A review of the effects of the grinding environment on the flotation of copper sulphides

The reported effects of the grinding method and grinding medium upon the flotation performance of sulphide minerals has shown that the pulp chemical environment, the ore composition, the properties and type of the grinding media, the size reduction method employed, pre-conditioning stages prior to flotation, and reagent interactions during grinding (and conditioning) can influence the subsequent flotation process. These factors are reviewed and discussed in relation to the flotation of copper sulphide minerals. Galvanic interactions between sulphide minerals and steel grinding media increase iron levels, lower the dissolved oxygen concentration in the slurry, and result in the formation of iron hydroxides. These changes can be deleterious to copper flotation. It has been shown that chrome alloy balls can have beneficial effects on flotation performance in some systems by limiting the formation of hydroxides in the pulp. As well, galvanic interactions between the sulphide minerals can occur, depending on the mineralogy of the ore, and they can influence the separation efficiency in flotation. While reagent additions, such as collector, lime, or cyanide, during milling can alter the pulp chemistry during grinding, there is little clear evidence in the literature that their addition during grinding has any strong influence on the subsequent floatability of copper sulphide particles. Improvements in copper recovery by flotation following fully autogenous milling in comparison with conventional milling using steel rod and ball mills at the same grind size have been noted in several laboratory and plant studies. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.