Title of Invention	AN IMPROVED PROCESS FOR THE RECOVERY OF NICKEL
Abstract	An improved process for the recovery of nickel by dissolving nickel containing matrix in 2m mineral acid in an extracting nickel selectively in an extractant selected from bis (2,4,4 -trimethylpentyl) dithiophosphinic acid in diluent selected from hydrocarbon solvent to obtain nickel in the organic phase, followed by stripping of nickel from the organic phase by known method.

Full Text

The present invention relates to an improved process for the recovery of nickel. The present invention particularly relates to the recovery of Ni(II) from nickel containing matrices such, as spent catalyst and electroplating bath residue. The method more particularly relates to the recovery of pure (>95%) nickel in solution by using bis (2,4,4 -trirnethylpentyl) dithiophosphinic acid (I). Nickel finds extensive applications in electroplating industry and as an alloying metal for the manufacture of special steels. Nickel is also consumed in preparing catalysts for the petrochemical industry, hydrogenation of oils etc. This strategic metal is not available in quantities sufficient to meet its requirements. Thus it becomes inperative to develop met! )ds to recover the metal from the secondary sector. deference may be made to some high molecular weight amines [SE, Bryan and M.L. Good, J. inorg. Nucl. Chem., 21, 339 (1961); S.E. Bryan, M.L. Good and G.J. Maus, J Inorg. Nucl. Chem, 25, 595 (1963); M. Verhaege, G. Glaus and P. Van, Bull. Soc Chem. Beig., 91 (10), 869 (1982); J. S. Preston, Sep. Sci. Techno!., 17 (5), 697 (1982) arid H. Matsunaga and T. Yatsuyangi, Nippon Kagaku Kaishi, 5, 785 (1982)] which have been used earlier for the extraction of Ni(II). The process using these reagents are likely to suffer from the drawback of emulsion formation. References may also be made to some carbo.xylic acids [ K. Inoue, M. Goya and M Taniguc,' i, Mydrornetailurgy, 13, 155 (1984); A. Izquierdo, M. D. Prat and A. Garbayo, Talanta, 35 (12), 949 (1988) and H. Yamada. Y Matsui, Y. Kuroki and H. Wada, Anal. Sci., 13 (2), 237 (1997)] which have been used to extract Ni(ll), but there is an extractant loss due to aqueous solubility of the acids. Reference may also be made to some organophosphorous compounds [ F. Otake, 1. Komazawa and Y. Higaki, Autumn Meeting, Nagoya (Japan) (1979), X. Yang, M. Chen, D. Zheng, D. Lin and L . Ji, Zhongshan Daxue Xuebao, Ziran Kexueban, 2, 37 (1986); J. Yu, Youkuangye, 6 (2), 34 (1987); D Qiu, L. Zheng and R. Ma, Solvent Extr. Ion Exch., 7 (6), 937 (1989); J.S. Preston, Hydrornetallurgy, 9, 115 (1982); W A. Rickelton, D.S. Flett and D.W. West, Solvent Extr. Ion. Exch , 2 (6), 815 (1984); X. Fu and J.A. Golding, Solvent Extr. Ion Exch. 5 (2), 205 (1987), X. Fu, S. Zhao, Z Hu, S. Sui, J. Hao and J.A. Golding, Proc. Sep. Sci., Technol. Conf., Hamilton (Canada), I, 205 (1989) and M.M. Oriv, MA. Olazabal, L.A. Fernandez and J.M. Madariaga, Solvent Extr. Ion Exch., 10 (5), 787 (1992)] which have been employed for the extraction of Ni(II) but they require strict control of pH. The present invention reports the use of extractant (I) ror the recovery of nickel for the first time. Extractam (I) not only shows higher extraction of Ni(ll) but under certain aqueous and organic phase conditions is selective for Ni(II) over many commonly associated metal ions. Because of the poor aqueous solubility of the extractant ihere is a little extractant loss in each extiaction cycle and the reagent exhibits a good recycling capacity. The main object of the present invention is to provide an improved process for the recovery of the nickel is to provide a procedure for the separation of Ni(II) in the presence of commonly associated metal ions. Another object of the present project is to provide a process for the separation of nickel from nickel bearing matrices like spent catalyst and electroplating bath residue. Still another object of the present invention is to provide an improved process for the recovery of Ni, using bis (2.4,4 - trimethylpentyl) dithiophosphinic acid. Yet another object of the present invention is to use extractant which enables the separation of Ni(II) from Cr(lII), Fe(IlI), Mn(II), Co(II), Cu(II) and Zn(Il). Still another object of the present invention is to provide a process wherein there is a negligible loss of the extractant in each extraction-stripping cycle, resulting in an economical process. Yet another object of the present invention is to recover Ni from the extractant phase in a form so that it can be easily processed for subsequent applications. Accordingly the present invention provides an improved process for the recovery of nickel which comprises of dissolving nickel bearing matrix in a mineral acid, adjusting the acid n/olarity of the aqueous phase as required, extracting nickel selectively in an extractant sue"; as bis (2/1,4 -trimethylpently) dithiophosphinic acid in an appropriate diluent to obtain nickel in organic phase by known methods. In an embodiment of the present invention the nickel matrix may be as such. as a spent catalyst or electroplating bath residue. In another embodiment of the present invention the mineral acid used may be such as sulphuric acid, nitric acid or hydrochloric acid and mixture thereof. In another embodiment of the present invention the diluent used may be such as n-hexane, kerosene (160° - 200(1C), xylene, toluene and cyciohexanone. In yet another embodiment of the present invention the known method for stripping nickel may use reagents such as 0.1M oxalic acid, 0.1M tartaric acid, 0.1M citric acid, O.IM Na2EDTA, 0 IM Na2S2O3.5H20, 6M HC1, 3M H2SO4, 5% (NH4)2CO3 and 5% NH4C1 in 10 - 75% NH3. In other embodiment of the present invention the extraction behaviour of Ni(Il), Cr(III), Fe(IIl), Mn(II), Co(Il), Cu(II) and Zn(Il) from 5.0 x 10-5M to 5.0M HbSO4 was studied using 0.1M toluene solution of (I). Ni(II) and Co(II) showed quantitative extraction in the range 1.0 x 10"4M to 5.0 x 10"2M I-bSC^ and then its extraction declines to almost negligible value at 5.0M h^SO^ Cu(II) and Zn(II) show a constant and quantitative extraction in the entire investigated range of acid rnolarities except at 5.0 x l0-5M H2SO4 where the extraction of Cu(Il) declines to around fifty percent. The extraction of Fe(IlI) remains constant up to 0.1M H2SO4 and then decreases with increasing rnolarity. Cr(III) and Mn(II) shows negligible extraction ( The extraction of Ni(l!) in (1) was studied using different solvents such as n-hexane, kerosene (160() - 200^C), xylene, toluene and cyclohexanone. At 5.0 x lO'^M H2S04 effect could not be discerned because of a quantitative extraction of Ni(II) in all of them Also the effect could not be distinguished at 0.25M as lower extractions ( observed in all the diluents except in n-hexane which shows around 20% extraction. In cyclohexanone a slow phase separation was observed. Toluene was chosen for the present study. The kerosene fraction can replace toluene without any significant change in extraction behaviour. The effect of concentration of (I) (1.0 x 10-3 - 0.10 M) on the extraction of Ni(ll) has been studied There is an increase in the extraction with the increase in the concentration of the extractant. The effects of metal ion concentration (1.0 x 10"^ - 5.0 x 10~2 M) on the extraction of Ni(ll) has been investigated using 0.10M toluene solution of (I). Results revealed that (I) can hold the metal ion to a maximum of about one tenth of its molar concentration. Various stripping reagents like 0.1M oxalic acid, 0.1M tartaric acid, 0.1M disodium salt of ethylenediammine tetraacetic acid, 0.1M sodium thiosulphate, 3% H2O2, 6M HC1, 3M H2SO4; 5% (NH4)2CO3, 5% (NH4)2CO3 in 10% N)I3, 5% NH4C1, and 5% NH4C1 in 10 - 75% NH3, were employed for the back extraction of Ni(II) from organic layer. When NH3 solution is used as stripping agent phase transfer is slow. The problem is circumvented by using NH3 containing NH4C1. Therefore a 5% NH4C1 in 3:4 NH3 is used for stripping Ni(ll) from organic phase. Around 70% Ni(ll) from organic phase is extracted in a single contact and for more than 90% recovery of Ni(II) the organic phase was contacted thrice with equal volumes of this stripping solution. The stripped organic phase can be regenerated by washing it twice with half its volume of 1M H2S04 and subsequently with water. Experiments were conducted on successive extraction stripping cycles for Ni(II) from 5.0 x 10-3 M H2S04 in 0.10M toluene solution of (I) upto ten cycles. The results revealed practically no change in the efficiency of the extractant up to ten cycles. Extractant (I) selectively extracts Ni(ll) in the presence of other commonly associated metal ions. Only ten fold excess of the extractant to the metal ion is required for the quantitative extraction of Ni(II). Because of poor aqueous solubility there is a little extractant loss in subsequent extraction-stripping cycles. The reagent exhibits good recycling capacity. Toluene can be replaced by kerosene fraction and this appreciably cuts down the cost on the process. The stripping reagent used is simple in composition and yields a quantitative recovery. The following examples are given by way of illustrations of the present invention and should not be constructed to limit the scope of the present invention Example 1 1 g. of the dried powdered spent catalyst is left overnight with 10 ml of 2M HC1. The solution is filtered and diluted to 2.5 lit. This solution is further diluted ten times keeping the overall pH to 2.5. 10 ml. of this solution are equilibrated twice with 10 ml of toluene solution of 0.l0M extractant. Ni(li) along with Fe(III), Co(Il), Cu(II) and Zn(Il) is extracted into the organic phase leaving behind Cr(III) and Mn(II) in aqueous phase The organic phase is washed with 10 ml. of 6M HC1 to strip collectively Fe(HI), Co(ll) and Zn(II) leaving Ni(II) and Cu(II) in the organic layer. Ni(Il) is subsequently stripped by employing 5% NH4Cl in 75% NH3 The solution is then boiled to expel NH3. It is difficult to disengage Cu(ll) from the organic phase but its small amount does not present problems and the extractant can be repeatedly used for several cycles without affecting its efficiency. Ni(ll) is precipitated as hydroxide by the addition of NaOH and the precipitate is washed thoroughly with water. Nickel hydroxide is used to maintain the concentration of a nickel electrolytic bath which is used to deposit nickel. The electrolyte cell uses aluminium and lead as a cathode and anode materials, operates at 3.1 volt and the concentration and pH are maintained at 60g/lit Ni and 2.5, respectively. Example 2 1 g. of the dried powdered plating bath residue is left overnight with 10 ml of 2M HCI. The solution is filtered and diluted to 2.5 litres. This solution is further diluted twenty five times keeping the overall pH to 2.5. 10 ml. of this solution are equilibrated twice with 10 ml of toluene solution of 0.10M extractant. Ni(Il) along with Fe(lll), Co(Il), Cu(ll) and Zn(II) is extracted into the organic phase leaving behind Cr(III) and Mn(II) in aqueous phase. The organic phase is washed with 10 ml. of 6M HCI to strip collectively Fe(Ill), Co(Il) and Zn(ll) leaving Ni(Il) and Cu(ll) in the organic layer. Ni(Il) is subsequently stripped by employing 5% NH4C1 in 75% NH3. The solution is then bailed to expel NH3. It is difficult to disengage Cu(II) from the organic phase but its small amount does not present problems and the extractant can be repeatedly used for several cycles without affecting its efficiency. Ni(Il) is precipitated as hydroxide by the addition of NaOH and the precipitate is washed thoroughly with water. Nickel hydroxide is used to maintain the concentration of a nickel electrolytic bath which is used to deposit nickel. The electrolyte cell uses aluminium and lead as a cathode and anode materials, operates at 3.1 volt and the concentration and pH are maintained at 60g/lit Ni and 2.5, respectively. The main advantages of the present invention are: 1 Recovery of pure nickel solution from the solution of a complex matrix in a relatively convenient way 2. The hydrolytic stability and good regeneration power of the extractant favours the cost effectiveness of the process. 3. Fast mass transfer and phase separation add towards the utility of the process for scaling up. 4. Only a ten-fold excess of the extractant is required for the quantitative extraction of Ni(II). 5. The stripping reagent used is simple in composition and yields a quantitative recovery. 6. The recovery of nickel by this process is around 95% with a purity of >95%. We claim : 1 . An improved process for the recovery of nickel which comprises of dissolving nickel containing matrix such as herein described in 2m mineral acid in an extracting nickel selectively characterised that an extractant selected from bis (2,4,4 -trimethylpentyl) dithiophosphinic acid is used in diluent selected from hydrocarbon solvent to obtain nickel in the organic phase, followed by stripping of nickel from the organic phase by known method. 2. An improved process as claimed in claim 1, wherein the nickel matrix used is spent hydrogenation catalyst and electroplating bath residue. 3. An improved process as claimed in claims in 1 and 2 wherein the mineral acid used is hydrochloric, nitric or sulphuric or a mixture thereof. 4. An improved process as claimed in claims 1-3 wherein the hydrocarbon solvent used for the extraction is selected from n-hexane, kerosene (160° - 200°C), xylene, toluene and cyclohexanone. 5. An improved process as claimed in claims 1-4 wherein the known method for stripping nickel uses 5% NH4C1 in 10-75% NH3. 6. An improved process for the recovery of nickel substantially as described herein with reference to the examples.

Documents:

802-del-1999-abstract.pdf

802-del-1999-claims.pdf

802-del-1999-correspondence-others.pdf

802-del-1999-correspondence-po.pdf

802-DEL-1999-Description (Complete).pdf

802-del-1999-form-1.pdf

802-del-1999-form-19.pdf

802-del-1999-form-2.pdf