Comprehensive investigation of the adsorption of 2-carboxyethylphenylphosphinic acid on cassiterite

Abstract

ABSTRACT The structure–property relationship and adsorption mechanism of a novel collector for cassiterite, 2-carboxyethylphenylphosphinic acid (CEPPA), were comprehensively investigated and compared with those of styrene phosphonic acid (SPA) by density functional theory (DFT) calculations and flotation tests. The net Mulliken charge and frontier molecular orbital (FMO) theory study results indicated that CEPPA exhibited stronger electron-donating ability and higher chemical reactivity than SPA. The flotation test results demonstrated that CEPPA had stronger collecting ability for cassiterite in a much wider effective pH range than SPA. The adsorption simulation results confirmed that the CEPPA molecule was adsorbed on cassiterite (110) surface by two hydrogen bonds. CEPPA monoanion and dianion were adsorbed on cassiterite (110) surface by a series of O-Sn bonds, and the interactions between the O atoms in CEPPA phosphinic group with the Sn atoms on cassiterite (110) surface were stronger than those between the O atoms in CEPPA carboxyl group with the Sn atoms on cassiterite (110) surface. The formation of the O-Sn bonds was mainly contributed from the 2p orbital of O atoms and 5s and 5p orbitals of Sn atoms. The various adsorption configurations of CEPPA on cassiterite accounted for the better collecting ability of CEPPA for cassiterite than that of SPA. The quantitative analysis results were in good agreement with the qualitative experimental test results in a previous paper.