CA1146762A - Recovery process for indium - Google Patents
Recovery process for indiumInfo
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- CA1146762A CA1146762A CA000352965A CA352965A CA1146762A CA 1146762 A CA1146762 A CA 1146762A CA 000352965 A CA000352965 A CA 000352965A CA 352965 A CA352965 A CA 352965A CA 1146762 A CA1146762 A CA 1146762A
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Abstract
RECOVERY PROCESS FOR INDIUM
ABSTRACT OF THE DISCLOSURE:
Indium is recovered effectively from an aqueous leached solution containing indium ions, together with other ions such as ferric ions, zinc ions, etc. if any, by adjusting the pH of the aqueous solution to 0.25-4.5, extracting the indium ions from the aqueous solution with an organic solvent solution formed by diluting an extraction reagent containing a monoalkylphosphoric acid and/or a dialkylphosphoric acid and a trialkylphosphoric acid in 1 : 2-5 by volume ratio with a phase-stabilizing water-immiscible organic solvent and then back-extracting the indium ions in the organic solvent solution with an aqueous sulfuric acid solution.
ABSTRACT OF THE DISCLOSURE:
Indium is recovered effectively from an aqueous leached solution containing indium ions, together with other ions such as ferric ions, zinc ions, etc. if any, by adjusting the pH of the aqueous solution to 0.25-4.5, extracting the indium ions from the aqueous solution with an organic solvent solution formed by diluting an extraction reagent containing a monoalkylphosphoric acid and/or a dialkylphosphoric acid and a trialkylphosphoric acid in 1 : 2-5 by volume ratio with a phase-stabilizing water-immiscible organic solvent and then back-extracting the indium ions in the organic solvent solution with an aqueous sulfuric acid solution.
Description
~ h-Ls invention relate~ to a procesa of recovering indium and, more particularly, to a proce~ of obtaining lndium by 3electively extracting indium ions from an aqueous solution containing indium ions by a liquid-liquid ion-exchange proce~s and then back-extracting the indium ions into an aqueous solution acidified by sulfuric acid.
Indium does not occur as ores by itself but exists in very ~mall quantities in ores mainly for zinc and lead. Therefore, a~ industrial raw material for indium is mainly an intermedi~ta product containing concentrated indlum by-produced in a smelting step for zinc, etc., from the ores described above~ A ~eneral process o~ recovering indium includes a wet process wherein a raw material for indium, i. e., the above-de~cribed intermediate by-product i~ leached by a mineral acid, etc., and an indium component ln the leached solution is separated from components of other metals and purified into a concentrated ~orm. As a conventional wet process~
there is included a neutralization process for the leached solution, an ion-echange process, and a liquid-liquid ion-exchange process.
The neutralization process is mainly composed of a technique for precipitating indium hydroxide from an aqueous leaching solution of the above-described ores but since the product obtained by such a process is poor in purity, it is ~ 3 --required for obtaining the commercial grade product to repeat the purification of the indium product. The purification entails many steps such as a crude neutralization, filtration, dissolution, copper removal, neutralization for purification, etc., and hence the process is complicated and lacking in economic value.
The ion-exchange process uses an ion-exchange resin but in the process the separation efficiency between indium and iron is poor and the concentration ratio of indium is low.
Furthermore, since the process requires a highly concentrated acid solution containing hydrochloric acid or a halide sllch as chloride for eluting indium from the ion-exchange resin, the process is unsuitable for the treatment of indium-containing solution employed in a general wet-system zinc smeltery. In other words, intermixing of a halide or a halogen acld in the wet-system zinc smelting system ~ (sulfuric acid system) causes various troubles in the zinc `~ electrolysis step and others.
- The liquid-liquid ion-exchange proce~ a ~olvent extraction process using an organic solvent immi~cible with water and as the-organic 301uvent used for the process, : there are known ether~ i~obutyl methyl ketone (MI~K), tributylphosphorlc acid (TBP), a tertiary fatty acid, a monoalkylpho~phoric acid, and a dialkylpho~phoric acid.
The ether extraction process and MIBK extraction process amorlg the liquid-liquid ion-exchange processes described above cannot be applied to the extraction of ' ' .1 .
~4~7~i~
-- 4 ~
indium from a sulfuric acid~acidic solution containing indium but an aqueous halogenic acid solution containing indium is mainly treated by these processes. There are problems in the application of these processes to a general wet-type zinc smelting system. Also, in these processes there is a fault in that a large amount of ether or MIBK is dissolved in an aqueous solution treated, which results in increasing the loss of the solvent as well as causing a problem that the solvent dissolved in the aqueous solution has undesirable effects on other steps.
The tributylphosphoric acid (TBP) extraction process is mainly employed for the extraction of indium from a hydrochloric acid-acidic ~olution since the extraction efficiency of indium from a sulfuric acld-acidic solution by the proceYs is very low and the process i9 relatively widely used in the field without causing the di~solution of the ~olvent in the aqueous solution. IIowever, the solvents also extract all metals which are able to form chlorocomplex saits and hence in 20 order to recover indium alone? additional positive separation ~teps are required, which restrlct~ the utilization of the proces~. .
The extraction process u~ing a tertiary fatty acid : can be applied to extract indium ~rom aqueous ~olution other than an aqueous halogenic acid-acidic solution, such as an aqueous sulfuric acid-acidic solution but Rince - s -the solvent extracts ferric ions (Fe ) more preferentially ~han indium ions, it is necessary first to reduce ferric ions in the aqueous solution to ferrous ions (Fe ). Also, the pH at which the solvent extracts indium is limited to a relatively narrow range of 2.5-3.5 and the separation efficiency of indium from other heavy metal ions is low;
the purity of indium in a back-extracted solution obtained tends to be easily reduced. Consequently, for purifying the back-extracted solution, other processes such as the above described TBP extraction process must be also employed ~: together.
The inventors have found that a mixed solvent of a monoalkylphosphoric acid and/or a dialkylphosphoric acid and a trialkylphosphoric acid in a definite ratio has an extracting property for heavy metal ions and a back-extractive property never previously attained in the use of the monoalkylphosphoric acid, dialkylphosphoric acid, or trialkylphosphoric acid individually, and have discovered the present invention as the result of investigations on the utilization of the properties of the solvent mixture for the effective recovery of indium from an aqueous solution - containing indium.
The object of this invention is, therefore, to provide a process of obtaining a substantially pure indium concentrate by a liquid -liquid ion-exchange process wherein . indium ions are effectively extracted with an organic solvent 7~
solution from an aqueous ~olution contalning indium ions and back-extracting the indium ions with an aqueous sulfuric acid-acidic solution.
Thus, according to this invention, there ~a provided a procesa of recov~ring indium including the steps o~ ad~usting the pH of an aqueou~ solution containing indium lons to 0,2~-4.5~ mixing the aqueous solution with an organlc solvent ~nlutlon prepared by diluting an extracting reagent co~taining a monoalkylpho~phoric acid and/or a diQlkylphosphoric acid and a trialkrlphosphoric acid in 1 : 2-~ by volume ratio with a phase-stabilizing water-immiscible organi.c solvent to extract the indium ions into the organic solvent solution, and then mixing the organic ~ol~ent soiution with an aqueou~ sulfuric acid-acidic solution containing 100-500 g/liter of free sulfuric acid, so that the indium ions are back-extracted from the organic solvent solution into the aqueous sulfuric ~: acid-acidic solution to provide a substantially pure aqueous sulfuric acid-acidic solution containing indium in concentrated state.
In the accompanying drawings:
Eig. 1 is a graph showing the extraction equilibrium curves of In3 , Fe3 , and Zn2+ from an aqueous sulfuric acid solution by a D2EHPA solvent solution, 1~4~'7~ ~
P`ig. 2 i8 ~I graph showing the extraction equllibrium curves of In3~, Fe3+, and Zn2+ from an aqueous ~ulfurio acid ~olution by the organic ~olvent solution ln thi~ invention, and Fig, 3 and Fig. 4 are gre.ph~ ~howlng the relation between the extractabilities of In3+ and Fe3+ re~pectively from an aqueous sulfuric acid solution by the organic solvent solution of this inventlon and the extraction tlme required for the extractions By the convent~ onal extraction process using a monoalkylphosphoric ~cid and/or a dialkylpho~phoric acid, indium ions can be recovered by extraction from an , aqueous solution thereof having a relatlvely high sulfuric acid concentration, i. e., the aqueou~ sulfuric acid solution (sulfuric acid content of 500-12 g/liter) having a pH of --10 to 0 6 pH as shown in Fig. 1 of th~3 accompanying drawings. FigD 1 i9 ~I graph showing thet extraction .
equilibriums of` indium ions, ferric ion~ and zinc ions in the case of mixing 100 ml of each aqueou~ sulfuric acid--acidic ~0 solution having each different sulfuric acid concentration containing 52~-588 mgi/liter of indlum ion~ (In3+), 122--225 mg/liter of ferric ions (Fa3+) and 246--250mg/liter of : zinc ions (Zn2+) with 100 ml of each organic solvent solution comprising a mixture of di(Z--ethylhexyl)phosphoric acid (D2E~PA~ and a para$`finic organic solvent, MSB 210 : .
, ~ 2 (t~ade name, made by Shell Chemical Co.) in 5 : 95 by volume ratio as an extractiny solution. In Fig. 1, the ordinate axis indicates the extractability and the abscissa the pH
of a sulfuric acid-acidic solution.
As can be seen from the Fig.!l, under the pH
condition for extracting indium ions in the above described prior art process, ferric ions are simultaneously extracted and hence one should first reduce the ferric ions dissolved in an aqueous solution to ferrous ions. However, it is not always easy to effect comple~e reduction of the ferric ions in an aqueous solution, the accumulation of ferric ions in the solvent repeatedly used in practical steps is unavoidable, and hence the employment of back-extraction or stripping must be considered. For the back-extraction of ferric ions from an extracted solvent solution, an aqueous sulfuric acid-acidic solution cannot be substantially used and hence a halogenic ~olution, intermixing of which in an indium extraction system is undesirable, must be employed at ,- . .
present in a wet-sy~tem zinc 4meltery as de~cribed above.
~urthermore, the back-extraction of indium lon itself require~ two kind3 of halogen acld solutions each having different concentration and thus, two stage~ of back-extraction steps for ferric ion~ and indium ions are ultimately required. : -~ .
~L4~ 2 The tcrm "monoalkylphosphoric ac~d" and/or"dlalkylphosphorlc acid" include~ ~n alkylpyrophosphoric acid, a monoalkylphosphinic ac~d, and a dialkylphosphinic acid in ~ddition to a monoalkylphosphoric acid and a dialkylpho~phoric acid~ and it is preferred a~ an oil-soluble compo~md that the molecular welght of the alkyl --substituent be sufficiently large and the carbon number thereof be 8-20.
Practical examples of the preferred monoalkyl-phosphoric acids or dialkylphosphoric acids used in thisinvention are di(2-ethylhexyl)phosphoric acid (D2EHPA)~ di(l-methylheptyl)phosphoric acid, 2-ethylhexylpyropho~phoric acid, octylpyrophosphoric acid, 1,2-methylpropyl-395-dimethylhexylphosphoric acid, 2-ethylhexylphosphoric acid, and mixtures of the abo~e-described organic phosphoric acids The trialkylphosphoric acids used in this in~ention include a trialkylphosphate, a trialkylphosphine oxide, an alkyldialkylphosphinate, and a dialkylalkylphospho-nate. It is preferred that the carbon number of thealkyl substituent be 4-8~ Practical examples of the preferred trialkylphosphoric acid are tributylphosphoric acid (TBP), trioctylphosphoric acid9 tripentylphosphoric acid, trihexylphosphoric acid, triheptylphosphoric acid, dibutylbutyl phosphonate, butyldibutyl phosphinate, and mixtures of them.
.
~67~Z
The extraction reagent containing the above-described organic phosphoric acids is diluted by a phase-stabilizing water-immiscible organic solvent. The diluting solvent is insoluble in water and acts to dissolve an organic phosphoric acid and an organic phosphorus compound in a stable manner and reduce the viscosity thereof. Other necessary factors for solvent are chemical stability, low toxicity, and high flash point. Thus, there are aliphatic hydrocarbons, aromatic hydrocarbons, and alkylaromatic hydrocarbons induced from petroleum sources which comprise useful solvents. Practical examples of solvents are toluene, xylene, kerosene, various flash naphtha cuts, and mixtures of them. A particularly preferred solvent is a deodorized mineral spirit which is a mixture of higher paraffin hydrocarbons. (Commercially available solvents used in this invention are MSB 210, MSB 210L, DOSB-X, HAWS, Shell Sole A, Shell Sole AB, Eskaid 100, etc., and trade names, made by Shell Chemical Co.).
The properties of the organic solvent solution (hereinafter referred to as "organic phase A") formed by diluting the extraction reagent with the above-described organic solvent are described below in detail~
Fig, 2 is a gra~h showing the extraction equilibrium of indium ions (In3 ), ferric ions (Fe3 ), and zinc ions (Zn +) b~ the organic phase A in the experiment ' - lOa -7~;~
of thi~ invention, The equilibrlum curves are ln the case of mixing 100 ml of each aqueous sulfuric acld solution containing 478-613 mg/liter of In3+~ 60-2Z5 mg/liter of ~e3 , and 246-2go mg/liter of Zn2+ with 100 ml o~ an organic phase A formed by mixing di(2-ethylhexyl)phosphoric acid (D2EHPA), tributylphosphoric acid (TBP), and solvent paraffin MSB 210 (trade name, made by Shell Chemical Co.) in 3 : 12 : 85 by volume ratio and th~ axis of ordinate indicate~ extractability and the axis of abscissa the pH value of an aqueous suifuric 10 acid-acidic solution , As is shown in ~ig. 2, the organic phase A
shows a substantial indium extraction effect at pH higher than 0.25 Also, indium ions precipitate a9 the hydroxide at pH higher than 4.~ and hence the upper limit in the liquid-liquid ion-exchange for indium is pH 4 5. That is, the pH range for the extraction of indium by the organic phase A is o,25-4.5. The pH range i9 shifted to a lower acid side than the pH range for the extraction of indium in the case of using a monoal~ylphosphoric acid or dialkylphosphoric lO acid alone and hence the extraction treatment can be per~ormad easily. The particularly remarkable feature of the organic phase A is that it has a selective extracting property for indium ions and the use of an aqueous sulfuric acid solution ~or the back-extraction of indium ions becomes possible by the u9e of the organic phase A of this invention as will be described later, thereby the practicability of the solvent extraction can be greatly increased. f It is preferred that the mixing ratio of a monoalkylphosphoric acid or a dialkylphosphoric acid to a 20 trialkylphosphoric acid in the organic phase A used in this invention be 1 to 2-5. If the proportion o~ the trialkylphosphoric acid is higher than the mixing ratio, the extracting property for indium ions reduces, while if the proportion is lower than the mixing ratio, the back-extracting property by an aqueous sulfuric acid solution reduce9 In either case, the use of such organic solvent solution causes undesirable problems ~L~4~62 Also, as i9 clear rrom Fig~ 2, the organie phase A does not extract zinc lons at pH lower than 1.5 and henee when an aqueous solution contain9 zinc ions together with indium ions, indium ions only can be extracted by selecting the pH range for the extraction to 0.25-1,5, An indium raw material usually eontains iron, in particular iron in ferrie state in addition to zinc and the aqueous leached solution thereof contains ferric ions.
The separation of the ferrie ions and indium ions ean be easily practiced in the pH ran~e of this invention, whieh is one o~ the novel features of this invention.
As i9 clear from the extraetion equilibrium eurves of indium ions and ferrie ions in Fig. 2, the extracting property for ferric ions becomes greatly poor in the organic phase A when the pH of the aqueou~ solution is lower than 1.0, in particular, lower than 0.7 and hence indium ions can be selectively extracted in the pH range of 0.25-1.0, preferably 0.2~-0.7.
The results shown in Fig. 2 are in equilibrium ~0 states and in practical extraction the extraction rates also take part in the extraction. The organic phase A of this lnvention possesse~ a property that the extractien rate for indium ions i~ far higher than that for ferric ions even in an aqueous solution containing a considerable amount of ferric ions. Therefore, it becomes possible by the use of the organic phase A to substantially completely separate indium ions from ferric ions.
~4f~7~i2 This i9 clear from ~lg. 3 and ~ig. 4. Fig. 3 and Fig. 4 are the experimental results made by the inventors 9 which sho~ the relation~ between the extraction time and the extractabilities for indium lons and ferric ions in case of using the organic phase A.
The original aqueous solution used for obtainin~
the above results is 500~ml of an aqueous sulfuric acid-acidic solution having a pH of 0,7 containing 90 mg/li-ter of In3~ and 140-154 mg/liter of Fe3~ and the organic phase A as the extracting reagent i~ 50 ml of an organic solution consisting of 3% by volume D2EHPA, 12~o by weight TBP, and 85% by volume MS~ 210.
As is understood from these figures, the indium ions are extracted into the organic phase A in an amount of about 60-70~ thereof by the mixing contact for 10 minutes, while the ferric ions are not in the least extracted for the first 5 minutes and about 0. 2% only of the ion~ are extracted after the mixing contact of 10 minutes. ~urthermore, the extraction rate for ferric ions is lgw even after then and the extractability for ferric iohs after 60 minutes is about 1% only.
As described above, the organic phase A shows an excellent effect for the separation of indium ions from ferric ions by the separability by the extraction equilibrium and the difference in extraction rate and ~uch an effect has never been attained by a conventional organic solvent.
Then, the back-extraction or stripping of indium ~ons extracted in the organic phase A i9 explai~ed below.
As described above, the extraction of total indium ion~ can also be practiced by a conventionally known extracting reagent containing a monoalkylphosphoric acid or dialkylphosphoric ~cid individually but when the indium ions are back-extracted ~rom the solution using an aqueous sulfuric acid solution, the back-extraction is still - imperfect even using a highly concentrated sulfuric acid solution containing 490 g/liter of 9ulfuric aicd. Also, in the mixing contact with a sulfuric acid 901ution containing over 500 g/liter of sulfuric acid, a third phase form~ between the solvent solution and the sulfuric acid solution to reduce the phase separation and hence an aqueous sulfuric acid-acidic solution cannot substantially be used for the back-extraction of indium ions from the solvent solution. This is al90 true in case of ferric ions in the solvent solution.
On the other hand, when using the organic phase A, it is possible almost completely to baek-extract the indium 20 ions extracted in the organic phase A with an aqueous sulfurie acid-acidie solution and by inereasing the treatment eycle times, the back-extraction of indium ions with 100 g/liter (pH-0.3) of an aqueous sulfurie acid-acidie solution beeomes possible. When using an aqueous solution of a low proportion of sulfurie aeid, it is effieient to operate the proeess in a multi-stage contact hy a eounter-eurrent system.
7~2 However, even when using the organic phase A, a third phase forms in the mixing contact with an aqueous sulfuric acid-acidic solution containing over 500 g/liter of sulfuric acid as in the case of using a monoalkylphosphoric acid or a dialkylphosphoric acid and hence the concentration of the sulfuric acid-acidic solution used for the back-extraction of indium ions from the organic phase A is in the sulfuric acid range of 100-500 g/liter.
In other words, it is an important feature of this invention that by using the organic phase A as an extracting solution for indium, an aqueous sulfuric acid-acidic solution can be used for the back-extraction of the indium ions from the extracting solution and ultimately, a sulfuric acid-acidic indium concentrate can be obtained, thereby the practicabiliLy of the extraction process of indium is greatly improved.
The condition for the sulfuric acid concentration in the back-extraction from the organic phase A is 100-500 g/liter as described above. Within that range the back-extracting property of indium ions is better when the concentration of sulfuric acid is as high as possible and also the back-extraction property is better when the ratio of a trialkylphosphoric acid to a monoalkylphosphoric acid - and/or dialkylphosphoric acid is higher but if the back-extraction is repeatedly practiced, the back-extraction can be performed effectively even by employing the lower - 16 ~ 7~
range in each cass In this invention the above--described ratio is defined in the range of 1: 2-5 eonsidering the seleetive extraeting property of indium ions from an original aqueous 901ution eontaining them and the workability in the repeating baek-extraetlon of indium ions with an aqueous sulfurie aeid solution.
Prior to extraetion of indium ions, the ferrie ions in the organie phase A are baek-extraeted under sueh a baek-extraetion eondition for indium ions. This means that the lO organie phase A ean be regenerated by the baek-extraetion treat-ment with the same sulfurie aeid solution, whieh is one of the merits of this invention.
As described above, sinee the extraeting property for ferric ions with the organic phase A from an original aqueous solution is poor~ the amount of` ferrie ions contained in the organic phase A is very small and henee the amount of ferric ions entering the aqueous sulfuric acid solution in the back--extraetion i9 also very small and the existence of such a small amount of ferrie ions gives no 20 bad influences on the praeticability of the proeess of this invention.
In addition, when the reeovery of the indium ions from the back-ex-tracted sulfurie acid solution is praeticed by a cementation process with aluminum, the ferric ions in the sulfuric acid solution are easily reduced into ferrous ions, whieh remain, in situ, in the solution, and henee they give almost no had influenees on the purity of indium ~ ~7 metal reco~ered.
The cementation spent ~olution from which indium has been recovered can be backed, as it i9, into the leaching step in a ~.inc smeltery or indium extraction step That is, ferrous ions in the cementation spent solution are not extracted in the indium e~traction system together with zinc and aluminum, when the solution i9 returned, and there i9 no problem about the accumulation of ferrous and ferric ion in the indium extraction system.
~urthermore, as an effect by the liquid-liquid ion-exchange process of this invention using the organic phase A, there is the advantageous separating property of indium ions from other element ions than iron and zinc ions.
That is 9 the process of this invention can be suitably applied to the recovery of indium from an indium-containing solution which contains also other elements than iron and zinc, for example dusts containing such elements as -tin, chlorine, fluorine, arsenlc, etc., which al~o means that the proces3 of this inventioh can be utilized for the recovery of a very small amount of indium.
Among the above-described element~, tin has a strong affinity with indium and the separation of it is very difficult even by other ion-exchange process as well as general chemical treatment. Ho~ever, the organic phase A
extracts almost no tin ion~ in the condition range~ for extracting indium ions of this invention.
As described above, the organic phase A of this - 18 - i ~ ~ 4~ i2 invention alleviates positively the problems occuring in case of the indlvidual u9e of A monoalkylphosphoric acid, dialkylphosphoric acid~ or trialkylphosphoric acid constituting the organic phase A, i. e., the organic phase A extracts selectively lndium ions from an aqueous 901ution containing the indium ions together with, in particular, ferric ions under the conditions defined in this invention and make~ it possible to back-extract the indium ions into an aqueou3 sulfuric acid solution.
The indium recovery process of this invention can be easily applied to the practical operation without any trouble in addition to the simplification of steps, and hence the significance of the invention is large.
In addition, in the process of this invention, an aqueou~ sulfuric acid-acidic solution can be used as the back-extracting solution but a leached solution of an indium raw material, i. e., a solution to be treated by the extraction process of this invention is not limited to a sulfuric acid-acidic solution but may be a sillcofluoric acid solution, a hydrochloric acid qolution, a nitric acid solution or other halogenic acid solution.
Now, the following examples will serve to illustrate the process of this invention.
.
ExamDle 1 While changing the pH of an indium-containing aqueous solution, the extraction test for indium ions was performed An aqueous sul~uric acid solution having a pH
of 0.70 to -0~30 containing 0.457 g/liter of indium ions was prepared. Al~o, an organic phase consisting of lO
parts by volume of D2EHP~, 40 parts by volume of TBP, and 40 parts by volume of kerosene was prepared. In a 150 milllliter separa1:ory funnel were placed 50 ml of the aqueous solution prepared above and 50 ml of the organic phase, the mixture was shaked for 5 minutes and then allowed to stand.
The ra~finate, i. e., an aqueous ~olution extracted of the extraction re~t was separated, the indium concentration in the raffinate was analyzed, and then the extractability o~ indium ions in the organic phase was determined based on the concentration of indium in the original aqueous solution prepared. The results are shown in Table l.
:;
Table 1 , ", , ~
Extracta-pH in aq. In concn. in In concn. in bility of In soln. orig. aq. soln. raf~inate in org. phase g/llter g/liter ~o . . . _ _ . . . _ _ _ -7 o.457 o.oll 97.6 0.60 lt 0.014 96.g 0.52 ~ 0.020 95.6 o.46 l~ 0.023 95.o o.40 " 0.029~ 93.5 0-35 " o.o40 91.2 0-30 " o.o40 91.2 0~12 ~' o.o50 89.1 o.oo ll o.o60 86.9 -O.lo " 0.155 66.1 -0.18 l~ 0.169 63.o -0.24 " o.235 ~8.6 o 30 " 0,26~ 41.3 . . . ~
That is, the indium extractability obtained was higher than 90% at the pH of the indium-containing aqueous solution of higher than 0.30 and was 98/ at the pH of 0.~0.
Example 2 While changing the ratio of the organic phase to the aqueous sulfuric acid solution containing indium ions and zinc ions, the extraction test was performed.
An aqueous sulfuric acid solution having a pH of 0.60 containing 0. 457 g/liter of indium ions and 100 g/liter - 21 ~
~4~7~i2 of zinc ions was prepared and also an organic pha~e having the same composition as in Example 1 was prepared. While ehanging the ratio o~ the organie phase to the aqueous solution (~hown by 0/A)~ the extraetabilities of indium and zlne ln the organic phase were measured by the same ways as in Example 1. The results obtained are shown in Table 2.
Table 2 /A ratio Concn. in Concn. in Extracability orig. aq. soln. raffinate in org. phase _ __ er g/liter % -In Zn_ In Zn In ¦ ~n _ 0.25 0.457 100.0 0.043 100.09U ~ 0.0 0.50 tl l 0.034 100.092.6 0.0 0.75 ~ ~l 0.025 100.094.5 0.0 1.00_ . ,~ 0.020 100~095.5 0.0 That is, at the pH of o.6 the extractability of indium wa~ increased a~ the amount of the organic phase brought into contact with the aqueous solution in the range of 1/4 to 1/1 was larger. The extractability for indium ions was higher than 90% in each case but the extractability of zinc was 0, which showed the excellent SepQrating property of indium from zinc.
~ 2~ -76;~:
Example ~
The back-extraction test of indium from the organic phase containing indium wa9 performed by aqueous ~ulfuric acid solutlon for back-extraction while changing the concentration of the aqueous solution.
An organic phase having the same composition a~
in Example l was prepared and the content of indium was o.424 g/liter. Then, 100 ml of the organic phase were vigorously mixed with 40 ml of a back-extracting solution 10 con~isting of an aqueous sulfuric acid solution in a separatory funnel for 5 minutes. The results obtained on the back-extractabilities of the organic phase to back-extracting solution having different sulfuric acid concentrations are shown in Table 3.
~ ' .
Concn. of_ Concn. of sulfuric acid Concn. of In in in back- In in org. extracted' Back-extrac-extracting soln. phase soln. tability g/liter g/liter g/liter o~
_ _ _ 130 o.424 0.860 84.7 180 ll 0.874 94,2 210 1~ 1~022 96.2 240 ~ 1.040 96.3 270 ~l 1.02Z 96.2 300 " 1.072 lO0.0 33 ., 1.072 100.0 360 ll 1.072 100.0 . _ _ , ~L4~7~;2 That is, the back-extractability by one mixing contact of both ~olution~ was higher than 90~o when the eoncentration of ~ulfuric aeid wa~ higher than 180 g/llter and became 100% when the concentration was over 300 g/liter.
Example 4 Back-extraction test was performed whi~e changing the ~olume ratio (0/A) of a charged organic phase (0) to a back-extracting sulfuric acid solution (A), A back-extracting solution having a constant sulfuric acid solution of 180 g/liter was used and the composition of an organic phase was same as in Example 1 and the indium concentration in the org~anio phase was 0.444 g/liter. The ~tirring period of time for back-extraction was 5 minutes. The results obtained are shown in Table 4.
~ - ~
Table 4 0/A In concn. in In concn. in In concn. in Back ratio loaded org. org. phase back-extracted extrac-phase after back- qoln. tability g/liter extn, g/liter g/liter %
__ , ._ .. ... __ _ .
0.1 0.444 0.084 3.60 81.1 O.Z 1. 0.032 2.06 92.8 0.4 l l I o,0~3 1 1.08 1 97 , ' ~67~%
That is, lndium can be easily recovered with a smaller amount of a back-extracting solution in a concentrated state.
Example 5 Repeating test of a back-extraction was performed.
A back-extracting sulfuric acid solution having a constant sulfuric acid concentration of 183 g/liter was used and the mixing volume ratio 0/A in the back-extraction was kept at a constant value of 10/1. A back-extractability of indium from the loaded organic phase was measured when the back-extraction was performed thrice.
Each back-extraction was performed fo~ 10 minutes.
The organic phase composed of 3 parts by volume of D2EHPA7 12 parts by volume of TBP, and 8$ parts by volume of MSB 210 - made by Shell Chemical Co. and loaded with 2.36 g/liter of indium, The result~ are shown in Table 5.
~ ' i Table ~
!
_ ___ . . . _ __ . -- _ . __ . . _ .... _ __ .. ~
Back~extraction repeating no. 0 1 2 3 .
Concn. of In in back-g/liter 0 l9.0 4.60 4.60 . ... ., __ l phase g/liter 2.36 o.46 0.00 0.00 Integrated back-extractability % 0 80.5 10.00 10.00 . . ..
~4~t7~2 That is, when the sulfuric acid concentration of a back-extracting solution is low, a sufficient back-extract could be practiced by repeating the back-extracting operation.
Example 6 Indium, zinc and iron were di3solved in an aqueous sulfuric acid solution together with dusts containing fluorine~ chlorine, tin and ar~enic to provide an aqueous solution having a sulfuric acid concentration of 9.36 g/liter (pH 0.72) and u9ing the organic phase of this invention, a 3 stage counter current continuous extraction was performed by means of a mixer settler. The organic phase used in the back-extraction was composed of 3 parts by volume of D2EHPA, 12 part3 by volume of TBP, and 85 parts by volume of MSB 210 made by Shell Chemical Co. The extraction and back-extraction were repeated several times.
The volume of the organic phase prepared wa~ 40 liter3 and while performing the continuous extraction, sampling was performed when the extraction system reached equilibrium and the 9ample9 were analyzed. The results are shown in Table 6.
-- ~6 ~
3 146'7~2 , __ p~ ~ ~ ~q IJ.
. -, o~
'1 w ~ l-aq a~ w ~ 1- ~n . ~ p ~ O
u~ ~ P
~t ~ m P~ ~ ~
o~ag aq ~3 aq aq ag _ ~, W
~w :~ ~.~ , ~ ~ .-. , . W O
o ~o ~ ~ ~
o ~n W ~ O O O ~' ~. ~
O ~ ~ ~ O O W 1-~ W Ct~ H
O ~ ~ g W~ O~ p 1-~ OOOOO~
~ ~ ~ 1-- ~O ~D ~O O O ~ ~1 N
. ~ ~ n P~ ..
'O O O ,0 ,W,WW ,OW OD ~ ~ ..
~ ~ ~ O W ~~ O W l_~ ~
1~ 1~1--~ 0~ ~ O
.~ . ~ P
O O O O O O O O O ~_ . ~
CO OD Ot) O O O O O O .tl~
O O O O ~ W ~ O ~ ~nP
~0 ~ ~ ~ O ~ ~0 J O ~ ~ ~ O ~ ~
n O O O O O i~
W ~ ~ ~ C> O ~D
~- ~
O O O O O O O O O 7- .
~ 1~ ~ O ~ O i~ Y ~1 ~ ~ ~n ~ W 8 ~ ~D
o o o o ~ ~ ~ o ~ W
O O O O h~ ~ ~ O ~ ~ P
o~ a~ o ~ I_ _ __ ~:~4~762 That i8 ~ the extractability for iron wa9 about 10%
and tho~e ~or other elements were greatly low, while that for indium was 100%. These results show the sufficient ~ep=rat~on e~fect by the ~nvention.
Example 7 An organic phase having the same compo~ition as in Example 6 was loaded by indium and other elements ions as in the ~ame example and then the back-extraction of indium from the loaded organic phase was performed in counter current 3 9tages by means of a mixer settler using a sulfuric acid Rolution.
In addition, the concentratio~ of sulfuric acid in the aqueous ~olution used in the back-extraction wa9 305.2 g/liter and the ratio 0/A in the back-extraction was 10.75.
; The results are shown in Table 7.
.
7~
. -- 28 --,~, ~ td ~ b . ~ p~a~ ~ ' p ~
W ~ ~, X ~ y. ~ o ~ 1 ~ ~1 P tn ~ p P~ P~ - P~ P' ~ as bO ~ tn to t~
~ ~ ~ ~u. O ~ O
p) ~ ~ O ~ P t~
a~ aq aq P uq ~q cq aq aq P P~
~D
_ . _ ~ _ - I
a ~ ~n a ~ N 1\~ P ~1 . ~
~ . _ _ ~D
~ 1 ; ~~ '1 I
Wo :~ - - ~3 ~n ~U~
10 ~0 ~ O ~_ ~ t\) , ~ ~ O 1-- H ..
'~ ~ ~- g o ~ ~ 'ol ~ \n ;l ~ ~ W O ~ O O O O P~
1\7 ~ 1_ . ~ P~
: , Oo ~o O O ~n ~ O ' ~ ~
1~) ~ 00 OQ ~ ~ ~) N
. W O O~ ) (D
GO ~ ~ O O O O O O ~
. ~ 0 0~ ~ O O C~ O : .
.' W ~ I' I' o ~ ~0 ~-~ O O O O. O O ~
OD 00 00 O O O O O ~
~ ~o ~o ~ $ o o 8: g ~
W ,~ ~ o o o o o o 8 '' o o ~ ~ o o o ~
~O ~n ~ O O O O O O
~o oo . . . . .
. . . o r~ o o ~ ~ ~O ~ ~ ~ 1V ~D
w ~ ~ o a~
o ~ ~ o o o o o o o . . o , C:~ o o 'O ~n ~ g ~ P
,' _ , That is, the back-extractability for tin was low R9 well as sufficient back-extractions were obtained on other elements, ancl th~ recycling use of the organic phase was sufficiently pos~ible. In addition, since the extractability for tin from an original aqueous solution was greatly low and the content thereof in the loaded organic pha~e was also low, the existence of such a small amount of tin gave substantially less problems.
Indium does not occur as ores by itself but exists in very ~mall quantities in ores mainly for zinc and lead. Therefore, a~ industrial raw material for indium is mainly an intermedi~ta product containing concentrated indlum by-produced in a smelting step for zinc, etc., from the ores described above~ A ~eneral process o~ recovering indium includes a wet process wherein a raw material for indium, i. e., the above-de~cribed intermediate by-product i~ leached by a mineral acid, etc., and an indium component ln the leached solution is separated from components of other metals and purified into a concentrated ~orm. As a conventional wet process~
there is included a neutralization process for the leached solution, an ion-echange process, and a liquid-liquid ion-exchange process.
The neutralization process is mainly composed of a technique for precipitating indium hydroxide from an aqueous leaching solution of the above-described ores but since the product obtained by such a process is poor in purity, it is ~ 3 --required for obtaining the commercial grade product to repeat the purification of the indium product. The purification entails many steps such as a crude neutralization, filtration, dissolution, copper removal, neutralization for purification, etc., and hence the process is complicated and lacking in economic value.
The ion-exchange process uses an ion-exchange resin but in the process the separation efficiency between indium and iron is poor and the concentration ratio of indium is low.
Furthermore, since the process requires a highly concentrated acid solution containing hydrochloric acid or a halide sllch as chloride for eluting indium from the ion-exchange resin, the process is unsuitable for the treatment of indium-containing solution employed in a general wet-system zinc smeltery. In other words, intermixing of a halide or a halogen acld in the wet-system zinc smelting system ~ (sulfuric acid system) causes various troubles in the zinc `~ electrolysis step and others.
- The liquid-liquid ion-exchange proce~ a ~olvent extraction process using an organic solvent immi~cible with water and as the-organic 301uvent used for the process, : there are known ether~ i~obutyl methyl ketone (MI~K), tributylphosphorlc acid (TBP), a tertiary fatty acid, a monoalkylpho~phoric acid, and a dialkylpho~phoric acid.
The ether extraction process and MIBK extraction process amorlg the liquid-liquid ion-exchange processes described above cannot be applied to the extraction of ' ' .1 .
~4~7~i~
-- 4 ~
indium from a sulfuric acid~acidic solution containing indium but an aqueous halogenic acid solution containing indium is mainly treated by these processes. There are problems in the application of these processes to a general wet-type zinc smelting system. Also, in these processes there is a fault in that a large amount of ether or MIBK is dissolved in an aqueous solution treated, which results in increasing the loss of the solvent as well as causing a problem that the solvent dissolved in the aqueous solution has undesirable effects on other steps.
The tributylphosphoric acid (TBP) extraction process is mainly employed for the extraction of indium from a hydrochloric acid-acidic ~olution since the extraction efficiency of indium from a sulfuric acld-acidic solution by the proceYs is very low and the process i9 relatively widely used in the field without causing the di~solution of the ~olvent in the aqueous solution. IIowever, the solvents also extract all metals which are able to form chlorocomplex saits and hence in 20 order to recover indium alone? additional positive separation ~teps are required, which restrlct~ the utilization of the proces~. .
The extraction process u~ing a tertiary fatty acid : can be applied to extract indium ~rom aqueous ~olution other than an aqueous halogenic acid-acidic solution, such as an aqueous sulfuric acid-acidic solution but Rince - s -the solvent extracts ferric ions (Fe ) more preferentially ~han indium ions, it is necessary first to reduce ferric ions in the aqueous solution to ferrous ions (Fe ). Also, the pH at which the solvent extracts indium is limited to a relatively narrow range of 2.5-3.5 and the separation efficiency of indium from other heavy metal ions is low;
the purity of indium in a back-extracted solution obtained tends to be easily reduced. Consequently, for purifying the back-extracted solution, other processes such as the above described TBP extraction process must be also employed ~: together.
The inventors have found that a mixed solvent of a monoalkylphosphoric acid and/or a dialkylphosphoric acid and a trialkylphosphoric acid in a definite ratio has an extracting property for heavy metal ions and a back-extractive property never previously attained in the use of the monoalkylphosphoric acid, dialkylphosphoric acid, or trialkylphosphoric acid individually, and have discovered the present invention as the result of investigations on the utilization of the properties of the solvent mixture for the effective recovery of indium from an aqueous solution - containing indium.
The object of this invention is, therefore, to provide a process of obtaining a substantially pure indium concentrate by a liquid -liquid ion-exchange process wherein . indium ions are effectively extracted with an organic solvent 7~
solution from an aqueous ~olution contalning indium ions and back-extracting the indium ions with an aqueous sulfuric acid-acidic solution.
Thus, according to this invention, there ~a provided a procesa of recov~ring indium including the steps o~ ad~usting the pH of an aqueou~ solution containing indium lons to 0,2~-4.5~ mixing the aqueous solution with an organlc solvent ~nlutlon prepared by diluting an extracting reagent co~taining a monoalkylpho~phoric acid and/or a diQlkylphosphoric acid and a trialkrlphosphoric acid in 1 : 2-~ by volume ratio with a phase-stabilizing water-immiscible organi.c solvent to extract the indium ions into the organic solvent solution, and then mixing the organic ~ol~ent soiution with an aqueou~ sulfuric acid-acidic solution containing 100-500 g/liter of free sulfuric acid, so that the indium ions are back-extracted from the organic solvent solution into the aqueous sulfuric ~: acid-acidic solution to provide a substantially pure aqueous sulfuric acid-acidic solution containing indium in concentrated state.
In the accompanying drawings:
Eig. 1 is a graph showing the extraction equilibrium curves of In3 , Fe3 , and Zn2+ from an aqueous sulfuric acid solution by a D2EHPA solvent solution, 1~4~'7~ ~
P`ig. 2 i8 ~I graph showing the extraction equllibrium curves of In3~, Fe3+, and Zn2+ from an aqueous ~ulfurio acid ~olution by the organic ~olvent solution ln thi~ invention, and Fig, 3 and Fig. 4 are gre.ph~ ~howlng the relation between the extractabilities of In3+ and Fe3+ re~pectively from an aqueous sulfuric acid solution by the organic solvent solution of this inventlon and the extraction tlme required for the extractions By the convent~ onal extraction process using a monoalkylphosphoric ~cid and/or a dialkylpho~phoric acid, indium ions can be recovered by extraction from an , aqueous solution thereof having a relatlvely high sulfuric acid concentration, i. e., the aqueou~ sulfuric acid solution (sulfuric acid content of 500-12 g/liter) having a pH of --10 to 0 6 pH as shown in Fig. 1 of th~3 accompanying drawings. FigD 1 i9 ~I graph showing thet extraction .
equilibriums of` indium ions, ferric ion~ and zinc ions in the case of mixing 100 ml of each aqueou~ sulfuric acid--acidic ~0 solution having each different sulfuric acid concentration containing 52~-588 mgi/liter of indlum ion~ (In3+), 122--225 mg/liter of ferric ions (Fa3+) and 246--250mg/liter of : zinc ions (Zn2+) with 100 ml of each organic solvent solution comprising a mixture of di(Z--ethylhexyl)phosphoric acid (D2E~PA~ and a para$`finic organic solvent, MSB 210 : .
, ~ 2 (t~ade name, made by Shell Chemical Co.) in 5 : 95 by volume ratio as an extractiny solution. In Fig. 1, the ordinate axis indicates the extractability and the abscissa the pH
of a sulfuric acid-acidic solution.
As can be seen from the Fig.!l, under the pH
condition for extracting indium ions in the above described prior art process, ferric ions are simultaneously extracted and hence one should first reduce the ferric ions dissolved in an aqueous solution to ferrous ions. However, it is not always easy to effect comple~e reduction of the ferric ions in an aqueous solution, the accumulation of ferric ions in the solvent repeatedly used in practical steps is unavoidable, and hence the employment of back-extraction or stripping must be considered. For the back-extraction of ferric ions from an extracted solvent solution, an aqueous sulfuric acid-acidic solution cannot be substantially used and hence a halogenic ~olution, intermixing of which in an indium extraction system is undesirable, must be employed at ,- . .
present in a wet-sy~tem zinc 4meltery as de~cribed above.
~urthermore, the back-extraction of indium lon itself require~ two kind3 of halogen acld solutions each having different concentration and thus, two stage~ of back-extraction steps for ferric ion~ and indium ions are ultimately required. : -~ .
~L4~ 2 The tcrm "monoalkylphosphoric ac~d" and/or"dlalkylphosphorlc acid" include~ ~n alkylpyrophosphoric acid, a monoalkylphosphinic ac~d, and a dialkylphosphinic acid in ~ddition to a monoalkylphosphoric acid and a dialkylpho~phoric acid~ and it is preferred a~ an oil-soluble compo~md that the molecular welght of the alkyl --substituent be sufficiently large and the carbon number thereof be 8-20.
Practical examples of the preferred monoalkyl-phosphoric acids or dialkylphosphoric acids used in thisinvention are di(2-ethylhexyl)phosphoric acid (D2EHPA)~ di(l-methylheptyl)phosphoric acid, 2-ethylhexylpyropho~phoric acid, octylpyrophosphoric acid, 1,2-methylpropyl-395-dimethylhexylphosphoric acid, 2-ethylhexylphosphoric acid, and mixtures of the abo~e-described organic phosphoric acids The trialkylphosphoric acids used in this in~ention include a trialkylphosphate, a trialkylphosphine oxide, an alkyldialkylphosphinate, and a dialkylalkylphospho-nate. It is preferred that the carbon number of thealkyl substituent be 4-8~ Practical examples of the preferred trialkylphosphoric acid are tributylphosphoric acid (TBP), trioctylphosphoric acid9 tripentylphosphoric acid, trihexylphosphoric acid, triheptylphosphoric acid, dibutylbutyl phosphonate, butyldibutyl phosphinate, and mixtures of them.
.
~67~Z
The extraction reagent containing the above-described organic phosphoric acids is diluted by a phase-stabilizing water-immiscible organic solvent. The diluting solvent is insoluble in water and acts to dissolve an organic phosphoric acid and an organic phosphorus compound in a stable manner and reduce the viscosity thereof. Other necessary factors for solvent are chemical stability, low toxicity, and high flash point. Thus, there are aliphatic hydrocarbons, aromatic hydrocarbons, and alkylaromatic hydrocarbons induced from petroleum sources which comprise useful solvents. Practical examples of solvents are toluene, xylene, kerosene, various flash naphtha cuts, and mixtures of them. A particularly preferred solvent is a deodorized mineral spirit which is a mixture of higher paraffin hydrocarbons. (Commercially available solvents used in this invention are MSB 210, MSB 210L, DOSB-X, HAWS, Shell Sole A, Shell Sole AB, Eskaid 100, etc., and trade names, made by Shell Chemical Co.).
The properties of the organic solvent solution (hereinafter referred to as "organic phase A") formed by diluting the extraction reagent with the above-described organic solvent are described below in detail~
Fig, 2 is a gra~h showing the extraction equilibrium of indium ions (In3 ), ferric ions (Fe3 ), and zinc ions (Zn +) b~ the organic phase A in the experiment ' - lOa -7~;~
of thi~ invention, The equilibrlum curves are ln the case of mixing 100 ml of each aqueous sulfuric acld solution containing 478-613 mg/liter of In3+~ 60-2Z5 mg/liter of ~e3 , and 246-2go mg/liter of Zn2+ with 100 ml o~ an organic phase A formed by mixing di(2-ethylhexyl)phosphoric acid (D2EHPA), tributylphosphoric acid (TBP), and solvent paraffin MSB 210 (trade name, made by Shell Chemical Co.) in 3 : 12 : 85 by volume ratio and th~ axis of ordinate indicate~ extractability and the axis of abscissa the pH value of an aqueous suifuric 10 acid-acidic solution , As is shown in ~ig. 2, the organic phase A
shows a substantial indium extraction effect at pH higher than 0.25 Also, indium ions precipitate a9 the hydroxide at pH higher than 4.~ and hence the upper limit in the liquid-liquid ion-exchange for indium is pH 4 5. That is, the pH range for the extraction of indium by the organic phase A is o,25-4.5. The pH range i9 shifted to a lower acid side than the pH range for the extraction of indium in the case of using a monoal~ylphosphoric acid or dialkylphosphoric lO acid alone and hence the extraction treatment can be per~ormad easily. The particularly remarkable feature of the organic phase A is that it has a selective extracting property for indium ions and the use of an aqueous sulfuric acid solution ~or the back-extraction of indium ions becomes possible by the u9e of the organic phase A of this invention as will be described later, thereby the practicability of the solvent extraction can be greatly increased. f It is preferred that the mixing ratio of a monoalkylphosphoric acid or a dialkylphosphoric acid to a 20 trialkylphosphoric acid in the organic phase A used in this invention be 1 to 2-5. If the proportion o~ the trialkylphosphoric acid is higher than the mixing ratio, the extracting property for indium ions reduces, while if the proportion is lower than the mixing ratio, the back-extracting property by an aqueous sulfuric acid solution reduce9 In either case, the use of such organic solvent solution causes undesirable problems ~L~4~62 Also, as i9 clear rrom Fig~ 2, the organie phase A does not extract zinc lons at pH lower than 1.5 and henee when an aqueous solution contain9 zinc ions together with indium ions, indium ions only can be extracted by selecting the pH range for the extraction to 0.25-1,5, An indium raw material usually eontains iron, in particular iron in ferrie state in addition to zinc and the aqueous leached solution thereof contains ferric ions.
The separation of the ferrie ions and indium ions ean be easily practiced in the pH ran~e of this invention, whieh is one o~ the novel features of this invention.
As i9 clear from the extraetion equilibrium eurves of indium ions and ferrie ions in Fig. 2, the extracting property for ferric ions becomes greatly poor in the organic phase A when the pH of the aqueou~ solution is lower than 1.0, in particular, lower than 0.7 and hence indium ions can be selectively extracted in the pH range of 0.25-1.0, preferably 0.2~-0.7.
The results shown in Fig. 2 are in equilibrium ~0 states and in practical extraction the extraction rates also take part in the extraction. The organic phase A of this lnvention possesse~ a property that the extractien rate for indium ions i~ far higher than that for ferric ions even in an aqueous solution containing a considerable amount of ferric ions. Therefore, it becomes possible by the use of the organic phase A to substantially completely separate indium ions from ferric ions.
~4f~7~i2 This i9 clear from ~lg. 3 and ~ig. 4. Fig. 3 and Fig. 4 are the experimental results made by the inventors 9 which sho~ the relation~ between the extraction time and the extractabilities for indium lons and ferric ions in case of using the organic phase A.
The original aqueous solution used for obtainin~
the above results is 500~ml of an aqueous sulfuric acid-acidic solution having a pH of 0,7 containing 90 mg/li-ter of In3~ and 140-154 mg/liter of Fe3~ and the organic phase A as the extracting reagent i~ 50 ml of an organic solution consisting of 3% by volume D2EHPA, 12~o by weight TBP, and 85% by volume MS~ 210.
As is understood from these figures, the indium ions are extracted into the organic phase A in an amount of about 60-70~ thereof by the mixing contact for 10 minutes, while the ferric ions are not in the least extracted for the first 5 minutes and about 0. 2% only of the ion~ are extracted after the mixing contact of 10 minutes. ~urthermore, the extraction rate for ferric ions is lgw even after then and the extractability for ferric iohs after 60 minutes is about 1% only.
As described above, the organic phase A shows an excellent effect for the separation of indium ions from ferric ions by the separability by the extraction equilibrium and the difference in extraction rate and ~uch an effect has never been attained by a conventional organic solvent.
Then, the back-extraction or stripping of indium ~ons extracted in the organic phase A i9 explai~ed below.
As described above, the extraction of total indium ion~ can also be practiced by a conventionally known extracting reagent containing a monoalkylphosphoric acid or dialkylphosphoric ~cid individually but when the indium ions are back-extracted ~rom the solution using an aqueous sulfuric acid solution, the back-extraction is still - imperfect even using a highly concentrated sulfuric acid solution containing 490 g/liter of 9ulfuric aicd. Also, in the mixing contact with a sulfuric acid 901ution containing over 500 g/liter of sulfuric acid, a third phase form~ between the solvent solution and the sulfuric acid solution to reduce the phase separation and hence an aqueous sulfuric acid-acidic solution cannot substantially be used for the back-extraction of indium ions from the solvent solution. This is al90 true in case of ferric ions in the solvent solution.
On the other hand, when using the organic phase A, it is possible almost completely to baek-extract the indium 20 ions extracted in the organic phase A with an aqueous sulfurie acid-acidie solution and by inereasing the treatment eycle times, the back-extraction of indium ions with 100 g/liter (pH-0.3) of an aqueous sulfurie acid-acidie solution beeomes possible. When using an aqueous solution of a low proportion of sulfurie aeid, it is effieient to operate the proeess in a multi-stage contact hy a eounter-eurrent system.
7~2 However, even when using the organic phase A, a third phase forms in the mixing contact with an aqueous sulfuric acid-acidic solution containing over 500 g/liter of sulfuric acid as in the case of using a monoalkylphosphoric acid or a dialkylphosphoric acid and hence the concentration of the sulfuric acid-acidic solution used for the back-extraction of indium ions from the organic phase A is in the sulfuric acid range of 100-500 g/liter.
In other words, it is an important feature of this invention that by using the organic phase A as an extracting solution for indium, an aqueous sulfuric acid-acidic solution can be used for the back-extraction of the indium ions from the extracting solution and ultimately, a sulfuric acid-acidic indium concentrate can be obtained, thereby the practicabiliLy of the extraction process of indium is greatly improved.
The condition for the sulfuric acid concentration in the back-extraction from the organic phase A is 100-500 g/liter as described above. Within that range the back-extracting property of indium ions is better when the concentration of sulfuric acid is as high as possible and also the back-extraction property is better when the ratio of a trialkylphosphoric acid to a monoalkylphosphoric acid - and/or dialkylphosphoric acid is higher but if the back-extraction is repeatedly practiced, the back-extraction can be performed effectively even by employing the lower - 16 ~ 7~
range in each cass In this invention the above--described ratio is defined in the range of 1: 2-5 eonsidering the seleetive extraeting property of indium ions from an original aqueous 901ution eontaining them and the workability in the repeating baek-extraetlon of indium ions with an aqueous sulfurie aeid solution.
Prior to extraetion of indium ions, the ferrie ions in the organie phase A are baek-extraeted under sueh a baek-extraetion eondition for indium ions. This means that the lO organie phase A ean be regenerated by the baek-extraetion treat-ment with the same sulfurie aeid solution, whieh is one of the merits of this invention.
As described above, sinee the extraeting property for ferric ions with the organic phase A from an original aqueous solution is poor~ the amount of` ferrie ions contained in the organic phase A is very small and henee the amount of ferric ions entering the aqueous sulfuric acid solution in the back--extraetion i9 also very small and the existence of such a small amount of ferrie ions gives no 20 bad influences on the praeticability of the proeess of this invention.
In addition, when the reeovery of the indium ions from the back-ex-tracted sulfurie acid solution is praeticed by a cementation process with aluminum, the ferric ions in the sulfuric acid solution are easily reduced into ferrous ions, whieh remain, in situ, in the solution, and henee they give almost no had influenees on the purity of indium ~ ~7 metal reco~ered.
The cementation spent ~olution from which indium has been recovered can be backed, as it i9, into the leaching step in a ~.inc smeltery or indium extraction step That is, ferrous ions in the cementation spent solution are not extracted in the indium e~traction system together with zinc and aluminum, when the solution i9 returned, and there i9 no problem about the accumulation of ferrous and ferric ion in the indium extraction system.
~urthermore, as an effect by the liquid-liquid ion-exchange process of this invention using the organic phase A, there is the advantageous separating property of indium ions from other element ions than iron and zinc ions.
That is 9 the process of this invention can be suitably applied to the recovery of indium from an indium-containing solution which contains also other elements than iron and zinc, for example dusts containing such elements as -tin, chlorine, fluorine, arsenlc, etc., which al~o means that the proces3 of this inventioh can be utilized for the recovery of a very small amount of indium.
Among the above-described element~, tin has a strong affinity with indium and the separation of it is very difficult even by other ion-exchange process as well as general chemical treatment. Ho~ever, the organic phase A
extracts almost no tin ion~ in the condition range~ for extracting indium ions of this invention.
As described above, the organic phase A of this - 18 - i ~ ~ 4~ i2 invention alleviates positively the problems occuring in case of the indlvidual u9e of A monoalkylphosphoric acid, dialkylphosphoric acid~ or trialkylphosphoric acid constituting the organic phase A, i. e., the organic phase A extracts selectively lndium ions from an aqueous 901ution containing the indium ions together with, in particular, ferric ions under the conditions defined in this invention and make~ it possible to back-extract the indium ions into an aqueou3 sulfuric acid solution.
The indium recovery process of this invention can be easily applied to the practical operation without any trouble in addition to the simplification of steps, and hence the significance of the invention is large.
In addition, in the process of this invention, an aqueou~ sulfuric acid-acidic solution can be used as the back-extracting solution but a leached solution of an indium raw material, i. e., a solution to be treated by the extraction process of this invention is not limited to a sulfuric acid-acidic solution but may be a sillcofluoric acid solution, a hydrochloric acid qolution, a nitric acid solution or other halogenic acid solution.
Now, the following examples will serve to illustrate the process of this invention.
.
ExamDle 1 While changing the pH of an indium-containing aqueous solution, the extraction test for indium ions was performed An aqueous sul~uric acid solution having a pH
of 0.70 to -0~30 containing 0.457 g/liter of indium ions was prepared. Al~o, an organic phase consisting of lO
parts by volume of D2EHP~, 40 parts by volume of TBP, and 40 parts by volume of kerosene was prepared. In a 150 milllliter separa1:ory funnel were placed 50 ml of the aqueous solution prepared above and 50 ml of the organic phase, the mixture was shaked for 5 minutes and then allowed to stand.
The ra~finate, i. e., an aqueous ~olution extracted of the extraction re~t was separated, the indium concentration in the raffinate was analyzed, and then the extractability o~ indium ions in the organic phase was determined based on the concentration of indium in the original aqueous solution prepared. The results are shown in Table l.
:;
Table 1 , ", , ~
Extracta-pH in aq. In concn. in In concn. in bility of In soln. orig. aq. soln. raf~inate in org. phase g/llter g/liter ~o . . . _ _ . . . _ _ _ -7 o.457 o.oll 97.6 0.60 lt 0.014 96.g 0.52 ~ 0.020 95.6 o.46 l~ 0.023 95.o o.40 " 0.029~ 93.5 0-35 " o.o40 91.2 0-30 " o.o40 91.2 0~12 ~' o.o50 89.1 o.oo ll o.o60 86.9 -O.lo " 0.155 66.1 -0.18 l~ 0.169 63.o -0.24 " o.235 ~8.6 o 30 " 0,26~ 41.3 . . . ~
That is, the indium extractability obtained was higher than 90% at the pH of the indium-containing aqueous solution of higher than 0.30 and was 98/ at the pH of 0.~0.
Example 2 While changing the ratio of the organic phase to the aqueous sulfuric acid solution containing indium ions and zinc ions, the extraction test was performed.
An aqueous sulfuric acid solution having a pH of 0.60 containing 0. 457 g/liter of indium ions and 100 g/liter - 21 ~
~4~7~i2 of zinc ions was prepared and also an organic pha~e having the same composition as in Example 1 was prepared. While ehanging the ratio o~ the organie phase to the aqueous solution (~hown by 0/A)~ the extraetabilities of indium and zlne ln the organic phase were measured by the same ways as in Example 1. The results obtained are shown in Table 2.
Table 2 /A ratio Concn. in Concn. in Extracability orig. aq. soln. raffinate in org. phase _ __ er g/liter % -In Zn_ In Zn In ¦ ~n _ 0.25 0.457 100.0 0.043 100.09U ~ 0.0 0.50 tl l 0.034 100.092.6 0.0 0.75 ~ ~l 0.025 100.094.5 0.0 1.00_ . ,~ 0.020 100~095.5 0.0 That is, at the pH of o.6 the extractability of indium wa~ increased a~ the amount of the organic phase brought into contact with the aqueous solution in the range of 1/4 to 1/1 was larger. The extractability for indium ions was higher than 90% in each case but the extractability of zinc was 0, which showed the excellent SepQrating property of indium from zinc.
~ 2~ -76;~:
Example ~
The back-extraction test of indium from the organic phase containing indium wa9 performed by aqueous ~ulfuric acid solutlon for back-extraction while changing the concentration of the aqueous solution.
An organic phase having the same composition a~
in Example l was prepared and the content of indium was o.424 g/liter. Then, 100 ml of the organic phase were vigorously mixed with 40 ml of a back-extracting solution 10 con~isting of an aqueous sulfuric acid solution in a separatory funnel for 5 minutes. The results obtained on the back-extractabilities of the organic phase to back-extracting solution having different sulfuric acid concentrations are shown in Table 3.
~ ' .
Concn. of_ Concn. of sulfuric acid Concn. of In in in back- In in org. extracted' Back-extrac-extracting soln. phase soln. tability g/liter g/liter g/liter o~
_ _ _ 130 o.424 0.860 84.7 180 ll 0.874 94,2 210 1~ 1~022 96.2 240 ~ 1.040 96.3 270 ~l 1.02Z 96.2 300 " 1.072 lO0.0 33 ., 1.072 100.0 360 ll 1.072 100.0 . _ _ , ~L4~7~;2 That is, the back-extractability by one mixing contact of both ~olution~ was higher than 90~o when the eoncentration of ~ulfuric aeid wa~ higher than 180 g/llter and became 100% when the concentration was over 300 g/liter.
Example 4 Back-extraction test was performed whi~e changing the ~olume ratio (0/A) of a charged organic phase (0) to a back-extracting sulfuric acid solution (A), A back-extracting solution having a constant sulfuric acid solution of 180 g/liter was used and the composition of an organic phase was same as in Example 1 and the indium concentration in the org~anio phase was 0.444 g/liter. The ~tirring period of time for back-extraction was 5 minutes. The results obtained are shown in Table 4.
~ - ~
Table 4 0/A In concn. in In concn. in In concn. in Back ratio loaded org. org. phase back-extracted extrac-phase after back- qoln. tability g/liter extn, g/liter g/liter %
__ , ._ .. ... __ _ .
0.1 0.444 0.084 3.60 81.1 O.Z 1. 0.032 2.06 92.8 0.4 l l I o,0~3 1 1.08 1 97 , ' ~67~%
That is, lndium can be easily recovered with a smaller amount of a back-extracting solution in a concentrated state.
Example 5 Repeating test of a back-extraction was performed.
A back-extracting sulfuric acid solution having a constant sulfuric acid concentration of 183 g/liter was used and the mixing volume ratio 0/A in the back-extraction was kept at a constant value of 10/1. A back-extractability of indium from the loaded organic phase was measured when the back-extraction was performed thrice.
Each back-extraction was performed fo~ 10 minutes.
The organic phase composed of 3 parts by volume of D2EHPA7 12 parts by volume of TBP, and 8$ parts by volume of MSB 210 - made by Shell Chemical Co. and loaded with 2.36 g/liter of indium, The result~ are shown in Table 5.
~ ' i Table ~
!
_ ___ . . . _ __ . -- _ . __ . . _ .... _ __ .. ~
Back~extraction repeating no. 0 1 2 3 .
Concn. of In in back-g/liter 0 l9.0 4.60 4.60 . ... ., __ l phase g/liter 2.36 o.46 0.00 0.00 Integrated back-extractability % 0 80.5 10.00 10.00 . . ..
~4~t7~2 That is, when the sulfuric acid concentration of a back-extracting solution is low, a sufficient back-extract could be practiced by repeating the back-extracting operation.
Example 6 Indium, zinc and iron were di3solved in an aqueous sulfuric acid solution together with dusts containing fluorine~ chlorine, tin and ar~enic to provide an aqueous solution having a sulfuric acid concentration of 9.36 g/liter (pH 0.72) and u9ing the organic phase of this invention, a 3 stage counter current continuous extraction was performed by means of a mixer settler. The organic phase used in the back-extraction was composed of 3 parts by volume of D2EHPA, 12 part3 by volume of TBP, and 85 parts by volume of MSB 210 made by Shell Chemical Co. The extraction and back-extraction were repeated several times.
The volume of the organic phase prepared wa~ 40 liter3 and while performing the continuous extraction, sampling was performed when the extraction system reached equilibrium and the 9ample9 were analyzed. The results are shown in Table 6.
-- ~6 ~
3 146'7~2 , __ p~ ~ ~ ~q IJ.
. -, o~
'1 w ~ l-aq a~ w ~ 1- ~n . ~ p ~ O
u~ ~ P
~t ~ m P~ ~ ~
o~ag aq ~3 aq aq ag _ ~, W
~w :~ ~.~ , ~ ~ .-. , . W O
o ~o ~ ~ ~
o ~n W ~ O O O ~' ~. ~
O ~ ~ ~ O O W 1-~ W Ct~ H
O ~ ~ g W~ O~ p 1-~ OOOOO~
~ ~ ~ 1-- ~O ~D ~O O O ~ ~1 N
. ~ ~ n P~ ..
'O O O ,0 ,W,WW ,OW OD ~ ~ ..
~ ~ ~ O W ~~ O W l_~ ~
1~ 1~1--~ 0~ ~ O
.~ . ~ P
O O O O O O O O O ~_ . ~
CO OD Ot) O O O O O O .tl~
O O O O ~ W ~ O ~ ~nP
~0 ~ ~ ~ O ~ ~0 J O ~ ~ ~ O ~ ~
n O O O O O i~
W ~ ~ ~ C> O ~D
~- ~
O O O O O O O O O 7- .
~ 1~ ~ O ~ O i~ Y ~1 ~ ~ ~n ~ W 8 ~ ~D
o o o o ~ ~ ~ o ~ W
O O O O h~ ~ ~ O ~ ~ P
o~ a~ o ~ I_ _ __ ~:~4~762 That i8 ~ the extractability for iron wa9 about 10%
and tho~e ~or other elements were greatly low, while that for indium was 100%. These results show the sufficient ~ep=rat~on e~fect by the ~nvention.
Example 7 An organic phase having the same compo~ition as in Example 6 was loaded by indium and other elements ions as in the ~ame example and then the back-extraction of indium from the loaded organic phase was performed in counter current 3 9tages by means of a mixer settler using a sulfuric acid Rolution.
In addition, the concentratio~ of sulfuric acid in the aqueous ~olution used in the back-extraction wa9 305.2 g/liter and the ratio 0/A in the back-extraction was 10.75.
; The results are shown in Table 7.
.
7~
. -- 28 --,~, ~ td ~ b . ~ p~a~ ~ ' p ~
W ~ ~, X ~ y. ~ o ~ 1 ~ ~1 P tn ~ p P~ P~ - P~ P' ~ as bO ~ tn to t~
~ ~ ~ ~u. O ~ O
p) ~ ~ O ~ P t~
a~ aq aq P uq ~q cq aq aq P P~
~D
_ . _ ~ _ - I
a ~ ~n a ~ N 1\~ P ~1 . ~
~ . _ _ ~D
~ 1 ; ~~ '1 I
Wo :~ - - ~3 ~n ~U~
10 ~0 ~ O ~_ ~ t\) , ~ ~ O 1-- H ..
'~ ~ ~- g o ~ ~ 'ol ~ \n ;l ~ ~ W O ~ O O O O P~
1\7 ~ 1_ . ~ P~
: , Oo ~o O O ~n ~ O ' ~ ~
1~) ~ 00 OQ ~ ~ ~) N
. W O O~ ) (D
GO ~ ~ O O O O O O ~
. ~ 0 0~ ~ O O C~ O : .
.' W ~ I' I' o ~ ~0 ~-~ O O O O. O O ~
OD 00 00 O O O O O ~
~ ~o ~o ~ $ o o 8: g ~
W ,~ ~ o o o o o o 8 '' o o ~ ~ o o o ~
~O ~n ~ O O O O O O
~o oo . . . . .
. . . o r~ o o ~ ~ ~O ~ ~ ~ 1V ~D
w ~ ~ o a~
o ~ ~ o o o o o o o . . o , C:~ o o 'O ~n ~ g ~ P
,' _ , That is, the back-extractability for tin was low R9 well as sufficient back-extractions were obtained on other elements, ancl th~ recycling use of the organic phase was sufficiently pos~ible. In addition, since the extractability for tin from an original aqueous solution was greatly low and the content thereof in the loaded organic pha~e was also low, the existence of such a small amount of tin gave substantially less problems.
Claims (6)
EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS
FOLLOWS:
1. A process of recovering indium, comprising the steps of adjusting the pH of an aqueous solution containing indium ions to 0.25-4.5, bringing the aqueous solution into contact with an organic solvent solution prepared by diluting an extracting reagent containing a monoalkylphosphoric acid and/or a dialkylphosphoric acid and a trialkylphosphoric acid in 1 : 2-5 by volume ratio with a phase-stabilizing water-immiscible organic solvent to extract the indium ions in the organic solvent solution and then bringing the organic solvent solution into contact with an aqueous sulfuric acid-acidic solution containing 100-500 g/liter free sulfuric acid to back-extract the indium ions into the aqueous sulfuric acid-acidic solution to provide an indium concentrate.
2. The process as claimed in claim 1 wherein the pH of an aqueous solution containing indium ions is adjusted to 0.25-0.5.
3. The process as claimed in claim 1 wherein the pH of an aqueous solution containing indium ions is adjusted to 0.25-1Ø
4. The process as claimed in claim 1 wherein the monoalkylphosphoric acid or the dialkylphosphoric acid is di(2-ethylhexyl)phosphoric acid.
5. The process as claimed in claim 1 wherein the trialkylphosphoric acid is tributylphosphoric acid.
6. The process as claimed in claim 1 wherein the phase-stabilizing water-immiscible organic solvent comprises one or more of aliphatic hydrocarbons, aromatic hydrocarbons or alkylaromatic hydrocarbons.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000352965A CA1146762A (en) | 1980-05-29 | 1980-05-29 | Recovery process for indium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000352965A CA1146762A (en) | 1980-05-29 | 1980-05-29 | Recovery process for indium |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1146762A true CA1146762A (en) | 1983-05-24 |
Family
ID=4117056
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000352965A Expired CA1146762A (en) | 1980-05-29 | 1980-05-29 | Recovery process for indium |
Country Status (1)
| Country | Link |
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| CA (1) | CA1146762A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112877550A (en) * | 2021-01-11 | 2021-06-01 | 北京高能时代环境技术股份有限公司 | Indium-germanium combined leaching and extraction process |
-
1980
- 1980-05-29 CA CA000352965A patent/CA1146762A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112877550A (en) * | 2021-01-11 | 2021-06-01 | 北京高能时代环境技术股份有限公司 | Indium-germanium combined leaching and extraction process |
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