The depressing role of sodium alginate in the flotation of Ca2+-activated quartz using fatty acid collector

Abstract The ions activation of quartz is a thorny problem that deteriorates the flotation of metal ore. Polymer inhibitors have exhibited excellent depression performance in the selective flotation of metal-ion activated minerals. In this study, the inhibitory role of sodium alginate (NaAl) in the flotation of Ca2+-activated quartz was thoroughly explored by zeta potential, dynamic light scattering (DLS), Fourier transform infrared (FTIR) analysis, X-ray photoelectron spectroscopy (XPS) analysis and adsorption test. The flotation results suggested that NaAl could inhibit the flotation of Ca2+-activated quartz in sodium oleate (NaOl) system to different degrees, depending on the addition sequence of NaOl and NaAl. More significant depression of Ca2+-activated quartz could be achieved when NaAl was added prior to NaOl. It was found that prominent mutual interaction existed among Ca2+, NaOl and NaAl in the bulk solution, probably forming calcium alginate–calcium oleate crosslink product, which was not affected by the addition sequence of these two reagents. However, the interfacial behaviors of these two reagents on Ca2+-activated quartz surfaces differed under different reagent conditions. The addition of NaAl after NaOl could not only partially desorb the pre-adsorbed NaOl from mineral surfaces, but also decrease the mineral surface hydrophobicity by polymer coating, which therefore deteriorated the flotation of Ca2+-activated quartz. In contrast, when NaAl was added prior to NaOl, the pre-adsorption of NaAl made the further adsorption of NaOl rather difficult, which was likely attributed to the reticulated structure of NaAl and the associated steric hindrance effect. As a result, the flotation of Ca2+-activated quartz was tightly depressed.