Abstract
Mineral concentrators are becoming increasingly aware of the importance of the quality of the water that they feed into their milling and flotation circuits. It is speculated that different inorganic constituents of process water may yield different flotation results owing to the electrolyte–reagent–mineral interactions occurring in the pulp phase. These interactions are said to be specific to ion type, reagent type, and mineral or ore type. It therefore stands to reason that there is a need to develop an understanding of the specific ion effects on both the pulp phase and the froth phase phenomena, such that the chemistry and the quality of process water can be monitored and controlled in a manner that does not negatively affect the flotation performance. Previous research has shown that inorganic electrolytes may impact the hydrophobicity and the floatability of mineral particles and could in turn affect froth stability, entrainment, and thus mineral grades and recoveries. In this study, the floatability of a Cu-Ni-PGM-bearing Merensky ore is tested on a bench-scale flotation system in various single salt solutions, viz., CaCl2, CaSO4, Ca(NO3)2, MgCl2, Mg(NO3)2, MgSO4, NaCl, NaNO3, and Na2SO4, in order to examine specific ion effects on gangue recovery. Coagulation and zeta potential tests are conducted in order to establish the nature of the impact that specific ions have on the behavior of gangue in flotation. The findings of this work have shown that single salt solutions containing ions resulted in a strong depression of gangue compared to those solutions containing Cl− and SO42− ions. It was also shown that the divalent Ca2+ and Mg2+ showed a stronger depression of gangue compared to the monovalent Na+. Ca2+, in comparison to Na+, resulted in an increase in the coagulation of the ore as well as an increase in the zeta potential of talc. Overall, the findings of this paper suggest that the presence of Ca2+ and Mg2+ in process water would most likely create conditions that promote gangue depression.
Highlights
It is acknowledged that water should be considered as a reagent in flotation and, as such, the quality of process water becomes an important factor to consider as it may alter the pulp chemistry and thereby affect the flotation (Corin et al, 2011; Corin and Wiese, 2014)
The findings of this paper suggest that the presence of Ca2+ and Mg2+ in process water would most likely create conditions that promote gangue depression
A study conducted by Muzenda (2010) showed that recycled process water containing Cu2+, Pb2+, and Fe2+ had adverse effects on the flotation of a PGM ore from the UG2 reef of the Bushveld Igneous Complex of South Africa in that there occurred an inadvertent activation of non-sulfide gangue which decreased the concentrate grades
Summary
It is acknowledged that water should be considered as a reagent in flotation and, as such, the quality of process water becomes an important factor to consider as it may alter the pulp chemistry and thereby affect the flotation (Corin et al, 2011; Corin and Wiese, 2014). A study conducted by Muzenda (2010) showed that recycled process water containing Cu2+, Pb2+, and Fe2+ had adverse effects on the flotation of a PGM ore from the UG2 reef of the Bushveld Igneous Complex of South Africa in that there occurred an inadvertent activation of non-sulfide gangue which decreased the concentrate grades. This could be explained by a more recent study by Liu et al (2014) which suggested that some electrolytes in process water could inhibit the adsorption of xanthates on sulfide minerals due to competition for adsorption onto the mineral surface. Biçak et al (2012) concluded that dissolved metal ions and sulfide ions mainly in the form of SO42− and S2O32− alter the surface chemistry of minerals in the pulp phase. Ikumapayi et al (2012) showed that galena was GRAPHICAL ABSTRACT | A schematic summary of the research findings presented in this paper
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