CA1188105A - Process for the recovery of indium from lead- containing materials - Google Patents

Abstract

Abstract Process for recovering indium from materials con-taining lead, especially flue dusts, comprising leaching with sulfuric acid, neutralizing the leach liquor, preferably with fresh feed, and recovering indium from the solution by solvent extraction.

Description

)5 ~escription PROCESS FOR 'l'HE RF,COVE~Y
OF INDIU~l l'RO~l L~AD-CONTAINING ~TEI~I~LS

Tecllrlical ~ield -05 This invention is a process for the recovery of indium from lead-eontainin~ ma-terials, primarily ore processinc3 residues. The process ineludes the separation of indium from other metals in the residues, such as zine, arsenic and antimony.

Bac]cgroun Ar-t ancl Prior ~rt Statement Indium is useful as a component of low meltin~
alloys and solders, as a eoatin~J on wires or eonnectors in electrieal cireuits, as a eomponent of infrared deteetors, as a eoatincl for bearilltJs, and in eonnection with solar ener~y. Since 1972, indium procluc-tion in the United States }-las been c~enerally declinirl~ while im~orts have increased. Indium is found in conunercial quanti-ties in flue dus-ts, residues, and sla~s, primarily from zirlc and lead processing.
United States Bureau of Mines Bulle-tin Number 55 (1956) describes a proeess for recoverin~ indium, alon~
with tin, from crude leacd bullion. 'I`he T?rocess involves -the separatiorl of indium chloride from a ~round mi~ture made by fusing indium, lead, zinc ancl tin chloricles. Thc mi~ture is leached with sulfuric acid and allowed to stand in eon-taet with metallie indium for preeipitation of tin and lead. Indium is recovered from the purifiecl filtrate by cementation with zine rods.
The reeovery of indium from lead-zinc smelter dross is also deseribed in the same bulletin. The dross is leached i31 sulfuric aeid, eemented from the puri-fied solution by zine, and melted under sodium eyanide, then refined, redisso]ved in aeid and electroplatecl.

~ )nitcd States ~3ureau oE Mines l3ulletlll Number 630 (1965) descLibes a proeess Eor recovering indium from ZillC
oxide fume recoverecl from lead blast furnace slag The slacJ is lcached with dilute sulfurie acid to remove zinc, 05 then with stronger sulfuric aeid to clissolve -the indium.
Indium is tl-ell preeipitated Ly the addition of ~inc oxicle and sodium bisulfite, and leaehed with a strong sodium hydroxide solution. The preeipitate is redissolved in eoneentrated sulfurie acid, and heavy metals are re-moved with hydrocJell sulfide. ~luminurn is then addcd tocement an indium metal sponc3e.
This bulle-tin also describes a process for recover-ing indium from the insoluble residue produced durinc~
leachincJ zinc oxide Lor the electrolytic Z:illC process.
Lead and residual zinc are removed by smeltin~ I`he flue dust is thell processed by leaellilly zinc ancl re-turnill(J the indium to the smelter where it cloes into tlle lead bullion and the slag. 'l`he slag is processed by slag fuming, leaching and returnillg the indium to the smelter Indiulll in the bullion is recovered with the bullion dross, whicll is retrea-ted for removal of copper matte and lead, the slag containing 2.5~ indium, whic}l is electrolytically increased to 20-25~. Fllrtller chemical and electrolytic purifieation steps are then yerEormed.
~lso described in this bulletin is a process Eor indium recovery from old platincJ solutions involving separating silver, lead, eopE~er, cadmiuln, zinc alld nic~el by suceessive aeidifications, Eil-trations, and neutralizations, leaving a precipitate of indium, iron and tin hydroxide, WhiCIl are dissolved in hydrochloric acid, and the indium recovered by electrolysis.

Disclosure oE the Invention Indium is recovered from materials such as lead-indium smelter residues, which may also contain other metals such ,~ .
~ ",............ .
. . -- . . .
,' f: . ' , _ ' as arsenic, zinc, antimony, copper and cadmi~lm, by means of an acid pressure leach with sulfuric acid to solubilize indium, zinc, and the other metals, leaving lead sulfate in the residue which may be returned to the smel-ter. The solution is then contacted with a neutralizing material such as fresh feed in order to leach additional values and raise the pEI of the solution as necessary for solvent extraction or phosphate precipitation. The solution is filtered and may be treated with iron powder to reduce any ferric to ferrous ion and the indium is recovered from the solution, preferably by solvent extraction with an organic agent such as di-(2-ethylhexyl) phosphoric acid (DEHPA), followed by hydrochloric acid stripping, tributyl phosphate (TBP) extraction, and water stripplng.
Indium is recovered from the final strip solution preferably by cementation with aluminum, or by precipitatlon with phos phate or zinc dust. Indium is recovered from aluminum as a 95~ plus cake.
In accordance with the present teachings, a process is provided for separating indium from a solution containing sulfuric acid and at least one metal value selected from the group arsenic, zinc, antimony, copper, cadmium and iron, wherein the process comprises separating indium from the other metal values by solvent extraction wherein the solvent extraction agent is di-(2-ethylhexyl) phosphoric acid.
The raffinate from the first solvent extraction step containing zinc, and usually antimony, arsenic, cadmium, copper, and iron, may be further processed, such as by neutrali~ing with calcium oxide and calcium carbonate to precipitate the metal values. After filtration, the water may be recycled to aid in filtration and wash of the residue from the neutralizing leach. The metal-containing tails may be sent to disposal.
Brief Description of the Drawing The figure comprises a flow sheet of a preferred embodi-ment of the invention._referred Embodiments The process of the present invention is useful for separating and recovering indium from lead-containing residues, primarily smelter residues also containin(J
arsenic, zine, antimony, copper, eadmium, and iron.
~ typical sueh residue con-tains 0.2 to 0.35~ indiuln, 20-55% lead., 0.06 to 0.2~j copper, ~.5 to 10% zine, 10 to 05 12.5~ arsenic, 1 to 76 antimony, 0.5 to 1.5~ eaclmiurrl and 1 -to 3% iron. Typically the lead is present as lead oxide.
~s an optional stepr -the feed material may be pre-leached -to remove arsenie.
'rlle indiurn reeovery proeess is most efEieiently conducted as a cyclic process wherein fresh indium-lead material is first contacted in an aeid-eonsurmillcJ
leaeh with the aeidie solution from an aeid pressure leaeh to be deseribed. This solution preferably contains between about 200 and 300 yrams per liter of sulfuric aeid, as well as indium, zine, and other metals solu-bilized duriny the aeid pressure leaell.
The fresh feed material is contaeted with this aeidic solution eontaining solubilized indium pri-marily to consume enouyh of the aeid in the solu--tion to prepare it for a solvent ex-traetion proeess r for reeovery of indium therefrom, or for other indium reeovery processes. The solution aeidity attained duriny this aeid-consuminy leach should be low enouyh to make the solution amenable to indium recovery by solvent extraction, preferably less than 100 grams per liter }12SO4 and more preferably about 50 yrams per liter.
The aeicl~eonsuminy leaeh is eondueted for a period sufficient to aehieve the desired aeid reduc-tion, pre-ferably for a period of between about 2 and about 4.5 hours, and more preferably for between about 3 and about 4 hours.

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Preferab].y the acid consuminy leach is conduct(d at atmospheric pressure at temperatures suficient to promote the acid consumption reac-tion, preferably betweeri about room temperature and about the boiling ternperature 05 of the solution, more preferably between about ~0 C and about 100 C, and most preferably between about 90 C
and about 95 C.
To ac}lieve the desired p~-l the percen-t solids in the leach should be adjusted accordiny to -the acid- r 10 consl1ming capacity of the feed material which is typi-cally between about 750 and about 900 lb. sulfuric acid per ton of feed (about 0.35 to about 0.45 grams sul-furi.c acid per gram of feed). Preferably, therefore, solids in the leach will be between about 35 and 45 15 percent.
Duriny this acid-consuming leach typically between about 30 and 40~ of the indium in the feed will be solu-bilized.
As an alternative to the acid consumincJ leach using 20 fresh feed material, the pil of the acidic solution can be rai.sed with caustic agen-ts such as calcium carbonate, however, this requires subsequen-t filtration -to separate the liquid from the solids generated by the addition of a caustic reayent, with high wash water requirements, and 25 results in losses of indium from solution.
When fresh feed has been used to consume the acid in the indium-containing solution as previously described, a liquid-solid separation is performed, followiny which the solids may be washed with water. This water may be 30 recycled filtrate from the neu-tralization of arsenical tails as shown in the flow chart.
The solids are -then further treated for extrac-tion of up to 92% of the indium originally present in the feed by a sulfuric acid pressure leach. Typically 35 indiuM in the feed is tied up in -the matrix of ~.he . :,; , . .
., , .

3~
~, leacl oxide ma-terial in -the Leed, and can be freed by convertinc3 the oxides -to sulfates, t}lUS producing a lead sulfate residue suitable for recycle to a lcad smc:Lter or other lead extrac-tion process. This frec-ing and solu-05 bilizing of the leach is pre~erably accomplisl-led by leachincJ the Eeed material wi-th a solution contain:ing sulfuric acid in a concentration preEerably from about 200 to about 600 yrams per li-ter sulfuric acid, and more preferably between abou-t 200 and about 300 grams per liter.
~he leach is conducted under pressure at tempera--tures above the boiling temperature of the solu-tion, preferably at least about 150 C. I~ic3her temperatures have not been found to be detrimental -to the process.
Pressures necessary to achieve the foregoing tempera-tures and to promote the indium solubilization ran(3e between about 50 and about 160 psig, and preferably be-tween about 90 and 110 psig. Iligher pressures have not been founcl to be detrimental to the process.
To achieve up to 92% indium extraction, it has been Eound preferable to use between about 30% and about 40%
solids in the leach by weigh-t.
The leach is conducted for a period of time suffi-cient to achieve the desired extraction, typically Erom about 2.0 to about 4.5 hours, and preferably from about 4.0 to about 4.5 hours.
The indium is kept in solution durinc3 the leach by conducting the leach under oxidizing conditions, such as oxyc3en pressure~ The oxyc3en demand is slight. It has been found that indium solubilization is enhanced when small amounts of pyri-te are added to the leach, especially when the feed material is low in iron. The pyrite is added in amounts sufficient to dissolve the ~.
~ . .
.~ ,. .~

_ ~8~L05 necessary oxyge~ y forminy ferric ions ~hicll th~n servc as the oxidant -to prevellt reprecipitation of the ind~ m.
Preferably the amount of pyrite used is from about 20 to about S0 grams per lltcr.
05 Indium extrac-tion is maximized when the acid con-centration at the end of the leach remclins hicJh, p~eferably between about 200 and about 300 yrams per liter sul-furic acid, and mos-t preferably be-tween about 240 and ahout 260 grams per li-ter.
Followinc3 -the leach a licluid-solid separation is performed, ancl the solution may be recycled to the acid consuminc3 leach such as with fresh feed as previously described, or is treated by other means to raise the pH
-to a value suitable for indium recovery therefrom.
The solution leaving the acid pressure leach may contain up to 92Qo of the indium, up -to 91% of the arsenic, up to 44O of the antimony, up to 99~O of the zinc, up to 99% of the copper, Up to 92% of the cadmium, and up to 90O of the iron presen-t in the original feed material. ~ssentially all of -the lead, tin and silver remains in -the residue.
Similar extractions are obtained when the feed material for the acid pressure leach is fresh feed as opposed to the repulped solids from the acid-consuming 25 leach using fresh feed material previously described.
Following pll adjustment of the solution as pre-viously described, the solution may be furtller treated to prepare it for indium recovery by the addition of iron powder as needed to reduce ferric iron to the ferrous state, typically in an amount of from about 3 to about 40 grams per liter.
The solution is then processed for indium recovery, preferably by means of solvent extraction. Typical:Ly, the solution contains between about 0.2 and abou-t 0.4 , .. . .. ,.. _ _ _._ ~
~, , .
~ '~' ' -, -._ ~r `~ -`

-~3 grams per liteL^ indium. Good separation of indium is ob-tained with arsenic contents in excess of 25 yraIms per liter, arItimony and iron in exc~ss oE 0.35 ~Jrams per liter, and cadmium in excess of 2 grams per :Liter.
05 The solvent extraction process may be carriecl out so as to achieve at least about 95~ extraction of the indium.
The preferred extractant is di- (2-ethylhexyl) phos-phoric acid (DE~IPA) in kerosene or a similar diluent.
ln The concen-tration necessary to achieve the desire(l ex-traction is t~pically between al~out 0.1 and 0.6 mo:lar, and preferably between about 0.25 and 0.35 molar.
The preferred oryanic to aqueous ratio is ~re-ferably between about 0.5:1 and 1.5:1, and preferahly about 1.0:1. The solvent extraction is performed pre-ferably at temperatures between about 30 C and about 50 C, and preferably between about 35 C and about 45 C. Several stayes are required to reach the de-sired extraction, and it has been found that three to four stages, preferably four stages, provide the best results, usiny a mix -time for each sta~e of preferably about 5 minutes.
T}le loaded organic is then pre-ferably scrubbed with sufficient water to remove entrained aqueous impurities such as arsenic, preferably at an organic to aqueous ratio of about 5:]
Following the DF~IP~ extraction, most of the zinc, cadmium, arsenic, antimony and iron have been rejected in the raffinate.
The loaded organic is then stripped for indium, pre-ferably with I~Cl at a preferred concentration at leas-t about 3.0 N. Lesser concentrations may also be used, but are not as efficient in supplying the hydrogen ions necessary to regenerate -the oryanic extractant _9- ~ S

and dlsplace the inclium. The preEerred orgallic to aqueous ratio for pcrforming this strippincJ stcp is between about 2.0:1 and 3.0:1, and preferably a~out

2.5:1.
05 It is often desirable to produce a Einal less acidic solution of indium for recovery of elemental indium by cementation or other means. To produce a solution of indium in water, the indium in the EICl strip solution may be fur-ther extrac-ted with an agent such as tributyl phosphate (TBP) which ma~ be stripped for indium with water.
Preferably the TBP is used at a concentration oE about 50~ in a diluent SUCIl as kerosene.
The T~P extraction is performed preferably at a temperature between about 30 C and about 50 C alld preferably about 40 C, in two to four stages, as necessary to extract essentially all the indium present.
The preferred organic to aqueous ratio for this eYtrac-tion is preferably at least about 1:2, and more preferably about 1:1.
Following the TBP extrac-tion, the loaded organic may be stripped with water preferably a-t a pEI of between about 2 and 4. The preferred reagen-t for this pll adjus-tment is l-ICl. The preferred organic to aqueous ratio for this water strip is about 2:1.
~ n optional method for treatincl the loaded l-l~l strip solution resulting from the stripping of the D~EIP~ extraction agent to make it less acidic is to neutralize the solution with caustic to -the pre-ferred pll for indium recovery of between about 2 andabout ~.
Indium is recovered from the final pE~-adjusted aqueous solution preferably by cermentation with alu-rninum sheet. The indium collects on the aluminum sheet, and in orcler to ~romote slougllillg o~ of thc indium from the aluMinum surface in order to rnaintain .. .. .. ...

os --1()--a clear surface for continued cementa-tion, inclium concen-tration in -the final strip solution should be allowed to build up by means of strip solu-tion recycle or eva-poration. Concentrations of between about 5 and 15 n5 grams per liter indium are preferred.
Indium may be recovered from the cement cake by slouyhing or scraping into a cone bottom tank, and periodically draining to a pan il-ter for filtration, washiIlg and transfer to a forced air tray oven. 'L`he r high purity cement usually contains 95~ or more indium, about 0.03% antimony, about 0.05 arsenic, and about 1.5' aluminum.
~ s alternatives to solvent extraction, indium may also be recovered from the acid pressure leach solution, which has been adjusted to pl-I at leas-t about 1.0 as pre-viously described, by other means known to the art, such as precipitation Wit]I zinc dust or as the hydroxide or phospIlate. The method chosen depends on antimon~ and arsenic levels in the strip solution, with the zinc preci.pitation being preferred wheIl these metals are present. The indium precipitate may then be fused Wit]l sodium hydroxide and cast i.nto anodes for electrorefininy in a sodium chloride electrolyte.
When the solvent extraction method of indium re-covery is used, raffina-te from the DFIIT'~ extraction step may be neutralized with calcium oxide and/or calcium carbonate, -the la-tter screened to minus 200 mesh. Re-mainiIlg metals are thus precipitated and may be sent. to disposal followiny a liquid/solid separa-tion, while the filtrate may be returned to aid in fil-tration and wash of the residue from the acid consumption leach.
From the foregoing it can be seen -tha-t an inte-grated process has been disclosed comprising several novel steps in combination to provide indium e~-traction ... ..

s from the feed composi-te o.E up -to 92Qo ~ recovery :Erom solution of approximately 95~, with an overall r~covery of up to 84%, and good rejection of all other metals, including antimony.

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3~

E:XAMI'[~
NE'UTRALlZING I,EACII
~ neutra:Lizing leach was performed on 300 cJrarlls of master composite Eeed havincJ the following compo-0 5 S i-tiOIl:
Indium 0.30% Copper 0.1~26 ~rsenic 10.7% Cadmlum 1.02%
~inc 3.49% I.ead 49.4O
Antimony 4.03% Tin 0.47%
10 500 cc of 250 grams per liter sulEuric acid plus re-cycled pressure leach primary filtrate and wash was used.
The leach was perEormed for 2 hours at 90 C, and the materials filtered. The solids were then repulped and leached with 3G0 cc oE 250 c,rams per liter sulfuric acid under oxyc3en pressure with a 300 cc per minute o~ygen bleed. The materials were again fil-tered.
Results are shown in Table 1. Total indium ex-trac-tion is given in the Table as indium in the resiclue as a percent of indium in the feed material by weicJht.

1-`

.

'1 N
~ O -~
;rl r-l N
~:j ) O~
rl ~g ..
c~
O I_ U) ~ N
~N
~ + ~r r rl O ~
r~ (~ O t~
r-l ~ L ~1 r-l ~L~ U~ ~
~1a~ al u, ~
~, ~ ~r \
'~'~
U~ U~ Ln O
(I) nl r~ ~1 ~1 O O
(_) Ll^l r-l E~ ~_1 N
.
r-l r~l N~ ! r~
~ :~ `~ ~ ~

U~ ~ ir~l ~ ~L~ ('~
r-J
r I
C.) ~ rl ~ a~
æ rl U~ cTl N (~;
~ r~

il8~

EXA~PLE 2 SULI;`URIC ~CID PRESSUR~ LEAC~I
Samples of the master composite clescri.bed in ~.xample 1 were leaclled witll sulfuric acid under VaryincJ conclitions 05 of ten-pc-~rature, pressure, free acid concentration ancl pyrite adclition. A 300 cc per minute oxyyen bleed was used :Eor tests 2 throuyh 5. Results are set forth in Table 2.

. ~ . ~ ~ .

S
. ..~

co r ~o r~ o r~ r~
r~J r; o r; c~ c~; ~o ~o r~ c~ a~ c~ c~ c~ cr~
r\
O r Lr~ r~ c~ ~
(r' 'tC~r1 C I ~'n r r~x ~ In ~o ~1 r ~1 r ~ r~ c~ r~ o r~ ro r~ c~ cs~

~D C~ O C~ LO C~ 'S
.......
~1 o~D cr~ rr~ c~ rx~ I
r~ r~ I~ ~ r~ r~

rr ,~ ~d ~t~ rtrl ,~ ~ r~ c~
tn r~ '`'J~ ~ o .n ~ ~r ~ o o ~ _ I~ cx~ ~r ~r~ ~I L~ tn r~Jr,~ ~ ~ (ls ~) 0~ rS

rn r~
~ ,~ .~
tn tn o o o o o o o t) O
rl) ~ L~ In o ~ ~ Inrrs ~
_ J~
~ r.~ r~
b~ '' n .n ~ In 1n ~
rl 1 d~ rn r~ ~ o ~ cr ~r V~ ~3 r ~ r- r~
rJ) C \ O o o ~o r ~ ~o r~ L~~ n 1~O rr~l r~

~: O
r~ r~ r n ~O r-- ~U 1:~
.rJ -~ ) ~ I ) tV O
rn rn tn rn rn rnrn P~
r~ r'l'r~ r~ rv ~ r¢v -~ :~

3~B81~5 L " .

I`XAMl'l,l: 3 COMI'AI~ISON L~:A('IILi:S FOR INDI~M F,XTI~TION
___ _ 50 yram samples of master composite described in Example 1 were leached w:ith: IICl and br.ine, followecl by 05 leacl sulfate precipitation with sulfuric acid in 'rest l;
mi~ed sodium chloride/calcium chloride br.ine w.ith sod:ium chlorate in Test 2; sulfuric acid acti.vated with nitric acid in Test 3; and ammonium sulfate in Test 4 (Usilly a 30 c3ram sample of master composite feed). Results are described in Table 3.

. ~ ..,; ~ .
..
. ,, _~
. , = ,~

~ l~si (I) r~
Q rn~ 0~ r-l r~
~ o~
u', I l, ~ r~ ~ ~r co ù`~ ~ . .
CO o~ Ln o o ~t) ~ ~D ~D I_ n; tn o o~ 1 u~
~ CO ~) ~I r- 1 r~ Ul L~ ~ ~r 0> o~ o~ ~
r ~ r~ ~!
H t~O O~ Ln ~O
CO In ~r ~
~n o ~ l ~i~ o F~ ~! f~Ln ~1 t~lt`\l (~1 _, O
''1 r~3 c~ o o Ln Ln E~ - ~ C~' l l o o o~ ~r '~_ ~ r~l ~ O
t~ ~ t~ ~r C~ ~ 0 O. \ ~ ~ tn~ ~ t~ 5~ t'3 t, o ~ o o o o o O o O o o Ln O ~ ~r ~l ~r t\l n ~ Ln ~ ~

u~ t~ ~
~r U Pt~ ~ 0 ~, C~ r~ o ~ \ O~r \ O O~r t~l L', ~ tl~ C~ C~ tn O
c~ ~ .~ ~ ~ ~ æ
Z . ~ , r-~ ~r .~ ~ ~
tn u~ U~ U~
,~

LX~ME'LI;` 4 Primary filtrate from a neutralizillcJ :Icach o~- thc master composite oE l~xample 1, containinc3 76 c3pl 1l2XO~
and 0.674 c3pl In, 8.67 c~pl As, 0.379 c3pl Sb, 28.9 c~pl 05 zn, alld 1.94 c3pl Cd, was extracted with 10~ (0.3 N) D~ll]?~ in keroselle at an orc~anic -to aqueous ratio of 0.71:1 in three stages. The loaded orc3anic was thcn scrubbed wi-th 1 N l-ICl, at an orc3anic to aclueous ratio of 5:1, then stripped with 3.0 N I~Cl at an orc3anic to aqueous ratio of 2.1:1. Results are summarized in Table 4.

O i O Lt- ~J O 1~1 Cl~ t\l O r-l ~ O. . . ~ O. ~ ~ ~ O. ~. ~
t~l OCi )O O r-lr~1~ 0 0(~J Oa~ O O O
r Ia~ I-- ~r--IC~ r--¦

r I~01~ r-l ~Ln ~o r I
~i Q)o . . .o . . .o ,r~ r~ l ''' "'~'' ' '~ '~ I ~'' ~' ~) r I (~)~J'C~lr-l r I r-l r I C~l (~1 I
C~
a) rL~ O ~O r-l O ~r a) ~)O o o . . .o r~, r Ir-l O O rl~1 1-- 1-- ~J
~1 1 ~ r~
o ~)1-- ~ Or I O1--0 O ~1 r-l ~t' O
~r 5~O . . .. O~ . ~ . O
L1l U~ OCi) O Orlr~ ~Irlr-l O r-l (\I rl f~l O
~)r ~a~ o r- I
a~
P~
Inr-lr-l ~D OC;~~Ir~lO O r~ r i O
U~ O . ~ ~ ~O ~ O
O CO O O r-l r-lt~O O Or-l C\l O O C>
r-l a~ o o r~ r-l a~~r ~ ~r ~r-l~O ~) CO 1~ 1_ ~1 0 . . . .O .. . . O
r- I Or 1';J' a~ Or ~o ~ ~ O ~o r I CC ~) ~~o a~ r~r-l r--CCr-l r-l ~ a~
r~ 0~O 0~O u~
~: ~
~ o o o r 1 ~ r r U U
.~ ,~ ~) ~1 rX r~

,~Lr)LnC~~ ~Da~ o o Ln a~
o ~oCl~1-- t~lt~ ~ . t~
O 1~1~ r-Jr ~ r~t~') Lr) Ll ) ~0 ~> ~ O Or-l ~r r I r-l r~r-lr-l r-l ,1 ~
o E~
~ O ~ O _~ O
U ~ tl) Z'; ~ tl) Z ~I tl) Z
~) rl 1~ ~ r-l ~ ~ r-l . ,~ _ rl (1~ ~ rl rd O ~ 1~ ~. ~ 1 ,r ~i .r~ Q n, ~ Q n, ri Q
P~ r~ rl ~ L~ rl ~tJ L~ ~ ~
a) rd U 11 a) rd O ~ c) rd U .LJ
h ~ U~ rl7 rl, ¢, U~ r,~ h ¢. tl~ U~

~1 rO r-l (~1 E~

~:~o-~:X~ll'L,~ 5 Strip solution yenerated ~rom the procc~dure descri.bed in ~ample 4, and containillc3 0.795 ypl In, 0.01 qpl As, 0.010 ypl Sb, 0.013 ypl Zn, 0.001 cJpl Cd and 0.232 clpl Fe was e~-tracted with 50~ TBP in kerosene at an or(;anic to aqueous ra-tio of 1:1 i.n two stac~es. I`he loadecl orcJanic was then stripped wi-th water adjusted to pll 2-4 with IICl in two stayes at an orc~anic to aqueous ratio of 2:1. Results are sum~larized in I'able 5.

r~
- ~ .

. .~

~8~ S

t~r L. Or-lCOCT~ O~D ~ r o r-l 1(~ Cr~
I~ C~ . . .O . . . O
r-l ~11(~ Cl~r-J In ~:1' ~r r-l r-1 ~:) L~
r-l Or~ r~S~r-~ ~-1 1~ r-~

LJ
a) a) O1--L~l r~ OCi~~r r-~ O CT~ r-l r-o . . . o . . . o r-lr-l LnC~) r i O 1-- CT~ r-l O r~l c~ r~ CT~ ~D cr~ ~D C~
r~
~) r~ ~ O O O O Ul O
r~ ~) O O O O I o I o ~ r~ r-l O r-l I--1 ~_1 o L~
(1) ~ o o l-- o o o Ln o o o o o U U~ O ~ ~ ~ O ~ . ~ O t~) C~
!-1 r-l Or.~ O r-l Or,o Or-l r--l ~ Ln r~Ln ~r P~
u) oo o o o o o o o o c~ o ,,... o o o o o r--lr-l O O r-l r~ O Or~ r~
Ln r o ~1 r. o 1-- o ~D Ln ~r o ct) ro ~ H O. . . O . . . O
1~ r-l Ln o ~rr I r~L(') Or-l r~) r~'~ LD
E I c~ c~ CT~ cr~ r-l I
o\o o~o o\o L~ L~ L
r~ ~ r~
-1~ ;
U U
5~ ~1 (~
.J
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Claims (26)

1. A process for separating indium from a solution containing sulfuric acid and at least one metal value selected from the group arsenic, zinc, antimony, copper, cadmium and iron, the process comprising separating indium from said other metal values by solvent extraction wherein the solvent extraction agent is di(2-ethylhexyl) phosphoric acid.

2. The process of Claim 1 wherein the acid concentration of the solution is adjusted to less than about 100 grams per liter prior to solvent extraction.

3. The process of Claim 2 wherein the acid adjustment is accomplished by contacting the solution with a solid feed material containing indium.

4. The process of Claim 1 wherein the solution is contacted with elemental iron to substantially reduce all ferric iron present prior to solvent extraction.

5. The process of Claim 1 wherein the di(2-ethyl-hexyl)phosphoric acid solvent extraction agent is present in a concentration of between about 0.3 and 0.6 N in kerosene.

6. The process of Claim 1 wherein indium in the di(2-ethylhexyl)phosphoric acid is stripped with an aqueous solution of hydrochloric acid at a concentration of at least about 3.0 N.

7. The process of Claim 6 in which indium in the hydrochloric acid strip solution is re-extracted with tri-butyl phosphate.

8. The process of Claim 7 in which indium in the tributyl phosphate organic is stripped with water at a pH
between about 2 and about 4.

9. The process of Claim 8 wherein indium is recovered from the water strip by cementation with aluminum sheet.

10. The process of Claim 9 wherein the indium concentration in the strip is adjusted to between about 5 and about 15 gpl.

11. The process of Claim 6 in which the pH of the hydrochloric acid strip is raised to between about 2 and about 4 by means of a caustic reagent, and indium recovered therefrom by cementation.

12. A process for recovering indium from a material containing at least the metals indium and lead comprising:
(a) leaching the material with sulfuric acid, (b) contacting the leach solution with an acid-consuming material so as to raise the pH of the leach solution to a value permitting recovery of the indium therefrom; and (c) recovering indium from the leach solution of step (b) by the process of Claim 1.

13. The process of Claim 12 in which the feed material contains lead as lead oxide.

14. The process of Claim 13 in which the feed material is smelter flue dust.

15. The process of Claim 12 in which the acid-consuming material of step (b) is fresh feed material.

16. The process of Claim 12 in which the acid concentration of the leach solution immediately following step (a) is between about 200 and about 300 grams per liter.

17. The process of Claim 12 in which the pH of the solution immediately following step (b) is at least about 1Ø

18. The process of Claim 12 in which the leach solution of step (b) contains at least one additional metal selected from the group consisting of arsenic, zinc, antimony, copper, cadmium and iron.

19. The process of Claim 12 in which pyrite sufficient to absorb sufficient oxygen to improve extraction of indium is added to the leach of step (a).

20. The process of Claim 12 in which the leach of step (a) is conducted at a temperature sufficient to extract at least about 80% of the indium from the feed material.

21. A process for separating indium from a material containing indium and lead oxide in which the lead is converted to an unsolubilized sulfate while the indium and other metals including at least one of the metals arsenic, zinc, copper, cadmium, iron and antimony are solubilized by leaching with sulfuric acid at a concentration of between about 200 and about 300 grams per liter at temperatures above the boiling point of the solution sufficient to solubilize at least about 80% of the indium in the feed material; and the solubilized indium is recovered from the solution by solvent extraction using di(2-ethylhexyl)phosphoric acid.

22. The process of Claim 21 in which the acid content of the leach liquor is reduced to less than about 100 grams per liter by contacting the liquor with a material selected from the group consisting of calcium carbonate, an alkali or alkaline earth metal hydroxide, and fresh feed material.

23. A process for separating indium from lead comprising leaching a material containing indium and lead at atmospheric pressure with a solution containing solubilized indium and sufficient sulfuric acid to solubilize at least about 30% of the indium of the feed material to the exclusion of substantially all the lead and recovering the indium by solvent extraction using di(2-ethylhexyl) phosphoric acid.

24. A process for recovering indium from a material containing at least indium and lead oxide comprising:
(a) leaching the material with sulfuric acid to solubilize indium to the exclusion of lead, and performing a liquid solid separation;
(b) contacting the leach solution with fresh feed material so as to raise the pH of the leach solution to a value permitting recovery of the indium therefrom; and (c) recovering indium from the leach solution of step (b) by solvent extraction using di(2-ethylhexyl) phosphoric acid.

25. The process of Claim 1 wherein said solvent extraction is followed by a hydrochloric acid strip, re-extraction with tributyl phosphate and stripping with an aqueous solution.

26. A process for separating indium from a material containing indium and lead oxide in which the lead is converted to an unsolubilized sulfate while the indium and other metals including at least one of the metals arsenic, zinc, copper, cadmium, iron, and antimony are solubilized by leaching with sulfuric acid at a concentration of between about 200 and 300 grams per liter at temperatures above the boiling point of the solution; then reducing the acid content of the leach liquor to less than about 100 grams per liter by contacting the liquor with fresh feed material;
and recovering indium from the solution by solvent extraction with di(2-ethylhexyl)phosphoric acid followed by hydrochloric acid stripping, further extraction with tributyl phosphate followed by aqueous stripping, and cementation.