U.S. patent application number 13/643376 was filed with the patent office on 2013-03-21 for method for extracting gallium from fly ash.
This patent application is currently assigned to CHINA SHENHUA ENERGY COMPANY LIMITED. The applicant listed for this patent is Junzhou Chi, Dazhao Gu, Zhaohua Guo, Yinshan Jiang, Nan Li, Wen Ling, Cundi Wei, Dianfan Yang, Ping Zou. Invention is credited to Junzhou Chi, Dazhao Gu, Zhaohua Guo, Yinshan Jiang, Nan Li, Wen Ling, Cundi Wei, Dianfan Yang, Ping Zou.
Application Number | 20130068628 13/643376 |
Document ID | / |
Family ID | 42956444 |
Filed Date | 2013-03-21 |
United States Patent
Application |
20130068628 |
Kind Code |
A1 |
Ling; Wen ; et al. |
March 21, 2013 |
METHOD FOR EXTRACTING GALLIUM FROM FLY ASH
Abstract
Disclosed is a method for extracting gallium from fly ash, which
comprises the following steps: crushing the fly ash and removing Fe
by magnetic separation; then dissolving it by using hydrochloride
acid (2) to obtain hydrochloric acid leachate; adsorbing gallium in
the hydrochloric acid leachate with macro-porous cationic resin,
followed by eluting to obtain the eluent (5) containing gallium;
adding sodium hydroxide (6) solution into the eluent containing
gallium to react and obtaining sodium metaaluminate solution
containing gallium (8); introducing CO.sub.2 into the sodium
metaaluminate solution containing gallium (8) for carbonation,
followed by separating gallium from aluminum and obtaining
aluminum-gallium double salt (15) with the gallium to alumina mass
ratio being more than 1:340; adding the aluminum-gallium double
salt (15) into sodium hydroxide (17) to react, followed by
alkalinity-adjustment concentration to obtain alkali solution
containing gallium and aluminum; electrolyzing (10) the alkali
solution containing gallium and aluminum to obtain metal gallium
(11). The method simplifies the process and improves extraction
efficiency of gallium.
Inventors: |
Ling; Wen; (Beijing, CN)
; Jiang; Yinshan; (Beijing, CN) ; Wei; Cundi;
(Beijing, CN) ; Li; Nan; (Beijing, CN) ;
Gu; Dazhao; (Beijing, CN) ; Guo; Zhaohua;
(Beijing, CN) ; Yang; Dianfan; (Beijing, CN)
; Chi; Junzhou; (Beijing, CN) ; Zou; Ping;
(Beijing, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ling; Wen
Jiang; Yinshan
Wei; Cundi
Li; Nan
Gu; Dazhao
Guo; Zhaohua
Yang; Dianfan
Chi; Junzhou
Zou; Ping |
Beijing
Beijing
Beijing
Beijing
Beijing
Beijing
Beijing
Beijing
Beijing |
|
CN
CN
CN
CN
CN
CN
CN
CN
CN |
|
|
Assignee: |
CHINA SHENHUA ENERGY COMPANY
LIMITED
Beijing
CN
|
Family ID: |
42956444 |
Appl. No.: |
13/643376 |
Filed: |
April 27, 2011 |
PCT Filed: |
April 27, 2011 |
PCT NO: |
PCT/CN2011/073402 |
371 Date: |
December 10, 2012 |
Current U.S.
Class: |
205/339 |
Current CPC
Class: |
C22B 3/10 20130101; C22B
7/007 20130101; C22B 58/00 20130101; Y02P 10/234 20151101; C22B
7/02 20130101; Y02P 10/20 20151101; C22B 3/42 20130101; C25C 1/22
20130101; B03C 1/03 20130101; C22B 3/44 20130101; B03C 1/032
20130101; B03C 1/0335 20130101; B03C 2201/18 20130101 |
Class at
Publication: |
205/339 |
International
Class: |
C25C 1/22 20060101
C25C001/22 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 27, 2010 |
CN |
201010161837.6 |
Claims
1. A method for extracting gallium from fly ash, comprising the
following steps: a) crushing the fly ash to a size of 100 mesh or
smaller, removing iron by wet magnetic separation, such that the
ferric oxides content in the fly ash is reduced to 1.0 wt % or
less, then adding hydrochloride acid into the de-ironed fly ash to
perform an acid-leaching reaction, and subjecting the reaction
product to solid-liquid separation to yield a hydrochloric leachate
having a pH value in the range of 1-3; b) adsorbing gallium in the
hydrochloric leachate by passing the same through a column loading
with a macro-porous cationic resin; eluting the column with water
or hydrochloride acid as an eluting agent when the adsorption
reaches saturation to obtain a gallium-containing eluent; c) adding
sodium hydroxide solution into the gallium-containing eluent to
react, separating precipitates after reaction by filtration to
obtain a gallium-containing sodium metaaluminate solution; d)
subjecting the gallium-containing sodium metaaluminate solution to
carbonation by introducing carbon dioxide therein, and then
separating gallium from most aluminum to obtain a gallium-aluminum
double salt with the mass ratio of gallium to alumina being more
than 1:340; and e) adding the gallium-aluminum double salt into a
sodium hydroxide solution, subjecting the reactant to evaporation
and concentration to obtain a base solution containing gallium and
aluminum with the contents of gallium and alumina being .mu.mol/l
or more respectively, and then electrolyzing the base solution to
obtain metal gallium, wherein in the acid leaching reaction of step
a), the reaction temperature is 100-200.degree. C., the reaction
pressure is 0.1-2.5 MPa, and in step b), the macro-porous cationic
resin is selected from any one of D001, 732 and 742.
2. The method according to claim 1, wherein, in step a), the
concentration of the hydrochloride acid is 20-37 wt %; the molar
ration of HCl contained in the hydrochloride acid to alumina
contained in the fly ash is 4:1-9:1.
3. The method according to claim 2, wherein, in the acid-leaching
reaction of step a), reaction time is 0.5-4.0 hours.
4. (canceled)
5. (canceled)
6. The method according to claim 3, wherein, in step b), adsorbing
gallium in the hydrochloric leachate by passing the hydrochloric
leachate through the column from the bottom to top with a volume
flux of 1-4 times over resin volume per hour at 20-90.degree.
C.
7. The method according to claim 6, wherein, in step b), eluting
said macro-porous cationic resin with 2-10 wt % hydrochloride acid
as an eluting agent, and preferably, the eluting temperature is
20-60.degree. C., the amount of the eluting agent used is 1-3 times
over the volume of the resin, and the eluting rate is 1-3 times
over resin volume per hour.
8. The method according to claim 1, wherein, in step c), the
concentration of sodium hydroxide solution is 180-240 g/l;
preferably, the reaction temperature is 20-100.degree. C.
9. The method according to claim 1, wherein, in step d), the
carbonation by introducing carbon dioxide into the
gallium-containing sodium metaaluminate solution comprises the
steps of: performing a primary carbonation: introducing carbon
dioxide into the gallium-containing sodium metaaluminate mother
solution obtained in step c), in which the flow rate of carbon
dioxide is in the range of 80-160 ml/min, the reaction temperature
is controlled in the range of 40-90.degree. C., the carbonation
time is in the range of 4-10 h, the pH value at the end of the
reaction is in the range of 10.6-9.7, then separating the
precipitates from the solution by filtration, so as to separate
gallium from aluminum for the first time; performing a secondary
carbonation: further introducing carbon dioxide into the solution
obtain from the primary carbonation after the separation of the
aluminum hydroxide precipitates, in which the flow rate of carbon
dioxide is in the range of 100-160 ml/min the reaction temperature
is controlled in the range of 30-60.degree. C., the carbonation
time is in the range of 3-7 h, the pH value at the end of the
reaction is in the range of 9.8-9.0, so as to precipitate all
aluminum and most gallium; subjecting the reactant to filtration to
obtain gallium-aluminum double salt; then crystallizing sodium
carbonate in the filtrate obtained from the filtration by
evaporization and concentration and separating the crystallized
sodium carbonate from the solution; and then recycling the filtrate
containing a small amount of gallium obtained after the separation
of sodium carbonate to the beginning of the secondary carbonation
for further carbonation.
10. The method according to claim 9, wherein, in step d), when the
mass ratio of gallium to alumina in the gallium-aluminum double
salt obtained after the primary carbonation and secondary
carbonation is equal to or less than 1:340, dissolving the double
salt in a sodium hydroxide solution or the sodium metaaluminate
mother solution and repeating the primary carbonation and the
secondary carbonation until the mass ratio of gallium to alumina in
the last gallium-aluminum double salt is more than 1:340.
11. The method according to claim 1, wherein, in step e), the
concentration of sodium hydroxide solution is 180-245 g/l;
preferably, the reaction temperature in step e) is 20-100.degree.
C.
12. The method according to claim 1, wherein, in step e), when the
base solution containing aluminum and gallium is electrolyzed,
platinum electrodes are used as the negative and positive
electrodes, electrolysis current is in the range of 180-200 mA/l,
electrolysis voltage is in the range of 4V and electrolytic bath
temperature is in the range of 35-45.degree. C.
13. The method according to any claim 1, wherein, in step a), the
apparatus used for de-ironing by wet magnetic separation is a
vertical ring magnetic separator which comprises a rotating ring,
an inductive medium, an upper iron yoke, a lower iron yoke, a
magnetic exciting coil, a feeding opening, a tailing bucket and a
water washing device, wherein the feeding opening is used for
feeding the coal ash to be de-ironed, the tailing bucket is used
for discharging the non-magnetic particles after de-ironing, the
upper iron yoke and the lower iron yoke are respectively arranged
at the inner and outer sides of the lower portion of the rotating
ring, the water washing device is arranged above the rotating ring,
the inductive medium is arranged in the rotating ring, the magnetic
exciting coil is arranged at the periphery of the upper iron yoke
and the lower iron yoke so as to make the upper iron yoke and the
lower iron yoke to be a pair of magnetic poles for generating a
magnetic field in the vertical direction, and wherein the inductive
medium is layers of steel plate meshes, each steel plate mesh is
woven by wires, and the edges of the wires have prismatic sharp
angles.
14. (canceled)
15. The method according to claim 13, wherein the vertical ring
magnetic separator further comprises a pressure balance chamber
water jacket disposed adjacent to the magnetic exciting coil.
16. The method according to claim 15, wherein the steel plate mesh
has a medium layer spacing of 2-5 mm, preferably 3 mm; and the
steel plate mesh is made of 1Cr17.
17. The method according to claim 16, wherein the steel plate mesh
has a thickness of 0.8-1.5 mm, a mesh grid size of 3 mm.times.8
mm-8 mm.times.15 mm, and a wire width of 1-2 mm, preferably, the
steel plate mesh has a thickness of 1 mm, a mesh grid size of 5
mm.times.10 mm, and a wire width of 1.6 mm.
18. The method according to claim 17, wherein the vertical ring
magnetic separator further comprises a pulsating mechanism, which
is coupled with the tailing bucket via a rubber plate.
19. The method according to claim 18, wherein the inductive medium
is provided in the entire circle of the rotating ring.
20. The method according to claim 19, wherein the magnetic exciting
coil is a flat wire solenoid coil which is double glass envelope
enamelled aluminum.
21. The method according to claim 20, wherein the magnetic field
strength of the vertical ring magnetic separator is 15,000 Gs or
more, preferably 15,000-20,000 Gs, further preferably 15,000-17,500
Gs.
22. A method for extracting gallium from fly ash, comprising the
following steps: a) crushing the fly ash to a size of 100 mesh or
smaller, removing iron by wet magnetic separation, such that the
ferric oxides content in the fly ash is reduced to 1.0 wt % or
less, then adding hydrochloride acid into the de-ironed fly ash to
perform an acid-leaching reaction, and subjecting the reaction
product to solid-liquid separation to yield a hydrochloric leachate
having a pH value in the range of 1-3; b) cooling the hydrochloric
leachate till its temperature is 90.degree. C., then pumping the
hydrochloric leachate into a column loaded with JK008 Resin to
enrich gallium, wherein the flow flux of the hydrochloric leachate
is 4 times over resin volume per hour; and when the adsorption
reached saturation, eluting the column with 2 wt % hydrochloride
acid as an eluting agent at 60.degree. C. to obtain a gallium-rich
eluent, wherein the flow flux of the hydrochloride acid is 1 time
over resin volume per hour, and the total amount of the eluting
agent used for elution is 2 times over the volume of the resin; c)
adding sodium hydroxide solution into the gallium-containing eluent
to react, separating precipitates after reaction by filtration to
obtain a gallium-containing sodium metaaluminate solution; d)
subjecting the gallium-containing sodium metaaluminate solution to
carbonation by introducing carbon dioxide therein, and then
separating gallium from most aluminum to obtain a gallium-aluminum
double salt with the mass ratio of gallium to alumina being more
than 1:340; and e) adding the gallium-aluminum double salt into a
sodium hydroxide solution, subjecting the reactant to evaporation
and concentration to obtain a base solution containing gallium and
aluminum with the contents of gallium and alumina being 1 mol/l or
more respectively, and then electrolyzing the base solution to
obtain metal gallium, wherein in the acid-leaching reaction of step
a), the reaction temperature is 100-200.degree. C., the reaction
pressure is 0.1-2.5 MPa.
23. A method for extracting gallium from fly ash, comprising the
following steps: a) crushing the fly ash to a size of 100 mesh or
smaller, removing iron by wet magnetic separation, such that the
ferric oxides content in the fly ash is reduced to 1.0 wt % or
less, then adding hydrochloride acid into the de-ironed fly ash to
perform an acid-leaching reaction, and subjecting the reaction
product to solid-liquid separation to yield a hydrochloric leachate
having a pH value in the range of 1-3; b) cooling the hydrochloric
leachate till its temperature is 40.degree. C., then pumping the
hydrochloric leachate into a column loaded with SPC-1 Resin to
enrich gallium, wherein the flow flux of the hydrochloric leachate
is 1 time over resin volume per hour; and when the adsorption
reached saturation, eluting the column with 10 wt % hydrochloride
acid as an eluting agent at 30.degree. C. to obtain a gallium-rich
eluent, wherein the flow flux of the hydrochloride acid is 3 times
over resin volume per hour, and the total amount of the eluting
agent used for elution is 1 time over the volume of the resin; c)
adding sodium hydroxide solution into the gallium-containing eluent
to react, separating precipitates after reaction by filtration to
obtain a gallium-containing sodium metaaluminate solution; d)
subjecting the gallium-containing sodium metaaluminate solution to
carbonation by introducing carbon dioxide therein, and then
separating gallium from most aluminum to obtain a gallium-aluminum
double salt with the mass ratio of gallium to alumina being more
than 1:340; and e) adding the gallium-aluminum double salt into a
sodium hydroxide solution, subjecting the reactant to evaporation
and concentration to obtain a base solution containing gallium and
aluminum with the contents of gallium and alumina being .mu.mol/l
or more respectively, and then electrolyzing the base solution to
obtain metal gallium, wherein in the acid-leaching reaction of step
a), the reaction temperature is 100-200.degree. C., the reaction
pressure is 0.1-2.5 MPa.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for extracting
metal gallium from fly ash and in particular relates to a method
for extracting metal gallium from circulating fluidized-bed fly
ash.
BACKGROUND
[0002] Gallium is an important semiconductor material and widely
used. The price of gallium is very high in the international market
and thus gallium has a bright prospect. However, the reserve of
gallium is low, only approximately 0.015% in the earth's crust.
Gallium almost does not form minerals, but exists with other
minerals in form of isomorphism. Therefore, extraction of gallium
is considerably difficult. Gallium is often found in conjunction
with aluminum and zinc in minerals in nature. As such, sulfide
deposits of zinc and bauxite ore serve as a primary source of the
extraction of gallium. Nowadays, more than 90% of gallium in the
world is extracted from the by-product of alumina industry in which
bauxite is used as a main raw material. The mother liquid used for
the enrichment and separation of gallium is the mother liquid
obtained from carbon precipitation (or seed precipitation) during
the process for producing alumina. The main component of such
mother liquid obtained from carbon precipitation (or seed
precipitation) is a base sodium metaaluminate solution containing
gallium. Main methods for extracting gallium from such base
solution include a method for removing aluminum via lime cream and
carbonation, dealumination method of carbonated lime milk two-stage
decomposition method, precipitation method and resin adsorption
method which develops in recent years.
[0003] The recent studies have shown that the fly ash obtained from
some places contains a large amount of gallium which even
overpasses the gallium level of mineral deposit. It has been
verified by researches that the gallium content in the fly ash is
usually 12-230 .mu.g/g. As compared with the gallium contents of
other resources, the fly ash deserves to be extracted for metal
gallium as a raw material. In light of different conditions of
calcinations, the fly ash is classified into pulverized coal-fired
boiler fly ash and circulating fluidized-bed fly ash. The
pulverized coal-fired boiler fly ash is produced when coal is
burned at a very high temperature (1400-1600.degree. C.), in which
alumina is in glassy state or present as a mineral form of mullite
crystals or corundum crystals of hot aluminum mineral which make
such alumina very stable. While the combustion temperature of
circulating fluidized-bed fly ash is much lower than that of
traditional pulverized coal-fired boiler fly ash, only about
850.degree. C. Different combustion temperatures make a substantial
difference in phase composition between the pulverized coal-fired
boiler fly ash and circulating fluidized-bed fly ash, that is,
amorphous kaolinite enters into the main phase composition of the
circulating fluidized-bed fly ash, in which silicon dioxide,
alumina and ferric oxide or the like possess excellent
activity.
[0004] CN 200810051209.5 discloses a method for extracting both
alumina and gallium from fly ash. In the method, sodium
metaaluminate solution containing gallium is obtained by
acid-leaching and alkali-leaching processes, and then gallium is
enriched and separated via multiple-stage carbon
precipitation-sodium hydroxide dissolution process.
[0005] CN 200710065366.7 discloses a method for extracting silicon
dioxide, alumina and gallium oxide from high-alumina fly ash. The
method comprises steps of treating the residues produced after the
extraction of silicon dioxide from fly ash to obtain sodium
metaaluminate solution containing gallium, using such solution as
the mother liquid to enrich gallium via multiple-stage carbon
precipitation-sodium hydroxide dissolution process and resin
adsorption process.
[0006] CN 200710145132.3 discloses a method for co-producing
gallium and alumina. The method comprises steps of treating fly ash
to obtain sodium metaaluminate solution containing gallium,
enriching gallium by the Bayer dissolving system and then
separating the enriched gallium by adsorption process using
chelating resin.
[0007] CN 200710141488.X discloses a method for producing gallium.
The intermediate product, i.e. mother liquid of carbon
precipitation, obtained from the process for producing alumina from
fly ash is used as a raw material and reacts with sodium
bicarbonate, and then subjects to a thorough carbonation, so as to
obtain a gallium concentrate.
[0008] In the above patent documents, the mother liquid of carbon
precipitation (or seed precipitation) obtained from the process for
producing alumina from fly ash is used as a raw material for the
enrichment and separation of gallium, that is, the mother liquid
used for extracting gallium is a base sodium metaaluminate solution
containing gallium.
[0009] CN 200810017872.3 discloses a process for extracting gallium
from fly ash and coal gangue. In the process, an adsorption method
via absorbent columns is used for extracting gallium from an
aluminum chloride solution containing gallium which is obtained by
mixing fly ash and sodium carbonate, subjecting the mixture to
calcination followed by water leaching and carbon precipitating and
then reacting with hydrochloride acid. Such process, as fly ash and
sodium carbonate are mixed and calcined at a very high temperature
before acid leaching, is suitable for extracting gallium from
pulverized coal-fired boiler fly ash which has weak activity.
[0010] Jiazhen He et al. has reported "a research on technique of
recycling gallium from fly ash" (Scientific Research, 2002, No. 5,
p23-26), in which the fly ash reacts directly with hydrochloride
acid to yield an aluminum chloride solution containing gallium,
without being calcined at a very high temperature, and then gallium
is extracted by resin adsorption. The reaction temperature of the
fly ash and hydrochloride acid is low (60.degree. C.), which makes
the leaching efficiency of gallium very low (35.2%). Moreover, the
resin for extraction used in the method is levextred resin
(CL-TBP). The adsorptin principle of such resin is similar to that
of solvent extraction. Such resin is obtained by polymerizing and
curing the active group of an extracting agent with the base resin.
Consequently, the adsorption efficiency of the resin is very low
and the production cost is very high.
SUMMARY OF THE INVENTION
[0011] The object of the invention is to provide an improved method
for extracting metal gallium from circulating fluidized-bed fly
ash.
[0012] The method for extracting metal gallium from circulating
fluidized-bed fly ash according to the invention comprises the
following steps:
[0013] a) crushing the fly ash to a size of 100 mesh or smaller,
removing iron by wet magnetic separation, such that the ferric
oxides content in the fly ash is reduced to 1.0 wt % or less, then
adding hydrochloride acid into the de-ironed fly ash for
acid-leaching reaction, and subjecting the reaction product to
solid-liquid separation, so as to yield a hydrochloric leachate
having a pH value in the range of 1-3;
[0014] b) adsorbing gallium in the hydrochloric leachate by passing
the same through a column loading with a macro-porous cationic
resin; eluting the column with water or hydrochloride acid as an
eluting agent when the adsorption reaches saturation to obtain a
gallium-containing eluent;
[0015] c) adding sodium hydroxide solution into the
gallium-containing eluent, separating precipitates after reaction
by filtration to remove iron in the eluent and thus obtaining a
gallium-containing sodium metaaluminate solution;
[0016] d) subjecting the gallium-containing sodium metaaluminate
solution to carbonation by introducing carbon dioxide therein,
followed by separating gallium from most aluminum and obtaining
gallium-aluminum double salt with the mass ratio of gallium to
alumina being more than 1:340; and
[0017] e) adding the obtained gallium-aluminum double salt into a
sodium hydroxide solution, followed by subjecting the reactant to
evaporation and concentration to obtain a base solution containing
gallium and aluminum with the contents of gallium and alumina being
1 mol/l or more respectively, and then electrolyzing the base
solution to obtain metal gallium.
[0018] Hereinafter the method according to the invention will be
further described in detail, but the present invention is not
limited thereto.
[0019] In step a) according to an embodiment of the invention, the
fly ash includes, but is not limited to circulating fluidized-bed
fly ash. In light of particle size distribution of the fly ash, the
fly ash is crushed to a size of 100 mesh or smaller, removing iron
contained in the crushed fly ash before the acid-leaching, such
that the iron content in the fly ash is reduced to 1.0 wt % or
less. The methods for removing iron may be any conventional methods
for removing iron, such as magnetic separation. Preferably, wet
magnetic separation is used in the present invention. Any
conventional magnetic separator suitable for removing iron from
powder-like material may be used for the wet magnetic separation in
the present invention, as long as the iron content of the fly ash
can be reduced to 1.0 wt % or less. The iron content in the fly ash
is calculated on the basis of the weight of the dried fly ash
containing no water.
[0020] Preferably, the magnetic separator used for fly ash is a
vertical ring magnetic separator. Further preferably, the vertical
ring magnetic separator comprises a rotating ring, an inductive
medium, an upper iron yoke, a lower iron yoke, a magnetic exciting
coil, a feeding opening, a tailing bucket and a water washing
device, in which the feeding opening is used for feeding the coal
ash to be de-ironed, the tailing bucket is used for discharging the
non-magnetic particles after de-ironing, the upper iron yoke and
the lower iron yoke are respectively arranged at the inner and
outer sides of the lower portion of the rotating ring, the water
washing device is arranged above the rotating ring, the inductive
medium is arranged in the rotating ring, the magnetic exciting coil
is arranged at the periphery of the upper iron yoke and the lower
iron yoke so as to make the upper iron yoke and the lower iron yoke
to be a pair of magnetic poles for generating a magnetic field in
the vertical direction, and the inductive medium is layers of steel
plate meshes, each steel plate mesh is woven by wires, and the
edges of the wires have prismatic sharp angles.
[0021] Preferably, the upper iron yoke and the lower iron yoke are
formed integrally, and are arranged, in a plane perpendicular to
the rotating ring, to surround the inner and outer sides of the
lower portion of the rotating ring.
[0022] Preferably, the vertical ring magnetic separator further
comprises a pressure balance chamber water jacket disposed adjacent
to the magnetic exciting coil.
[0023] Preferably, the steel plate mesh is made of 1Cr17.
[0024] Preferably, the magnetic exciting coil is a flat wire
solenoid coil which is double glass envelope enamelled
aluminum.
[0025] Preferably, the steel plate mesh has a medium layer spacing
of 2-5 mm. More preferably, the steel plate mesh has a medium layer
spacing of 3 mm.
[0026] Preferably, the steel plate mesh has a thickness of 0.8-1.5
mm, a mesh grid size of 3 mmx 8 mm-8 mmx 15 mm, and a wire width of
1-2 mm. More preferably, the steel plate mesh has a thickness of 1
mm, a mesh grid size of 5 mm.times.10 mm, and a wire width of 1.6
mm.
[0027] Preferably, the vertical ring magnetic separator further
comprises a pulsating mechanism, which is coupled with the tailing
bucket via a rubber plate.
[0028] Preferably, the inductive medium is provided in the entire
circle of the rotating ring.
[0029] When the above-said vertical ring magnetic separator is used
for magnetic separation for de-ironing, it is necessary to timely
test the iron content in the slurry subject to the magnetic
separation. When the iron content in the slurry is equal to or
lower than a predetermined value, the slurry is discharged; when
the iron content is higher than the predetermined value, the slurry
is returned to the feeding opening for further magnetic separation.
Such magnetic separation may be repeated 2-4 times, preferably 2-3
times.
[0030] Preferably, when the slurry is magnetically separated by the
vertical ring magnetic separator, the vertical ring magnetic
separator provides a magnetic field strength of 15,000 Gs or more,
further preferably 15,000-20,000 Gs, more preferably 15,000-17,500
Gs.
[0031] In step a) according to an embodiment of the invention, the
filtered cake of the circulating fluidized-bed fly ash subject to
magnetic separation is placed into an acid-resistant reactor and
then the hydrochloride acid with a preferred concentration of 20-37
wt % is added therein to perform acid dissolving reaction. In a
preferred embodiment, the molar ratio of HCl contained in the
hydrochloride acid to alumina contained in the fly ash is 4:1-9:1;
the fly ash and hydrochloride acid reacts at a temperature in the
range of 100-200.degree. C. and under a pressure in the range of
0.1-2.5 MPa and the reaction time is 0.5-4.0 hours; and then the
reaction product is subjected to a solid-liquid separation and
rinse to yield an hydrochloric leachate having a pH value in the
range of 1-3. The process for the solid-liquid separation may be
any of conventional methods, such as settling separation, vacuum
filtration, pressure filtration or centrifugation or the like.
[0032] In step b) according to an embodiment of the invention, said
macro-porous cationic resin is preferably any one selected from
D001, 732, 742, 7020H, 7120H, JK008 and SPC-1.
[0033] In step b) according to an embodiment of the invention, said
macro-porous cationic resin may be strong-acid-cationic resin, such
as styrene resins or acrylic resins. The essential performances of
the resin include moisture content of 50.0-70.0%, exchange capacity
of 3.60 mmol/g or more, volume exchange capacity of 1.20 mmol/g or
more, bulk density in wet state of 0.60-0.80 g/ml, particle size of
0.315-1.250 mm, available particle size of 0.400-0.700 mm and
maximum working temperature of 95.degree. C.
[0034] The gallium contained in the hydrochloric leachate obtained
from step a) is adsorbed by passing the same through a column
loading with the macro-porous cationic resin. The process for the
adsorption may be any of conventional methods. However, it is
preferred to conduct the adsorption in such a way that the
hydrochloric leachate passes through the resin column from bottom
to top at 20-90.degree. C., such that the acid leachate flows
upwards piston-like in the gaps of the resin, with a volume flux of
1-4 times over resin volume per hour. The resin column may be
single column or two cascaded columns. In the step, while gallium
in the hydrochloric leachate is enriched by being absorbed by the
macro-porous cationic resin, iron in the hydrochloric leachate is
simultaneously effectively adsorbed, so that a refined aluminum
chloride solution with a low iron content is obtained, which can be
then used for preparing aluminum chloride crystal and
metallurgical-grade alumina with low iron content.
[0035] The macro-porous cationic resin may be eluted by an eluting
agent to obtain a gallium-containing eluent when the adsorption
reaches saturation. Preferably, the eluting agent is water or 2-10
wt % hydrochloride acid. The conditions of elution may include that
the eluting temperature is 20-60.degree. C., the amount of the
eluting agent is 1-3 times over the volume of the resin, the volume
flux of the eluting agent is 1-3 times over resin volume per hour,
and the eluting agent passes through the resin column in a top-in
and bottom-out way during the elution.
[0036] The macro-porous cationic resin may regain adsorption
capacity via regeneration. The resin may be regenerated with 2-10
wt % hydrochloride acid. During the regeneration, the temperature
is 20-60.degree. C., the amount of the hydrochloride acid is 1-2
times over the volume of the resin, and the volume flux of the
hydrochloride acid is 1-3 times over resin volume per hour, the
hydrochloride acid passes through said resin column in a top-in and
bottom-out way.
[0037] In step c) according to an embodiment of the invention,
sodium hydroxide solution is added into the eluent under stirring
and the mass ratio of alumina in the eluent to sodium hydroxide is
1:1-2:1, the eluent reacts with the sodium hydroxide solution at
20-100.degree. C., such that aluminum chloride and gallium chloride
contained in the eluent react with sodium hydrochloride to produce
sodium metaaluminate/sodium metagallate and ferric chloride
precipitates in form of ferric hydroxide. The reaction product is
subjected to a solid-liquid separation and rinse to yield
gallium-containing sodium metaaluminate solution. Preferably, the
concentration of sodium hydroxide solution used in step c) is
180-240 g/l.
[0038] In step d) according to an embodiment of the invention, an
appropriate amount of carbon dioxide may be fed into the
gallium-containing sodium metaaluminate solution, so as to conduct
the carbonation once or several times, till the mass ratio between
gallium and alumina is more than 1:340 in the obtained
gallium-aluminum double salt. Particularly, the carbonation(s) may
comprise the following steps.
[0039] Primary carbonation: carbon dioxide is introduced with a
flow rate of 80-160 ml/min into the gallium-containing sodium
metaaluminate mother solution for a smooth carbonation, in which
the reaction temperature is controlled to 40-90.degree. C., the
carbonation time is 4-10 h, the pH value at the reaction end is
10.6-9.7. After the reaction, most aluminum is precipitated in form
of aluminum hydroxide, whereas gallium is retained in the solution.
The precipitate is removed from the solution, so as to separate
gallium and most aluminum for the first time;
[0040] Secondary carbonation: to the solution obtained from the
primary carbonation separating the aluminum hydroxide precipitates,
carbon dioxide is further introduced with a flow rate of 100-160
ml/min for additional carbonation reaction, in which the reaction
temperature is controlled to 30-60.degree. C., the carbonation time
is 3-7 h, the pH value at the reaction end is 9.8-9.0, so as to
precipitate all aluminum and most gallium. The precipitate is
separated by filtration to obtain a gallium-aluminum double salt.
The filtrate is concentrated by vaporization, and then sodium
carbonate is crystallized out of the solution. After removing the
crystallized sodium carbonate, the solution containing a small
amount of gallium is recycled to the solution obtained from the
primary carbonation at the beginning of the secondary
carbonation.
[0041] If the mass ratio of gallium and alumina in the
gallium-aluminum double salt obtained through the primary
carbonation and the secondary carbonation is equal to or less than
1:340, such double salt can be dissolved in sodium hydroxide
solution or sodium metaaluminate mother solution to conduct the
primary carbonation and the secondary carbonation again till the
mass ratio of gallium and alumina in the gallium-aluminum double
salt is more than 1:340. The gallium content is measures in
accordance with the method of Standard of the People's Republic of
China GB/T 20127.5-2006 "Steel and Alloy-Determination of Trace
Elements Contents Part V: Determination of Gallium Content by
Extraction Separation-Rhodamine B Photometric Method". The aluminum
hydroxide content is calculated by 100% minus the measured gallium
hydroxide content, which is then calculated to the alumina content.
In the present invention, the aluminum hydroxide and sodium
carbonate obtained from the steps for enriching and separating
gallium can be recycled as by-product.
[0042] In step e) according to an embodiment of the invention, the
gallium-aluminum double salt obtained from the secondary
carbonation is added into a sodium hydroxide solution to prepare
the base solution containing gallium and aluminum. Preferably, the
concentration of the sodium hydroxide solution is 180-245 g/l. Both
gallium content and sodium hydroxide content in the base solution
are adjusted to 1 mol/l or more by adjusting the alkalinity and/or
concentrating. Then, the base solution is electrolyzed with
platinum electrodes used as the negative and positive electrodes,
electrolysis current of 180-200 mA/l, electrolysis voltage of 4V
and electrolytic bath temperature of 35-45.degree. C., so as to
obtain the metal gallium product.
[0043] Preferably, the reaction temperature of the gallium-aluminum
double salt precipitate and the sodium hydroxide solution is
20-100.degree. C.
[0044] In the present invention, the sodium salts contained in the
electrolyzed solution with a high content can be recycled by
evaporation and the evaporated water can be re-used.
[0045] As compared with processes in the prior art, the method
according to the present invention is simple, the extraction
efficiency of gallium is high, the production coast is low, and the
product quality is steady. The circulating fluidized-bed fly ash
with high activity is adopted as the raw material for the invention
and gallium is extracted from the fly ash via direct acid-leaching
process, which saves the step of calcination and activation with
presence of sodium carbonate at a very high temperature and thus
simplifies the procedures and reduces the production cost. The acid
leaching of the fly ash occurs in acid-resistant reactor at a
moderate temperature (in the range of 100-200.degree. C.), and thus
the leaching efficiency of gallium is high, being 80% or more. The
effective adsorption efficiency of gallium in hydrochloric leachate
is 96% or more when lower-cost macro-porous cationic resin is used
for adsorbing gallium. During enriching gallium in the hydrochloric
leachate by the macro-porous cationic resin, iron in the
hydrochloric leachate is also effectively removed, so as to obtain
a refined aluminum chloride solution with low iron content which
can be used for preparing aluminum chloride crystal and
metallurgical-grade alumina with low iron content.
[0046] In addition, the experimental study has indicated that,
since the magnetic separation apparatus according to the present
invention is used, the iron removing efficiency is improved by 20%
or more, and the iron removing rate is improved from 60% to 80%,
which significantly relieves the burden of de-ironing from solution
in the subsequent processes, and thereby reducing the production
cost and improving the production efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] FIG. 1 is a flow diagram of the method according to the
present invention;
[0048] FIG. 2 is a flow diagram of the multiple-stage carbonation
process according to the present invention;
[0049] FIG. 3 is a schematic diagram of the vertical ring magnetic
separator used in one preferred embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0050] Hereafter the method according to the present invention will
be further described in detail with reference to the drawings,
however, it should be understood that the present invention is not
limited thereto in any way.
[0051] The structure of vertical ring magnetic separator used for
the following Examples is shown in FIG. 3. The vertical ring
magnetic separator comprises a rotating ring 101, an inductive
medium 102, an upper iron yoke 103, a lower iron yoke 104, a
magnetic exciting coil 105, a feeding opening 106 and a tailing
bucket 107, and also comprises a pulsating mechanism 108 and a
water washing device 109.
[0052] The rotating ring 101 is a circular ring shaped carrier in
which the inductive medium 102 is carried. When the rotating ring
101 is rotated, the inductive medium 102 and the matters adsorbed
thereon move together, so as to separate the adsorbed matters. The
rotating ring 101 may be made of any suitable material, such as
carbon steel etc.
[0053] An electric motor or other driving device can provide power
to the rotating ring 101 such that the rotating ring 101 can rotate
in a set speed.
[0054] When parameters, such as iron content or treating amount of
the material to be treated is lower than a predetermined value, a
relatively low rotating speed, such as 3 rpm, may be used, in order
to make the ferromagnetic impurities having sufficient time to be
adsorbed onto the inductive medium meshes under the act of magnetic
field, and being separated.
[0055] The inductive medium 102 is arranged in the rotating ring
101. The magnetic field generated by the magnetic exciting coil 105
makes the upper iron yoke 103 and the lower iron yoke 104 to be a
pair of magnetic poles generating magnetic field along the vertical
direction. The upper iron yoke 103 and the lower iron yoke 104 are
arranged at the inner and outer sides of the lower portion of the
rotating ring 101 such that the rotating ring 101 rotates
vertically between the magnetic poles. When the rotating ring 101
rotates, the inductive medium 102 in the rotating ring 101 will
pass the pair of magnetic poles made up of the upper iron yoke 103
and the lower iron yoke 104 and be magnetized for removing the
iron.
[0056] The inductive medium 102 may be layers of steel plate
meshes. The steel plate meshes are made of 1Cr17. Each layer of
steel plate meshes is woven by wires, with the mesh grid having a
rhomb shape. The edges of the wires have prismatic sharp angles.
The upper iron yoke 103 is communicated with the feeding opening
106 and the lower iron yoke 104 is communicated with the tailing
bucket 107 which is used for discharging materials. The steel plate
meshes have a medium layer spacing of 3 mm. The magnetic exciting
coil 105 is formed of flat wire solenoid coil which is double glass
envelope enamelled aluminum and is solid conductor. The current
passing through the magnetic exciting coil 105 is continuously
adjustable, and thus the strength of the magnetic field generated
by the magnetic exciting coil 105 is also continuously
adjustable.
[0057] The vertical ring magnetic separator further comprises a
pulsating mechanism 108 coupled with the tailing bucket 107 via a
rubber plate 111. The pulsating mechanism can be achieved by an
eccentric link mechanism, such that the alternating force generated
by the pulsating mechanism 108 pushes the rubber plate 111 to move
forth and back, it is possible for the mineral slurry in the
tailing bucket 107 to generate pulsations.
[0058] The water washing device 109 is arranged above the rotating
ring 101, for flushing the magnetic particles into the concentrate
hopper by water flow. The water washing device 109 may be various
suitable flushing or spraying device, such as a spraying nozzle,
water pipe, etc.
[0059] The feeding opening 106 is communicated with a side of the
upper iron yoke 103, such that the fly ash can pass through the
rotating ring. The feeding opening 106 may be a feeding hopper or a
feeding pipe. The feeding opening 106 is configured for feeding the
mineral slurry, such that the mineral slurry enters the upper iron
yoke 103 with a relatively small fall for preventing the magnetic
particles from penetrating the inductive medium 102 due to gravity,
thus improving the effect of magnetically separating and impurities
removing.
[0060] The vertical ring magnetic separator further comprises a
cooling device 112, which is provided adjacent to the magnetic
exciting coil for decreasing the working temperature of the
magnetic exciting coil. The cooling device is a pressure balance
chamber water jacket. The pressure balance chamber water jacket is
made of stainless steel material, and thus is not prone to scale.
As pressure balance chambers are respectively mounted to the inlet
and outlet of the water jacket, they ensure that the water flows
uniformly through each layer of water jacket and fills throughout
the inside of the jacket, thus preventing any local water from
taking a shortcut which otherwise would affect heat dissipation.
Each layer of water jacket has a water passage with a large
cross-section area, and thus it is possible to completely avoid
blocking due to scaling. Even if there is a block somewhere, the
normal flowing of the circulating water in the water jacket will
not be affected. Moreover, the water jacket is in close contact
with the coil by a large contacting area, thus most heat generated
by the coil can be taken away by the water flow.
[0061] The pressure balance chamber water jacket, as compared with
the common hollow copper tube for heat dissipation, shows high heat
dissipation efficiency, small temperature rise of the windings, and
low exciting power. In case of a rated exciting current of 40 A,
the magnetic separator with the pressure balance chamber water
jacket for heat dissipation can be reduced from 35 kw to 21 kw.
[0062] When the magnetic separator apparatus is working, the fed
mineral slurry flows along a slot of the upper iron yoke 103 then
through the rotating ring 101. As the inductive medium 102 in the
rotating ring 101 is magnetized in the background magnetic field, a
magnetic field with very high magnetic induction strength (such as
22,000 Gs) is formed at the surface of the inductive medium 102.
The magnetic particles in the mineral slurry, under the effect of
the very high magnetic field, are adhered to the surface of the
inductive medium 102, and rotated with the rotating ring 101 going
into the region without magnetic field at top of the rotating ring
101. Then, the magnetic particles are flushed into the concentrate
hopper by the water washing device 109 located above the top of the
rotating ring. The non-magnetic particles flow along the slots of
the lower iron yoke 104 into the tailing bucket 107 and then are
discharged via a tailing exit of the tailing bucket 107.
[0063] Hereafter the method according to the present invention will
be further described in detail with reference to the Examples,
however, it should be understood that the present invention is not
limited thereto in any way.
[0064] In the following Examples, the circulating fluidized-bed fly
ash discharged by a thermal power plant is used as the raw material
and its chemical components are shown in Table 1. The gallium
content in the fly ash is 0.0042 wt %.
TABLE-US-00001 TABLE 1 Chemical components of circulating
fluidized-bed fly ash (wt %) SiO.sub.2 Al.sub.2O.sub.3 TiO.sub.2
CaO MgO TFe.sub.2O.sub.3 FeO K.sub.2O Na.sub.2O LOS SO.sub.3 Total
34.70 46.28 1.48 3.61 0.21 1.54 0.22 0.39 0.17 7.17 1.32 95.77
Example 1
[0065] The experimental procedures used in the example are as
follows.
[0066] (1) Crushing the circulating fluidized-bed fly ash to a size
of 200 mesh, removing iron by wet magnetic separation using the
vertical magnetic separator as illustrated in FIG. 3, such that the
ferric oxide content in the fly ash was reduced to 0.8 wt %;
putting the filtered cake of the fly ash obtained after magnetic
separation into an acid-resistant reactor and adding industrial
hydrochloride acid having a concentration of 37 wt % therein to
perform acid dissolving reaction, wherein the molar ratio of HCl
contained in the hydrochloride acid to alumina contained in the fly
ash was 4.5:1, the reaction temperature was 200.degree. C., the
reaction pressure was 2.1 MPa and the reaction time was 1 hour; and
then pressure-filtering the discharged reaction product by means of
plate-and-frame filter press and washing to yield a hydrochloric
leachate having pH of 1.7, wherein the leaching efficiency of
gallium from the fly ash was measured to be 84.2%.
[0067] (2) Cooling the hydrochloric leachate till its temperature
was 65.degree. C. by means of heat-exchange, then pumping the
hydrochloric leachate through corrosion-resistant pump into resin
column (single-column and loaded with D001 Resin (Anhui Wandong
Chemical Plant)) to enrich gallium, wherein the flow flux of the
hydrochloric leachate was 2 times over resin volume per hour; and
when the adsorption reached saturation, eluting the resin column
with 4 wt % hydrochloride acid as eluting agent at 25.degree. C. to
obtain gallium-rich eluent, wherein the flow flux of the
hydrochloride acid was 2 times over resin volume per hour, and the
total amount of the eluting agent used for elution was 2 times over
the volume of the resin; and regenerating the resin with 4 wt %
hydrochloride acid, wherein the adsorption efficiency of gallium in
the acid leachate was measured to be 96.4%.
[0068] (3) Adding 180 g/l sodium hydroxide solution into the
eluent, so that the mass ratio of alumina to sodium hydroxide in
the solution was 1.0, and keeping reacting at 20.degree. C.,
subjecting the reaction product to filtration to remove ferric
hydroxide precipitate to obtain a gallium-containing sodium
metaaluminate solution.
[0069] (4) Introducing carbon dioxide gas with a flow rate of 80
ml/min into 100 ml of the gallium-containing sodium metaaluminate
mother solution obtained from step (3) at 65.degree. C., the pH
value at the end of reaction was 10.5, then filtering the resultant
to finish the primary carbonation; subjecting the filtrate obtained
from the primary carbonation to the secondary carbonation: further
introducing carbon dioxide gas with a flow rate of 100 ml/min at
60.degree. C., the pH value at the end of the reaction was 9.8,
then filtering the resultant to obtain a gallium-aluminum double
salt precipitate. The mass ratio of gallium to alumina in the
double salt was 1/330. The gallium content was measured in
accordance with the method of Standard of the People's Republic of
China GB/T 20127.5-2006 "Steel and Alloy-Determination of Trace
Element Contents Part V: Determination of Gallium Content by
Extraction Separation-Rhodamine B Photometric Method". The aluminum
hydroxide content was 100% minus gallium hydroxide content, and
thereby the alumina content was calculated.
[0070] (5) Adding the aluminum-gallium double salt obtained from
step (4) into a sodium hydroxide solution of 180 g/l and keeping
the reaction at 25.degree. C. to obtain a base solution rich of
gallium, then adjusting the gallium content to 1.5 mol/l and
electrolyzing with platinum electrodes as the negative and positive
electrodes, the electrolysis current of 200 mA/l, electrolysis
voltage of 4V and electrolytic bath temperature of 40.degree. C. to
obtain metal gallium product. The gallium content in the product
was measured to be 99.9% according to the method of "YS/T520-2007
Methods for Chemical Analysis of Gallium".
Example 2
[0071] The operation conditions were the same as those of Example 1
except step (1). Step (1) was adjusted as follows:
[0072] Crushing the circulating fluidized-bed fly ash to a size of
150 mesh, removing iron by wet magnetic separation using the
vertical magnetic separator as illustrated in FIG. 3, such that the
ferric oxide content in the fly ash was reduced to 0.8 wt %;
putting the filtered cake of the fly ash obtained after magnetic
separation into an acid-resistant reactor and adding industrial
hydrochloride acid having a concentration of 28 wt % therein to
perform acid dissolving reaction, wherein the molar ratio of HCl
contained in the hydrochloride acid to alumina contained in the fly
ash was 5:1, the reaction temperature was 150.degree. C., the
reaction pressure was 1.0 MPa and the reaction time was 2 hours;
and then pressure-filtering the discharged reaction product by
means of plate-and-frame filter press and washing to yield a
hydrochloric leachate having pH of 1.5, wherein the leaching
efficiency of gallium from the fly ash was measured to be
82.8%.
[0073] The gallium content in the obtained product was measured to
be 99.9%.
Example 3
[0074] The operation conditions were the same as those of Example 1
except step (1). Step (1) was adjusted as follows:
[0075] Crushing the circulating fluidized-bed fly ash to a size of
200 mesh, removing iron by wet magnetic separation using the
vertical magnetic separator as illustrated in FIG. 3, such that the
ferric oxide content in the fly ash was reduced to 0.8 wt %;
putting the filtered cake of the fly ash obtained after magnetic
separation into an acid-resistant reactor and adding industrial
hydrochloride acid having a concentration of 20 wt % therein to
perform acid dissolving reaction, wherein the molar ratio of HCl
contained in the hydrochloride acid to alumina contained in the fly
ash was 8:1, the reaction temperature was 100.degree. C., the
reaction pressure was 0.1 MPa and the reaction time was 4 h; and
then pressure-filtering the discharged reaction product by means of
plate-and-frame filter press and washing to yield a hydrochloric
leachate having pH of 1.4, wherein the leaching efficiency of
gallium from the fly ash was measured to be 80.1%.
[0076] The gallium content in the obtained product was measured to
be 99.9%.
Example 4
[0077] The operation conditions were the same as those of Example 1
except step (2). Step (2) was adjusted as follows:
[0078] Cooling the hydrochloric leachate till its temperature was
90.degree. C. by means of heat-exchange, then pumping the
hydrochloric leachate through corrosion-resistant pump into the
resin columns (two columns in series and loaded with JK008 Resin
(Anhui Wandong Chemical Plant)) to enrich gallium, wherein the flow
flux of the hydrochloric leachate was 4 times over resin volume per
hour; and when the adsorption reached saturation, eluting the resin
column with 2 wt % hydrochloride acid as eluting agent at
60.degree. C. to obtain gallium-rich eluent, wherein the flow flux
of the hydrochloride acid was 1 time over resin volume per hour,
and the total amount of the eluting agent used for elution was 2
times over the volume of the resin and 4 wt % hydrochloride acid
was used for the regeneration of the resin, wherein the adsorption
efficiency of gallium in the acid leachate was measured to be
96.9%.
[0079] The gallium content in the obtained product was measured to
be 99.9%.
Example 5
[0080] The operation conditions were the same as those of Example 1
except step (2). Step (2) was adjusted as follows:
[0081] Cooling the hydrochloric leachate till its temperature was
70.degree. C. by means of heat-exchange, then pumping the
hydrochloric leachate through corrosion-resistant pump into the
resin columns (two columns in series and loaded with 732 Resin
(Anhui Sanxing Resin Ltd., Co)) to enrich gallium, wherein the flow
flux of the hydrochloric leachate was 1 time over resin volume per
hour; and when the adsorption reached saturation, eluting the resin
column with water as eluting agent at 60.degree. C. to obtain
gallium-rich eluent, wherein the flow flux of the water was 1 time
over resin volume per hour, and the total amount of the eluting
agent used for elution was 3 times over the volume of the resin and
the adsorption efficiency of gallium in the acid leachate was
measured to be 96.2%.
[0082] The gallium content in the obtained product was measured to
be 99.9%.
Example 6
[0083] The operation conditions were the same as those of Example 1
except step (2). Step (2) was adjusted as follows:
[0084] Cooling the hydrochloric leachate till its temperature was
40.degree. C. by means of heat-exchange, then pumping the
hydrochloric leachate through corrosion-resistant pump into the
resin column (single-column form and loaded with SPC-1 Resin
(Shanghai Resin Plant)) to enrich gallium, wherein the flow flux of
the hydrochloric leachate was 1 time over resin volume per hour;
and when the adsorption reached saturation, eluting the resin
column with 10 wt % hydrochloride acid as eluting agent at
30.degree. C. to obtain gallium-rich eluent, wherein the flow flux
of the hydrochloride acid was 3 times over resin volume per hour,
and the total amount of the eluting agent used for elution was 1
time over the volume of the resin and the adsorption efficiency of
gallium in the acid leachate was measured to be 96.5%.
[0085] The gallium content in the obtained product was measured to
be 99.9%.
Example 7
[0086] The operation conditions were the same as those of Example 1
except step (3). Step (3) was adjusted as follows:
[0087] Adding 240 g/l sodium hydroxide solution into the eluent, so
that the mass ratio of alumina to sodium hydroxide in the solution
was 2, and keeping reacting at 90.degree. C., subjecting the
reaction product to filtration to remove ferric hydroxide
precipitate to obtain a gallium-containing sodium metaaluminate
solution.
[0088] The gallium content in the obtained product was measured to
be 99.9%.
Example 8
[0089] The operation conditions were the same as those of Example 1
except step (4). Step (4) was adjusted as follows:
[0090] Introducing carbon dioxide gas with a flow rate of 160
ml/min into 100 ml of the gallium-containing sodium metaaluminate
mother solution obtained from step (3) at 90.degree. C., the pH was
controlled to 9.8, then filtering the resultant to finish the
primary carbonation; subjecting the filtrate obtained from the
primary carbonation to the secondary carbonation: further
introducing carbon dioxide gas with a flow rate of 150 ml/min at
60.degree. C., the pH was controlled to 9.0, then filtering the
resultant to obtain gallium-aluminum double salt precipitate. The
double salt was dissolved in the sodium metaaluminate mother
solution, and under the same conditions, the above primary and
secondary carbonations were repeated to obtain gallium-aluminum
double salt precipitate again. The mass ratio of gallium to alumina
in the latest double salt was measured to be 1/290.
[0091] The gallium content in the obtained product was measured to
be 99.9%.
Example 9
[0092] The operation conditions were the same as those of Example 8
except step (4). In step (4), after the twice carbonations as
described in Example 8, under the same conditions, the carbonation
was repeated for the third time to obtain a gallium-aluminum double
salt precipitate. The mass ratio of gallium to alumina in the
double salt was measured to be 1/120.
[0093] The gallium content in the obtained product was measured to
be 99.9%.
Example 10
[0094] The operation conditions were the same as those of Example 8
except step (5). Step (5) was adjusted as follows:
[0095] Adding the gallium-aluminum double salt obtained from step
(4) into a sodium hydroxide solution with a concentration of 240
g/l, and keeping reacting at 25.degree. C. to obtain a base
solution rich of gallium, then adjusting the gallium content to 1.1
mol/l and electrolyzing the base solution to obtain metal gallium
product.
[0096] The gallium content in the obtained product was measured to
be 99.9%.
* * * * *