Extraction of nickel from ammoniacal solutions using LIX 87QN

Abstract

Extraction of nickel from ammoniacal-ammonium carbonate solutions using LIX 87QN as the extractant has been studied in detail. The effects of pH (ammonia concentration) and ammonium carbonate concentration on nickel extraction were studied using an aqueous solution containing 5.577 kg/m 3 of nickel and 10 vol% LIX 87QN diluted with kerosene (distilling between 170 and 240°C). The concentration of nickel in the organic phase decreased from 4.43 to 1.82 kg/m 3 when the equilibrium pH was increased from 8.6 to 10.0. When the ammonium carbonate concentration of the aqueous phase was increased from 45 to 150 kg/m 3, the concentration of nickel in the organic phase decreased from 4.43 to 3.55 kg/m 3. The loading capacity of a 10 vol% solvent in kerosene, obtained from an aqueous solution containing 60 kg/m 3 of ammonium carbonate and at an equilibrium pH of 9.95 was found to be 4.24 kg/m 3. For a solution containing 5.21 kg/m 3 of nickel and 60 kg/m 3 of ammonium carbonate it was found that complete nickel extraction is possible in two counter-current stages at an A:O phase ratio of 2:3. The loaded organic was found to contain 0.15 kg/m 3 of ammonia, which has been selectively stripped by a single-stage scrubbing with dilute sulphuric acid at an equilibrium pH of > 7. There was no loss of nickel during this operation. From the ammonia-free loaded organic, nickel stripping was carried out in two counter-current stages at an A:O ratio of 5:4 with a spent electrolyte of pH 1.55 containing 57 kg/m 3 of nickel, 12 kg/m 3 each of sodium sulphate and boric acid. The stripping efficiency was found to be about 98%.