Effect of reducing grinding conditions on the flotation behaviour of low-S content PGE ores

The effect of grinding environment on the flotation behaviour of sulphide–poor platinum group element (PGE) ores was studied with 3 different ores containing Ni, Cu and PGE. The sulphur content of the investigated ore samples varied from 0.3% to 0.6%. Grinding tests were performed with a Magotteaux Mill® which is instrumented for measurement and monitoring of pulp properties. Flotation tests were done with a 5L Magotteaux float cell. Pulp potential, pH and dissolved oxygen (DO) levels were measured continuously during grinding. Pulp oxidation–reduction potential (ORP) and DO were adjusted by the addition of CO2, N2 and nitric acid. Iron or 30% chrome containing balls were used in grinding. In this study, a number of grinding and flotation tests were done with natural ore samples into which 1 g of synthetic sperrylite was added. This study presents some aspects of the effect of a reducing grinding environment on the flotation response of low-S content PGE containing ores. Highly reducing grinding environment created with CO2 was found to have a positive effect on flotation behaviour of PGE minerals from low-S content ores.

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► The effect of grinding environment was studied with three different Ni–Cu–PGE ores.
► The study was carried out with Magotteaux Mill®.
► CO2 atmosphere in grinding was studied.
► Highly reducing grinding environment can be created with CO2.
► Highly reducing grinding environment has a positive effect on flotation response.