Manganese in copper solvent extraction a

In the copper solvent extraction–electrowinning (SX–EW) process, Mn²⁺ entrained in the organic solution may be transferred to the loaded electrolyte, where it is oxidised during copper EW, forming high-oxidation state manganese which can return to the SX circuit. This study investigates the mechanisms of organic degradation due to manganese recycles from copper EW to SX through laboratory-scale simulations. During the trials, Mn²⁺ in the electrolyte was oxidised primarily to Mn³⁺ and further to MnO₂, with no evidence of Mn⁴⁺. The presence of manganese species correlated with increased phase disengagement times and stable emulsion formation, with most organic oxidation and emulsion issues associated with Mn³⁺ rather than MnO₂. Various degradation products of hydroxyoxime extractants were identified using gas chromatography and high-performance liquid chromatography techniques. Notably, the deterioration in phase separation was linked to specific degradation products, particularly 5-nonyl salicylic acid, with ongoing research aimed at confirming the effect of polar species on phase separation processes. This work underscores the critical impact of manganese oxidation states in copper SX–EW processing.