Journal of Scientific & Industrial Research Vol .58, December 1 999, pp 948-953

Vanadium Sludge - An Useful Byproduct of Alumina Plant

Rajeev, J Pradhan , S N Das and R S Thakur Regional Research Laboratory, Bhubaneswar 75 1 0 1 3, India

Received: 1 2 May 1 999; accepted: 1 6 September 1 999

During the production of alumina from bauxite by the Bayer's process, a sludge containing fairly higher quantity of vanadium is obtained. Various workers have used different methods to recover vanadium from the sludge. Some of these methods either deal with the neutralization of the alkaline sludge followed by the precipitation of vanadates of ammonium or sodium or use lime or other calciulll salts to precipitate calcium vanadate. Some techniques involve solvent extraction, and ion-exchange. The paper reviews the work carried out in this direction.

Introduction During the production of alumina from bauxite by the

Bayer's process, a byproduct containing fairly high quan­tity of vanadium ranging from 1 0 to 20 per cent as vana­dium pentoxide is obtained. This byproduct, known as Bayer's sludge or vanadium sludge, is a potential source of vanadium and for the past few decades several efforts have been made to recover vanadium from this sludge. The wel l known Bayer 's process involves treating baux­ite with alkali under high pressure forming Bayer 's l i­quor which in addition to alumina contains substantial amounts of vanadium salts along with minor amounts of fluoride, phosphate, and arsenate. Higher concentrations of vanadate have detrimental effect on alumina precipi­tation and consequently on the qual ity of the final prod­uct. Therefore, it is mandatory on the part of alumina manufacturers to remove vanadium salts, if present in Bayer's l iquor. However the concentration of these salts, depends on the nature of bauxite used. When vanadium impregnated Bayer's l iquor is cooled down or air is blown through it, the vanadium sludge gets precipitated . This sludge contains sodium salts of phosphate, aresenate, alu­minate, vanadate along with alkal i . Therefore, separa­tion of these extraneous constituents and enrichment of vanadium content of the l iquor should precede vanadium recovery. Several re'liews deal ing with the subject have already appeared in literature 1 .2

. Literature related to the recovery of vanadium from

the Bayer ' s s ludge mainly deals with the precipitation of ammonium vanadate from sodium aluminate solution, precipitation by caJcium to enrich vanadate, solvent ex­traction, ion exchange or sometimes elec'trolysis . Some studies have also been made on kinetics and thermody­namics of various dissolution and precipitation reactions. Different investigators have attempted different schemes/

routes for vanadium recovery from sludges obtained from various alumina plants. Studies other than directly re­lated to vanadium s ludge, wherever relevant to the sub­ject, are also referred here to enhance the understanding of the developments in related areas .

The present paper critically reviews the work done by earl ier workers on the recovery of vanadium from Bayer's sludge. There is much more scope to recover other values l ike As, P, F, and alkali values besides va­nadium as the main product. The work reported may help in a better understanding of the process of recovery of the values avoiding pollution caused by minor salts and, therefore, encourage development of new and more economical processes for complete util i sation of the sludge.

Vanadium Recovery by Chemical Methods

Froges and Camargue3 recovered vanadium as am­monium metavanadate or sodium hexametavanadate and subsequently as oxides by first partial ly neutral izing the alkaline salts containing vanadium, phosphorus, arsenic, fluorine, and sodium from Bayer's sludge and then pre­c ipitating by ammonia . E lmer4.5 attempted s imi lar method with sludge obtained from the alumina plants in Ajka and Mosonmagyaroo' var. The authors worked on the sludge which contained approximately 30.0 to 4 1 .5 per cent moisture and 1 .82 - 4.0 1 per cent V 20S besides other constituents. He treated 2 kg of the residue/sludge with hot water and fil tered. Then filtrate was evapo­rated to half of its original volume and then cooled and sol id containing 7- 1 0 per cent V20S got crystal l ized . It was removed and mixed with the undissolved portion . The mixture was d issolved in hot water. Concentrated HCI or H2S04 added to the solution so as to bring the

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RAJEEV et at. : VANADIUM SLUDGE 949

pH to 5 .5 and the l iquid was cooled and fi ltered. The filtrate was once again evaporated to half its volume and filtered. Thus, about 3 per cent of the original vanadium content was obtained as solid, while the filtrate was treated with NH40H to attain pH 8.0. HCI was then added to bring the pH to 3.0 and the solution was allowed to stand for 24 h . A yellow-green percipitate containing approx. 48 per cent of the vanadium contents was sepa­rated. The filtrate containing approx. 2.5 per cent V Ps' however, was lost. A pilot plant with the yield 80-85 per cent V 20S was also proposed.

Dachselt6 has described the stepwise production of V20S from the sludge similar to the one reported ear­lier3 . According to Dachselt the phosphate, fluoride, arsenate and vanadate were precipitated as their mixed salts by cooling sodium hydroxide sludge l iquor to 40°C. This was further digested with 40 per cent NaOH to pu­rify and partially dissolve sodium vanadate. He then fol­lowed calcium hydroxide precipitation method to sepa­rate As, P and F. However, Dachselt and Elsner7. subse­quently found the step involving neutralization of alka­l ine sodium vanadate with strong acid as superfluous. Instead the hot alkaline solution was cooled, thereby separating crystall ine sodium vanadate. Slaked l ime was used to remove phsophorus and arsenic. Michal and Nilsen8 have described a similar method of recovering vanadium pentoxide from sodium vanadate solution. The leached extract after NaOH roasting of the ore contained aluminium, sodium, and vanadium salts. To remove alu­minium as hydroxide the solution was treated at 60°C with 40-95 per cent H2S04 to lower the pH from 9- I 2 to approx. 7 and the residue was filtered. The filtrate at 50-60°C was treated with additional H2S04 to attain pH 6. Ammonium salt with H2S04 was added while main­taining pH 6 so as to provide NH/V ratio between 0. 1 3-0 .26 for 20 min . More of the H2S04 was then added to lower the pH further to 1 .5-3.0 and then heated to 90-95°C for 1 5-60 min to precipitate V20S of high purity by hydrolysis. Ammonium ions were removed by calcina­tion. Vasil ica and Pintea9 have studied the recovery of vanadium from the Bayer 's process for the bauxite of Oradea, Romania which contained 0.06-0.07 per cent vanadium. During the process 30-34 per cent of the va­nadium present passed into alkal ine solution of alumi­nates. Vanadium was separated from the concentrated solutions containing 280-290g of NaPk and 1 80-200g ofN�O/1 by agitating and cooling for 6 h . Below 40°C, extraction of vanadium improved. The solution contain­ing vanadium also contained P, As and F as dissolved

salts while Si02, AI203 and iron oxides remained in­soluble. The purified solution contained 20-30 gil V20S' 0.005 P, 1 .0 As20s and fluoride 0. 1 to 0. 1 5 gil. The sepa­ration of vanadium from purified solution was carried out by hydrolys i s and V was obtained as sodium poly vanadate .

Nasyrov and Ravdonikas lO have also described a simi­lar method for vanadium sludge from processing of hydrargill itic bauxite. The impure solution after alkal i treatment of the ore contained 1 .0-2.5 gil V 20S ' The au­thors reported a two step process starting with the heat­ing the solution to 40-6SoC for 1 -2 h which precipitated appreciable amounts of sulphate, carbonate and fluoride of alkali metals while in the second step the filtrate was diluted and cooled to 20-30°C for 6- 1 2 h. This resulted in precipitation of the sludge which contained mainly N�O, P205, water and most of the vanadate. Thakur et ai. I I have reported recovery of vanadium from Indian bauxite residues by soda ash roasting. The work indi­cates that recovery of vanadium increased with the in­crease in the quantity of sodium carbonate. At a red mud to sodium carbonate (500: 1 25) the recovery reached 83-89 per cent. lelacic and Andric l 2 have studied the distri­bution of vanadium contents in the products of bauxite processing and accordingly suggested that while two­third of the V Ps was precipitated in the red mud, most of the remainder was precipitated as crystals of 2 Na3 (V, P, As) 04.NaF. 1 9H20. which got accumulated in the exit pipes of the autoclave. This contained about 6.5 per cent V 20S ' Yet the method of recovery of vanadium from it was not suggested by them.

Thakur et al. 1 3 treated the vanadium sludge with wa­ter, HC1, and NH4CI to produce a vanadium rich residue which was then treated with aq.Na2C03 to dissolve va­nadium. Ammonium chloride and hydrochloric acid were added to i t in order to precipitate ammonium vanadate, which after filtration and washing, was more than 99 per cent pure. In another communication, Thakur and Sant 1 4 have reported the use of excess of ammonium salt to dissolve phosphates and fluorides. The authors treated vanadium containing residue from the filtrate with NaOH that d issolved the vanadate but not the alumina and sil ica. The sodium vanadate thus obtained was treated with ammonium salt to precipitate h igh purity ammo­nium vanadate. In another study, Thakur and Sant l S

prepared V 20S and Na2S04 from vanadium sludge by the reaction of ammonium sulphate in sulphuric acid medium. Ammonium vanadate precipitate was fi l tered while recovering Na2S04 from the mother l iquor. The

950 J SCI IND RES VOL.58 DECEMBER 1 999

prec ipitate was heated at SOO°C for 1 -2 h and the dried product contained 54 per cent V:O,;'

An a l ternate approach to recover vanad i u m has been

to usc ca lc ium as scavenger of phosphate and fl u or i d e .

To recover vanad i u m from the s l udge, Dac hsc l t{' at­

tempted to remove phosphorou� and arsen ic as Ca,(PO)2 and Ca,( As04)2 prec ip itates by l I s i ng cal c i u m hydrux­

ide, which enriched the vanadium content also. Dachcsc l t and EIsner7 cooled t h e hot a l ka l i vanadate so lut ion to crystal l ize crude sodium vanadate salt . They reported a

process i n which 5 kg of a n lo i s t crude vanadiu l ll s a l t

containing 5 .3 per cent of V:,0:'i ' 1 1 . 8 per cent P2C,\ and O .S per cent As)O� was dissolved i n 1 5 I of water at SlO"C S laked l i me was added to the so lu t ion thereby prec i p i ­

tat ing quant i tat ive ly the phosphorous and arsen ic . The

mother l iquor ( 1 4 I), after the removal of As. contai ned about 1 4 .3 g of V)O-. After a l lowing i t to c ool for 24 11 , - :> 800 g of hydrated Na vanadate got separated .

Mohanty et at. 1 6 have reported recovery of vanadium from Bayer 's process l i quor. The sodium complex sa l t obtained from this process contained approx. 30 per cent A I )Ol as insoluble residue wh i le vanadium and phos­phorus dissolved in water. S ince the l iquor was h ighly alkal ine, addi ti on of NH.jCl did not separate NH.j YO, along with a lumina res idue. Attempts to remove P by crysta l l izing Na2P04 after partial neutral izat ion did not yie ld good resu I ts . CaC 1 2 was then added and al most al l the phosphorus was precipitated along with some vana­dium as coprecipitate. At pH 9.0, 3 I .35 per cent vana­dium precip itated along with ca lc ium phosphate. The authors also recommended prec ip i tation of vanadium in i t ia l ly as ammonium vanadate a t pH 6.0 with a recov­ery of 90 per cent of the vanadium and treatment of the re­

sidual i iquor with Cael, for the recovery of phosphorous. Bojall 17 ped'ormed ,�n experiment to detcnnine the rea­

son for relat ive ly poor seperation of P:P:; by l i me from the t3 i l i ngs generated during the production of a lu­min ium. He a l so studied the select iv i ty i n separat ion of vanadiltes from phosphates and arsenates, for which ex­periments were conducted with synthetic solut ions of sodium vanadate, arsenate and phosphate whi le phos­phate and arsenate were prec ip i tated us ing d ifferent amounts of l ime. The experimental solution contai ned N a2P04. I 2H20 and NaHAs04 . 4H20. The solution af­ter the addit ion of CaCO, was heated to 9SoC for 4 h under continuous mix ing . This was then a l lowed to cool to room temperature for 24 h. Precipitate , when fi l tered off, was analysed to determine V, P and As contents. Bojan 1 7 did not get reproducible resu lts and suggested that under the conditions 'app l ied, As and P cou ld not be

removed withont cop rec ip i t<l t i ng large amounts or \ � l n a ­

cl i u ll1 . Zazu hi l11 ('f (//. I �: have suggested t h e usc ( ) f t � ;.: c e " s of gypsu ill to prcc i p i t ; ' t c phosp hate i n a m e t hod for I IL' : ! I ­ment of van �lcl i u l l l s l i me for proci u c i n g tec h n i c a l [! racic V el}, . The s l i m e s , g:enL:rateci 1101ll a l u i ll i n a llla n lJ l � IC l l l r­

i ng . con tai ned 1 2 . 2 per ce nt V20" . .'l . W') per ce l l t 1'/ \. 7 .2 per c e n t A I 20 " 2� . .'i per c e n t I <120. 2 . 0 per Cl:n t F and O.Sl2 per cent A�, i n add i t ion iO srmi l l a mou n t ... of organ i c substal lces.

Petitjean and Ro l l et 1 <) h ave deseribL'd al lot her s tudy on i mproved al u m in ; l product ion which suggcst l'd t i l e

part i a l removal of vanad i u m from sod iu m a l u m i n ate ob­

tai ned from sod ium hydrox ide treatment of baU X i te hy prec ip i tat ion w i t h Crl l OH )2 at 1 00" e I t was suggeslt.'d

that the sod i u m a lu m i nate so lu tion shou l d conta in 5 0-1 7 5 g Na20/1 and should have mol ar rat i o Na} ) : ,<\ 1/) , o f 1 . 5-3 .0 and t h e l i me s h o u l d b e added in sl ich ; 1 pro­port ion that CaO to NaoO weight rat i o should be less than 0. 1 . B hattacharya �nd Roopchand

20 h ave reported

s i mple experi ments on mi xed sal ts/ vanadiu lll s l udge obtained from Bayer's process, to separate F and P from most of the vanadium by precipitating P as Ca,( PO.!)2 with F contaminati on. Accord ing to thei r process , 82 per cent of technical grade VoOs cou ld be recovered in the fi rst prec ipi tat i on after the separation of ca lc ium phos­phate. Shakhtakht insk i i and Khal i love l c arried out a study on a system for the prec ip i tation of vanadium frolll c i r­cu latory a luminate solut ion by Ca(OH)2 with subsequent separation of vanadium from H ,P04 and I ' S p re c i p i ta­t ion as the vanadate. A concentrated a lumina :e solut ion, after the seperation of sulphates, was di luted with a l u­

min ium hydroxide wash water to 1 30- I 40 g NaP/I . Ca(OH):: i n different port i ons ( hav ing CaO-V 20:; ratio of 1 8 : I ) was added to th is solut ion to prec ip i tate V and P. After mix ing at 85-90"C for about 3 h, t h e s ludge thus formed was fi l tered and washed wi th hot condensate and t he fi l trate was rec ircu lated. 2.5 per cent H 2S0.j solut ion with a sol id l iquid ratio I : 30 was added to th i s s l udge and 1 0 per cent NaOH was added to the m i xt ure so as to reach pH 7-8. Perhydrol was added at the rate of 2 mg/g of s ludge, sti rred for 3 h and fi l tered . The so lut ion was used for the production of pure VoOs'

Oku et aU2 have reported a m�th'od of prec i p i tat i n g vanadium from the Bayer's s ludge by contro l l ing the ratio of carbon ( in organic form) to vanadium to less than 0 .3 : 1 .0 . The amount of organic compound formed by the hydrolys is of humic ac id was determ ined by KMnO,j t i tration. To part of the by-product conta in ing 5 per cent vanadium, 3 .S per cent phosphorous, 3 . 5 per cent arsenic and S per cent carbon were d issol ved in J parts of water

RAJEEV et at. : VANADIUM SLUDGE 95 1

at 60°C, then about 0.8 parts of CaO was added and the mixture was stirred for 3 h at 80°C and then filtered. The pH of the filtrate containing 1 3 .4 per cent V, 7 per cent As and 20 per cent carbon was adjusted to 6.0 and treated with 0.08 1 , 0.084 and 0.097 parts of CaCI2. while main­taining CIY ratio at 0.25, 0.2 and 0 respectively. More than 98 per cent vanadium was recovered when the last filtrate was treated with NaOH so as to bring pH to 8 and with the addition of 0. 1 3 part of ammonium sul­phate per one part solution and stirring at 80nC for I h . Ammonium vanadate was precipitated when cooled to 30°e. Yashunin et al.2J have also reported the use of compounds containing calcium ox ide for the removal of vanadium from the aluminate solution. Calcined dolo­mite was added for decreasing the loss of alumina.

Other studies on the basic properties of vanadium or vanadyl ions have contributed significantly towards un­derstanding different methods of vanadium recovery from Bayer's sludge. Zolotavin and Kraeva24 have de­termined the position of vanadyl ion in sorption series with respect to some selected adsorbents. They have reported sorptions of various cations on sulphocarbon, zeolite and aluminate form of alumina. It is interesting to note that sodium aluminate is produced during the Bayer's process and the adsorption studies are impor­tant for vanadium recovery. Veres25 has outlined a method of recovering vanadium from the red muds of Hungar­ian bauxite. The degree of distribution in the ore, rela­tive effects of degree of oxidation, concentration of so­dium fluoride and temperature of the solution have been discussed. Similarly, Klug et al.26 have described the de­gree of dissolution of vanadium at different stages of Bayer's process. The authors analysed several solid as wel l as l iquid samples for the study. The relations amongst the vanadium with bauxite the disso lved salt and the precipitated salt were examined and the effect of oxidising agents and the roasting parameters of the bauxite ore on the degree of dissolution of vanadium in the l iquor were discussed . Klug et al.26 described lhat the roasting of bauxite at 700° C for 2 h raised the de­gree of vanadium solution in the decomposing l iquor from 30-40 per cent to 80 per cent.

Zambo et al. 26,27 while looking for the cause of par­tial dissolution of the vanadium contents in the Bayer 's processing of Hungarian bauxites observed that although distribution of vanadium was uniform, a close correla­tion existed between iron and vanadium contents . The amount of vanadium dissolved during bauxite process­ing was proportional to the concentration of hematite. The recovery of vanadium frl)m goethite phase of baux-

i te improved between 300-320°e. The authors reiterated similar observations made earlier by Klug et al. 28 that dissolution of vanadium increased with roasting of baux­ite and opined that complete recovery of vanadium could be achieved only by leaching of the iron oxide contents . Partial dissolution of vanadium could be attributed to the fact that vanadium was found as an isomorphous impurity in iron mineral and thue thermal/hydrothermal decomposition or reduction of the goethi te structure might lead to better recovery.

Vanadium Recovery by Electrolysis, Solvent Extrac­tion and Ion-exchange Methods

Techniques of electrolysis, solvent extraction and ion exchange have also been applied for the recovery of va­nadium from the aluminate solutions. Hayashi29 dis­solved impure crystals containing vanadium, phospho­rous and sodium components obtained from sodium alu­minate solution in H,P04 and the neutral solution was fed to a chamber formed by an anion and cation exchange resin fi lm and was electrodialysed fil l ing anode and cath­ode chambers with H3P04, and NaOH respectively. A solution containing 1 00 g of the crystal (35 per cent Na20, 1 3 .6 per cent P20S' and 68 per cent V20S) dis­solved in 1 00 ml. H'1P04 at 50°C was electrolysed at approx. 4.5 V and 2 A/m2 by using platinum electrodes. When the sodium hydroxide concentration reached I gl I (reported as Na20 gil) the solution was taken out and ammonium vanadate was precipitated. It was reported that by this method more than 99.8 per cent NH4 V03 was precipitated as compared to the usual ammonium chloride precipitation in HCI medium which gave only 90.2 per cent NH4 VO, recovery.

Artemenko et al. 30· have described a process of ex­tracting of vanadium from aluminate solution by reduc­tion during electrolysis . Molten metal cathode made of Wood's metal (melting point lower than 1 00°C) was used in the electrolyser. The vanadium containing precipitate was subsequently filtered from the electrolytic solution. Sinka et al. 3 1 also reported the use of wood's metal in the electrowinning of vanadium. According to them, mol­ten Wood's metal was best as cathode material since hydrogen formation rate was relatively slower and re­mained constant during the process. Reduction rate of VOl to V203 (solid) increased with stirring. Optimum cathodic current density and mixing rate were reported to be 50 Alm2 and 3 .33 revolution/s, respectively. The use of Wood' s metal as a replacement of mercury as cath­ode was preferred as this was environmental ly safe and ecofriendly.

l)52 J SCI IND RES VOL.58 DECEMBER 1 999

Anashkin et al.32 have studied the crystal l isation of sodium vanadate from sodium aluminate solution . They studied the effect of addition of zinc sulphide in the range of less than 40 gil as seeding for the precipitation of sodium vanadate. The optimal reaction parameters like temperature maintained at 30°C, amount of ZnS added, extent of seeding which was 1 0 per cent, crystallisation time of 0.5- 1 h were also reported. Anashkin et al:13, in another study, reported on kinetics of precipitation of pentavalent vanadium from the aluminate solution. Kozlov et al.34 reported the studies on thermodynamic functions like enthalpy, entropy, and free energy varia­tions during the dissolution of sodium vanadate, arsen­ate phosphate, fluoride, and alumina at different tem­peratures for optimisation of vanadium recovery from the byproduct of alumina production. Increasing solu­bil i ty in the order: Na2C03 < Na3P04 < Na)As04 < Na3 V04 and high efficiency of fluorine removal during leaching have been explained by thermodynamic data. S vyatov and S afonov3s have reported on the crystall isation efficiency of vanadium salts from alumi­nate solutions containing approximately V 20S (2.5 1 -3 .25) and Na20 (200 gil) and also the optimum condi­tions for vanadium recovery in terms of V20S to NaF ratio as wel l as the temperatures of crystal lisation .

Recovery of vanadium from solution using ion ex­change and solvent extraction methods has been a com­mercially established practice. In most of the cases, these methods are very selective. Miskei and Orban36 have reported a method to obtain V20S of more than 99.5 per cent purity from the Bayer's sludge using ion exchange seperat ion . Thus, an aqueous solution containing 20-22 g VP/I (at pH 8 .0), 1 2-25 per cent P20S' 2.5-5.5 per cent As20S and 3-8 per cent F was passed through a Varian AT-660 anion-exchange resin (CI- form) at 55-60°C and the resin was washed and eluted with a mix­ture of 0.63 M NaOH and 0.63 M NaCI solution . The elute was treated with NH4CI to precipitate NH4 VO) which on heating at 500°C gave high purity V20S (con­taining 0. 1 1 per cent Na20, 0.004 per cent P205' 0.002 per cent As and 0.0 I per cent F as impurities). Martens et al. 3? have reported techno-economic comparison of the different methods used for the recovery of vanadium from crude vanadium salt recovered from Bayer 's pro­cess and showed that l iquid-liquid extraction and ion­exchange methods lead to 1 0 per cent h igher y ield of vanadium. In many cases where solvent extraction method was employed, vanadium was extracted with organo-phosphorous reagents which function as cationic

extractant in acidic media. Reagents l ike water insoluble amines of higher molecular weights were also investi­gated as extractants for vanadium. A combination of organophosphorous acid and tertiary amine-Alamine 336 was developed by General Mills Chemicals, Inc . , USA which was effective between 1 .2-2.0 pH only, but a quternary salt l ike tricaprylyl methyl ammonium chlo­ride developed by the same company and named Al i ­qllot 336 was effective in both acid and alkaline media as vanadium extractant . Deleon38 has reported 99 per cent recovery of pure ammonium vanadate from alumina production plants by batch and continuous extraction with Al iquot 336 in kerosine. The optimum extraction parameters reported were pH 9, vanadium concentration 52g/l, Al iquot 336 concentration of 7 per centin kero­sine and aqueous to organic phase ratio 1 -2 . Thakur ef at. 39,40 adopted A l iquot 336 extraction for the recovery of vanadium from vanadium bearing s ludge . They seperated fluoride, phosphate and sodium ions prior to vanadium recovery. Miskei et ai. 4 1 used fractional crystall isation and ion exchange purification for Hun­garian bauxi tes cons t i tu t ing about 0 . 1 1 -0 . 1 5 per centV 205" Anashkin et at. 42 studied the inhibitive effect of organic substances on the crystal l ization of vanadium salts from aluminate solution of Bayer's process. They reported a decrease in crystal l isation induction period from 90 min to 2 min on decreasing the concentration of organic substances from 3 .3 to 2.4 gil . Removal of or­ganic substances through adsorption labsorption by red mud, zinc sulphide, alumina or hydroxide form of an anion exchanger (AV- 1 7 ) was recommended for the crystal lisation of sodium vanadate. Edi llbaeva ef al.43 have reported vanadium recovery from the byproduct of alumina industry optimising experimental conditions of a solvent extraction method. They described organic solvent to solid phase ratio, pH of operation, concentra­tion of sulphuric acid used and stirring rate. Simi larly, Zipperian and Raghavan44 have reported a method for purification of vanadium solution by ion-exchange and solvent extraction using Dowex 2 1 K anion-exchange resin .

Vanadium Recovery by Adsorption Methods

RetelsdOlf et al.45 have reported on economic pro­cess ing of various vanad ium bear ing materi a l s . Processsing of vanadium sludge has been reported, yet another method using carbon adsorption and desorption phenomena where recovery of pure vanad ium oxide from Bayer's sludge was achieved. The process developed

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RAJEEV et a!. : VANADIUM SLUDGE 953

includes leaching of the sludge in hot water to dissolve vanadium contents, adsorption of vanadium on activated charcoal and subsequent desorption of vanadium with a suitable eluent, followed by precipitation of vanadium bearing cake from the strip solution and finally calcin­ing the cake to get pure vanadium pentoxide. Mukheljee et al .46 have reported the influences of various opera­tional parameters in the process . Conclusions

It is evident that in all these processes the main ob­jective was to recover vanadium values from other mi­nor or major constituents. Bayer 's sludge is an impor­tant secondary source of vanadium where as the primary source is the vanadi-ferrous ore. However, by primari ly working for vanadium, we are rejecting other values like phosphate, fluoride, and arsenic in the effluents. Of course, there are no reports yet of pol lution due to these constituents but decidedly they are pollutants. Thus, knowingly or unknowingly, vanadium producers may be polluting some unknown sites.

Recovery of other chemicals along with NaOH wi l l be a boon to the industry. Alkali loss i s subtantial and industry looses nearly 0.2 tonnes of alkali in some form for every tonne of V 205 produced. Alkali is a corrosive waste, if disposed material remains untreated . It is sug­gested that efforts may be directed towards economic recovery of associated values l ike phosphate, fluoride, arsenate, along with alkali from vanadium sludge, mak­ing it zero waste industry.

References

2

3

4 5

6

7

8

9

1 0

I I 1 2

1 3

1 4

Konopicky K, Brennstojf Chem, 36 ( 1 955) 1 5 1 .

Bogardi E, Proc Int SYI11P (ICSOBA ) , 3 ( 1 97 1 )349.

Froges Alais & Camargue, Brit Pat 600, 833, 20 April 1 948; Chem Abstr, 42 ( 1 948)7225f

Elmer Papp, Aluminium, Budapest, 1 ( 1 949)49.

Elmer Papp, A luminium, Budapest, 1 ( 1 949)73.

Dachselt Ernst, ChemTech,Berlin, 9 ( 1 957)42.

Dachselt Ernst & Elsner Erwin, Gel' Pat 1 0865, 02 December 1 955;Chem Abstr, 52 ( 1 958) I 7067g.

Michal Ellgen J & Nilsen Arnold E, US Pat 3472,6 1 2 , 1 4 Oc­tober 1 969; Chem Abstr, 71 ( 1 969) 1 26589h.

M itran Vasi l ica & Pintea L, Rev Chem Bucharest, 2 1 ( 6 ) ( 1 970)337.

Nasyrov G Z & Ravdonikas V, US Pat 3876,386. 08 April 1 975; Chem Abstr, 83 ( I 975)46228x.

Thakur R S, Muralidhar J & Sant B R, Res Ind, 20(2) ( 1 975)66.

Jelacic Cirilo & Andric Zivko, Fourth lilt Congr Study: Ballx­ites, Alumina. Alum, 3 ( 1 978) 1 54.

Thakur R S, Muralidhar 1 & Sant B R, Indian Pat 1 45,899, 1 3 January 1 979; Chem Abstr, 91 ( 1 979) 1 953 1 3p.

Thakur R S & Sant B R, Indian Chem Mallufact, 1 9( 8 ) ( 1 98 1 ) 23 .

1 5 Thakur R S & Sant B R, Indian Pat l N l 53 ,384 1 4 1uly 1 984; Chell! Abstr, 1 02 ( 1 985) 1 52796b.

1 6 Mohanty M S , Dey T C, Srinivasan S R & Bhatnagar P P. N M

L. Technol J, 9 (4)( 1 967 )9. 1 7 Bojan Drzaj , Nova Proi�\ '(}d, 19( 5 ) ( 1 %8) 1 53 . 1 8 ZazlIbim A I , Shalavira E L, Tarasenk V Z & Tyurekhodzhacva

T S h . Tr Inst Mel Ohogasheh A kad Nail/; Kaz USSR. 2 1

( 1 968)75. 1 9 Petitjean Marc & Rollet George, France Pal 1 ,52:1 .40:1 , 03

May 1 968; Chem A iJstr, 71 ( 1 969) I 26584e. 20 Bhallacharyya B N & Roopchand J, Res In £I, 14( I ) ( 1 969)5. 2 1 Shakhtakhlinski i G B & Khalilov K h S , Issled Obi Ne(lIp, Fiz

Khim, ( 1 970)278. 22 Oku Tsurumi, Yamada Koichi , Hashi moto Tadanori & Nakano

Kazuhiko, JapallKokai Pat 7378,0 1 3 , 1 9 OClober I 973;Chelll Abstr, 80( 1 974)624 1 7b.

23 Yashunin P B , Arlyuk B I , Volkova N S & Tuntsova N V, USSR Pat 4 5 2 , 6 1 6 , 05 December 1 97 4 ; Chem A bstr, 82 ( 1 975) I 74064g.

24 Zolotavin V L & Kraeva A I, Anal Khim, 6 ( 1 955)37 1 . 25 Veres Imre, Acta Technol Acad Sci Hung, 41(3 ,4) ( 1 962)259. 26 Zambo lanos & Molnar Lajos, Ml/sZ Tud, 45( 1 -2) ( 1 972) 1 5 3 . 27 Zambo Janos & Molnar Lajos, Acw Tech Budapest , 73( 1 -2)

( 1 972) 1 5 1 .

28 Klug Otto, Gel Vi lmos & Molnar Lajos, Fel11ip Kl/t llllez Kozlem, 10 ( 1 97 1 )45.

29 Hayashi Hitoshi, Japan Pat 69,23,968, I I October 1 969; Chelll Abstr, 72 ( 1 970)23024111.

30 Artemenko S A, Tsimmerguki V A, Balak 0 S, Kondrllk E 1 & Lavrova G V, USSR Patent, 43 1 752 , 1 4 1anuary 1 975; Chem Abstr, 83 ( 1 975) I 35496a.

3 1 Sinka Gabor, M iskei M ihaly & Vigvari Mihaly, Banyasz Kohasz Lapok Kohasz, 116(3) ( 1 983 ) 1 37.

32 Anashkin V S, Grachev V V, Rubbinhtein G M & Kuznetsov S I , Izv \ryssh Uchebn Zaved Isvetn Metall, 3 ( 1 978)72.

33 Anashkin V Z, Grachev V V & Kuznetsov S I , Izv V),.I'sh Uchebll

Zaved Isvetn Mewll, 5 ( 1 978)55. 34 Kozolv V A Yusupov B A & Batrakova L Kh, Komplekin

Ispol 'z Miller Syr 'ya, 8 ( 1 984)82. 35 Svyatov B A & Safonov A V, Komplekin lspol 'z Miller SrI' 'ya,

12 ( 1 99 1 )55. 36 Miskei Mihaly & Orban Lajos, Hungel)' Pat Teljes 2970, 22

November 1 97 1 ; Chem Abstr, 76 ( 1 972)357 1 6). 37 Martens H, Gerisch S, Tietgens H & Ziegenbalg S, Proc Sec­

olld lilt SYlllp ICSOBA , 3 ( 1 97 1 )369. :1 8 Deleon A , Proc Secolld 1111 Symp ICSOBA , 3 ( 1 97 1 )359. 39 Thakur, R S. Muralidhar 1 & Sam B R, Miner Mewls Rev,

27(4) ( 1 978) 1 36. 40 Thakur, R S, Muralidhar J & Sant B R , II/dian Pat IN 1 5 1 ;036,

1 2 February 1 983; Chelll Ahslr, 99 ( 1 983 )40630f

4 1 Miskei M , TOlh B & Bogardi E, Trav Com lilt Etl/de Bl/xite. Alumina, A lulIl, 14 ( 1 978)4 1 .

42 Anashkin V S, Grachev V V & Kuzneslsov S I . hI' V\'ssh Uchebn Zaved. Tsvelll Metall, 2 ( 1 982)44.

43 Edil lbaeva G I, Ruzinov L p, Ekhanin M V, Baikerurova A 0 & Tanirbergenova Zh E, �eslll Akac/ Nauk Kax SSR, 7 ( 1 986)76.

44 Zipperian D C & Raghavan S, Hydrometllurgy, 13 ( 1 985)265. 45 Retelsdrof H 1, Rothmann H & Fichte R, Sci Technol Aerosp

Rep, 2I( I ) 1 983, Abstr No. N83- 1 0630.

46 Mukherjee T K, Chakraborty SP, Bidaye A C & Gupta C K, Millei' Eng, 3(3 and 4) ( 1 990)345.