The Influence of Common Monovalent and Divalent Chlorides on Chalcopyrite Flotation

Abstract

Much attention has been paid to the flotation of chalcopyrite using saline seawater. However, the influence of salt ions on mineral flotation is complex, and different salts may play various roles-either beneficial or detrimental. This study investigated the effects of common chlorides (Cl − ) of Na + , K + , Mg 2+ , and Ca 2+ in seawater on chalcopyrite floatability. The presence of Na + , K + , and Ca 2+ resulted in greater chalcopyrite recovery, with this effect being more pronounced for the monovalent cations. In contrast, the addition of Mg 2+ resulted in decreased chalcopyrite flotation efficiency. Contact angle measurements showed that the presence of monovalent cations increased the hydrophobicity of the chalcopyrite surface, while the presence of divalent cations reduced its hydrophobicity, depending on the concentration. Zeta potential, pulp species, and X-ray photoelectron spectroscopy (XPS) cross-confirmed the precipitation of Mg(OH) 2 on the chalcopyrite surface when Mg concentration was 10 −2 M and pulp pH was 10.

The Influencing Mechanisms of Sodium Hexametaphosphate on Chalcopyrite Flotation in the Presence of MgCl2 and CaCl2

“…A similar deteriorative chalcopyrite recovery in ultrapure water controlled at strong alkaline condition was found by Liu and Zhang [39] while detrimental effects of both salts on chalcopyrite recovery were reported in [17,28]. Nagaraj and Farinato [23] reported that Ca 2+ had a negligible effect while Li et al [16] reported a slightly beneficial effect on chalcopyrite flotation in the solution containing Ca 2+ . The differing flotation behaviors of chalcopyrite in salt solution may be attributed to various collectors (e.g., sodium diisobutyl dithiophosphate vs. sodium butyl xanthate) and pulp densities (35 wt % vs. 8 wt %) [40].…”

“…In a Cu-Au ore flotation with chalcopyrite as the major valuable Cu mineral in the presence of bentonite, Wang et al [22] found that divalent cations of Mg 2+ and Ca 2+ had a more significant role than monovalent cations of Na + and K + in reducing bentonite viscosity due to stronger compression of electrical double layers of bentonite particles, thereby increasing flotation efficiency, similar to that found in Hirajima et al [17]. Recently, Li et al [16] reported that at pH 10, the presence of Na + , K + , Ca 2+ increased chalcopyrite recovery due to lower energy barrier for bubble-particle attachments through compressing electrostatic double-layer while the addition of Mg 2+ decreased chalcopyrite flotation efficiency due to the adsorption of formed Mg(OH) 2 precipitation onto chalcopyrite surface to reduce its hydrophobicity. Although these studies focused on the effects of salts on chalcopyrite flotability through investigating the change of particle surface properties, the flotation results varied and even conflicted, keeping underlying mechanisms unclear.…”

“…In the flotation process, the presence of salt ions can increase the complexity of flotation pulp environment by changing pulp water structure, mineral particle properties (e.g., hydration and electrical double layer) and bubble properties (e.g., bubble coalescence and froth stability), which in turn influencing the mineral-bubble attachment and flotation efficiency [2,[11][12][13]. For instance, some monovalent salts (i.e., NaCl and KCl) were found to enhance mineral flotability by compressing electrical double layers, reducing the energy bar for particle-bubble attachment and even changing bubble stability [14][15][16]. In contrast, the presence of some divalent cations such as Ca 2+ and Mg 2+ might form metal hydroxyl-complexes and colloidal precipitation onto hydrophobic mineral surfaces under alkaline conditions, reducing mineral surface hydrophobicity and the adsorption of collectors [17][18][19].…”

“…All XPS spectra were fitted through XPS Peak4.1 software using Shirley methods for backgrounds corrections [38]. More details regarding the analysis can be referred to that shown in Li et al [16]. Figure 2 shows chalcopyrite recovery as a function of pH from 4 to 12.…”

“…Subsequently, a droplet of ultrapure water (0.25 µL) was placed onto the prepared chalcopyrite slab surface through micro-syringe, thereafter the profile of contact angle was imaged and measured by a sessile drop device (JC2000C1, Shanghai Zhongchen Digital Technology Company, Shanghai, China), with the operating procedures being the same to our previous studies [16]. At least three different areas were selected on each chalcopyrite slab surface and the average value was reported herein.…”