The effect of individual complexed metals on hydroxyoxime stability in the LIX 63–Versatic 10–tributyl phosphate synergistic solvent extraction system under synthetic nickel laterite extract conditions

The effect of nil metal complexation and complexing nickel, cobalt, copper, zinc and manganese, both individually and collectively, on the chemical stability of LIX® 63 hydroxyoxime (‘hydroxyoxime’) when in the presence of Versatic 10 and tributyl phosphate (TBP) under synthetic nickel laterite extract conditions at 45 °C has been assessed. Hydroxyoxime degradation was observed at pH 5.5–6.0 even in the absence of metal complexation, resulting in half lives of 53–56 weeks. Although loading up to 0.2 g/L of copper, cobalt or zinc had no material effect, progressively increasing the loading of these individual metals up to 3 g/L resulted in hydroxyoxime half lives decreasing to 12, 21 and 28 weeks, respectively. Manganese loading of 0.5–2.0 g/L also had an adverse effect, with a half life of 31 weeks. In contrast, nickel loading up to 4.6 g/L had little or no adverse effect on half life (48 weeks). Based on the present results, increasing hydroxyoxime half life can be achieved by minimising copper and manganese loading.

► The effect of individual complexed metals on LIX 63 stability was assessed.
► LIX 63 hydroxyoxime half life under metal-free extract conditions was determined.
► Nickel loading up to 4.6 g/L had little or no adverse effect.
► Both copper and cobalt loading at 3.0 g/L had an adverse effect.