example 15(a) was
repeated using 3.15 ppm silver (I). The results are shown in Table
XII below.
TABLE-US-00014 TABLE XII Silver I (ppm) Control 3.15 24(a) SRM-3
filtrate N.D.
[0073] The results demonstrate that SRM-3 is a good sorbent for
silver ion.
Example 25
[0074] This example shows sorption of gold I by sulfidized red mud
(SRM). The procedure of Example 19 (a) was repeated using 0.703 ppm
gold III. The results are shown in Table XIII below.
TABLE-US-00015 TABLE XIII Gold III (ppm) Control 0.703 25(a) SRM-3
filtrate 0.227
[0075] The results demonstrate that SRM-3 is a good sorbent for
gold (III).
Example 26
[0076] This example illustrates sorption of cadmium II by
sulfidized red mud (SRM) and by red mud (RM). The procedures of
Examples 19 (a) and (b) were repeated using 1.850 ppm cadmium. The
results are shown in Table XIV below.
TABLE-US-00016 TABLE XIV Cadmium II (ppm) Control 1.850 26(a) SRM-3
filtrate 0.009 26(b) RM-1 filtrate 0.035
[0077] The results show that SRM-3 is significantly more efficient
in removing cadmium II from water than is RM-1.
Example 27
[0078] This example shows sorption of lead ion .sup.+2 by
sulfidized red mud (SRM) and by red mud (RM). The procedures of
Examples 19 (a) and (b) were repeated using 2 ppm lead ion
(.sup.+2). The results are shown in Table XV below.
TABLE-US-00017 TABLE XV Lead II (ppm) Control 2.0 27(a) SRM-3
filtrate 0.007 27(b) RM-1 filtrate 0.058
[0079] The results show that SRM-3 reduced lead content to about
one-eighth of the content achieved by RM-1. The lead content of the
SRM filtrate (7 ppb) met drinking water standards (currently 15
ppb).
Example 28
[0080] This example shows sorption of selenium by sulfidized red
mud (SRM) and red mud (RM). The procedures of Examples 19 (a) and
(b) were repeated using 2.5 ppm selenium. The results are shown in
Table XVI below.
TABLE-US-00018 TABLE XVI Selenium (ppm) Control 2.5 28(a) SRM-3
filtrate 0.24 28(b) RM-1 filtrate 2.10
[0081] The results show that SRM-3 reduced Se by about 90% while
RM-1 only reduced Se by about 16%.
Example 29
[0082] This example illustrates sorption of uranium by sulfidized
red mud (SRM-3) and red mud (RM-1). The procedures of Examples
19(a) and (b) were repeated using a Uranium Atomic Absorption
Standard Solution containing 1000 micrograms of U (as uranyl
nitrate--UO.sub.2(NO.sub.3).sub.2) and made up in varying
concentrations (1.13, 10.1, and 38.0 ppm), and then treated with
sulfidized red mud (SRM-3) and red mud (RM-1). In addition, a third
test was performed on each uranium solution using a mixture of 5 g
sulfidized red mud (SRM-3) and 5 g red mud (RM-1). The results are
shown in Table XVII below.
TABLE-US-00019 TABLE XVII Uranium (ppm) Control A 1.13 29(a) SRM-3
filtrate 0.040 29(b) RM-1 filtrate 0.074 29(c) RM-1/SRM-3 0.031
Control B 10.1 29(d) SRM-3 filtrate 0.494 29(e) RM-1 filtrate 2.450
29(f) SRM-3/RM-1 filtrate 1.610 Control C 38.0 29(g) SRM-3 filtrate
3.950 29(h) RM-1 filtrate 6.900 29(i) SRM-3/RM-1 filtrate 4.660
[0083] The data in Table XVII (29(f)-(i)) confirm that sulfidized
red mud is significantly more efficient for extraction of uranium
than is red mud. Moreover, combinations of sulfidized red mud and
red mud (1:1) are more effective than red mud alone. The
combination of SRM and RM allows the complimentary extraction of
elements while eliminating the leaching of other elements from
RM.
[0084] Table XVIII below summarize the results of Examples 19-27.
The last column indicates the amount (in wt %) of the target
material that was removed by SRM.
TABLE-US-00020 TABLE XVIII Control RM SRM % Removed Example Element
(ppm) (ppm) (ppm) by SRM 19 Chromium III 2.240 0.018 0.005 99.997
20 Copper II 1.550 0.028 <0.004 99.997 Copper II 6.250 0.054
0.038 99.993 Copper II 30.500 0.073 0.040 99.999 21 Zinc II 1.850
0.035 0.009 99.995 Zinc II 2.380 0.103 0.022 99.990 22 Silver I
3.15 ND* ND 99.999 23 Gold I 0.703 ND 0.227 67.7 24 Cadmium II
1.850 0.035 0.009 99.995 25 Lead II 2.0 0.058 0.007 99.996 26
Selenium 2.5 2.1 0.24 99.904 27 Uranium II 1.13 0.074 0.04 99.964
Uranium II 10.1 2.45 0.494 99.951 Uranium II 38.0 6.90 3.95 99.896
*ND = not detectable
Example 30
[0085] This example compares SRM and RM for sorption of As, Co, Mn,
and Sr. The procedure of Example 9 was repeated using solutions of
arsenic (III), arsenic (V), cobalt II, manganese (II), and
strontium (I), with results summarized in Table XIX.
TABLE-US-00021 TABLE XIX Control RM-1 % SRM-3 % Element (ppm) ppm
Removed Ppm Removed Arsenic III 0.60 0.11 81.7 0.36 60.0 Arsenic V
1.60 0.21 87.8 1.15 72.0 Cobalt II 2.75 0.013 99.5 0.046 98.3
Manganese II 1.63 0.135 91.7 0.548 66.4 2.10 0.72 65.7 0.792 37.7
Strontium II 1.90 0.10 94.7 1.10 42.1 9.0 0.08 99.1 4.60 48.9 27.0
0.19 99.3 11.0 59.2
[0086] These experiments reveal that the efficiency of red Mud
(RM-1) is significantly better than SRM-3 in the case of As (III),
As (V), Mn (II), and Sr (II). However, the use of red mud as a
sorbent is limited by the leaching of undesirable elements which
can and have caused serious problems. Use of sulfidized red mud in
combination with red mud allows utilization of the latter because
sulfidized red mud sorbs undesirable leaching of extraneous metals
from red mud itself.
Example 31
[0087] This example shows sorption of Hg (II) by various sulfidized
red muds, as summarized in Table XX below.
TABLE-US-00022 TABLE XX Concentration of Hg (II) in Leachate (ppm)
Concentration of Hg (II) in SRM-4 SRM-5 SRM-6 SRM-3 Original 5% %
5% % 5% % H.sub.2S % solution (ppm) (NH.sub.4).sub.2S Removed
Na.sub.2S Removed CaS.sub.x Removed pressure Removed 4.5 0.001 100
0.449 90.0 0.005 99.9 0.004 99.9 19.6 0.0229 99.9 15.4 21.4 3.16
83.8 0.02 99.9
[0088] Each of SRM-3, -4, and -6 gave excellent sorption results
from solutions of Hg (II) at two concentration (4.5 ppm and 19.6
ppm). It is significant that SRM-4 reduced Hg to 1 ppb, thus
meeting current drinking water standards (2 ppb maximum). SRM-5
made form red mud by treatment with Na.sub.2S was much less
efficient. Ammonium sulfide treatment (SRM-4) was the most
effective sorbent despite the fact it had the lowest S content as
shown by the analysis in Example 7.
Example 32
[0089] This example illustrates treating mercury metal with red mud
and sulfidized red mud (wet). In part (a), a mixture of 10 g
mercury metal, 50 g red mud, and 100 g demineralized water was
rapidly mixed in a Waring Blender for 10 minutes. The aqueous
slurry of red mud was separated from mercury in a reparatory
funnel. The slurry was filtered, dried at 80.degree. C. for 4
hours, then ground in a coffee grinder for 3 minutes, and submitted
for mercury analysis.
[0090] In part (b), the procedure of part (a) was repeated using
SRM-2. In part (c), the procedure of part (a) was repeated using
SRM-410, which was prepared by reaction of red mud and 10% ammonium
sulfide. Results for parts (a)-(c) are shown in Table XXI
below.
TABLE-US-00023 TABLE XXI Example Reagent % Hg 32(a) RM-1/Hg 1.27
32(b) SRM-2/Hg 0.55 32(c) SRM-410/Hg 1.65
[0091] The results show that sulfidized red mud SRM-410 of Example
32(c) was about 30% more effective than red mud (RM-1) in sorbing
mercury.
Example 33
[0092] This example illustrates treating mercury metal with red mud
and sulfidized red mud (dry). In part (a), a mixture of 10 g
mercury metal and 50 g red mud was rapidly mixed in a Waring
Blender for 10 minutes. Demineralized water (100 g) was added to
the mixture and mixing in the blender resumed for 5 minutes. The
aqueous slurry of red mud was separated from mercury in a
reparatory funnel. The slurry was filtered, dried at 80.degree. C.
for 4 hours, then ground in a coffee grinder for 3 minutes, and
submitted for mercury analysis.
[0093] In part (b), the procedure of part (a) was repeated using
SRM-2. In part (c), the procedure of part (a) was repeated using
SRM-410, which was prepared as described in Example 32 above. The
results are provided in Table XXII below.
TABLE-US-00024 TABLE XXII Example Reagent % Hg 33(a) RM-1/Hg 1.84
33(b) SRM-2/Hg 6.34 33(c) SRM-410/Hg 5.58
[0094] The results show that sulfidized red mud SRM-2 and SRM-410
sorbed over three times as much mercury than did red mud (RM-1).
The sorption procedure in Example 33, which used direct contact of
the sulfidized red mud and mercury (without water present
initially), was much more effective than the procedure in Example
32, which initially added water to the mercury and sulfidized red
mud.
Example 34
[0095] This example shows sorption of thorium (IV), as
Th(NO.sub.3).sub.4.H.sub.2O, by RM-1 and
[0096] SRM-3. In part (a), 10 g of sulfidized red mud (SRM-4) was
slurried for 30 minutes with 1 kg demineralized water containing 1
ppm thorium. The slurry was filtered and analyzed for thorium.
[0097] In part (b), the procedure of part (a) was repeated using 5
ppm thorium. In part (c), the procedure of part (a) was repeated
using 10 ppm thorium. In part (d), the procedure of part (a) was
repeated using 20 ppm thorium. The procedures of parts (a)-(d) were
then repeated using red mud. The results are summarized in Table
XXIII below.
TABLE-US-00025 TABLE XXIII Example Control SRM-4 RM-1 34(a) 0.956
ND* 0.051 34(b) 4.930 ND 0.260 34(c) 10.500 ND 0.564 34(d) 19.400
ND 0.921 *ND = not detectable
[0098] The results show that sulfidized red mud SRM-4 was very
effective (essentially quantitative) for thorium sorption.
Example 35
[0099] This example compares sedimentation rates of SRM-3 and RM-1.
In the course of tests on metal sorption from aqueous solutions by
sulfidized red mud and red mud, it was found that in all cases,
sulfidized red mud exhibited significantly faster filtration rates
than red mud. Red mud is very hydrophilic but conversion of red mud
to sulfidized red mud transforms it to a lyophobic particle which
is more readily dewatered. The unexpected improvement of dewatering
behavior is shown in the following experiment:
[0100] A dispersion of 50 grams of RM-1 in 500 ml demineralized
water was prepared by rapid mixing in a Waring Blender for 10
minutes. The experiment was repeated using 50 grams of SRM-3 in 500
ml demineralized water.
[0101] Both freshly prepared slurries were allowed to settle
undisturbed at ambient temperature (25.degree. C.) for a period of
72 hours. After 72 hours, the RM-1 dispersions had settled to give
a clear supernatant layer of only 1 cm. The remaining slurry
consisted of dispersed RM-1 with no visible sediment.
[0102] During the 72 hour period, the SRM-3 slurry completely
settled to furnish a sedimentary layer about 1 cm deep and a clear
supernatant layer 11.5 cm above the sediment.
[0103] These results clearly show the total alteration of surface
chemistry and dewatering characteristics of red mud by relatively
small degrees of sulfidation.
Example 36
[0104] Five kilograms of sulfidized red mud from Example 4 was
mixed with three kilograms of water containing 50 grams of sodium
silicate in a rotating spherical pelletizer (candy pan) for 30
minutes and then screened to reject and recycle plus 6 mm and minus
3 mm particles. The resulting pellets were dried for four hours at
110.degree. C. The pellets were packed in a filter bed 60 cm deep
and used to filter dilute solutions of heavy metals.
[0105] While particular embodiments of the present invention have
been described and illustrated, it should be understood that the
invention is not limited thereto since modifications may be made by
persons skilled in the art. The present application contemplates
any and all modifications that fall within the spirit and scope of
the underlying invention disclosed and claimed herein.
* * * * *