LIX® 63 stability in the presence of Versatic 10 under proposed commercial extract and strip conditions, part I:: Operation at high temperature

The combination of LIX (R) 63 with Versatic 10 exhibits synergistic properties, enabling direct separation of Co and Zn from Mn, Mg and Ca, a process of interest to the proposed El Boleo copper/cobalt project. However, acceptable reagent stability is also required. The present work was undertaken to primarily assess the stability of LIX (R) 63 oxime ('oxime') when mixed continually over 54 days at both 40 and 50 degrees C under proposed El Boleo extract and strip conditions, along with the impact of the resulting degradation products on metal selectivity and phase disengagement properties. High temperatures were used to accelerate oxime degradation. Oxime degradation under strip conditions, which resulted in diketone and acyloin formation, was found to be associated with the presence of Versatic 10. Oxime half lives were 90 and 49 weeks at 40 and 50 degrees C, respectively. Degradation via this mechanism, which would occur throughout the circuit (extract and strip stages, mixing and settling), could be minimised by decreasing operating temperature. Oxime degradation under the extract conditions used was considered to occur primarily via cobalt and/or manganese-complex-catalysed oxidation, resulting in some diketone formation and a new species believed to contain both carbonyl and oxime groups ('keto-oxime'). Oxime half lives were 19 and 10 weeks at 40 and 50 degrees C, respectively. Despite considerable loss of oxime under extract conditions, negligible changes in the pH isotherms resulted. It is possible that degradation resulted in a product with synergistic capabilities comparable to those of oxime. An alternative explanation involving oxime isomer inter-conversion is also proposed. The presence of oxime degradation products including (but not necessarily limited-to) diketone, acyloin and keto-oxime did not result in any clearly adverse effect on phase disengagement time. Crown Copyright (C) 2007 Published by Elsevier B.V. All rights reserved.