Application of a new amidoxime surfactant in flotation separation of scheelite and calcite: Adsorption mechanism and DFT calculation

Abstract

With its high electrical conductivity, thermal creep resistance and compression modulus, tungsten take an irreplaceable position in modern industry, defense, and high technology. Scheelite, as the main raw material of tungsten resources, usually adopts Petrov’ process: steam heating 80 °C-90 °C, stirring in a tank containing 2%-4% sodium silicate solution for more than half an hour to make sodium oleate desorbed on the calcite surface, and repeated cleaning. Herein, a new amidoxime surfactant 3-dodecylamine propyl amidoxime (DPA), had been synthesized and used as a collector for the first time in the flotation separation of scheelite and calcite at room temperature without any sodium silicate, and compared with the traditional collector sodium oleate (NaOL). The flotation behavior of DPA was studied by micro-flotation and mixed binary mineral flotation tests, which showed that DPA has good collection ability and excellent selectivity for scheelite. Meanwhile, the interaction mechanism of DPA on the mineral surface was discussed by FTIR analysis, zeta potential test, contact angle measurement and density functional theory (DFT). FTIR analysis and zeta potential test confirmed that DPA collector had adsorption on scheelite surface but had little effect on calcite. DFT calculation further confirmed that the positively charged –C(NOH)N+H3 group in DPA had electrostatic adsorption on the negatively charged scheelite surface. The contact angle measurement results revealed that DPA can enhance the surface hydrophobicity of the scheelite particles. Therefore, this highly selective DPA surfactant can achieve effective separation of scheelite and calcite, contributing to environmental protection and sustainable green development of resources.