Recycling of Jarosite For Recovery of Valuable Metals and its Utilisation

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1 Interntionl journl of scientific nd technicl reserch in engineering (IJSTRE) Volume 1 Issue 4 ǁ July 216. Recycling of Jrosite For Recovery of Vluble Metls nd its Utilistion Mnorm Swin, b K K Shu, c B N Roy M.Tech student, BIT Sindri, Dhnbd,Indi b Principl Scientst, Ntionl Metllurgicl Lbortory, Jmshedpur, Indi c ssistnt professor, BIT Sindri, Dhnbd, Indi BSTRCT: bout, 8% of world s totl zinc is produced through conventionl hydro-metllurgicl process i.e. Rost-lech-electrolysis (RLE) process.. The process rejects iron in the form of jrosite, crystlline nd esily filterble solid residue. jrosite contins higher concentrtion of toxic elements like led, zinc, sulfur, cdmium, chromium nd copper etc. Due to these chrcteristics, jrosite itself is cosidered highly hzrdous mteril universlly nd hs detrimentl effects on environment s well s humn helth. Jrosite residue collected from HZL is treted to recover different metl vlues. s such jrosite is very stble mtrix nd ll the metls present in it is in insoluble form. Direct dissolution of different metls from jrosite mtrix ws found very poor. Therefore, combined sulftion rosting leching process ws developed for selective nd quntittive dissolution nd recovery. Sulphuric cid rosting followed by wter leching could recover Zn, Cd nd other minor bse metls quntittively. The led enriched in residue is recovered by leching in brine solution of suitble composition. Finlly S & XRD nlysis is done for chrcteristion of mterils. From the nlysis, we conclude tht fter second stge brine leching process recovery of zinc 98.58%, cdmium 99.99%, led 99.92% nd iron 86.34%. KEYWORDS: Hzrdous jrosite,vluble metl recovery, wter leching, brine leching. ` I. INRODUCTION During hydrometllurgicl extrction nd purifiction of Zinc sulphide ore, huge mount of jrosite is relesed universilly s solid residues. The process rejects iron in the form of jrosite, crystlline nd esily filterble solid residue. The mjor portion of jrosite consists of oxides of iron, sulphur nd zinc. Most of the impurities present in the lech solution re lso incorported in to the mtrix of Jrosite. Thus jrosite contins higher concentrtion of toxic elements like led, zinc, sulfur, cdmium, chromium nd copper etc. Due to these chrcteristics, jrosite itself is cosidered highly hzrdous mteril universlly nd hs detrimentl effects on environment s well s humn helth. Therefore the residue is usully dumped in the designted sites following proper guidelines. Sfe dumping of the residue not only occupies costly griculturl lnds but lso incurred huge cost. Even with sfe dumping, in long run due to wethering /bcteril ction there is relese of toxic elements in soluble form which ultimtely contminte the soil, ground wter nd qutic life. Thus sfe dumping of the jrosite residue my not be good option to tke cre of the environment. In this regrd n ttempt hs been mde in the present study to develop n environmentlly friendly process to provide workble solution for sfely treting of hzrdous jrosite wste with simultneous recovery of ll the vluble nd toxic metls present in it. In Indi,Hindustn Zinc Limited (HZL) hs multi-unit mining nd smelting estblishment hving instlled cpcities of 3.49 million tonnes per yer Zinc mnufcturing from four smelters locted in the sttes of Rjsthn, ndhr Prdesh, Bihr. Debri Zinc Smelter plnt is one of the lrgest units hving mmonium Jrosite process of Electrolytic extrction method. The current Zinc production cpcity of HZL is 9,3, tonnes per nnum nd bout 5 lkh mtric tonnes Jrosite is relesed per nnum.the jrosite is cidic in nture nd PH is less thn 3.5. There re severl techniques tht hve been developed world wide by severl reserchers for remedition of hzrdous wste contining priority toxic elements.solidifiction/stbilistion (s/s) process is one of the techniques,now commonly used to inhibit the trnsport of hevy pollutnt elements into the surrounding environment nd offers impoveement in the physicl chrcteristics tht reduce the lechblity of toxic metls. Rusen et l. developed process of cid leching nd brine leching to reclim Zn nd Pb, respectively. bout 71.9% Zn nd 98.9% Pb cn be recovered. [1] Turn et l. Developed process of blending, rosting, Mnuscript id Pge 36

2 Recycling of Jrosite For Recovery of Vluble Metls nd its Utilistion wter leching, nd finlly NCl leching to recover Zn nd Pb, respectively. bout 86% Zn, 89% Pb cn be extrcted from the residue. These studies hd not showed how to recover Cd nd Cu presented in the wste. Leching of gold,silver nd led from plumbo-jrosite contining hemtite in HCl-CCl 2 medi is lso studied by some reserchers[2] Shohu 211Ju developed process for recovery of Pb, Cu, g nd Cd from jrosite by using NH 4 Cl leching round 93% of ech metls recovered. [3] There is possibility of using jrosite s substitute for nturl gypsum in cement production [4]. Jrosite wste cn be detoxified through immobiliztion by mking composite products using other inorgnic industril wstes s dditives which re cusing mjor environmentl problems. Col Combustion Residues (CCRs), Pond Col Combustion Residues (PCCRs) nd Mrble Processing Residues (MPRs) cn be used s dditives long with cly using solidifiction / stbiliztion (s/s) nd sintering process [4, 5]. The physico-chemicl chrcteristics of jrosite indictes tht there is utiliztion potentil of jrosite-snd mixture s building mterils like bricks, blocs, cement, tiles, composites [6]. Development of lterntive nd lightweight building blocks for the substitute to the existing fired cly bricks [7]. Jrosite my lso be reprocessed nd iron s hemtite cn be obtined from it [8]. The physico-chemicl chrcteristics of jrosite indictes tht there is utiliztion potentil of jrosite-snd mixture s building mterils like bricks, blocs, cement, tiles, compositesjrofix, stble mteril obtined by mixing jrosite with 2% lime nd 1% cement, itself hve the potentil to be utilized for the construction of rod embnkment. While jrofix-soil mix (5-75%) nd jrofix-bottom sh mix (5-75%) hve the potentil to be utilized for the construction of embnkment nd my be used for construction of sub-grde lyer of rod pvement [9-14] Jrosite seems to be potentil resource which hs to be recycled in techniclly fesible nd environment friendly mnner. The min objective of this project is Recovery of ll vluble metls from jrosite. Reducing the toxic effect of jrosite before its disposl to the environment by recovering of toxic metls from jrosite. Development of suitble process for recovery of metls from jrosite. II. Mterils nd methods 2.1 Smple collection nd processing Jrosite smples were collected from the existing dump yrd outside the plnt re t Debri, Hindustn Zinc Limited, Rjsthn, Indi. The mteril ws observed to be fine grined, light weight nd resemble conventionl soils.the smples were ir-dried, sieved through 2mm size nd stored in glss continer. For chrcteristion smpling ws done from the ir-dried smple dopting conning nd qurtering method. 2.2 Chemicl nd minerlogicl chrcteristion Before the chrcteristion of mterils dry cid digestion method ws performed. For dry cid digestion.5g of jrosite smple ws tken in beker. Then the smple ws treted with HCl, HNO 3 nd perchloric cid seprtely. Then the digested smple ws filtrted nd diluted for chemicl nlysis by tomic bsorption spectrometer.the qulittive nlysis of jrosite hs been crried out by S. The phses in the originl jrosite smple were nlysed by XRD. 2.3 Instruments used for chrcteristion of the smple The microscopic nlysis of the smple were crried out by Scnning Electron Microscope. The chemicl chrcteristion of the smples were crried out by tomic bsorption spectrometer. The phses were nlysed by X-ry diffrction spectrometer were 2-thet vlue is 9º. Mnuscript id Pge 37

3 Recycling of Jrosite For Recovery of Vluble Metls nd its Utilistion III. EXPERIMENTL DETILS 3.1 Preliminry cid leching study Initilly, HNO 3 nd mlic cid leching of jrosite smple were studied to provide reference results. ll the preliminry leching experiments were crried out in flsks tht were mgneticlly stirred using 1% pulp density where concentrtion of cid ws (2-6gpl), rosting temperture (2⁰C 75⁰C) nd leching temperture 7⁰C for period of 4 hours. fter leching, the lech residue were wshed with distilled wter nd the solution ws tken for S nlysis. 3.2 Rosting of jrosite residue- mixture n pproprite mount of ws mixed with 1g of jrosite smple in porcelin dish nd plced in Muffle furnce preheted to the required temperture. t the end of the predetermined heting period, the smple ws removed from the furnce, cooled in desicetor, weighted, ground nd preserved in closed vessels to wit nlysis. The effects of vrious prmeters such s rosting temperture (2-75ºC), rosting time (12min), /jrosite rtio (.1. 3) on the rosting of the smples were exmined. 3.3 Wter leching of jrosite residue- mixture Prior to use, the rosting jrosite residue ws leched with tp wter t 4ºC for 6 min t 1% pulp density with mechnicl stirrer t 6 rpm to improve the recovery in the subsequent stge of chloride leching. fter filtrtion, the solution ws nlyzed by tomic bsorption spectrometer for zinc,led nd iron. The residue ws dried, ground, sieved, nd physiclly chrcterized to determine the prticle size distribution. Then the residue ws chemiclly nlyzed for zinc, iron, nd led using n tomic bsorption spectrometer, nd its minerlogicl structure ws identified by X-ry diffrction nlysis. 3.4 Leching for Led Extrction fter wter leching, the jrosite residue ws subjected to chloride leching to recover led. Commercil grde slt (NCl), s chep gent, ws used to prepre brine solution. Industril grde HCl ws used for ph djustment. The effects of NCl concentrtion (22g/l), wter lech residue round 1% pulp density, leching temperture t 8⁰C nd leching time for 6 min nd stirring speed 7 rpm were investigted. fter brine leching the brine lech residue ws once gin subjected to brine leching so tht led could be thoroughly segregted from the jrosite residue. The lech liquor of both the brine leching ws tken for S nlysis nd lech residue for XRD nlysis. IV. RESULTS ND DISCUSSION 4.1 Chemicl nd minerlogicl chrcteristion The mjor portion of jrosite consists of oxides of iron, led nd Zinc chemicl nlysis of originl jrosite s shown Tble 4.1. The mjor minerl phses of the jrosite re potssium iron sulphte hydroxide KFe 3 (SO 4 ) 2 (OH) 6 nd qurtz (SiO 2 ). The phses in the originl jrosite smple were nlysed by XRD s shown in the Fig.4.1 below. Tble 4.1:Chemicl nlysis of originl Jrosite smple Sl No Formul Concentrtion(%) 1 Fe 2 O SO SiO ZnO 9.11% 5 PbO l 2 O K 2 O.7 8 MnO.46 Mnuscript id Pge 38

4 Intensity Recycling of Jrosite For Recovery of Vluble Metls nd its Utilistion 9 CO.24 1 CuO MgO TiO P 2 O Cl.6 15 V 2 O g.4 17 CdO.3 18 Cr 2 O Rb 2 O 89PPM KFe 3 (SO 4 ) 2 (OH) 6 B-SiO B B B B B B Thet Fig. 4.1 XRD nlysis of Originl Jrosite Smple 4.2 Preliminry cid leching study Preliminry cid leching study of jrosite smple were crried out using 1% pulp density, HNO 3 nd mlic cid (2-6gpl) respectively vrying the rosting temperture (2-75ºC) for durtion of 4hrs. The S result of preliminry leching experiments using 1% pulp density were tbulted in Tble- 5.2 & Tble-5.3 below. Mnuscript id Pge 39

5 Recycling of Jrosite For Recovery of Vluble Metls nd its Utilistion Tble.4.2 The S result of HNO 3 leching experiments. Smple Nme %Pb %Zn Originl/HNO 3 /6gpl.134% 2.276% 2⁰C/HNO 3 /6gpl.237% 2.825% 4⁰C/HNO 3 /6gpl.57% 3.343% 6⁰C/HNO 3 /6gpl.48% 4.838% 75⁰C/HNO 3 /6gpl 1.6%.21% Tble.4.3 The S result of Mlic cid leching experiments. Smple Nme %Pb %Zn Originl/Mlic cid/6gpl.141%.1856% 2⁰C/Mlic cid/6gpl.144% 1.784% 4⁰C/Mlic cid/6gpl.212% 1.653% 6⁰C/Mlic cid/6gpl.21% 3.83% 75⁰C/Mlic cid/6gpl.93% 4.16% The mrginl dissolution of both zinc nd led ws obtined under ll the bove condition with vrition of either cid concentrtion or the rosting time. The mximum leching of Zinc ws obtined t 6ºC with cid concentrtion of 6gpl HNO 3 nd 75ºC, 6gpl mlic cid respectively s shown in the Tble -4.2 & Tble The effect of incresing temperture s well s cid concentrtion hs no significnt effect on the leching of led. Led ws not found in soluble form on incresing the concentrtion of either of the cids nd further increse in rosting temperture. s result of these preliminry cid leching studies, it cn be concluded tht led nd other ssocited metls could not be effectively leched from jrosite smple by using either HNO 3 or mlic cid under bove mentioned conditions. Mnuscript id Pge 4

6 Recycling of Jrosite For Recovery of Vluble Metls nd its Utilistion () Jrosite without rosting (b) t rosting temperture 4 ºC (c)t rosting temperture 6º C (d) t rosting temperture 75º C Fig. 4.2: Microstructure of Jrosite rosted t different temperture. Simple rosting of jrosite ws done to see if dissolution of ny specific metl selectively possible nd lso to see ny chnge in chrcteristics of the smple. The rosting temperture ws vried in the rnge 2ºC -75ºC. The microstructure of jrosite becomes finer with incresing rosting temperture (Fig. 5.2). 4.3 Rosting of jrosite- mixture The sulftion-rosting-leching process comprises three mjor steps : (1) Mixing the jrosite smple with sulphuric cid; (2) rosting nd (3) wter leching. The sulphtion rosting in the present study is crried out below nd ner the decomposition tempertures of the sulphtes, when the following rections tkes plce: During mixing nd the subsequent rosting stges, most of the oxides convert to their respective sulphtes.cited exmples re given below: ZnO + ZnSO 4 + H 2 O (1) PbO + PbSO 4 + H 2 O (2) Fe 2 O Fe 2 (SO 4 ) 3 + 3H 2 O (3) ZnFe 2 O ZnSO 4 + Fe 2 (SO 4 ) 3 + 4H 2 O (4) Mnuscript id Pge 41

7 % of Metl Recovery Recycling of Jrosite For Recovery of Vluble Metls nd its Utilistion t rosting tempertures of 6-75ºC, sulphtes with low therml stbility such s iron sulphte decompose to give their respective wter insoluble oxides. Fe 2 (SO 4 ) 3 Fe 2 O 3 + 3SO 3 (5) 4.4 Wter leching of jrosite - mixture Jrosite residues re SO 4 -bering residues nd the presence of excessive levels of sulfte dversely ffects the led extrction. In order to decompose the ferrite structure nd to recover wter soluble zinc such s ZnSO 4, wter leching step hs been found to be very effective. ZnSO 4 nd Fe 2 (SO 4 ) 3 re wter soluble but PbSO 4 is wter in soluble so during wter leching ZnSO 4 nd Fe 2 (SO 4 ) 3 come in to the solution nd PbSO 4 remins in the residue.s nlysis of wter leched smple shows tht zinc nd iron re present in the solution but led is completely bsent. XRD nlysis of wter leched residue shows tht PbSO 4 is present in the residue Effect of rosting temperture on leching Leching experiments were crried out t 2 ºC, 4 ºC, 6 ºC, 65 ºC, 7 ºC nd 75 ºC to investigte the effect of temperture on the dissolution behviour of iron nd Zinc. Smples were prepred with.3 mss rtio of Sulfuric cid) to- (Jrosite residue). Fig.4.3 shows the effect of rosting temperture on extrction of iron nd Zinc. It is obvious tht higher rosting tempertures will increse the decomposition kinetics of metl sulphtes. The percentge of iron dissolution increses t 2ºC up to 6ºC. t 6 ºC percentge of iron dissolution is mximum which is round 77%. Further increse in temperture to 65 ºC, results in prtil decomposition of iron sulphte to iron oxide. t rosting tempertures of 6-7ºC, sulphtes with low therml stbility such s iron sulphte decompose to give their respective wter insoluble oxides.the wtersoluble sulphtes, on the other hnd, re stble t such rosting tempertures nd they dissolve esily during the subsequent wter leching step leving the iron oxides in the residue. Iron nd Zinc dissolution re lower when rosting is performed t 7ºC compred to dissolution fter rosting t 65 ºC. By incresing the temperture from 65ºC to 75ºC, it is possible to decrese iron nd Zinc dissolution from 28% to < 1% nd from 98% to 4% respectively. 1 Zn Fe Rosting Temperture(degree C) Fig.4.3 : Effect of vrition of Rosting Temperture with sme cid concentrtion on % of Metl Recovery Effect of cid Concentrtion on Leching series of experiments were crried out by vrying the mss of sulphuric cid to Jrosite residue from (.1.3). The smples were rosted for 2hrs t fixed temperture of 6 ºC. fter rosting, the smples ws leched with wter for 1 hr. Fig. Shows the dissolution of iron nd Zinc t the rosting temperture of 6 ºC. t 6 ºC Mnuscript id Pge 42

8 % of Metl Recovery Recycling of Jrosite For Recovery of Vluble Metls nd its Utilistion the percentge of dissolution of iron nd Zinc increses with incresing cid concentrtion. Fig. Shows the dissolution of iron nd Zinc t the rosting temperture of 75ºC H 2 SO 4 /Jrosite residuertio(w/w) Zn Fe Fig.4.4 : Effect of vrition of cid concentrtion on % of Metl Recovery t Rosting Temperture 6ºC 4.5 Brine Leching follows wter leching for Led Extrction Brine leching is bsed on the formtion of complex chlorides of led in concentrted chloride solutions. Led sulfte is insoluble in wter, but soluble in sturted chloride solutions cidified by HCl, or chlorine wter. PbSO NCl PbCl 2 + N 2 SO 4 PbCl HCl H 2 [PbCl 4 ] In wter led sulfte hs low solubility (Ksp = 1-8 t 25 C), compred to led chloride which hs moderte solubility. The sturted solubility of PbC1 2 in wter is 9.9 g/l g t 2 C nd 33.4 g/l g t 1 C. The PbCl 2 solubility decreses rpidly with incresing chloride concentrtion due to the so clled common ion effect, but increses fter pssing through minimum becuse the incresing chloride ctivity which fvours the formtion of soluble led chloride complexes ccording to the following equtions: [15] PbCl 2+ + Cl - PbCl + k 1 = PbCl + + Cl - PbCl 2 k 2 = PbCl 2 + Cl - - PbCl 3 k 3 = 3.89 X 1-1 PbCl Cl - PbCl 4 k 4 = 8.82 X 1-2 fter wter leching, the jrosite residue ws subjected to brine leching to recover led. The effects of NCl concentrtion (22g/l), wter lech residue round 1% pulp density, leching temperture t 8⁰C nd leching time for 6 min nd stirring speed 7 rpm were investigted. fter first step brine leching the percentge of recovery of Zinc nd led present in the residue s found in S nlysis re shown in Tble nd Tble respectively. The recovery of Zinc is lmost 97% nd the recovery of led is round 99% fter brine leching. Mnuscript id Pge 43

9 Intensity Recycling of Jrosite For Recovery of Vluble Metls nd its Utilistion Tble-4.4 Recovery of Metls fter brine leching Sl No Tretment %Zn Recovery %Pb Recovery %Fe Recovery %Cd Recovery Condition 1 2ºC/3ml ºC/3ml ºC/1ml ºC/2ml ºC/3ml ºC/3ml ºC/1ml ºC/2ml ºC/3ml PbSO Thet Fig.4.5 XRD nlysis of cid rosted nd wter leched Jrosite residue t Rosting temperture 6 C with cid concentrtion of 3% Mnuscript id Pge 44

10 Intensity Recycling of Jrosite For Recovery of Vluble Metls nd its Utilistion Fe 2 O 3 b-sio b b b b Thet Fig.4.6 : XRD nlysis of brine leched Jrosite residue t Rosting temperture 6 C with cid concentrtion of 3%. () (b) (c) Fig(4.7) : Microstructure of cid rosted Jrosite with 3% cid rosted t 6º C, Fig(4.7b) Microstructure of cid rosted nd wter leched Jrosite residue. 3% cid Rosting temperture 6ºC Fig(4.7c) : Microstructure of brine leched Jrosite residue. Rosting temperture 6 C with cid concentrtion of 3%. Mnuscript id Pge 45

11 Recycling of Jrosite For Recovery of Vluble Metls nd its Utilistion XRD nlysis of cid rosted nd wter leched Jrosite residue t rosting temperture of 6 C nd cid concentrtion of 3% shows tht PbSO 4 is present in the residue. The microstructure shows tht iron sulphte, Zinc sulphte nd led sulphte re present in the residue fter rosting nd fter wter leching, wter soluble iron sulphte nd Zinc sulphte re leched nd wter insoluble led sulphte is present in the residue. XRD nlysis of brine leched Jrosite residue t rosting temperture of 6 C nd cid concentrtion of 3% shows tht Fe 2 O 3 nd SiO 2 is present in the residue. The Microstructure of brine leched Jrosite residue t Rosting temperture 6 C with cid concentrtion of 3% lso shows tht finer prticles re present in the residue nd these re Fe 2 O 3 nd SiO 2. V. CONCLUSION The recovery percentge of metls in first stge brine leching is led 99.83% Zn, 98.37%, Cd 99.99% nd iron 82.75%.The recovery percentge of metls in second stge brine leching is led 99.92%, Zinc 98.58%, cdmium 99.99% nd iron 86.34%. fter brine leching Jrosite is toxic free before its sfe disposl to the environment nd finlly the bright red color residue comprising minly Fe 2 O 3 nd SiO 2 cn find mrket s pigment. REFERENCES [1]. Rusen,.S. Sunkr, Y.. Topky, Zinc nd led extrction from cinkur lech residues hydrometllurgicl method, Hydrometllurgy 93 (28) [2] Leching of gold, silver nd led from plumbojrosite-contining hemtite tilings in HCl-CCl 2 medi Hydrometllurgy,Volume 26, Issue 2, Mrch 1991, Pges [3] Clen hydrometllurgicl route to recover zinc, silver, led, copper, cdmium nd iron from hzrdous Jrosite residues produced during zinc hydrometllurgy, Journl of Hzrdous Mterils 192 (211) [4] Ktsioti, M., et l. "Use of jrosite/lunite precipitte s substitute for gypsum in Portlnd cement." Cement nd Concrete Composites 27.1 (25): 3-9. [5] Pppu,., Sxen, M. nd solekr, S. (28). ppliction of col combustion residues nd mrble processing residues for immobilising nd recycling of hzrdous Jrosite wste, Proceedings of the Interntionl Conference on Wste Technology ;28, p1298 [6] Pppu, sokn, MohiniSxen, nd Shym R. solekr. "Jrosite chrcteristics nd its utilistion potentils." Science of the Totl Environment (26): [7] Council of Scientific & Industril Reserch, (214). composition for prepring nonhzrdous building blocks nd process for preprtion thereof. Ptent , 27 Mrch 214 [8] dolf VON Ropenck, Winfried Bohmer, Heiner Grimm. Method of Reprocessing Jrositecontining Residues. Ruhr-Zink Gmbh, ssignee. United Sttes Ptent Sept [9] Sinh,. K., et l. "Chrcteriztion of Jrofix wste mteril for the construction of rod."(213). [1] Sinh,. K., et l. "Design, Construction & Evlution of Jrofix Embnkment nd SubGrde Lyers." (212). [11] Sinh,. K., et l. "Recycling Jrofix wste s construction mteril for embnkment nd sub grde." The Journl of Solid Wste Technology nd Mngement 38.3 (212): [12] sokn, P., Sxen, M. nd solekr, S. (26). Hzrdous jrosite use in developing nonhzrdous product for engineering ppliction. Journl of hzrdous mterils, 137(3), pp [13] Pppu, sokn, MohiniSxen, nd Shym R. solekr. "Solid wstes genertion in Indi nd their recycling potentil in building mterils." Building nd Environment 42.6 (27): [14] Piskunov, V. M.,. F. Mtveev, nd. S. Yroslvtsev. "Utilizing Iron Residues from Zinc [15] Determintion of the Optimum Conditions for the Leching of Led from Zinc Plnt Residues in NCl C(OH) 2 Medi by the Tguchi Method Mnuscript id Pge 46