CA1158597A - Electrolytic recovery of gallium or gallium and vanadium in alumina production - Google Patents
Electrolytic recovery of gallium or gallium and vanadium in alumina productionInfo
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- CA1158597A CA1158597A CA000333996A CA333996A CA1158597A CA 1158597 A CA1158597 A CA 1158597A CA 000333996 A CA000333996 A CA 000333996A CA 333996 A CA333996 A CA 333996A CA 1158597 A CA1158597 A CA 1158597A
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- gallium
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
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Abstract
ABSTRACT OF THE DISCLOSURE
A process for electrolytically recovering gallium or gallium and vanadium from alkaline liquors of the alumina production comprises conducting electrolysis on solid elec-trodes with a cathode current density between 200 and 1000 A/m2, at a voltage between 3.4 and 4.5 V, and at 28 to 37 C
in the presence of a metal previously introduced to start-ing alkaline liquors, which forms when electrolytically reduced together with gallium an alloy therewith which is not passivated under the electrolysis conditions, the concen-tration of said metal being between 0.15 and 5.0 g/l with a gallium concentration between 0.15 and 0.5 g/l. The process for electrolytically recovering gallium or gallium and vanadium concentrate from alkaline liquors may find applica-tion in the alumina production.
A process for electrolytically recovering gallium or gallium and vanadium from alkaline liquors of the alumina production comprises conducting electrolysis on solid elec-trodes with a cathode current density between 200 and 1000 A/m2, at a voltage between 3.4 and 4.5 V, and at 28 to 37 C
in the presence of a metal previously introduced to start-ing alkaline liquors, which forms when electrolytically reduced together with gallium an alloy therewith which is not passivated under the electrolysis conditions, the concen-tration of said metal being between 0.15 and 5.0 g/l with a gallium concentration between 0.15 and 0.5 g/l. The process for electrolytically recovering gallium or gallium and vanadium concentrate from alkaline liquors may find applica-tion in the alumina production.
Description
S~37 The present invention relates to processes for elec-trolytic recovery of gallium or gallium and vanadium from alkaline liquors resulting from alumina production.
The process of the present invention is useful in the manufacture of gallium or gallium and vanadium from alkaline liquors resulting from alumina production which liquors contain aluminates, carbonates, silicates, vana-dates, gallates, phosphates, molybdates, zincates, ferrites, chlorides, fluorides, polyvalent-sulphur compounds with al-kali metals, as well as organic compounds.
Gallium and vanadium, owing to their valuable specific .
properties, find an extensive use in such industries as nuclear energy, electronic and semi-conductor instrument manufacture, rocket engineering, metallurgy, optics and medicine.
The direct production of gallium from ores is not com-mercially implemented. Gallium is produced from productsfrom processing buaxites to alumina which contain substan-tially i ,, j 35 .. . . .
,, ' ' : -,, .: .
, g'7
The process of the present invention is useful in the manufacture of gallium or gallium and vanadium from alkaline liquors resulting from alumina production which liquors contain aluminates, carbonates, silicates, vana-dates, gallates, phosphates, molybdates, zincates, ferrites, chlorides, fluorides, polyvalent-sulphur compounds with al-kali metals, as well as organic compounds.
Gallium and vanadium, owing to their valuable specific .
properties, find an extensive use in such industries as nuclear energy, electronic and semi-conductor instrument manufacture, rocket engineering, metallurgy, optics and medicine.
The direct production of gallium from ores is not com-mercially implemented. Gallium is produced from productsfrom processing buaxites to alumina which contain substan-tially i ,, j 35 .. . . .
,, ' ' : -,, .: .
, g'7
-2-the rollowing components, per cent by ~ ~ alumina 50-60, iron oYides 15-25; silica 2-5; calcium o~ide 1-3.
In addition to these comp~nents a number oi rare ele-ments are present in bauxites including 1-2 kg/ton oi vanadium pento~ide and 0.02-0~07 kg/ton Or gallium.
Processing oi bauYites by the Bayer's ~ethod comprises leaching o~ aluminium o~ldes contained in the core, by means Or a solutian of caustic soda. At the same time, into the re-sulting aluminate solution gallium passes i~ an amount of abo-ut 75 per cent by mass in the ~orm o~ sodium gallate. Upon de-composition of aluminate solutions the predominant amount of gallium remains in the solution due to the formation of more durable, compared to aluminium, comple~ compounds (mother alu-minate liqu~r). ~he mother aluminate liquor, after separation oi aluminium hydroYide, is evaporated to a return aluminate li-quor and reeycled to leaching oi a new portion oi bauxite.
During circulation these liquors get enriche~ in gallium.
Under stationary proces~ conditioas gallium concentra-tion in liquors becomes constant and varies within the range o~ from 0.15 to 0.50 g/l. ~he concentration value depends on the cont~nt oi gallium in bau~ite, bauYite composition and pro-cess technology employed in alumina production.
In a similar manner proces~ing oi vanadium is per~ormed 11 ~8 5 in the above-dsscribed Bayer ~9 method.
- ~here~ore, ~or a commercial production oi gallium and vanadium rrom bauYite~ as the ~tarting materials use can be made o~ alumi~ate liquors.
Enown in the art is a process ~or a direct recovery o~ gallium ~rom alkaline lLquors re~ulting ~rom alumina pro-duction o~ a mercury cathode ~J. of ~etals, 1956, 8, p. 1528;
/est G~A~
. SWi8S Patent No. ~33,264; 1958i~g~ Patent No. 1,051,827;
1959~. -In accordance with this process, the mother aluminate liquor resulting from the Bayer's process is subjected te electrolysis on a liquid mercur~ cathode and nickel a~ode.
~he electrolysis is conducted under the ~ollowing conditions:
anodic current density 1,000-1,200 A/m2, cathodic current densitg, 35 to 45 A/m , duration o~ electrolysis 24 hours.
Under the~e conditions gallium is reduced on the cathode and diffuses into the bulk o~ mercury. To ~acilitate the processes oi di~u~io~ and renewal o~ the cathode sur~ace, an intensive agitation of the liquor and mercury is eirected. The electro-ly8is i8 stopped when O.5-1.O~0 by mas~ of gallium amalgam is obtained, since ~olubilitg o~ gallium i~ mercury at the tem-perature of 50C is L 5% by 4~. Gallium amalgam i~ decomposed by means of a ~olution oi caustic soda at the boiling tempera-.
~lS8597 ture o~ the resulting solution in the presence of metallia iron. a~ter carryi~g out ~everal abo~e-mentioned operatio~s 0i the amalgam deGomposition, the co~tent o~ gallium in the resulting gailate solution is as high as 30 to 80 g/l. From this solution gall~um is recovered in an electrolyzer with ~ ic ~
a steel,/niokol/,or liquid gallium cathode.
This process, however, reatures a low r~te o~ t~e pro-G cess Or gallium recovery, the use Or ~ ~ophisticated process eguipment, large amounts of mercury empl0yed i~ circulation (up to 3,000 kg in the case oi a ilat-bottom electrolyzer).
Furthermore, mercury is an excellent collector ior a number oi metals there~ore, the thus_produced gallium is generally strongly contaminsted w~h iron , nickel, lead, copper, molyb-denum.
It should be also ~oted that mercury employed tn this prior art proce~s has a high toYicity, while t~e rate o~ con-sumption oi mercury in the process is 2 kg per one kg oi gall-iu~. De~pite the severe measures ~or ensurin~ sa~ety oi ope-ratio~ wit~ mercury, the operating perso~cl ~ rrom time to time withdrawn irom the main production shops. Another problem as~ociated ~ith the production 0r gallium by thi~ prooess is la¢~ oi u~ers oi the va~adium slime co~taminated with mercury , ~ ~
- , ~
5~-~
which is simultaneously obtained as a by-product.
To reduce the amount of the mercury employed, Landi (Italy) has proposed an improved design of the electrolyzer, wherein a rotary cathode is used in the form of a hollow steel drum with the surface thereof coated with a thin layer of mercury (Aluminio, 195g, 5, 219).
Also known in the art is a process for a direct elect-rochemical recovery of gallium on a solid cathode fromalkaline liquors resulting from alurnina production (cf. US
Patent No. 3,667,918; 1972).
This process comprises recovery of gallium from said liquors by electrolysis using, as the cathode, steel, lead, or copper. As the anode use is made of steel, nickel or graphite. The electrolysis in this process is conducted under the following conditions: cathodic current density 1,000 A/m2, voltage 4 V, temperature 60-80C.
The electrolysis is conducted after a preliminary ef-fective purification of the liquors from impurities hind-ering recovery of gallium, namely: vanadium, iron, copper and organic compounds.
Purification from vanadium is conducted by way of reducing soluble pentavalent vanadium compounds to tri-valent compounds insoluble in alkaline solutions.
In addition to these comp~nents a number oi rare ele-ments are present in bauxites including 1-2 kg/ton oi vanadium pento~ide and 0.02-0~07 kg/ton Or gallium.
Processing oi bauYites by the Bayer's ~ethod comprises leaching o~ aluminium o~ldes contained in the core, by means Or a solutian of caustic soda. At the same time, into the re-sulting aluminate solution gallium passes i~ an amount of abo-ut 75 per cent by mass in the ~orm o~ sodium gallate. Upon de-composition of aluminate solutions the predominant amount of gallium remains in the solution due to the formation of more durable, compared to aluminium, comple~ compounds (mother alu-minate liqu~r). ~he mother aluminate liquor, after separation oi aluminium hydroYide, is evaporated to a return aluminate li-quor and reeycled to leaching oi a new portion oi bauxite.
During circulation these liquors get enriche~ in gallium.
Under stationary proces~ conditioas gallium concentra-tion in liquors becomes constant and varies within the range o~ from 0.15 to 0.50 g/l. ~he concentration value depends on the cont~nt oi gallium in bau~ite, bauYite composition and pro-cess technology employed in alumina production.
In a similar manner proces~ing oi vanadium is per~ormed 11 ~8 5 in the above-dsscribed Bayer ~9 method.
- ~here~ore, ~or a commercial production oi gallium and vanadium rrom bauYite~ as the ~tarting materials use can be made o~ alumi~ate liquors.
Enown in the art is a process ~or a direct recovery o~ gallium ~rom alkaline lLquors re~ulting ~rom alumina pro-duction o~ a mercury cathode ~J. of ~etals, 1956, 8, p. 1528;
/est G~A~
. SWi8S Patent No. ~33,264; 1958i~g~ Patent No. 1,051,827;
1959~. -In accordance with this process, the mother aluminate liquor resulting from the Bayer's process is subjected te electrolysis on a liquid mercur~ cathode and nickel a~ode.
~he electrolysis is conducted under the ~ollowing conditions:
anodic current density 1,000-1,200 A/m2, cathodic current densitg, 35 to 45 A/m , duration o~ electrolysis 24 hours.
Under the~e conditions gallium is reduced on the cathode and diffuses into the bulk o~ mercury. To ~acilitate the processes oi di~u~io~ and renewal o~ the cathode sur~ace, an intensive agitation of the liquor and mercury is eirected. The electro-ly8is i8 stopped when O.5-1.O~0 by mas~ of gallium amalgam is obtained, since ~olubilitg o~ gallium i~ mercury at the tem-perature of 50C is L 5% by 4~. Gallium amalgam i~ decomposed by means of a ~olution oi caustic soda at the boiling tempera-.
~lS8597 ture o~ the resulting solution in the presence of metallia iron. a~ter carryi~g out ~everal abo~e-mentioned operatio~s 0i the amalgam deGomposition, the co~tent o~ gallium in the resulting gailate solution is as high as 30 to 80 g/l. From this solution gall~um is recovered in an electrolyzer with ~ ic ~
a steel,/niokol/,or liquid gallium cathode.
This process, however, reatures a low r~te o~ t~e pro-G cess Or gallium recovery, the use Or ~ ~ophisticated process eguipment, large amounts of mercury empl0yed i~ circulation (up to 3,000 kg in the case oi a ilat-bottom electrolyzer).
Furthermore, mercury is an excellent collector ior a number oi metals there~ore, the thus_produced gallium is generally strongly contaminsted w~h iron , nickel, lead, copper, molyb-denum.
It should be also ~oted that mercury employed tn this prior art proce~s has a high toYicity, while t~e rate o~ con-sumption oi mercury in the process is 2 kg per one kg oi gall-iu~. De~pite the severe measures ~or ensurin~ sa~ety oi ope-ratio~ wit~ mercury, the operating perso~cl ~ rrom time to time withdrawn irom the main production shops. Another problem as~ociated ~ith the production 0r gallium by thi~ prooess is la¢~ oi u~ers oi the va~adium slime co~taminated with mercury , ~ ~
- , ~
5~-~
which is simultaneously obtained as a by-product.
To reduce the amount of the mercury employed, Landi (Italy) has proposed an improved design of the electrolyzer, wherein a rotary cathode is used in the form of a hollow steel drum with the surface thereof coated with a thin layer of mercury (Aluminio, 195g, 5, 219).
Also known in the art is a process for a direct elect-rochemical recovery of gallium on a solid cathode fromalkaline liquors resulting from alurnina production (cf. US
Patent No. 3,667,918; 1972).
This process comprises recovery of gallium from said liquors by electrolysis using, as the cathode, steel, lead, or copper. As the anode use is made of steel, nickel or graphite. The electrolysis in this process is conducted under the following conditions: cathodic current density 1,000 A/m2, voltage 4 V, temperature 60-80C.
The electrolysis is conducted after a preliminary ef-fective purification of the liquors from impurities hind-ering recovery of gallium, namely: vanadium, iron, copper and organic compounds.
Purification from vanadium is conducted by way of reducing soluble pentavalent vanadium compounds to tri-valent compounds insoluble in alkaline solutions.
3 ~ ~
The reduction is effected by the addition, into the starting alkaline liquor resulting from alumina produc-tion, of sodium hydrosulphite at a temperature of from 60 to 80C under vigorous stirring. Reducing said vanadium compounds can also be effected by means of hydrogen which is obtained both by dissolution of granulated aluminum in the aluminate liquor and electrolysis of alkaline liquors with the use of amalgamated cathode. Satisfactory results are obtained also with the use of membranes made of un- -glazed porcelain which are placed around the electrodes.
Impurities OL copper and iron are eliminated from said liquor by reduction thereof with sodium hydrosulphite with a subsequent filtration of the purified liquor; for the removal of organic compounds the liquor is treated with activated coal at a temperature within the range of from 60 to 80C at the rate of 1 g of activated coal per one litre of the liquor.
This prior art process features the necessity of the preliminary effective freeing of aluminate liquors from impurities; sophisticated process equipment employed, a low current yield of gallium (0.27%) and a high rate of consumption of electric power (1,700 kW.hr per 1 kg of gallium) ~, s~
Another known process for electrolytic recovery of gallium from aluminate liquors (cf. French Patent No.
2,237,991;1975; British Patent No. 1,436,260; 1976) com-prises recovery of gallium at a cathodic current density of from 20 to 500 A/m2 on a solid cathode manufactured from a metal, whereinto reduced gallium diffuses till its con-tent in the superficial layer of the cathode is equal to 0.1-0.5~ by weight. As the cathode material use may be made of tin, lead, indium, zinc or an alloy of tin and lead made as a thin plate with a thickness of from 0.01 to 0.3X 103 micrometers or as a thick block of said metals.
The cathode may be also made of an inert material such as stainless steel coated with said metals to the thickness of from 1 to 50 micrometers. As the anode use is made of platinum, platinized titanium, stainless steel, nickel, aluminium. The electrolysis is conducted at a temperature within the range of from 25 to 80C.
Gallium is separated from the cathode by physical me-thods or by treating the cathode with a molten flux con-sisting of a molten alkali metal hydroxide at a temperature within the range of from 220 to 800C.
This prior art process, however, has the following disadvantages:
~:r - 7 -~ ", - 8 ~1~85~7 - a low rate of gallium recovery (the process duration is as long as 20 hours) which is associated with diffusion of.gallium into the bulk of the substrate metal;
- complicated process technology due to the use of consumable cathodes;
- the use, as the consumable cathodes, of rarely-avail-able and expensive metals;
- complicated and labour-consuming technology of reco-vering gallium from the cathode material.
The present invention provides such a process for elec-trolytic recovery of gallium or gallium and vanadium from alkaline liquors of alumina production which would make it possible to increase the degree of recovery of gallium or gallium and vanadium and enable the use of starting materials with substantially any contcnt of gallium and vanadium therein.
According to the present invention there is provided a process for electrolytic recovery of gallium or gallium and vanadium from alkaline liquors resulting from alumina production by electrolysis on solid electrodes, wherein, said electrolysis is effected at a cathodic current density ~:
of from 200 to 1,000 A/m , at a voltage of 3.4 to 4.5 V and at a tempjerature from 28 to 37 C in the presence of a metal ; ~rclimina~ily introduced into starting liquors which forms an alloy with gallium when it is electrolytically reduced together therewith (in the form of an electrolytic precipi-tate), which is not passivated under the electrolysis condi-tions, the concentration of such metal being between 0.15 and 5.0 g/l with th.e gallium concentration being between 0,15 and 0.5 g/l.
In accordance with the invention, a metal prcliminaYrily introduced into starting liquors is a metal selected from the group consisting of zinc, tin and lead. These metals form precipitates containing gallium or gallium and vanadium ,; :-.: f ' ' ~s~s~
during electrolysis, owing to their electrochemical pro-perties.
These metals are present in starting liquors in the form of an oxide, soluble inorganic salt, or pure metal.
In the process according to the invention, for recovery of gallium or gallium and vanadium, starting alkaline liqu-ors of the alumina production for gallium recovery should comprise a solution, selected from the group including mot~er aluminate Bayer process liquor, recirculation alum-inate Bayer process liquor, and mixture thereof, as well as recirculation aluminate Bayer process liquor diluted with water in a ratio (vol. ~):
recirculation liquor 10 - 90 water the balance.
This makes it possible to use liquors more concen-trated in terms of gallium compared to aluminate mother liquors and less concentrated compared to recirculation aluminate liquors.
To improve the efficiency of the process of electro-lytic recovery of gallium, the alkaline liquors of the alumina production should comprise filtered liquor which is prepared by repulping of sodium carbonate precipitate formed from the Bayer process recirculation liquor during its vaporization with water at between 50 and 100C.
~7 f~- _ g _ S~3';J
In the process according to the present invention, upon electrolysis of alkaline liquors resulting from alumina production use is made of DC, pulsating current, reversible current as well as various combinations thereof. This tech-nique makes it possible to substantially increase the degreeof recovery and current yield of gallium or gallium and vanadium, increase the content of these components in the electrolytic deposit, as well as reduce the rate of power consumption.
In order to eliminate contamination of the startin~
alkaline liquors resulting from alumina production and con-tamination of the desired products ~gallium or gallium and vanadium), in accordance with the present invention as the ~' , :
: .
." , " ~ ' ` ' ' ' ` ' 3'7 .
electrodes used should be made of metals resistant in alkaline media, i.e. steel, nickel, titanium. Said metals possess a satisfactory adherence to the electrolytic de-posit containin~ the metzlintroduced into the starting li-quor and gallium, or gallium and vanadium.
In the process according to the present invention, for increasing efficiency of the electrolytic recovery of gal-lium or gallium and vanadium use is made of water-cooled cathodes.
In the case where the starting alkaline liquor result-ing from alumina production contains polyvalent sulphur compounds it is advisable, for combining said sulphur com-pounds, to charge said metal, apart from the above-spe-cified amount thereof, into the liquor prior to the ele-ctrolysis in an additional amount stoichiometric in respect of the content of polyvalent sulphur compounds in the starting liquor. This enables an additional purification of alkaline liquors resulting from alumina production, improve quality of alumina and make use of bauxites with an increased content of pyrite minerals.
According to the process of the present invention, it is advisable that the electrolysis be effected to a resi-dual concentration of the metal introduced into the starting liquors resulting from alumina production equal to ~7 - 11 -; , :-: ' - , .. :
.
:
9~
0.020-0.005 g/l. This makes it possible to minimize contami-nation of alkaline liquors resulting irom alumina production with ~oreign impurities.
The process according to t~e present invention is simple, efiective and integrall~ combined wi~ the production o~ alu-mina; it makes possible to produce gallium or gallium and va-nadium directly ~rom alkaline liquors resulting ~rom alumina production o~ substantially any comp~sition, to use the start-ing materials with both high and low content of gallium, vana-dium 1 pyrite and carbonate minerals.
The process according to the present invention makes it possible to eliminate the preliminary puri~ication of al-kaline liquors resulting ~rom alumina productio~ ~rom impuri-ties hindering electrolysis such as vanadiu~, copper, iron, polyvalent sulphur compoundæ and organic compounds; eliminate the use and consumption o~ to~ic (mercury) and expe~sive (tin, indium, lead) materialæ; employ standard electrolyzers thus makin~ it possible to combine recovery o~ gallium o~ gallium and vanadium with a simultaneous p~rifioation of alkali~e li ~uors from harm~ul impurities (iron, lead, copper, titanium, polyvalent sulphur compounds).
~ he proce~s according to the present invention can be easily automated; it reduces capital e~penses ior the produc-~lS8~
tio~ o~ gallium. The repay period o~ a plant producing annual-ly 10 tons o~ gallium is not longer than one year.
The procéss according to the present invention is ei-fected in the ~ollowi~g manner.
A9 the starting alkaline liquors resulting from alumi~a produ¢tion use is made o~ the liquors obtained in processing o~ bauxites b~ the sinterin~ method or Bayer's method.
It i9 preferable to use aluminate li~uors resulti~g from Bayer's process owing to a higher content of galliu~ therein~
The mother liquors produced in proce~sing of bauxites according to Bayer contain, on the average, the ~ollowing com-po~ents in the amounts speci~ied hereinbelow, g/l: sodium oxide-- 130-180; alumina 60-80; silica 0~3-0.6; iron oxida 0.004 -- 0.006; organic compounds - 1.5 - 2.0 (a~ oalculated ~or oYy-ge~ b~ potassium permanganate), total sulphur 2.5-~.5 including ~ulphide sulphur 0~5-0.8, thiosulphate sulphur 1.0-1.2; sul-phite sulphur 0.2-0.4, sulphate sulphur 0.8-1.1~
f e. c, r C ~ o r7 C The Pe~u~n aluminate liquors contain, on the average, g/ls s~dium oYide 260-~20; alumina - 120-160; silica - 0.6-1.2 iro~ oxide - 0.01 - 0.015; organic compounds - 3.0-4.0; total sulphur - 5.0-7.0 including sulphide sulphur 1.0-1.6; thiosul-; phate sulphur 2.0-2.4; sulphite sulphur - 0.4-0.8; sulphate sulphur - 1.6-2.2.
.
~151 35~37 Concentration of gallium and vanadium in mother alu-minate liquors is respectively 0.15 - 0.25 and 0.16 - 0.28 g/l; in recirculation aluminate liquors concentration of gallium and vanadium is respectively 0.30 - 0.5G and 0.32 -0.56 g/l.
For electrolytic recovery of gallium or gallium andvanadium use can be made of both above-specified and other liquors. In both cases recovery of gallium into the ele-ctrolytic deposit within 4 hours of electrolysis is 40 to80%, that of vanadium is 10 to 40%. It has been found that the best results on recovery of gallium or gallium and vanadium occur in using a mixture of the above-men-tioned aluminate liquors (mother or recirculation) or re-circulation aluminate liquor of the Bayer process dilutedwith water with a ratio (vol. %):
recirculation liquor 10 - 90 water the balance.
The electrolysis of the recirculation aluminate liquor itself is hindered and economically inefficient due to a high concentration of sodium oxide therein and, con-sequently, increased viscosity and electrical resistance of this liquor thus causing a considerable foam-formation and voltage rise in the electrolyzer.
In order to increase the content of gallium in the liquor and lower concentration of sodium oxide therein, use is made of liquors prepared by repulpation with water at , 35 i ::
. , . , : ' ` :: :.... .
~8~
a temperature within the range of from 50 to 100C, of sodium carbonate precipitated from the recirculation al-uminate liquor resulting from the Bayer process during its vaporization.
Prior to electrolysis, into any of the above-specified ~ uors is introduced a metal forming, when the liquor is reduced electrolytically, together with gallium an alloy which is not passivated under the electrolysis conditions, the concentration of such'metal being between 0.15 and 5.0 g/l with a concentration of gallium of 0.15 - 0.5 g/l.
~urthermore, said metal has the structure and parameters of crystal lattice similar to those of gallium, as well as the recovery potential approaching that of gallium. The metal introduced into starting liquors is selected from the group consisting of zinc, lead and tin. This metal is introduced into hot alkaline solutions resulting from alumina production,either per se or in the form of an oxide, an inorganic salt soluble in said liquors. It is prefer-able to use zinc which is not passivated upon electrolysis,has a high overtension relative to hydrogen (~.7 V), a recoVery potential close to that of gallium (i e.-1.220 V
for Ga and -1.216 V for Zn), as well as similar structure and parameters of crystal lattice. During electrolysis zinc, while being deposited on a solid cathode, renews its surface, whereby the deposition of gallium or gallium and ` vanadium occurs on the zinc cathode. These factors facili-tate the process of re-"
~,' ~ ~ , ~ ~ , - -.
duction of ions of gallate and vanadate on the cathode.
In the case where in the starting alkaline liquor re-sulting from alumina production polyvalent sulphur com-pounds are present, for the purpose of introducing thelatter into said liquor, prior to electrolysis, an add-itional portion of the metal forming an alloy with gallium non-passivating under electrolysis conditions added in the stoichiometric amount relative to the polyvalent sulphur compounds. In doing so, taken into account is the de-composition of thiosulphate sulphur compounds during ele-ctrolysis to compounds of sulphide sulphur and sulphate sulphur.
An alkaline liquor from alumina production containing the introduced metal is subjected to electrolysis on solid electrodes under the following conditions:
cathodic current density of from 200 to l,000 A/m ;
voltage 3.4 to 4.5 V; process temperature of from 28 to 37C. As the electrode material use is made of metals resistant in alkaline media, namely: steel, nickel, titan-ium.
It is advisable that the cathode be cooled with water in order to raise the electrolysis temperature due to a lower temperature of the cathode surface and increased temperature within the bulk of the solution. As a result, the liquor vis-. ~ ,, , , ., , , ... , . ~ .- , ..
: :
.
s~
cosity is lowered and the voltage on the electrolyzer is decreased.
To improve the efficiency of the process, increase the current yield of gallium or gallium and vanadium, the electrolysis is conducted using direct, pulsating or reversing current, as well as various combinations of said currents.
The resulting electrolytic deposit is removed from the cathode by any conventional method such as mechanical or chemical ones, while the liquor with the residual con-centration of the introduced metal of from 0.02 to 0.005 g/l is recycled back to the production of alumina.
Gallium or gallium and vanadium are recovered from the resulting electrolytic deposit by any conventional method such as vacuum-thermal treatment. Furthermore, it is pos-sible to recover gallium or gallium and vanadium by dis-solution of the electrolytic deposit is acids or alkalis.Thereafter, gallium is recovered from the resulting solu-tions electrolytically, while vanadium remains in the solu-tion as a slime of vanadium concentrate and is then filter-ed-off. Gallium produced by this process contains, as the principal impurity, 2 to 6% by mass of the metal added to the liquor for electrolysis.
Production of metallic gallium conta;ning the above-.
; 35 , ~ - 17 -,. , ~ ~ , ~. I . , , , , . , ::
, ' . . ; 1', " . :
. ~ :
8~
mentioned amount of the metal added to the starting liquor, for example zinc, facilitates the production of gallium having much smaller amounts of other impurities. It is known that in the case of presence of zinc in gallium in the above-specified amount activity of gallium is lowered, wherefore solubility therein of other impurities is sub-stantially reduced. The removal of zinc by conventional methods such as acid treatment or vacuum-thermal treat-ment is performed without any troubles.
For a better understanding of the present invention, some specific Examples illustrating the process of re-covery of gallium or gallium and vanadium are given here-inbelow.
Example 1 A recirculation aluminate liquor resulting from Bayer's process in the amount of 48 1 having the following composi-tion as to the content of the main components, g/l; sodium oxide 310; alumina - 138; silica - 0.9; iron oxide -0.019; organic compounds - 3.89; gallium - 0.43; vanadium - 0 35, is diluted with 13 1 of water (in vol. ~) recircu-lation liquor - 78, water - 22. Then to the liquor heated to the temperature of 90C there are added 112 g of zinc oxide under stirring. The resulting liquor having the following composition, g/l: sodium oxide - 250; alumina -112; silica - 0.72; iron o~cide - 0.008; organic com-,:
1~ ~&~
pounds -3.14; gallium - 0.35; vanadium - 0.28 and zinc -1.5 is fed into the electrolyzer with the working `capacity of 60 litres. Electrolysis is carried out using direct current under the following conditions:
cathodic current density 650 A/m2, volt~ge 3.8 V, temperature 32C. The material of anode - steel lX18H9T, the material of cathodes - nickel.
After 4 hours of electrolysis the following metals are recovered as a percentage of their total amounts: gal-lium - 57; vanadium - 20; zinc - 98.
The thus-produced electrolytic deposit is removed from the cathode mechanically, while the liquor after electrolysis with the residual concentration of zinc of 0.03 g~l is recycled to the production of alumina.
The electrolytic residue is washed with water to re-move sodium oxide and other soluble impurities, dried and subjected to vacuum-thermal sublimation to remove zinc.
The residue obtained after the vacuum-thermal sublimation contains gallium and vanadium; this residue is dissolved in 3litres of a hot solution of caustic soda with the concentration of 150 g/l as calculated for sodium oxide.
The vanadium concentrate is precipitated and the precipi-tate is separated by filtration, while the solution con-taining gallium in the amount of 4 g/l .. ,~,,~ -- 1 9 ,~, "b~,"
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'''`'.`, ~ ''''.,"' ' ~''' ::""' ' ,.' ;`', `':':
115~S~7 is subjected to electrolysis on a nickel cathode a~ the cathodic current density of 1,200 A/m2 and the tempera-ture of 60C.
5The total amount of the recovered gallium is 11.4 g;
that of vanadium concentrate is 8.1 g.
The thus-produced metal contains, per cent by mass:
gallium - 96.997; zinc - 3.0; lead - 1.10 3; copper - 1.10 3, aluminium - 1~10 3; and other impurities are not detected.
The vanadium concentrate contains, per cen by mass:
vanadium pentoxide - 84.1; sodium oxide - 10.0; silica -2.Q; gallium- 0.2; zinc - 3.7.
After treatment of the resulting metallic gallium with hydrochloric acid diluted with water in the ratio of 1:2 (by volume) at the temperature of 60C, the content of gal-lium in the product is 99.998% by mass.
Example 2 The recirculation aluminate liquor resulting from Bayer's process in the amount of 40 1 having the composi-tion described in the foregoing Example 1 is mixed with 20 1 of the mother aluminate liquor from the Bayer process (in vol. %) mother liquor - 33.3 recirculation liquor -66.6 of the composition in terms of basic components, g/l:
sodium oxide -173; alumina -75.1; silica -~S859'7 - Q.42; iron oxide - 0.005; organic compounds - 1.94;
gallium - 0.19; vanadium - 0.17. The volume ratio of the liquors IS 1: O. 5. Then, into the resulting liquor 110 g of zinc oxide are added using the procedure described in the foregoing Example 1. The.resulting liquor having the following composition, g/l: sodium oxide - 264; alumina - 117; silica - 0.74; iron oxide - 0.008; organic substi-tutes - 3..24;.gallium -Ø35; vanadium - 0.29 and zinc - 1.5 is subjected to electrolysis in a manner similar to that of Example 1, except that the cathodic current density is equal to 1,000 A/m2 at the voltage of 4.1 V.
After 4 hours of electrolysis the following metals are recovered, as a percentage of their starting amounts;
gallium - 63; vanadium - 2~; zinc - 96.
The resulting electrolytic deposit is removed from the cathodes and processed to gallium and vanadium concentrate in a manner similar to that of Example 1 hereinabove.
The total amount of the recovered gallium is 12.5 g;
that of vanadium concentrate is 10.1 g.
The composition ofthe resulting products is similar to that indicated in Example 1.
Example 3 The recirculation and mother liquors resulting from 30 Bayer's pro- - -''' ~'"' . ' s .. . .~
. . :, :
.
:. : ...
.
~5~
cess haviny compositions according to Examples 1 and 2 res-pectively are mixed (in vol. %~ mother li~uor - 90 recir-culation liquox - 10 then..to 6Q 1 of the prepared liquor 67.5 g of zinc oxide are introduced by the method described in Example 1. The resulting solution having the following composition, g/l: sodium oxide - 187; alumina - 81.3;
silica - 0.47; iron oxide - 0.006; organic compounds - 2.13;
gallium - 0.21; vanad~um - 0.19 and zinc - 0.9 is subjected to electrolysis as described in Example 1.
After 4 hours of electrolysis the following metals are recovered, as a percentage of their starting amounts: gal-lium 48; vanadium - 15; zinc - 96.
The total amount of the recovered gallium is 5.7 g;
that of vanadium concentrate is 3.5 g.
The composition of the resulting products is similar to that of Example 1.
Example 4 Into 60 1 of a liquor prepared in a manner similar to that described in Example 3 there are introduced 109 g of zinc oxide. The resulting solution of the following compo-sition, g/l: 187 - sodium oxide; alumina 81.3; silica _ 0.47;
~ - 22 -115~SS:3 ~
iron oxide - Q.006; organic compounds - 2.13; gallium - 0.21; vanad~um - 0.19; Zinc - 1.47 is subjected to ele-ctrolysi~s as described in Example 1.
After 4 hours of electrolysis the following metals are recovered, percentage of their initial amounts: gal-lium - 65; vanadium - 37; zinc - 97.
The thus-produced electrolytic deposit is removed from the cathodes and processed to gallium and vanadium con-centrate in a manner similar to that of Example 1.
The total amount of the recovered gallium is 7.8 g;
that of vanadium concentrate is 8.5 g.
The composition of the resulting products is similar to that described in Example 1 hereinbefore. ~ .
Example 5 The liquor prepared in a manner similar to that de-scribed in Example 1 and having composition as indicated in the same Example 1, except that the content of zinc is 3.5 g/l is subjected to electrolysis as described in Example 1.
After 4 hours of electrolysis the following metals are recovered, percentage of their initial amounts: gallium - 38; vanadium - 10; zinc - 90.
: . . ; : .
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The resulting electrolytic deposit is removed from the cathodes and processed to gallium and vanadium concen-trate in a manner similar to that of Example 1.
The total amount of the recovered gallium:is 7.6 g;
that of vanadium concentrate is 5.8 g.
The composition of the resulting products is similar to that described in Example 1.
Example 6 The recirculation and mother liquors resulting from Bayer's process having the compositions indicated in Examples 1 and 2 respectively are mixed (invol. %) mother liquor - 10 and recirculation liquor - 90. Then to 60 1 of the prepared liquor 127 g of zinc oxide are added using the method described in Example 1 hereinbefore. The resulting liquor having the following composition, g/l: sodium oxide - 296; alumina - 132; silica - 0.85; iron oxide - 0.018;
organic substitutes - 3.69; gallium - 0.41; vanadium - 0.33 and zinc - 1.77 is subjected to electrolysis as described in Example 1, at a voltage of 4.5 V.
After 4 hours of electrolysis the following metals are recovered, percentage of their starting amounts: gallium - 40; vanadium - 13; zinc - 97.
~r - 24 -1~
~ he resultin~ electrolytic deposit is removed from the cathodes and processed to gallium and vanadium ooncentrate as described in Example 1.
The total amount o~ the recovered gallium i9 9.3 g;
that o~ vanadium concentrate is 5.4 g.
~ he composition of the resulting products i9 similar to that described in Example 1 hereinbefore.
~ xample 7 The residue obtained after settling and filtration o~
r C C / rc ~ f / ~
~r the roturn alumi~ate li~uor resulting from Bayer's process is repulped with water for 8 hours at the temperature of 60C.
Then the re~ulting solution is filtered-off to separate it from the residue insoluble in water. The resulting filtrate has the following composition, g/l: sodium oxide - 246; alu-mina - 92j gallium - 0.4; iron oxide - 0.04. Into this filt-rate taken in the amount of 60 litres 1.5 g/l of zinc are introduced as described in Example 1. Afterwards, electrolys-is is conducted u9ing DC under the ~ollowing conditions:
cathodic current density of 400 A/m2, v~ltage 3.4 V; tempe-rature 30C. The material of a~ode~ i9 steel 1~18~9T; material o~ the cathode~ is nickel.
A~ter 4 hours of electrolysis the following metals are ~' , ~ 5~
recovered, percentage of their initial amounts: gallium - 75; zinc - 98.
The removal of the residue and processing thereof to metallic gallium is effected as in Example 1.
The total amount of gallium recovered is 18 g.
The composition of the resulting product i.e. metallic gallium is similar to that indicated in Example 1 herein-before.
Example 8 lS The recirculation aluminate liquor resulting from Bayer's process and having the composition according to Example 1, but containing no vanadium is diluted with water (invol. %) recirculation liquor - 78,~ater - 22. Then to 60 1 of the solution heated to the temperature of 100C 45 g of lead 20 oxide are added under stirring. The resulting liquor having the following composition, g/l: sodium oxide - 250; alumina - 112; silica - 0.72; iron oxide - 0.008; organic compounds - 3.14; ~allium - 0.35; and lead - 0.7 is subjected to ele-ctrolysis as in Example 1. After 4 hours of the electroly-sis the following metals are recovered from the liquor, per-centage of their initial amounts: gallium - 69; lead - 98.
The resulting electrolytic deposit is removed from the cathode mechanically, while the liquor after electrolysis with the residual lead concentration of 0.005 g/l is re-cycled to the pro-.
5~
ductiqn of alumina.
The electrolytic deposi~t is dissolved in 3 1 of sul-phuric acid with the concentration of 210 g/l heated to the temperature of 60C. The lead-containing precipitate is separated by filtration and the solution is neutralized with a 5% solution of ammon~a to precipitate gallium hydr-oxide. The latter is dissolved in 3 1 of a solution of caustic soda with the concentration of 150 g/l as calculated for sodium oxide. The resulting solution with the concen-tration of gallium of 4.4 g/l is subjected to electrolysis in a manner similar to that described in Example 1.
The total amount of recovered gallium is 12.5 g.
The resulting metal contains gallium in the amount of 99.98% by mass.
Example 9 To 60 litres of the liquor prepared as described in Example 1, but containing no vanadium, 112 g of zinc oxide are added. The resulting liquor having the following com-position, g/l: sodium oxide 250; alumina 112; silica 0.72;
iron oxide 0.008; organic compounds 3.14; gallium 0.35 and zinc 1.5 is subjected to electrolysis as described in Example 1, but with the cathodic current density of 300 A/m2 at the voltage of 3.4 V.
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After 4 hours of electrolysis the following metals are recoyered, percentage of thei-r initial amounts:
gallium - 46; zinc - g8. The resulting electrolytic de-posit is removed from the cathodes and processed to gallium in a manner similar to that described in Example 1.
Example 10 The recirculation and mother liquors resulting from Bayer's process having compositions indicated in Examples 1 and 2 respectively but containing no vanadium are mixed (in vol. %) mother liquor - 44, recirculation liquor - 56.
Thereafter, 119 g of zinc oxide are added to 60 1 of the thus prepared liquor. Thus, liquor has the following com-position, g/l: sodium oxide - 250; alumina - 110; silica - 0.63; iron oxide - 0.012; organic compounds - 3.02; gal-lium - 0.32 and zinc - 1.6 is subjected to electrolysis using direct current under the following conditions: cath-odic current density 700 A/m2; voltage 3.9 V; temperature 30C. The material of the anodes is nickel; that of the cathodes is lead.
After 4 hours of electrolysis the following metals are recovered, percentage of their initial amounts: gallium - 70; zinc - 98.
The removal of the resulting electrolytic deposit and ~'f .....
S~3 processing thereo~ to metallic gallium i9 conducted in a man-ner similar to th~t described in B~ample 1.
The total amount oi reoovered gallium is 12.7 g. The thus-produced metal ¢ontai~s, % b~ ma~s: gallium -94.788;
zinc - 5 2, lead - 1.10-2; c0pper - 1.10-~; aluminium - 1.10-3.
,~ No other impurities are deteoted. ~iter treatment o~ the result-~ng metallic gallium with hydrochloric acid di~uted with ~ater in the volume ratio 0f 1:2 at t~e temperature of 60C it con-tains 99.988 ~ by mass oi gallium.
~xample 11 Preparation and electrolysis o~ liquors are efiected as in ~Yample 10, e~cept t~at electrolysis is a0nducted at the temperature o~ ~C and at the v01t~ge of 3.7 V. T~e ma-terial oi the anodes i8 niokel~ that oi eathode~ - steel 1~18H9T.
~he ¢athodes are cooled with water.
After 4 hours of ele¢trolysis the ~ollowing metals are rec0vered, percent~ge o~ their initi~l amounts: gallium - 65;
zina - 97~
~ he resulting electrolytic deposit i9 removed ~rom the cathodes and processed to gallium iollowing the procedure oi E~ample 1 hereinberore.
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The total amount of the recovered gallium i5 11. 9 g.
The composition of the product i.e. metallic gallium is similar to that indicated in Example 1.
Example 12 To 60 1 of the mother aluminate liquor resulting from Bayer's process and having the composition mentioned in Example 2 zinc is introduced in an amount of 1.9 g/l and electrolysis is conducted using direct current under the following conditions: cathodic current density 550 A/m ;
voltage 4.1 V; temperature 28C. The material of the anodes - steel lX18N9T; the material of the cathodes - tit-anium.
After 4 hours of electrolysis the following metals are recovered from the liquor, percentage of their initial amounts: gallium 51; zinc - 97.
The removal of the electrolytic deposit and processing thereof to metallic gallium are performed as in Example 1.
The total amount o~ the recovered gallium is 5.5 g.
The composition of the resulting product i.e. metallic gal-lium is similar to that indicated in Example 1 hereinbefore.
Example 13 10 1 of the liquor prepared as in Example 10 are sub-jected to electrolysis using pulsating current (current switch-11S8~9'7 :
Oir interval i8 0.5 sec; ~requency o~ ~witahin~ is 1 æwitch-ing per mi~ute) uuder the iQlloWi~g conditions: cathodic cur-rent density is 650 A/m2, voltage 3.8 V, temperature 30C. ~he material of the anodes i~ steel lX18H9~, that of the cathodeæ
- nickel. T~e cathodes are cooled with water.
Arter 4 hours oi electrolysis the following metalæ are recovered from the li~uor, percentage of their initial amo-unt~: gallium - 82; zinc - 98.
The removal Or the electrolytic deposit and processing t~ereof to metallic gallium are periormed as in Example 1.
~ he tobal amount oi the recovered gallium is 2.49 g.
f~'5cf~Cf~
The composition oi the resulti~g/gallium i8 similar to that described in hxample 1 hereinbefore.
Ex~mple 14 10 1 of the liquor prepared as in ~Xample 10, are su~-~ecbed to electrolysis using reversing current (time oi anodic polarization is 0.2 sec; frequency of switching - 4 switching~
per minute). ~h~ condition~ of electroly i~ and materials oi the elect~odes are the same as in the foregoing Example 13.
Arter 4 houre of electrolysis the iollowing metals are recovered from the liquor, percentage of their initial amounts gallium - 75; zinc - 98.
- ' ' . , .
, " . , , , , , . ,, ~ :~
The removal o~ the electrolytic deposit and process-ing thereof to metallic ~allium are conducted as in Example 1, The tobal amount of the recovered gallium is 2.28 g.
The resulting metal contains, % by mass: gallium - 95.
996; zinc - 4.0; lead - 1.10 3; copper - 1.10 3; aluminium - 1.10 3; iron - 1.10 3. No other impurities are detected.
After treatment of the resulting metallic gallium with hydrochloric acid di-l~ted with water in the volume ratio of 1:2 at the temperature of 60~C, the product contains gallium in the amount of 99.996% by mass.
Example 15 The recirculation aluminate liquor resulting from Bayer's process having the following composition, g/l: sodium oxide - 310; alumina - 138; silica - 0.9; iron oxide - 0.019;
organic compounds - 3.89; sulphide sulphur - 1.47; sulphite sulphur - 0.92; thiosulphate sulphur - 2.19; gallium - 0.43 is diluted with water (in vol. %): recirculation liquor - 78; water - 22. Then to 100 1 of the liquor heated to ~ ~C 609 g of zinc oxide are added under stirring, in-cludin~ 302 g consumed for binding sulphide sulphur in thestarting liquor and 89 g - for binding secondary sulphide sulphur formed during electrolysis upon decomposition of thiosulphate sulphur. The remaining amount of zinc oxide "~
- ` ~1S8~97 (218 g) $s consumed for electrolytic recovery o~ gallium.
The resulting liquor, after separation Or the precipi-tate oi zino sulphide, has the following eomposition~ g/1 : so-dium oxide - 253; ~lumina - 112; silica - 0.72; iron oxide -- 0.008; organic compounds - ~4; thiosulphate sulphur - 1.76;
sulphite sulphur - 0.70; g~llium - 0.35 and zinc - 1.75. This liquor in the amount of 60 litreæ is subjected to electrolysis.
Said electrGlysis is conducted using direct current under the following conditions: oathodic current densit~ 400 A/m2;
volt~ge 3.8 V; temperature 35C. The material of the an0des i9 nickel. ~jhat of the ¢athodes is steel 1X18H9~.
Aiter ~ hours of electrolysis th0 rollowing metals are recovered from the liquor, percentage of their initial amo-B untss gallium - 52; zinc - 9y~ ~he resulting electrolytic re-sidue is removed irom the cathode and processed to metallic gallium as in Bsample 1.
The total amount of the recovered gallium is 10.~ g.
~ roJ~ /. e., J The composition of the resulting/metallic gallium is similar to that indicated in Example 1 hereinbefore.
A~ter settling the ~pent liquor purified during the electrolysis from contaminating pol~valent sulphur compounds and lron and having the following composition, g/l: sodium oxide -, ,, , ~ .
-" .
.
255; alumina - 112; silica - 0.72; iron oxide - 0.001;
organic compounds - 2.90; sulphide sulphur - 0.07; sul-phite sulphur - 0.45; thiosulphate sulphur - 0.42; gallium - 0.17 and zinc - 0.017 is recycled to the production of alumina.
Example 16 Into 60 1 of the recirculation aluminate liquor re-sulting from Bayer's process and having the composition ascited in Example 2 57 g of zinc oxide are introduced by using the same technique as specified in Example 1. The resulting solution having the following composition, g/l:
sodium oxide - 173, aluminium oxide - 75.1; silica - 0.42 iron oxide - 0.005, organic substances - 1.94, gallium - 0.19, vanadium - 0.17, and zinc - 0.95 is subjected to electrolysis as described in Example 2.
After 4 hours of electrolysis the following metals are recovered from the liquor, percentage of their initial amounts: gallium - 48, vanadium - 15, and zinc - 97.
The resultant electrolytic precipitate is removed from the cathodes and processed to gallium and vanadium concen-trate as in Example 1.
The total amount of the recovered gallium was 4.99 gand of vanadiaum concentrate, 2.8 g.
The composition of the products obtained is similar to that specified in Example 1.
~'~'
The reduction is effected by the addition, into the starting alkaline liquor resulting from alumina produc-tion, of sodium hydrosulphite at a temperature of from 60 to 80C under vigorous stirring. Reducing said vanadium compounds can also be effected by means of hydrogen which is obtained both by dissolution of granulated aluminum in the aluminate liquor and electrolysis of alkaline liquors with the use of amalgamated cathode. Satisfactory results are obtained also with the use of membranes made of un- -glazed porcelain which are placed around the electrodes.
Impurities OL copper and iron are eliminated from said liquor by reduction thereof with sodium hydrosulphite with a subsequent filtration of the purified liquor; for the removal of organic compounds the liquor is treated with activated coal at a temperature within the range of from 60 to 80C at the rate of 1 g of activated coal per one litre of the liquor.
This prior art process features the necessity of the preliminary effective freeing of aluminate liquors from impurities; sophisticated process equipment employed, a low current yield of gallium (0.27%) and a high rate of consumption of electric power (1,700 kW.hr per 1 kg of gallium) ~, s~
Another known process for electrolytic recovery of gallium from aluminate liquors (cf. French Patent No.
2,237,991;1975; British Patent No. 1,436,260; 1976) com-prises recovery of gallium at a cathodic current density of from 20 to 500 A/m2 on a solid cathode manufactured from a metal, whereinto reduced gallium diffuses till its con-tent in the superficial layer of the cathode is equal to 0.1-0.5~ by weight. As the cathode material use may be made of tin, lead, indium, zinc or an alloy of tin and lead made as a thin plate with a thickness of from 0.01 to 0.3X 103 micrometers or as a thick block of said metals.
The cathode may be also made of an inert material such as stainless steel coated with said metals to the thickness of from 1 to 50 micrometers. As the anode use is made of platinum, platinized titanium, stainless steel, nickel, aluminium. The electrolysis is conducted at a temperature within the range of from 25 to 80C.
Gallium is separated from the cathode by physical me-thods or by treating the cathode with a molten flux con-sisting of a molten alkali metal hydroxide at a temperature within the range of from 220 to 800C.
This prior art process, however, has the following disadvantages:
~:r - 7 -~ ", - 8 ~1~85~7 - a low rate of gallium recovery (the process duration is as long as 20 hours) which is associated with diffusion of.gallium into the bulk of the substrate metal;
- complicated process technology due to the use of consumable cathodes;
- the use, as the consumable cathodes, of rarely-avail-able and expensive metals;
- complicated and labour-consuming technology of reco-vering gallium from the cathode material.
The present invention provides such a process for elec-trolytic recovery of gallium or gallium and vanadium from alkaline liquors of alumina production which would make it possible to increase the degree of recovery of gallium or gallium and vanadium and enable the use of starting materials with substantially any contcnt of gallium and vanadium therein.
According to the present invention there is provided a process for electrolytic recovery of gallium or gallium and vanadium from alkaline liquors resulting from alumina production by electrolysis on solid electrodes, wherein, said electrolysis is effected at a cathodic current density ~:
of from 200 to 1,000 A/m , at a voltage of 3.4 to 4.5 V and at a tempjerature from 28 to 37 C in the presence of a metal ; ~rclimina~ily introduced into starting liquors which forms an alloy with gallium when it is electrolytically reduced together therewith (in the form of an electrolytic precipi-tate), which is not passivated under the electrolysis condi-tions, the concentration of such metal being between 0.15 and 5.0 g/l with th.e gallium concentration being between 0,15 and 0.5 g/l.
In accordance with the invention, a metal prcliminaYrily introduced into starting liquors is a metal selected from the group consisting of zinc, tin and lead. These metals form precipitates containing gallium or gallium and vanadium ,; :-.: f ' ' ~s~s~
during electrolysis, owing to their electrochemical pro-perties.
These metals are present in starting liquors in the form of an oxide, soluble inorganic salt, or pure metal.
In the process according to the invention, for recovery of gallium or gallium and vanadium, starting alkaline liqu-ors of the alumina production for gallium recovery should comprise a solution, selected from the group including mot~er aluminate Bayer process liquor, recirculation alum-inate Bayer process liquor, and mixture thereof, as well as recirculation aluminate Bayer process liquor diluted with water in a ratio (vol. ~):
recirculation liquor 10 - 90 water the balance.
This makes it possible to use liquors more concen-trated in terms of gallium compared to aluminate mother liquors and less concentrated compared to recirculation aluminate liquors.
To improve the efficiency of the process of electro-lytic recovery of gallium, the alkaline liquors of the alumina production should comprise filtered liquor which is prepared by repulping of sodium carbonate precipitate formed from the Bayer process recirculation liquor during its vaporization with water at between 50 and 100C.
~7 f~- _ g _ S~3';J
In the process according to the present invention, upon electrolysis of alkaline liquors resulting from alumina production use is made of DC, pulsating current, reversible current as well as various combinations thereof. This tech-nique makes it possible to substantially increase the degreeof recovery and current yield of gallium or gallium and vanadium, increase the content of these components in the electrolytic deposit, as well as reduce the rate of power consumption.
In order to eliminate contamination of the startin~
alkaline liquors resulting from alumina production and con-tamination of the desired products ~gallium or gallium and vanadium), in accordance with the present invention as the ~' , :
: .
." , " ~ ' ` ' ' ' ` ' 3'7 .
electrodes used should be made of metals resistant in alkaline media, i.e. steel, nickel, titanium. Said metals possess a satisfactory adherence to the electrolytic de-posit containin~ the metzlintroduced into the starting li-quor and gallium, or gallium and vanadium.
In the process according to the present invention, for increasing efficiency of the electrolytic recovery of gal-lium or gallium and vanadium use is made of water-cooled cathodes.
In the case where the starting alkaline liquor result-ing from alumina production contains polyvalent sulphur compounds it is advisable, for combining said sulphur com-pounds, to charge said metal, apart from the above-spe-cified amount thereof, into the liquor prior to the ele-ctrolysis in an additional amount stoichiometric in respect of the content of polyvalent sulphur compounds in the starting liquor. This enables an additional purification of alkaline liquors resulting from alumina production, improve quality of alumina and make use of bauxites with an increased content of pyrite minerals.
According to the process of the present invention, it is advisable that the electrolysis be effected to a resi-dual concentration of the metal introduced into the starting liquors resulting from alumina production equal to ~7 - 11 -; , :-: ' - , .. :
.
:
9~
0.020-0.005 g/l. This makes it possible to minimize contami-nation of alkaline liquors resulting irom alumina production with ~oreign impurities.
The process according to t~e present invention is simple, efiective and integrall~ combined wi~ the production o~ alu-mina; it makes possible to produce gallium or gallium and va-nadium directly ~rom alkaline liquors resulting ~rom alumina production o~ substantially any comp~sition, to use the start-ing materials with both high and low content of gallium, vana-dium 1 pyrite and carbonate minerals.
The process according to the present invention makes it possible to eliminate the preliminary puri~ication of al-kaline liquors resulting ~rom alumina productio~ ~rom impuri-ties hindering electrolysis such as vanadiu~, copper, iron, polyvalent sulphur compoundæ and organic compounds; eliminate the use and consumption o~ to~ic (mercury) and expe~sive (tin, indium, lead) materialæ; employ standard electrolyzers thus makin~ it possible to combine recovery o~ gallium o~ gallium and vanadium with a simultaneous p~rifioation of alkali~e li ~uors from harm~ul impurities (iron, lead, copper, titanium, polyvalent sulphur compounds).
~ he proce~s according to the present invention can be easily automated; it reduces capital e~penses ior the produc-~lS8~
tio~ o~ gallium. The repay period o~ a plant producing annual-ly 10 tons o~ gallium is not longer than one year.
The procéss according to the present invention is ei-fected in the ~ollowi~g manner.
A9 the starting alkaline liquors resulting from alumi~a produ¢tion use is made o~ the liquors obtained in processing o~ bauxites b~ the sinterin~ method or Bayer's method.
It i9 preferable to use aluminate li~uors resulti~g from Bayer's process owing to a higher content of galliu~ therein~
The mother liquors produced in proce~sing of bauxites according to Bayer contain, on the average, the ~ollowing com-po~ents in the amounts speci~ied hereinbelow, g/l: sodium oxide-- 130-180; alumina 60-80; silica 0~3-0.6; iron oxida 0.004 -- 0.006; organic compounds - 1.5 - 2.0 (a~ oalculated ~or oYy-ge~ b~ potassium permanganate), total sulphur 2.5-~.5 including ~ulphide sulphur 0~5-0.8, thiosulphate sulphur 1.0-1.2; sul-phite sulphur 0.2-0.4, sulphate sulphur 0.8-1.1~
f e. c, r C ~ o r7 C The Pe~u~n aluminate liquors contain, on the average, g/ls s~dium oYide 260-~20; alumina - 120-160; silica - 0.6-1.2 iro~ oxide - 0.01 - 0.015; organic compounds - 3.0-4.0; total sulphur - 5.0-7.0 including sulphide sulphur 1.0-1.6; thiosul-; phate sulphur 2.0-2.4; sulphite sulphur - 0.4-0.8; sulphate sulphur - 1.6-2.2.
.
~151 35~37 Concentration of gallium and vanadium in mother alu-minate liquors is respectively 0.15 - 0.25 and 0.16 - 0.28 g/l; in recirculation aluminate liquors concentration of gallium and vanadium is respectively 0.30 - 0.5G and 0.32 -0.56 g/l.
For electrolytic recovery of gallium or gallium andvanadium use can be made of both above-specified and other liquors. In both cases recovery of gallium into the ele-ctrolytic deposit within 4 hours of electrolysis is 40 to80%, that of vanadium is 10 to 40%. It has been found that the best results on recovery of gallium or gallium and vanadium occur in using a mixture of the above-men-tioned aluminate liquors (mother or recirculation) or re-circulation aluminate liquor of the Bayer process dilutedwith water with a ratio (vol. %):
recirculation liquor 10 - 90 water the balance.
The electrolysis of the recirculation aluminate liquor itself is hindered and economically inefficient due to a high concentration of sodium oxide therein and, con-sequently, increased viscosity and electrical resistance of this liquor thus causing a considerable foam-formation and voltage rise in the electrolyzer.
In order to increase the content of gallium in the liquor and lower concentration of sodium oxide therein, use is made of liquors prepared by repulpation with water at , 35 i ::
. , . , : ' ` :: :.... .
~8~
a temperature within the range of from 50 to 100C, of sodium carbonate precipitated from the recirculation al-uminate liquor resulting from the Bayer process during its vaporization.
Prior to electrolysis, into any of the above-specified ~ uors is introduced a metal forming, when the liquor is reduced electrolytically, together with gallium an alloy which is not passivated under the electrolysis conditions, the concentration of such'metal being between 0.15 and 5.0 g/l with a concentration of gallium of 0.15 - 0.5 g/l.
~urthermore, said metal has the structure and parameters of crystal lattice similar to those of gallium, as well as the recovery potential approaching that of gallium. The metal introduced into starting liquors is selected from the group consisting of zinc, lead and tin. This metal is introduced into hot alkaline solutions resulting from alumina production,either per se or in the form of an oxide, an inorganic salt soluble in said liquors. It is prefer-able to use zinc which is not passivated upon electrolysis,has a high overtension relative to hydrogen (~.7 V), a recoVery potential close to that of gallium (i e.-1.220 V
for Ga and -1.216 V for Zn), as well as similar structure and parameters of crystal lattice. During electrolysis zinc, while being deposited on a solid cathode, renews its surface, whereby the deposition of gallium or gallium and ` vanadium occurs on the zinc cathode. These factors facili-tate the process of re-"
~,' ~ ~ , ~ ~ , - -.
duction of ions of gallate and vanadate on the cathode.
In the case where in the starting alkaline liquor re-sulting from alumina production polyvalent sulphur com-pounds are present, for the purpose of introducing thelatter into said liquor, prior to electrolysis, an add-itional portion of the metal forming an alloy with gallium non-passivating under electrolysis conditions added in the stoichiometric amount relative to the polyvalent sulphur compounds. In doing so, taken into account is the de-composition of thiosulphate sulphur compounds during ele-ctrolysis to compounds of sulphide sulphur and sulphate sulphur.
An alkaline liquor from alumina production containing the introduced metal is subjected to electrolysis on solid electrodes under the following conditions:
cathodic current density of from 200 to l,000 A/m ;
voltage 3.4 to 4.5 V; process temperature of from 28 to 37C. As the electrode material use is made of metals resistant in alkaline media, namely: steel, nickel, titan-ium.
It is advisable that the cathode be cooled with water in order to raise the electrolysis temperature due to a lower temperature of the cathode surface and increased temperature within the bulk of the solution. As a result, the liquor vis-. ~ ,, , , ., , , ... , . ~ .- , ..
: :
.
s~
cosity is lowered and the voltage on the electrolyzer is decreased.
To improve the efficiency of the process, increase the current yield of gallium or gallium and vanadium, the electrolysis is conducted using direct, pulsating or reversing current, as well as various combinations of said currents.
The resulting electrolytic deposit is removed from the cathode by any conventional method such as mechanical or chemical ones, while the liquor with the residual con-centration of the introduced metal of from 0.02 to 0.005 g/l is recycled back to the production of alumina.
Gallium or gallium and vanadium are recovered from the resulting electrolytic deposit by any conventional method such as vacuum-thermal treatment. Furthermore, it is pos-sible to recover gallium or gallium and vanadium by dis-solution of the electrolytic deposit is acids or alkalis.Thereafter, gallium is recovered from the resulting solu-tions electrolytically, while vanadium remains in the solu-tion as a slime of vanadium concentrate and is then filter-ed-off. Gallium produced by this process contains, as the principal impurity, 2 to 6% by mass of the metal added to the liquor for electrolysis.
Production of metallic gallium conta;ning the above-.
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mentioned amount of the metal added to the starting liquor, for example zinc, facilitates the production of gallium having much smaller amounts of other impurities. It is known that in the case of presence of zinc in gallium in the above-specified amount activity of gallium is lowered, wherefore solubility therein of other impurities is sub-stantially reduced. The removal of zinc by conventional methods such as acid treatment or vacuum-thermal treat-ment is performed without any troubles.
For a better understanding of the present invention, some specific Examples illustrating the process of re-covery of gallium or gallium and vanadium are given here-inbelow.
Example 1 A recirculation aluminate liquor resulting from Bayer's process in the amount of 48 1 having the following composi-tion as to the content of the main components, g/l; sodium oxide 310; alumina - 138; silica - 0.9; iron oxide -0.019; organic compounds - 3.89; gallium - 0.43; vanadium - 0 35, is diluted with 13 1 of water (in vol. ~) recircu-lation liquor - 78, water - 22. Then to the liquor heated to the temperature of 90C there are added 112 g of zinc oxide under stirring. The resulting liquor having the following composition, g/l: sodium oxide - 250; alumina -112; silica - 0.72; iron o~cide - 0.008; organic com-,:
1~ ~&~
pounds -3.14; gallium - 0.35; vanadium - 0.28 and zinc -1.5 is fed into the electrolyzer with the working `capacity of 60 litres. Electrolysis is carried out using direct current under the following conditions:
cathodic current density 650 A/m2, volt~ge 3.8 V, temperature 32C. The material of anode - steel lX18H9T, the material of cathodes - nickel.
After 4 hours of electrolysis the following metals are recovered as a percentage of their total amounts: gal-lium - 57; vanadium - 20; zinc - 98.
The thus-produced electrolytic deposit is removed from the cathode mechanically, while the liquor after electrolysis with the residual concentration of zinc of 0.03 g~l is recycled to the production of alumina.
The electrolytic residue is washed with water to re-move sodium oxide and other soluble impurities, dried and subjected to vacuum-thermal sublimation to remove zinc.
The residue obtained after the vacuum-thermal sublimation contains gallium and vanadium; this residue is dissolved in 3litres of a hot solution of caustic soda with the concentration of 150 g/l as calculated for sodium oxide.
The vanadium concentrate is precipitated and the precipi-tate is separated by filtration, while the solution con-taining gallium in the amount of 4 g/l .. ,~,,~ -- 1 9 ,~, "b~,"
., , `: .;. ' . ,' - :
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'''`'.`, ~ ''''.,"' ' ~''' ::""' ' ,.' ;`', `':':
115~S~7 is subjected to electrolysis on a nickel cathode a~ the cathodic current density of 1,200 A/m2 and the tempera-ture of 60C.
5The total amount of the recovered gallium is 11.4 g;
that of vanadium concentrate is 8.1 g.
The thus-produced metal contains, per cent by mass:
gallium - 96.997; zinc - 3.0; lead - 1.10 3; copper - 1.10 3, aluminium - 1~10 3; and other impurities are not detected.
The vanadium concentrate contains, per cen by mass:
vanadium pentoxide - 84.1; sodium oxide - 10.0; silica -2.Q; gallium- 0.2; zinc - 3.7.
After treatment of the resulting metallic gallium with hydrochloric acid diluted with water in the ratio of 1:2 (by volume) at the temperature of 60C, the content of gal-lium in the product is 99.998% by mass.
Example 2 The recirculation aluminate liquor resulting from Bayer's process in the amount of 40 1 having the composi-tion described in the foregoing Example 1 is mixed with 20 1 of the mother aluminate liquor from the Bayer process (in vol. %) mother liquor - 33.3 recirculation liquor -66.6 of the composition in terms of basic components, g/l:
sodium oxide -173; alumina -75.1; silica -~S859'7 - Q.42; iron oxide - 0.005; organic compounds - 1.94;
gallium - 0.19; vanadium - 0.17. The volume ratio of the liquors IS 1: O. 5. Then, into the resulting liquor 110 g of zinc oxide are added using the procedure described in the foregoing Example 1. The.resulting liquor having the following composition, g/l: sodium oxide - 264; alumina - 117; silica - 0.74; iron oxide - 0.008; organic substi-tutes - 3..24;.gallium -Ø35; vanadium - 0.29 and zinc - 1.5 is subjected to electrolysis in a manner similar to that of Example 1, except that the cathodic current density is equal to 1,000 A/m2 at the voltage of 4.1 V.
After 4 hours of electrolysis the following metals are recovered, as a percentage of their starting amounts;
gallium - 63; vanadium - 2~; zinc - 96.
The resulting electrolytic deposit is removed from the cathodes and processed to gallium and vanadium concentrate in a manner similar to that of Example 1 hereinabove.
The total amount of the recovered gallium is 12.5 g;
that of vanadium concentrate is 10.1 g.
The composition ofthe resulting products is similar to that indicated in Example 1.
Example 3 The recirculation and mother liquors resulting from 30 Bayer's pro- - -''' ~'"' . ' s .. . .~
. . :, :
.
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.
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cess haviny compositions according to Examples 1 and 2 res-pectively are mixed (in vol. %~ mother li~uor - 90 recir-culation liquox - 10 then..to 6Q 1 of the prepared liquor 67.5 g of zinc oxide are introduced by the method described in Example 1. The resulting solution having the following composition, g/l: sodium oxide - 187; alumina - 81.3;
silica - 0.47; iron oxide - 0.006; organic compounds - 2.13;
gallium - 0.21; vanad~um - 0.19 and zinc - 0.9 is subjected to electrolysis as described in Example 1.
After 4 hours of electrolysis the following metals are recovered, as a percentage of their starting amounts: gal-lium 48; vanadium - 15; zinc - 96.
The total amount of the recovered gallium is 5.7 g;
that of vanadium concentrate is 3.5 g.
The composition of the resulting products is similar to that of Example 1.
Example 4 Into 60 1 of a liquor prepared in a manner similar to that described in Example 3 there are introduced 109 g of zinc oxide. The resulting solution of the following compo-sition, g/l: 187 - sodium oxide; alumina 81.3; silica _ 0.47;
~ - 22 -115~SS:3 ~
iron oxide - Q.006; organic compounds - 2.13; gallium - 0.21; vanad~um - 0.19; Zinc - 1.47 is subjected to ele-ctrolysi~s as described in Example 1.
After 4 hours of electrolysis the following metals are recovered, percentage of their initial amounts: gal-lium - 65; vanadium - 37; zinc - 97.
The thus-produced electrolytic deposit is removed from the cathodes and processed to gallium and vanadium con-centrate in a manner similar to that of Example 1.
The total amount of the recovered gallium is 7.8 g;
that of vanadium concentrate is 8.5 g.
The composition of the resulting products is similar to that described in Example 1 hereinbefore. ~ .
Example 5 The liquor prepared in a manner similar to that de-scribed in Example 1 and having composition as indicated in the same Example 1, except that the content of zinc is 3.5 g/l is subjected to electrolysis as described in Example 1.
After 4 hours of electrolysis the following metals are recovered, percentage of their initial amounts: gallium - 38; vanadium - 10; zinc - 90.
: . . ; : .
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The resulting electrolytic deposit is removed from the cathodes and processed to gallium and vanadium concen-trate in a manner similar to that of Example 1.
The total amount of the recovered gallium:is 7.6 g;
that of vanadium concentrate is 5.8 g.
The composition of the resulting products is similar to that described in Example 1.
Example 6 The recirculation and mother liquors resulting from Bayer's process having the compositions indicated in Examples 1 and 2 respectively are mixed (invol. %) mother liquor - 10 and recirculation liquor - 90. Then to 60 1 of the prepared liquor 127 g of zinc oxide are added using the method described in Example 1 hereinbefore. The resulting liquor having the following composition, g/l: sodium oxide - 296; alumina - 132; silica - 0.85; iron oxide - 0.018;
organic substitutes - 3.69; gallium - 0.41; vanadium - 0.33 and zinc - 1.77 is subjected to electrolysis as described in Example 1, at a voltage of 4.5 V.
After 4 hours of electrolysis the following metals are recovered, percentage of their starting amounts: gallium - 40; vanadium - 13; zinc - 97.
~r - 24 -1~
~ he resultin~ electrolytic deposit is removed from the cathodes and processed to gallium and vanadium ooncentrate as described in Example 1.
The total amount o~ the recovered gallium i9 9.3 g;
that o~ vanadium concentrate is 5.4 g.
~ he composition of the resulting products i9 similar to that described in Example 1 hereinbefore.
~ xample 7 The residue obtained after settling and filtration o~
r C C / rc ~ f / ~
~r the roturn alumi~ate li~uor resulting from Bayer's process is repulped with water for 8 hours at the temperature of 60C.
Then the re~ulting solution is filtered-off to separate it from the residue insoluble in water. The resulting filtrate has the following composition, g/l: sodium oxide - 246; alu-mina - 92j gallium - 0.4; iron oxide - 0.04. Into this filt-rate taken in the amount of 60 litres 1.5 g/l of zinc are introduced as described in Example 1. Afterwards, electrolys-is is conducted u9ing DC under the ~ollowing conditions:
cathodic current density of 400 A/m2, v~ltage 3.4 V; tempe-rature 30C. The material of a~ode~ i9 steel 1~18~9T; material o~ the cathode~ is nickel.
A~ter 4 hours of electrolysis the following metals are ~' , ~ 5~
recovered, percentage of their initial amounts: gallium - 75; zinc - 98.
The removal of the residue and processing thereof to metallic gallium is effected as in Example 1.
The total amount of gallium recovered is 18 g.
The composition of the resulting product i.e. metallic gallium is similar to that indicated in Example 1 herein-before.
Example 8 lS The recirculation aluminate liquor resulting from Bayer's process and having the composition according to Example 1, but containing no vanadium is diluted with water (invol. %) recirculation liquor - 78,~ater - 22. Then to 60 1 of the solution heated to the temperature of 100C 45 g of lead 20 oxide are added under stirring. The resulting liquor having the following composition, g/l: sodium oxide - 250; alumina - 112; silica - 0.72; iron oxide - 0.008; organic compounds - 3.14; ~allium - 0.35; and lead - 0.7 is subjected to ele-ctrolysis as in Example 1. After 4 hours of the electroly-sis the following metals are recovered from the liquor, per-centage of their initial amounts: gallium - 69; lead - 98.
The resulting electrolytic deposit is removed from the cathode mechanically, while the liquor after electrolysis with the residual lead concentration of 0.005 g/l is re-cycled to the pro-.
5~
ductiqn of alumina.
The electrolytic deposi~t is dissolved in 3 1 of sul-phuric acid with the concentration of 210 g/l heated to the temperature of 60C. The lead-containing precipitate is separated by filtration and the solution is neutralized with a 5% solution of ammon~a to precipitate gallium hydr-oxide. The latter is dissolved in 3 1 of a solution of caustic soda with the concentration of 150 g/l as calculated for sodium oxide. The resulting solution with the concen-tration of gallium of 4.4 g/l is subjected to electrolysis in a manner similar to that described in Example 1.
The total amount of recovered gallium is 12.5 g.
The resulting metal contains gallium in the amount of 99.98% by mass.
Example 9 To 60 litres of the liquor prepared as described in Example 1, but containing no vanadium, 112 g of zinc oxide are added. The resulting liquor having the following com-position, g/l: sodium oxide 250; alumina 112; silica 0.72;
iron oxide 0.008; organic compounds 3.14; gallium 0.35 and zinc 1.5 is subjected to electrolysis as described in Example 1, but with the cathodic current density of 300 A/m2 at the voltage of 3.4 V.
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After 4 hours of electrolysis the following metals are recoyered, percentage of thei-r initial amounts:
gallium - 46; zinc - g8. The resulting electrolytic de-posit is removed from the cathodes and processed to gallium in a manner similar to that described in Example 1.
Example 10 The recirculation and mother liquors resulting from Bayer's process having compositions indicated in Examples 1 and 2 respectively but containing no vanadium are mixed (in vol. %) mother liquor - 44, recirculation liquor - 56.
Thereafter, 119 g of zinc oxide are added to 60 1 of the thus prepared liquor. Thus, liquor has the following com-position, g/l: sodium oxide - 250; alumina - 110; silica - 0.63; iron oxide - 0.012; organic compounds - 3.02; gal-lium - 0.32 and zinc - 1.6 is subjected to electrolysis using direct current under the following conditions: cath-odic current density 700 A/m2; voltage 3.9 V; temperature 30C. The material of the anodes is nickel; that of the cathodes is lead.
After 4 hours of electrolysis the following metals are recovered, percentage of their initial amounts: gallium - 70; zinc - 98.
The removal of the resulting electrolytic deposit and ~'f .....
S~3 processing thereo~ to metallic gallium i9 conducted in a man-ner similar to th~t described in B~ample 1.
The total amount oi reoovered gallium is 12.7 g. The thus-produced metal ¢ontai~s, % b~ ma~s: gallium -94.788;
zinc - 5 2, lead - 1.10-2; c0pper - 1.10-~; aluminium - 1.10-3.
,~ No other impurities are deteoted. ~iter treatment o~ the result-~ng metallic gallium with hydrochloric acid di~uted with ~ater in the volume ratio 0f 1:2 at t~e temperature of 60C it con-tains 99.988 ~ by mass oi gallium.
~xample 11 Preparation and electrolysis o~ liquors are efiected as in ~Yample 10, e~cept t~at electrolysis is a0nducted at the temperature o~ ~C and at the v01t~ge of 3.7 V. T~e ma-terial oi the anodes i8 niokel~ that oi eathode~ - steel 1~18H9T.
~he ¢athodes are cooled with water.
After 4 hours of ele¢trolysis the ~ollowing metals are rec0vered, percent~ge o~ their initi~l amounts: gallium - 65;
zina - 97~
~ he resulting electrolytic deposit i9 removed ~rom the cathodes and processed to gallium iollowing the procedure oi E~ample 1 hereinberore.
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.
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. . . . .
. , .
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The total amount of the recovered gallium i5 11. 9 g.
The composition of the product i.e. metallic gallium is similar to that indicated in Example 1.
Example 12 To 60 1 of the mother aluminate liquor resulting from Bayer's process and having the composition mentioned in Example 2 zinc is introduced in an amount of 1.9 g/l and electrolysis is conducted using direct current under the following conditions: cathodic current density 550 A/m ;
voltage 4.1 V; temperature 28C. The material of the anodes - steel lX18N9T; the material of the cathodes - tit-anium.
After 4 hours of electrolysis the following metals are recovered from the liquor, percentage of their initial amounts: gallium 51; zinc - 97.
The removal of the electrolytic deposit and processing thereof to metallic gallium are performed as in Example 1.
The total amount o~ the recovered gallium is 5.5 g.
The composition of the resulting product i.e. metallic gal-lium is similar to that indicated in Example 1 hereinbefore.
Example 13 10 1 of the liquor prepared as in Example 10 are sub-jected to electrolysis using pulsating current (current switch-11S8~9'7 :
Oir interval i8 0.5 sec; ~requency o~ ~witahin~ is 1 æwitch-ing per mi~ute) uuder the iQlloWi~g conditions: cathodic cur-rent density is 650 A/m2, voltage 3.8 V, temperature 30C. ~he material of the anodes i~ steel lX18H9~, that of the cathodeæ
- nickel. T~e cathodes are cooled with water.
Arter 4 hours oi electrolysis the following metalæ are recovered from the li~uor, percentage of their initial amo-unt~: gallium - 82; zinc - 98.
The removal Or the electrolytic deposit and processing t~ereof to metallic gallium are periormed as in Example 1.
~ he tobal amount oi the recovered gallium is 2.49 g.
f~'5cf~Cf~
The composition oi the resulti~g/gallium i8 similar to that described in hxample 1 hereinbefore.
Ex~mple 14 10 1 of the liquor prepared as in ~Xample 10, are su~-~ecbed to electrolysis using reversing current (time oi anodic polarization is 0.2 sec; frequency of switching - 4 switching~
per minute). ~h~ condition~ of electroly i~ and materials oi the elect~odes are the same as in the foregoing Example 13.
Arter 4 houre of electrolysis the iollowing metals are recovered from the liquor, percentage of their initial amounts gallium - 75; zinc - 98.
- ' ' . , .
, " . , , , , , . ,, ~ :~
The removal o~ the electrolytic deposit and process-ing thereof to metallic ~allium are conducted as in Example 1, The tobal amount of the recovered gallium is 2.28 g.
The resulting metal contains, % by mass: gallium - 95.
996; zinc - 4.0; lead - 1.10 3; copper - 1.10 3; aluminium - 1.10 3; iron - 1.10 3. No other impurities are detected.
After treatment of the resulting metallic gallium with hydrochloric acid di-l~ted with water in the volume ratio of 1:2 at the temperature of 60~C, the product contains gallium in the amount of 99.996% by mass.
Example 15 The recirculation aluminate liquor resulting from Bayer's process having the following composition, g/l: sodium oxide - 310; alumina - 138; silica - 0.9; iron oxide - 0.019;
organic compounds - 3.89; sulphide sulphur - 1.47; sulphite sulphur - 0.92; thiosulphate sulphur - 2.19; gallium - 0.43 is diluted with water (in vol. %): recirculation liquor - 78; water - 22. Then to 100 1 of the liquor heated to ~ ~C 609 g of zinc oxide are added under stirring, in-cludin~ 302 g consumed for binding sulphide sulphur in thestarting liquor and 89 g - for binding secondary sulphide sulphur formed during electrolysis upon decomposition of thiosulphate sulphur. The remaining amount of zinc oxide "~
- ` ~1S8~97 (218 g) $s consumed for electrolytic recovery o~ gallium.
The resulting liquor, after separation Or the precipi-tate oi zino sulphide, has the following eomposition~ g/1 : so-dium oxide - 253; ~lumina - 112; silica - 0.72; iron oxide -- 0.008; organic compounds - ~4; thiosulphate sulphur - 1.76;
sulphite sulphur - 0.70; g~llium - 0.35 and zinc - 1.75. This liquor in the amount of 60 litreæ is subjected to electrolysis.
Said electrGlysis is conducted using direct current under the following conditions: oathodic current densit~ 400 A/m2;
volt~ge 3.8 V; temperature 35C. The material of the an0des i9 nickel. ~jhat of the ¢athodes is steel 1X18H9~.
Aiter ~ hours of electrolysis th0 rollowing metals are recovered from the liquor, percentage of their initial amo-B untss gallium - 52; zinc - 9y~ ~he resulting electrolytic re-sidue is removed irom the cathode and processed to metallic gallium as in Bsample 1.
The total amount of the recovered gallium is 10.~ g.
~ roJ~ /. e., J The composition of the resulting/metallic gallium is similar to that indicated in Example 1 hereinbefore.
A~ter settling the ~pent liquor purified during the electrolysis from contaminating pol~valent sulphur compounds and lron and having the following composition, g/l: sodium oxide -, ,, , ~ .
-" .
.
255; alumina - 112; silica - 0.72; iron oxide - 0.001;
organic compounds - 2.90; sulphide sulphur - 0.07; sul-phite sulphur - 0.45; thiosulphate sulphur - 0.42; gallium - 0.17 and zinc - 0.017 is recycled to the production of alumina.
Example 16 Into 60 1 of the recirculation aluminate liquor re-sulting from Bayer's process and having the composition ascited in Example 2 57 g of zinc oxide are introduced by using the same technique as specified in Example 1. The resulting solution having the following composition, g/l:
sodium oxide - 173, aluminium oxide - 75.1; silica - 0.42 iron oxide - 0.005, organic substances - 1.94, gallium - 0.19, vanadium - 0.17, and zinc - 0.95 is subjected to electrolysis as described in Example 2.
After 4 hours of electrolysis the following metals are recovered from the liquor, percentage of their initial amounts: gallium - 48, vanadium - 15, and zinc - 97.
The resultant electrolytic precipitate is removed from the cathodes and processed to gallium and vanadium concen-trate as in Example 1.
The total amount of the recovered gallium was 4.99 gand of vanadiaum concentrate, 2.8 g.
The composition of the products obtained is similar to that specified in Example 1.
~'~'
Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for electrolytically recovering gallium or gallium and vanadium from alkaline liquors of the alumina production, comprising conducting an electrolysis on said alkaline liquors using solid electrodes, with a cathode current density between 200 and 1,000 A/m2, at a voltage be-tween 3.4 and 4.5 V and at a temperature from 28 to 37 C
in the presence of a metal ion of a metal previously intro-duced into said alkaline liquors, which metal ions form, when electrolytically reduced together with gallium, an alloy therewith which is not passivated under the electrolysis conditions, the concentration of the metal being between 0.15 and 5.0 g/l and the concentration of gallium 0.15 to 0.5 g/l.
in the presence of a metal ion of a metal previously intro-duced into said alkaline liquors, which metal ions form, when electrolytically reduced together with gallium, an alloy therewith which is not passivated under the electrolysis conditions, the concentration of the metal being between 0.15 and 5.0 g/l and the concentration of gallium 0.15 to 0.5 g/l.
2. A process according to claim 1, in which the metal previously introduced into the alkaline liquors is selected from the group consisting of zinc, lead, and tin.
3. A process according to claim 2, in which said metal is introduced into the alkaline liquors in the form of an oxide, soluble inorganic salt or pure metal.
4. A process according to claim 1, in which the alka-line liquor of the alumina production is a liquor selected from the group consisting of aluminate mother Bayer process liquor, recirculation aluminate Bayer process liquor,and a mixture thereof.
5. A process according to claim 4, in which alkaline liquor of the alumina production is recirculation Bayer pro-cess liquor diluted with water with the ratio: (in vol. %):
recirculation liquor - 10-90, water - the balance.
recirculation liquor - 10-90, water - the balance.
6. A process according to claim 1, in which for elec-trolysis of alkaline liquor of the alumina production use is made of direct, pulsed, reversible current or a combina-tion thereof.
7. A process according to claim 1, in which the elec-trodes are made of metals resistant to alkaline solutions.
8. A process according to claim 7, in which water cooled cathodes are used.
9. A process according to claim 1, in which compounds of polyvalent sulphur are present in alkaline liquor of the alumina production, and an additional quantity of said metal is introduced to said liquor before electrolysis in accord-ance with the stochiometric ratio with such polyvalent sul-phur compounds.
10. A process according to claim 1, in which the elec-trolysis is conducted to a residual concentration of the metal previously introduced to the alkaline liquor be-tween 0.005 and 0.02 g/l.
11. A process according to claim 1, in which the start-ing alkaline liquors of the alumina production comprise a filtered liquor prepared by repulping with water at 50-100°C, a sodium carbonate precipitate formed from the recirculation Bayer process liquor during its vaporization.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000333996A CA1158597A (en) | 1979-08-17 | 1979-08-17 | Electrolytic recovery of gallium or gallium and vanadium in alumina production |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000333996A CA1158597A (en) | 1979-08-17 | 1979-08-17 | Electrolytic recovery of gallium or gallium and vanadium in alumina production |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1158597A true CA1158597A (en) | 1983-12-13 |
Family
ID=4114946
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000333996A Expired CA1158597A (en) | 1979-08-17 | 1979-08-17 | Electrolytic recovery of gallium or gallium and vanadium in alumina production |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1158597A (en) |
-
1979
- 1979-08-17 CA CA000333996A patent/CA1158597A/en not_active Expired
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