Introduction

It is well known in the practice of flotation that mixtures of various collectors often behave with greater effectiveness than would be expected from their individual known characteristics. This phenomenon is a classical example of synergism in flotation, in which the combined effect exceeds the sum of the linearly weighted partial effects. Such phenomena are not only consciously applied by adding mixtures of reagents, especially collectors, but may also occur inadvertently since many industrial reagents are synthesized from less than absolutely pure chemicals, resulting in the presence of small amounts of different product molecules which are often capable of having a positive synergistic effect on the flotation behaviour. Such synergism can have a significant effect not only on the recovery but also on the selectivity of specific minerals in differential flotation. The manner in which reagents interact in order to achieve a synergis-tic effect is a complex function of their chemical nature as well as their chemisorptive or physisorptive properties. The former will determine whether the chemical composition of the reagent changes when another compound is present through, for example, a dimerization reaction. The latter will determine how competitive or synergistic adsorption will influence the ultimate flotation behaviour. The analysis of synergism between reagents in flotation is complicated by the fact that the roles and interactions of the different classes of reagents are difficult to isolate due to the complexity of the flotation process, viz. the frother is added to stabilize the froth zone but can also interact with the collector and affect the performance of the collection zone.

This review firstly discusses those properties of pure collectors, frothers, depressants and activators which are pertinent to their potential synergistic behaviour. The interactions between collectors, frothers and each other are then reviewed. The emphasis here is on sulfide minerals but similar effects have been extensively reported in the case of oxide flotation. Finally, an hypothesis is proposed to explain the synergism observed when mixtures of thiol collectors are used in the flotation of pyrite. This represents a typical sulfide mineral flotation system and will serve to highlight how the various sub-processes of flotation may be influenced in a synergistic manner, thus influencing the ultimate flotation performance.

Solar Panel Basics

Solar Panel Basics

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