| Abstract: | The solvent extraction of nickel and calcium from acidic solutions by mixtures of dinonylnaphthalene sulphonic acid (DNNSA) and different pyridinecarboxylate esters (2-, 3- and 4-C5H4.CO.OR, where R = n-octyl, 2-ethylhexyl and 2-octyl) in xylene was investigated. In contrast to extraction systems employing DNNSA alone, these mixtures permit the separation of nickel and calcium to be carried out, especially when an excess of the ester is used. The extractability of base metals from sulphate solutions by mixtures of DNNSA (0·25 M ) and isodecyl 3-pyridinecarboxylate (0·25 M ) in Shellsol K decreases through the series Cu > Ni > Al > Co > Ca > Zn > Fe(III) > Mg. Mixtures containing the 2- or 4-ester showed a slightly different selectivity series: Cu > Ni > Co > Zn > Al > Fe(III) ≥ Ca > Mg. In a batch countercurrent experiment, a simulated leach liquor containing Ni 2·15, Mg 5·05 and Ca 0·42 g dm−3 (initial pH 3·0) was extracted with the mixed reagent (0·25 M DNNSA plus 0·25 M 4-ester) in four stages at unit phase ratio, without any pH adjustment. The recovery of nickel was 91%, with co-extractions of calcium and magnesium of 14 and 8%, respectively. When the concentration of the 4-ester was increased to 0·50 M , the recovery of nickel increased to 95%, whilst the co-extractions of calcium and magnesium decreased to 4 and 3%, respectively. © 1998 SCI. |
