Mixtures of collectors have been widely used for many years in sulphide flotation, and a range of performance benefits have been reported for many different systems. The combinations of collector types have varied, as have the ratios that have been used. Synergistic effects have been obtained (greater than the sum of the parts) and in some cases the mechanisms of this improved behaviour have been identified. These benefits have been attributed to increased carrying capacity of the froth phase, faster kinetics, and more successful recovery of middling or coarse particles. It is the interaction between the various components of the mixed collector system, rather than the individual main effects, that dominate the performance benefits. The process benefits include increased paymetal recoveries and grades – as well as increased rates of recovery whilst using lower dosages of reagents (Lotter and Bradshaw, 2010).

This theory was successfully tested at an operating platinum mine in South Africa, where the standard collector suite was a single xanthate.  Laboratory testwork using mineralogy and a factorially designed set of flotation tests formulated a mixed collector suite comprising two xanthates and a dithiocarbamate.  This work predicted a 2.1% absolute gain in PGE recovery from this mixture as compared to the standard baseline xanthate.  Use of the on-off designed plant trial verified this gain to be 2.5%, as well as a gain in concentrate grade (Lotter et al., 2011).  These gains were significant at the 90% confidence level.

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Lotter, N.O., and Bradshaw, D.J., 2010.  The Formulation and Use of Mixed Collectors for Sulphide Flotation, Minerals Engineering, 23, (2010), pp. 945-951.

Lotter, N.O., Monnapula, R., Oliveira, J., Fragomeni, D., and Bradshaw, D.J., 2011.  Formulation and Plant Trial of a Mixed Collector Suite for Eland Platinum, proc. Canadian Mineral Processors, Ottawa, January 2011, Paper 10.