Experimental and density-functional theory simulation studies on the surface of Mn/Pb-activated scheelite

The results of this study indicate that lead and manganese ions can serve as effective activators for the flotation of scheelite using benzohydroxamic acid (BHA) collectors, and even the addition of a small amount of lead ions can significantly improve the recovery rate of scheelite. The roughness of scheelite treated with binary activators and BHA is 8.19 nm and 2.1 nm higher than that the roughness values of scheelite treated with Mn(NO3)2 and Pb(NO3)2 alone, respectively. The adsorbed products are uniformly distributed on the scheelite surface, and the adsorption forms a “strip-like and dot-like” morphology. Lead ions are mainly adsorbed on mineral surfaces through Pb-O(H)-Ca, and manganese ions are mainly adsorbed in the form of Mn (II) species (i.e., Mn-O-Ca). In the presence of BHA, compared with scheelite treated with manganese and lead ions alone, scheelite treated with binary activators exhibits a more negative zeta potential on its surface, a higher contact angle of 89.30°, and a more pronounced infrared adsorption characteristic peak (C-N-O). DFT calculations confirm that lead ions and manganese ions are adsorbed on the surface of scheelite (112) in the forms of Pb-O-W, Mn-O-W, and Mn-O(H)-Ca. Moreover, the Pb-O(H)-Mn structure covers the surface atoms of scheelite, forming a layer of active substance on the surface of scheelite, and the structure is more stable than in the case of single ion activation, according to the BHA adsorption calculations.