Benzohydroxamic acid adsorption on the surface of scheelite: New insights from experiments and AIMD simulations

Abstract

To explain the low recovery rate of scheelite during flotation using benzohydroxamic acid (BHA), we performed experiments and AIMD simulations. The results showed that scheelite floated only 50 % of BHA. The adsorption capacity of BHA on the scheelite surface was 1.63 × 10−5 mol/g, which caused the surface potential of scheelite to become negative, with a change of −10.5 mV at pH 9.05. After BHA adsorbed onto the scheelite surface, the surface roughness increased by 0.35 nm, and the water contact angle of the scheelite surface increased by 13.14°. Moreover, 1.76 % N was detected, representing BHA molecules, BHA-Ca complexes, and H-bonded BHA species·H2O adsorbed onto surface calcium ions and between adjacent calcium ions, while free, unadsorbed H2O molecules formed clusters. The added BHA repelled water adsorbed onto the Ca sites of the scheelite (112) surface via O atoms in C-N-O structure with an adsorption energy of −56.26 kJ/mol. AIMD simulations at 300 K revealed that temperature changed the adsorption of flotation agent molecules on scheelite surfaces, including the densification of hydration layers and the separation of BHA-Ca complexes from the scheelite surface.