SOLVENT-EXTRACTION OF NICKEL FROM ACIDIC SOLUTIONS USING SYNERGISTIC MIXTURES CONTAINING PYRIDINECARBOXYLATE ESTERS - PART 3 - SYSTEMS BASED ON ARYLSULFONIC ACIDS

The solvent extraction of nickel and calcium from acidic solutions by mixtures of dinonylnaphthalene sulphonic acid (DNNSA) and different py ridinecarboxylate esters (2-, 3- and 4-C5H4.CO.OR, where R = n-octyl, 2-ethylhexyl and 2-octyl) in xylene was investigated. In contrast to e xtraction systems employing DNNSA alone, these mixtures permit the sep aration of nickel and calcium to be carried out, especially when an ex cess of the ester is used. The extractability of base metals from sulp hate solutions by mixtures of DNNSA (0.25 M) and isodecyl 3-pyridineca rboxylate (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-est er showed a slightly different selectivity series: Cu > Ni > Co > Zn > Al > Fe(III) greater than or equal to Ca > Mg. In a batch countercurr ent experiment, a simulated leach liquor containing Ni 2.15, Mg 5.05 a nd Ca 0.42 g dm(-3) (initial pH 3.0) was extracted with the mixed reag ent (0.25 M DNNSA plus 0.25 M 4-ester) in four stages at unit phase ra tio, without any pH adjustment. The recovery of nickel was 91%, with c o-extractions of calcium and magnesium of 14 and 8%, respectively. Whe n the concentration of the 4-ester was increased to 0.50 M, the recove ry of nickel increased to 95%, whilst the co-extractions of calcium an d magnesium decreased to 4 and 3%, respectively. (C) 1998 SCI.