Effect of long term exposure of aliphatic ELIXORE 205 diluent to acidic and oxidising conditions on copper extraction

Abstract

The impact of six months continuous mixing of aliphatic diluent ELIXORE 205 at 50°C and 180g/L H2SO4 both with and without ongoing addition of potassium permanganate oxidant was assessed in both the absence and presence of 15% v/v Acorga M5640 extractant. Compositional changes were assessed using FT-IR, GC, GC–MS and HPLC analysis of the organic solutions. No diluent degradation was observed in the acid-only diluent or diluent plus Acorga M5640 systems, or in the oxidised system where Acorga M5640 was present. In the latter system, preferential degradation of the extractant occurred. Small quantities of ELIXORE 205 degradation products suspected to be ketone and alcohol species were evident in the oxidised diluent-only system.The impact of the organic ‘ageing’ process on copper loading, metal selectivity, extraction and stripping kinetics, phase disengagement times, and aqueous in organic entrainment was also assessed. This was achieved by adding fresh Acorga M5640 (and supplemental diluent as needed) to each degraded organic system to achieve a 10% v/v solution. The properties of these ‘aged’ solutions were compared to reference solutions containing only fresh extractant and diluent. Relative to the fresh reference solutions, extended exposure to acid conditions had no clear effect for either the diluent-only or the diluent plus extractant degraded systems. A small adverse effect in copper loading was evident in the oxidised diluent-only degraded system. A clear deterioration in performance was evident in the oxidised Acorga M5640-containing degraded system, expected under the very harsh conditions used.