The effect of sodium isobutyl xanthate on galena and chalcopyrite flotation in the presence of dithionite ions

Ngoni Mhonde,Leena-Sisko Johansson,Kirsten Corin,Nora Schreithofer

doi:10.1016/j.mineng.2021.106985

Ngoni Mhonde, Leena-Sisko Johansson + Show 2 more

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https://doi.org/10.1016/j.mineng.2021.106985

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Journal: Minerals Engineering	Publication Date: May 30, 2021
Citations: 17	License type: cc-by

Affiliation: Aalto University, University of Cape Town

Abstract

Sulphoxy anions in recycled flotation process waters possess the potential to reduce the flotation efficacy of flotation reagents. In this study, dithionite ions and their interaction with thiol collectors in solution and the surface modifications of galena and chalcopyrite surfaces in the presence of dithionite ions were investigated. Microflotation tests, zeta potential tests, electrochemistry studies, solution xanthate degradation kinetics and surface analyses were carried out. Microflotation results showed a reduction in chalcopyrite and galena recoveries in dithionite solutions even in the presence of xanthate. Zeta potential and rest potential measurements showed that the potential determining effect of dithionites on the sulphide mineral surfaces (zeta potentials) and the solution (pulp potential), inherently decrease collector-mineral interactions. Xanthate degradation tests showed that more than half of the collector in solution was consumed in 10 min of reacting 20 mg/L of xanthate with 500 mg/L of dithionites. Surface analyses results also revealed that dithionites strongly influenced the chemical state of the sulphide minerals under investigation by producing oxidised sulphur species in the form of sulphites on the galena surface and oxidised iron species in the form of oxides and hydroxides on chalcopyrite. The current study presents a complete view of dithionite behaviours in plant waters by considering the dithionite-mineral surface interactions and dithionite-collector interactions in addition to the traditionally agreed on pulp potential alterations.

Highlights

Short circuit recycling of flotation process waters entails the rein troduction of water from units such as thickeners and filters into the flotation circuit, bypassing tailings ponds
The current study presents a complete view of dithionite behaviours in plant waters by considering the dithionite-mineral surface interactions and dithionite-collector interactions in addition to the traditionally agreed on pulp potential alterations
Previous studies have shown that no significant xanthate decomposition occurs in deionised water at neutral to alkaline pH i.e., in the absence of sulphoxy compounds

Summary

Introduction

Short circuit recycling of flotation process waters entails the rein troduction of water from units such as thickeners and filters into the flotation circuit, bypassing tailings ponds. Owing to the complex chemistry of the multiple sulphoxy species, multiple oxidation–reduction couples are present in the system making it difficult to study the kinetics and speciation under various conditions (Miranda-Trevino et al, 2013; Negeri et al, 1999) Some of these sulphoxy species present in flotation solutions are often overlooked owing to their short residence time before decomposition and difficulty in identification using conventional analytical techniques. One such species is the dithionite ions (S2O42-), which are an intermediate product in the oxidation of tetrathionates to higher oxidation state sulphoxy compounds (Chander and Briceno, 1987; Peres, 1979). Dithionites react with water, but they are constituents of the suite of sulphoxy compounds in flotation process waters, and ought to be investigated as water recycling will lead to future increases of their concentrations in plant water

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