Effect of Mg2+ and Ca2+ as divalent seawater cations on the floatability of molybdenite and chalcopyrite

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

“…In the absence of SHMP, the contact angles of chalcopyrite surface treated in both MgCl 2 and CaCl 2 solution were significantly lower than that in ultrapure water, showing 35 • and 56 • , respectively, similar to those reported in Li et al [16] and Hirajima et al [17]. This suggests that the presence of CaCl 2 and MgCl 2 apparently reduced the chalcopyrite contact angle, possibly due to the adsorption of hydrophilic species formed on the chalcopyrite surface, consistent with the flotation results ( Figure 3).…”

“…In addition, when pH was controlled at 12, only 1% of chalcopyrite was recovered in the MgCl 2 solution. 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+ .…”

“…For instance, Haga et al [21] reported that the Cu grade was improved when conditioning Cu minerals (in which the main valuable mineral is chalcopyrite) into sea water. 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.…”

“…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].…”

“…For instance, Jeldres et al [24] reported that the addition of CaO-Na 2 CO 3 mixtures can remove cations before flotation. Hirajima et al [17] and Suyantara et al [28] found that emulsified kerosene was capable of reducing the adsorption of Mg(OH) 2 precipitation on chalcopyrite surface through forming kerosene and precipitation aggregates.…”