The aims of the flotation chemistry research programme are to develop an understanding of the chemical aspects of flotation and to explain the roles and interactions of the various chemical factors so as to establish their influence on the overall process, particularly with reference to the flotation of PGM and sulphide ores. The research hence includes the study of the interactions between collectors, depressants, activators, modifiers and the effect of factors such as pH, DO, Eh on the behaviour of the reagents. The interaction between the chemical environment in the comminution process and the subsequent flotation behaviour is a growing area of research. The research also includes studies of contact angles, bubble sizes and rheological factors impacting on flotation performance.
The creation of a favourable chemical environment is critical to the overall success of the flotation process. However, the process is complex and many of the influential factors interact, therefore ascertaining the contribution of each individual factor to the overall performance can be very difficult. Often the interactions mask or confuse the interpretation of the resulting performance.
One of the most important chemical factors that determine the flotation response of a pulp is the reagent suite that is added. This includes those that have specific roles, such as collectors, activators, frothers, pH modifiers and depressants. Other factors are those that could be modified if there was enough metallurgical or economic incentive, such as water quality or milling media. A third category of chemical factors is those that are fixed and are inherently part of the system, such as the nature of the desired minerals and gangue in the ore. Before the pulp chemistry of a plant can be optimised, it is necessary to elucidate the role of each of these factors in the process.
The aims of the research programme are to develop an understanding of the chemical aspects of flotation and to explain the roles and interactions of the various chemical factors so as to establish their extent of influence and controllability on the process, particularly with reference to the flotation of PGM and copper ores.
Traditionally, the group has focused on the development of more effective thiol collectors for the flotation of various sulphide ores such as those containing pyrite, copper and PGM minerals. This included the investigation of the efficiency of some of the flotation sub-processes such as adsorption and bubble loading. The programme has been extended to include the role and interactions of the collectors with copper sulphate, depressants and frothers on both the desired mineral and unwanted gangue. The effect of the oxidation-reduction potential of the pulp is also a means of chemical manipulation, and the electrochemical effects on flotation are being investigated. The scale-up of results from a laboratory to plant scale is being investigated with particular focus on the milling media and the effect of the water quality on flotation.
At the beginning of 2012 the Flotation Chemistry Group entered into a joint venture with the Beijing General Research Institute for Mining and Metallurgy (BGRIMM) in China.The University of Limpopo also formed part of this collaboration. The proposal aimed at carrying out fundamental and applied studies on the processing of platinum group minerals and complex sulphide ores by flotation, with work carried out jointly between the two South African Universities and BGRIMM. The key research topics addressed were: the effect of various milling methods on the floatability of different ores, the development of novel reagents using molecular modelling techniques and the use of electrochemistry in flotation. This three-year joint venture has been successfully completed. Over the duration of the project, workshops were held in Cape Town, Beijing, Polokwane and Viña del Mar, Chile. The joint venture has been extended for a second phase and a workshop to plan Phase 2 was held in Beijing during April 2015.