The separation of sulfide minerals from non-sulfide gangue minerals using froth flotation necessitates the utilisation of thickeners and filters to dewater concentrates and tailings. To facilitate the dewatering of flotation products, namely, concentrates and tailings, chemical reagents such as flocculants and coagulants are utilised in thickeners to increase the efficacy of dewatering unit operations. However, it is likely that residual amounts of these chemical reagents can be found in the clear supernatant and filtrate resulting from dewatering processes. Considering that the water recovered from dewatering unit operations is recycled back into milling and flotation, it is crucial to understand how the chemistry of these dewatering chemical agents may impact the behaviour of the pulp phase. Possible interactions may occur at the mineral surface between flotation reagents, residual flocculants and coagulants, and inorganic electrolytes present in the recovered and recycled process water. Surprisingly, there is a lack of information in the existing literature regarding the influence of flocculants and coagulants on the adsorption of depressants such as carboxymethyl cellulose onto non-sulfide gangue minerals. Therefore, the primary objective of this investigation was to understand the influence of flocculants and coagulants on the adsorption of depressants onto non-sulfide gangue minerals using labradorite as a proxy for non-sulfide gangue minerals that are typically present in complex sulfide ores. The results, from the adsorption and zeta potential studies, showed that the presence of residual coagulant concentration in recycled water was favourable and increased the adsorption of CMC onto labradorite. However, the presence of a flocculant in recycled water may be detrimental to the depression of non-sulfide gangue minerals as CMC adsorption onto labradorite significantly decreased. This implies that sulfide mineral flotation plants that recycle and reuse water from thickeners and tailings dams may need to carefully monitor and control residual dewatering aids in recycled water as residual concentrations of these species may have a significant bearing on flotation performance.
Author Contributions
Conceptualisation, M.S.M.; methodology, M.S.M., L.L.O., R.M.M. and K.C.C.; formal analysis, M.S.M., L.L.O., R.M.M. and K.C.C.; investigation, M.S.M., L.L.O., R.M.M. and K.C.C.; resources, M.S.M., L.L.O., R.M.M. and K.C.C.; data curation, M.S.M.; writing—original draft preparation, M.S.M.; writing—review and editing, M.S.M., L.L.O., R.M.M. and K.C.C.; project administration, M.S.M. and K.C.C.; funding acquisition, M.S.M. All authors have read and agreed to the published version of the manuscript.
Funding
This research was funded by the University of Cape Town and the National Research Foundation (NRF) of South Africa, grant number BAAP2204062284. Any opinions, findings, and conclusions or recommendations expressed in this paper are that of the authors and the NRF does not accept any liability in this regard.
Institutional Review Board Statement
Ethical review and approval were waived for this study since this investigation did not involve humans or animals.
Informed Consent Statement
Not applicable.
Data Availability Statement
The data are available on request from the corresponding author.
Acknowledgments
The authors would like to acknowledge members of the Reagents Research Group in CMR for their support.
Conflicts of Interest
The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the abstract; or in the decision to publish this work.
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