Patent Application: US-73409003-A

Abstract:
an organic solvent extraction mixture which includes a first extractant which is a substituted imidazole or benzimidazole , a non - selective strongly acidic cation second extractant , such as a sulphonic acid , to facilitate phase transfer of base metal ions from an aqueous weakly acidic sulphate solution into the organic phase , a modifier to improve the characteristics of the organic phase with respect to metal complex solubility to avoid third phase formation , completeness and ease of stripping , viscosity and phase disengagement , and a diluent .

Description:
the invention can be applied using any standard solvent extraction apparatus , consisting of an extraction section and a single or double stripping section , with an optional washing or scrubbing section in between , and suitable to simulate standard solvent extraction flow sheets as shown in any of the flow sheets in fig1 to 3 respectively . the flow sheets shown in fig1 to 3 are largely self - explanatory and are known in the art . they are therefore not described in detail hereinafter . in the following examples a comparison is made of the results obtained by using organic solvent extractant mixtures according to the invention and the results obtained using other extractants . examples 1 and 2 relate to the use of organic extraction mixtures which do not fall inside the scope of the invention while the remaining examples illustrate results obtained using organic extraction mixtures which fall within the scope of the invention . aqueous solutions of individual metal sulphate salts , at 0 . 001 molar , were contacted with an organic mixture containing 0 . 02 molar dnns in an iso - decanol ( 30 %)— shellsol a mixture . the ph of the aqueous phase was adjusted to the target value using either aqueous sulphuric acid or sodium hydroxide solutions . the residual metal concentration in the aqueous phase was determined to calculate the % extraction . occasionally , the organic phase was contacted with aqueous 1 . 0 molar sulphuric acid to strip the metals . the recovered metal in the strip solution was then also determined to calculate and verify the % extraction . the results in fig4 indicate that dnns is a non - selective extractant for divalent cations with optimum extraction in the ph range 1 . 00 to 3 . 0 . aqueous solutions of individual metal sulphate salts , at 0 . 001 molar , were contacted with an organic mixture containing 0 . 08 molar 2 -( 1 - butyl - aminomethyl )- 1 - decylimidazole ( badi ) in a mixture containing 30 % iso - decanol and shellsol a . the ph of the aqueous phase was adjusted to the target value using either aqueous sulphuric acid or sodium hydroxide solutions . the residual metal concentration in the aqueous phase was determined to calculate the % extraction . occasionally , the organic phase was contacted with aqueous 1 . 0 molar sulphuric acid to strip the metals . the recovered metal in the strip solution was then also determined to calculate and verify the % extraction . the results in fig5 indicate that , with badi only present , only copper is extracted but from an aqueous bisulphate medium . the other metals are only partly extracted , with an obvious reversal at ph & gt ; 3 . 50 when sulphate ions predominate . aqueous solutions of individual metal sulphate salts , at 0 . 001 molar , were contacted with an organic mixture containing 0 . 08 molar 2 -( 1 - butyl - aminomethyl )- 1 - decylimidazole ( badi ) and 0 . 01 molar dnns , in a mixture containing 30 % iso - decanol and shellsol a . the ph of the aqueous phase was adjusted to the target value using either aqueous sulphuric acid or sodium hydroxide solutions . the residual metal concentration in the aqueous phase was determined to calculate the % extraction . occasionally , the organic phase was contacted with aqueous 1 . 0 molar sulphuric acid to strip the metals . the recovered metal in the strip solution was then also determined to calculate and verify the % extraction . the results in fig6 indicate that , with both badi and dnns present , the metals are extracted over a wide ph range giving various opportunities for separations or purifications . one option would be the selective rejection of zn , mn , mg , ca and pb from the other compounds presents with a basic flow sheet as shown in fig1 with the option of rejecting cobalt or cadmium by appropriate scrubbing ( flow sheet as per fig2 ) or selective stripping ( flow sheet as per fig3 ). in the absence of iron species , nickel and copper could be extracted selectively at a lower ph , with selective stripping of nickel with a flow sheet as per fig3 . obviously , nickel selectivity could also be obtained by prior removal of copper , e . g . by sulphide precipitation . an aqueous solution of metal sulphates , obtained by bioleaching a nickel sulphide concentrate , after removal of dissolved iron , containing ni ( 6 . 33 g / l ), cu ( 19 . 7 ppm ), co ( 86 . 3 ppm ), zn ( 3 . 3 ppm ), mg ( 589 ppm ) and mn ( 11 . 3 ppm ) was contacted with an organic mixture containing 0 . 57 molar 2 -( 1 - butyl - aminomethyl )- 1 - decylimidazole ( badi ) and 0 . 15 molar dnns in a mixture containing 41 % iso - decanol in shellsol a . the ph of the aqueous phase was adjusted to the target value using either aqueous sulphuric acid or sodium hydroxide solutions . the residual metal concentration in the aqueous phase was determined to calculate the % extraction . occasionally , the organic phase was contacted with aqueous 1 . 0 molar sulphuric acid to strip the metals . the recovered metal in the strip solution was then also determined to calculate and verify the % extraction . the same aqueous solution of metal sulphates was also contacted with an organic mixture containing 1 . 14 molar 2 -( 1 - butyl - aminomethyl )- 1 - decylimidazole ( badi ) and 0 . 285 molar dnns in iso - decanol in the absence of shellsol a . the results in fig7 a and 7 b indicate that , in both instances , nickel can readily be separated from cobalt , zinc , magnesium and manganese using a flow sheet as per fig1 or 2 . copper can also be rejected using a flow sheet as per fig3 . an aqueous solution of nickel sulphate , at 0 . 001 molar , was contacted with an organic mixture containing 0 . 08 molar 2 -( 1 - butyl - aminomethyl )- 1 - decylimidazole ( badi ) and different concentrations of dnns in a mixture of iso - decanol ( 30 %) and shellsol a . the ph of the aqueous phase was adjusted to the target value using either aqueous sulphuric acid or sodium hydroxide solutions . the residual metal concentration in the aqueous phase was determined to calculate the % extraction . occasionally , the organic phase was contacted with aqueous 1 . 0 molar sulphuric acid to strip the metals . the recovered metal in the strip solution was then also determined to calculate and verify the % extraction . the results in fig8 indicate that complete nickel extraction is already obtained at a dnns concentration of 0 . 005 molar . extraction is very effective at dnns concentrations between 0 . 010 and 0 . 040 molar . with a large excess of dnns , and up to 0 . 06 molar for a 0 . 001 molar metal concentration , complete extraction is still possible but only at a higher ph . aqueous solutions of nickel sulphate , at 0 . 001 molar , were contacted with an organic mixture containing 0 . 1 molar 2 -( r 5 , r 6 - aminomethyl )- 1 - decylimidazole ( r - adi ), ( r 6 = h , r 5 = methyl , ethyl , butyl , pentyl , hexyl , octyl , ethylhexyl or decyl and r 5 = r 6 = ethyl ), 0 . 010 molar dnns in an iso - decanol ( 30 %)— shellsol a mixture . the ph of the aqueous phase was adjusted to the target value using either aqueous sulphuric acid or sodium hydroxide solutions . the residual metal concentration in the aqueous phase was determined to calculate the % extraction . occasionally , the organic phase was contacted with aqueous 1 . 0 molar sulphuric acid to strip the metals . the recovered metal in the strip solution was then also determined to calculate and verify the % extraction . the results in fig9 indicate that very effective metal extraction can be obtained with a mono - substituted amino group , in which the substituent is an aliphatic group containing between one and six carbon atoms . with a longer chain aliphatic substituent or with a double substituted amino group , extraction is less effective , requiring a higher ph for complete extraction . aqueous solutions of individual metal sulphate salts , at 0 . 001 molar , containing also chloride at a concentration of 0 . 77 molar , were contacted with an organic mixture containing 0 . 08 molar 2 -( 1 - butyl - aminomethyl )- 1 - decylimidazole ( badi ) and 0 . 01 molar dnns in a mixture of iso - decanol ( 30 %) and shellsol a . the ph of the aqueous phase was adjusted to the target value using either aqueous sulphuric acid or sodium hydroxide solutions . the residual metal concentration in the aqueous phase was determined to calculate the % extraction . occasionally , the organic phase was contacted with aqueous 1 . 0 molar sulphuric acid to strip the metals . the recovered metal in the strip solution was then also determined to calculate and verify the % extraction . the results in fig1 , together with those from example 3 ( fig6 ), indicate that the extraction of zinc is strongly enhanced by the presence of chloride in the aqueous phase . the extraction of copper and cobalt is only slightly enhanced and that of nickel is not affected at all . the extractability of manganese remains low and is not much affected either . the results show that the presence of chloride , either due to circumstances or by design , is advantageous for the selective separation of certain groups of base metals such as cu / zn and rejection of ca , mg and mn from ni / co . the separation between co and ni is smaller but remains adequate for effective removal if the cobalt is much lower than that of nickel , which is true in most instances . aqueous solutions of individual metal sulphate salts , at 0 . 001 molar , were contacted with an organic mixture containing 0 . 08 molar bis ( 2 - methyl - 1 - decylimidazole ) amine ( bmia ) and 0 . 01 molar dnns , in a mixture containing 70 % iso - decanol and shellsol a . the ph of the aqueous phase was adjusted to the target value using either aqueous sulphuric acid or sodium hydroxide solutions . the residual metal concentration in the aqueous phase was determined to calculate the % extraction . occasionally , the organic phase was contacted with aqueous 1 . 0 molar sulphuric acid to strip the metals . the recovered metal in the strip solution was then also determined to calculate and verify the % extraction . the results in fig1 indicate that , with bmia and dnns present , the metals are extracted over a wide ph range giving various opportunities for separations or purifications . one option would be the selective rejection of mn and mg ( and probably ca and pb as well ) from the other compounds present with a basic flow sheet as shown in fig1 with the option of rejecting nickel by appropriate scrubbing ( flow sheet as per fig2 ) or selective stripping ( flow sheet as per fig3 ). in the absence of iron species , cobalt could be recovered selectively from zinc and copper by selective stripping with a flow sheet as per fig3 . overall cobalt selectivity could also be obtained by prior removal of copper and zinc , e . g . by sulphide precipitation . 1 — j szymanowski , “ hydroxyoximes and copper hydrometallurgy ”, crc press , boca raton , usa , 1993 . 2 — s c das , p g krishna , “ effect of fe ( iii ) during copper electrowinning at higher current density ”, int . j . miner . process ., 46 , 1996 , pp 91 . 3 — k tanabe , t ohgai , t akiyama and h fukushima , “ characteristic behavior of iron - 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