Title of Invention | "AN IMPROVED METHOD FOR THE EXTRACTION OF TUNGSTEN |
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Abstract | An improved method for the extraction of tungsten by fusion of tungsten bearing matrix with strong alkali, leaching the fused mass with water and filtering adding acid till the acid molarity is reached upto 5M equilibrating with equal volume of organic solvent, extracting tungsten selectivity in an extractant such as a mixture of bis (2,4,4 -trimethylpentyl) octylphosphine oxide and Bis (2,4,4 -trimethyl-pentyl) phosphine oxide (85 : 15 w/w) in an organic solvent to obtain tungsten in the organic phase, followed by stripping of tungsten from the organic phase by known methods. |
Full Text | The present invention relates to an improved method for the extraction of tungsten. The present invention particularly relates to the extraction of _W from tungsten bearing matrices such as scheelite and wolframite ores. The method more particularly relates to the extraction of pure tungsten (> 99%) the from of W(VI) by using a mixture of bis (2,4,4-tri- methylpentyl)octylphosphine oxide and tris(2,4,4-trimethyl-pentyl)phosphine oxide (85:15, w/w) (I). Tungsten is one of the strategic high tech metals and used in electriclamps, electronics and other electrical devies. It is also used for cutting, mining and drilling tools, dies and armourpiercing projetiles. As a result of its wide spread use there is a need to develop efficient extraction procedures. Methods involving solvent extraction have certain advantages in comparison to the conventional methods with respect to better purity control, automation and capability to handle low grade ores. Reference may be made to some organophosphorus extractants di(2-ethylhexyl)phosphoric and tri-n-butyl phosphate [V.G. Maiorov, E.V. Shevyreva, A.I. Nikolaev, L.I. Medvedeva and V.K. Kopkov, Zh. Prikl. Khim., 81(2), 320 (1989); A.A. Plant, V.A. Reznichenko and L.G. Panfilova, Zh. Neorg. Khim. 22(12), 337 (1977); R.K. Biswas, Bangladesh J. Sci. Ind. Res., 20(1-4), 11(1985); A.N. Zelikman, G.M. Voldman and Y.M. Konyukhov, Khimiya Ekstraktsii, Novosibirsk, 226 (1984) and T. Sato and K. Saka, Hydrometallurgy, 37(3), 253 (1995)] Which have been used for mainly the separation of W from Mo only. Reference may also be made to an alkylphosphine extractant, tri-n-octylphosphine oxide (T.Sato, T. Takayanagi and T. Nakamura, Proc. Sym. Solvent Extr. Hamamatsu (Japan), 1(1983) which has been put to some very limited use for the extraction of tungsten. This could be due to the fact that tri-n-octylphosphine oxide is more or less projected as an universal extractant and attaining selectivity is a problem particularly when used singly. Extractant (I) not only quantitatively extracts tungsten but under certain aqueous and organic phase conditions is selective for W(VI) over many commonly associated metal ions. Because of poor aqueous solubility of the extractant (I) it exhibits good recycling capacity. The main object of the present invention for the extraction of tungsten is to provide a procedure for the separation W(VT) in the presence of commonly associated metal ions. Another object of the present invention is to provide a method for the separation of W from tungsten bearing matrices such as scheelite and wolframite ores. Still another object of the present invention is to provide an improved method for the extraction of tungsten using extractant such as (I). Yet another object of the present invention is to use extractant which enables separation of W(VI) from Mo(VI), Si(IV), Al(III), Fe(III), As(III), Ca(II), Mn(II), Zn(II), Cd(II), Pb(II), and Na(I). Still another object of the present invention is to provide a process wherein there is negligible loss of the extractant in each extraction-stripping cycle resulting in an economical process. Still another object of the present invention is to extract W from the extractant phase in a form so that it can be easily processed for subsequent applications. Accordingly the present invention provides an improved method for the extraction of tungsten which comprises fusion of tungsten bearing matrix with strong alkali, leaching the fused mass with water and filtering adding acid till the acid molarity is reached upto 5M equilibrating with equal volume of organic solvent, extracting tungsten selectivity in an extractant such as a mixture of bis (2,4,4 -trimethylpentyl) octylphosphine oxide and Bis (2,4,4-trimethyl-pentyl) phosphine oxide (85 : 15 w/w) in an organic solvent to obtain tungsten in the organic phase, followed by stripping of tungsten from the organic phase by known methods. In an embodiment of the present invention the tungsten matrix used may be tungsten ore such as scheelite and wolframite. In another embodiment the mineral acid used may be hydrochloric or sulphuric acid. In another embodiment the diluent used may be n-hexane, 0 kerosene (160-200 C), toluene, cyclohexanone and nitrobenzene. In yet another embodiment of the present invention the known method used for striping tungsten may use reagents such 1-5% NH C1, 1-5% (NH ) CO , 1:10 NH , as 1-5% NH Cl in 1:10 NH and 1- 4 4 2 3 3 4 3 5% (NH ) CO in 1:10 NH . 4 2 3 3 In another embodiment of the present invention the extrac tion behaviour W(VI), Mo(VI), V(V), Si(IV), V(IV), Al(III), Fe(III), As(III), Ca(II), Mn(II), Zn(II), Cd(II), Pb(II) and Na(I) from 1.0x10 to 5.0 M HCl was studied using 0.10 M kerosene solutin of (I). The extraction of W(VI) with increasing acid molarity first increases to attain a maximum value of 85% around 0.10 M HCl, decreases to a value of 60% at 1.0M HCl and then finally becomes quantitative at 5.0M HCl. Mo(VI) showed quantitiative extraction throughout the investigated acid molarity. The extraction of V(V) and V(IV) is more or less constant over a wide range of acid molarity and ranges between 40-50% and 10-40%, respectively. The percent extraction of Al(III) decreases with increasing concentration of hydrochloric -3 acid. Fe(III) shows quantitative extraction from 1.0x10 to -2 1.0x10 M HCl but is drops to 85% at 5.0 M HCl. The extraction of Zn(II) decreases with increasing concentration of hydrochloric acid upto 0.10 M HCl beyond which it increases. Si(IV), As(III), Ca(II), Mn(II), Pb(II) and Na(I) show very low extraction ( over the entire investigated acidity range. However, Cd(II) also shows poor extraction ( slight increase in extraction is observed. The extraction of all these metal ions excluding Pb(II) is more or less same in H SO 2 4 medium. The extraction of W(VI) was studied in various diluents like 0 n-hexane, kerosene (160-200 C), toluene cyclohexanone and nitrobenzene. At 1.0 M HCl the highest extraction is observed in nitrobenzene and the lowest in tolunene. The boiling point and 0 cost considerations of kerosene (160-200 C) fraction suggest it to be a preferred diluent. The effect of concentration of (I) on the extraction of W(VI) has been studied. There is an increase in the extraction with the increase in the concentration of the extractant. The effect of metal ion concentration on the extraction of W(VI) has been investigated using 0.10 M kerosene solution of (I). It is observed that the distribution ratio remains almost the same in the investigated range. The efficientcy of different reagents like 1-5% NH CI, 1-5% 4 (NH ) CO , 1:10 NH , 1-5% NH C1 in 1:10 NH and 1-5% (NH ) CO in 423 3 4 3 423 1:10 NH for the back extraction of W(VI) has been investigated. 3 1:10 NH , 5% NH C1/(NH ) CO in 1:10 NH quantitatively recovered 3 4 4 2 3 3 W(VI) from the organic phase. But in the case of 1:10 NH the 3 phase transfer is very slow and therefore 5% NH C1/(NH ) CO in 4 4 2 3 1:10" NH was used for the recovery of W(VI) from the organic 3 phase. The stripped organic phase can be regenerated by washing it twice with 1.0M HCl and subsequently with water. Experimetns were conducted on successive extraction-stripping cycles for W(VI) for 5.0 M HCl in the kerosene solution of (I) upto ten cycles. The results revealed practically no change in the efficiency of the extractant. Extractant (I) is a trialkyl phosphine oxide in which the alkyl groups are branched. The presence of highly branched alkyl chain may be expected to introduce greater degree of selectivity and making it a better reagent than tri-n-octylphosphine oxide for the separation of some closely associated metals. Under certain experimental conditions (I) quantitatively extracts W(VI) in the presence of others commonly associated metal ions. Because of poor aqueous solubility there is little extractant loss in each extraction-stripping cycle. The process becomes economically viable because of the good recycling capacity of the reagent and the use of kerosene as diluent. The stripping reagent used is simple in composition and yields a quantitative yield. The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of the present invention. Example 1 c.a. 1 g of the powdered scheelite ore is fused with 5 g of sodium hydroxide. The fused mass is leached with water and filtered. The filtrate and the washings are combined and the solution acidified. The volume is made to a fixed volume keeping the overall molarity of HCl to 5 M. A known aliquot of this solution is equilibrated with equal volume of 0.10 M kerosene solution of (I). W(VI) and Fe(III) are extracted in the organic phase leaving Si(IV), Al(III), As(III), Ca(II), Mn(II) and Na(I) in the aqueous phase. The organic layer is equilibrated twice with half the volume of 5% (NH ) CO in 1:10 NH . W(VI) is 4 2 3 3 stripped from the organic phase leaving Fe(III) in it. Fe(III) from the organic layer is stripped by washing it first with equal volume of 3M HCl and then twice with half the volume of 0.10 M oxalic acid. The recovery of W is around 98% and the impurities like Al is Example 2 About 1 g of the wolframite ore is fused with 5g of caustic soda. The fused mass is leached with water and filtered. The filtrate and the washings are combined and acidified with HCl. The volume is raised to a fixed volume keeping the overall molarity of acid to 5M. A known volume of this solution is equilibrated with equal volume of 0.10M kerosene solution of (I). W(VI), Mo(VI) and Fe(III) are extracted in the organic phase leaving Si (IV) , Al'(III) , As (III), Ca(II), Mn(II) and Na(I) in the aqueous phase. W(VI) and Mo(VI) are stripped from the organic layer by washing it twice with half the volume of 5% (NH ) CO in 4 2 3 1:10 NH Fe(III) remains in the organic phase. W(VI) and Mo(VI) 3 . are separated by adusting the pH of the solution to 3 and equilibrating it with equal volume of 0.10 M kerosene solution of (I). Mo(VI) passes in to the organic layer leaving W(VI) in the aqueous phase. Mo(VI) from the organic phase is stripped by washing it twice with half the volume of 5% (NH ) CO in 1:10 4 2 3 NH . Fe(III) from the organic phase is removed by washing it with 3 * equal volume of 3M HCl and then twice with half the volume of 0.10 M oxalic acid. The recovery of W(VI) is around 94% and the presence of impurities like Mo being 0.01%, Ca The main advantages of the present invention are 1. Recovery of pure tungsten solution from the solution of a complex matrix in a relataively convenient way. 2. The hydrolytic stability, good regeneration power of the 0 extractant and the use of kerosene (160-200 C) as diluent favour the cost effectiveness of the process. 3. Fast mass transfer and phase separation add towards the utility of the process for scaling up. 4. The stripping reagent used is simple in composition and yields a quantitative recovery. 5. The recovery of tungsten by this process is above 95% and the purity of the metal being > 99%. We claim: 1. An improved method for the extraction of tungsten which com prises fusion of tungsten bearing matrix with strong alkali, leaching the fused mass with water and filtering adding acid till tne acid molarity is reached upto 5M equilibrating with equal volume of organic solvent, extracting tungsten selectivity in an extractant such as a mixture of bis (2,4,4 -trimethylpentyl) octylphosphine oxide and Bis (2,4,4-trimethyl-pentyl) phosphine oxide (85 : 15 w/w) in an organic solvent to obtain tungsten in the organic phase, followed by stripping of tungsten from the organic phase by known methods. 2. An improved method as claimed in claim 1 wherein the tung sten bearing matrix used is tungsten ore such as scheelite and wolframite. 3. An improved method as claimed in claims 1 and 2 wherein the mineral acid used is hydrochloric or sulphuric acid. 4. An improved method as claimed as in claims 1-3 wherein the 0 organic solvent used is n-hexane, kerosene (160-200 C), toluene cyclohexaneone and nitrobenzene. 5. An improved process for the recovery of tungsten substan tially as described herein with reference to the examples. |
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2436-del-1997-complete specification (granted).pdf
2436-del-1997-correspondence-others.pdf
2436-del-1997-correspondence-po.pdf
2436-del-1997-description (complete).pdf
Patent Number | 197212 | |||||||||
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Indian Patent Application Number | 2436/DEL/1997 | |||||||||
PG Journal Number | 40/2008 | |||||||||
Publication Date | 03-Oct-2008 | |||||||||
Grant Date | 11-Aug-2006 | |||||||||
Date of Filing | 28-Aug-1997 | |||||||||
Name of Patentee | COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH | |||||||||
Applicant Address | RAFI MARG NEW DELHI-110001 INDIA. | |||||||||
Inventors:
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PCT International Classification Number | C22B 34/36 | |||||||||
PCT International Application Number | N/A | |||||||||
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PCT Conventions:
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