Non-toxic and biodegradable depressant Gum Arabic for flotation separation of calcite and magnesite: Experiments and MD simulations

In this study, Gum arabic (GA), a green, environmentally friendly, and biodegradable organic macromolecule reagent, is employed as a novel depressant for the reverse flotation separation of magnesite and calcite. The micro-flotation tests demonstrate that GA exhibits a selective depression impact on magnesite. From artificial mixed minerals, a concentrate with a MgO grade of 31.39 % and a MgO recovery of 80.31 % can be obtained using 70 mg/L of GA. The mechanism studies reveal that GA adsorbs on the magnesite surface mainly via chemical chelation between Mg sites on the magnesite surface and hydroxyl and carboxyl groups on GA, while it mainly adsorbs through hydrogen bonding on the calcite surface. After adding NaOL, it can further adsorb on the calcite surface, while its adsorption on magnesite is more difficult. Moreover, the spatial distribution of water molecules and the radial distribution function (RDF) provides microscopic proof that GA can expand the differences in hydrophobicity between magnesite and calcite surfaces. Eventually, the difference in the floatability of the two minerals increases significantly. Therefore, GA can be adopted as a novel and highly selective depressant for the reverse flotation separation of magnesite.