Mextral® 6103H/naphthenic acid/TOPO synergistic extraction system for recovery of nickel and cobalt from nickel laterite

Abstract

Combination of the α-hydroxyoxime and the carboxylic acids results in synergistic extraction of nickel and cobalt and exhibits excellent performance of separating nickel and cobalt from manganese, magnesium and calcium, but they have the drawbacks of slow nickel stripping kinetics. In this study, trioctylphosphine oxide (TOPO), as an accelerator, was used to improve the nickel stripping kinetics of the Mextral 6103H/naphthenic acid system. The results showed that the addition of 0.35 M TOPO to 0.35 M Mextral 6103H/0.5 M naphthenic acid system significantly improved the nickel stripping kinetics. After mixing for 3 min, 96% stripping efficiency was obtained with 15 g/L H2SO4 at an O/A ratio of 1:1 and 25 ℃. The extraction pH isotherms revealed that more than 99.0% copper, 99% cobalt, 97% nickel and 86% zinc were extracted at pH 5.5, and only 6% manganese, 0.08% magnesium and 0.24% calcium were co-extracted. At pH 5.0, 87% calcium, 96% manganese and 97% magnesium can be scrubbed, resulting in 5.3 mg/L manganese and less than 0.5 mg/L magnesium and calcium remained in the scrubbed organic solution. Full stripping of nickel and cobalt could be achieved in two stages with 50 g/L nickel and 150 g/L H2SO4 at an O/A ratio of 10:1 and 25 ℃. Thus, compared with TBP, TOPO was more efficient for improving the nickel stripping kinetics at room temperature, which can reduce the power consumption and lead to clear production.