Exploring the separation mechanism of Gemini surfactant in scheelite froth flotation at low temperatures: Surface characterization, DFT calculations and kinetic simulations

Scheelite is usually recovered using flotation, but separating the gangue minerals at low temperatures has been challenging. In this paper, Hexane-1,6-didodecyldimethylammonium bromide (HDDA) is used as a novel cryogenic collector instead of dodecylamine (DDA). Flotation tests have shown that the flotation efficiency of DDA is much weaker than HDDA at both ambient and low temperatures, and low temperatures reduced most of DDA's collector performance, while HDDA still maintained high flotation and collector performance. The adsorption mechanism of HDDA on scheelite and calcite was investigated by zeta potential, Fourier transform infrared spectroscopy (FTIR)-spectrum analysis, quantum chemical calculations, and molecular dynamics simulations. Frontier molecular orbital analysis clearly showed that there is no chemical interaction between HDDA molecules and scheelite or calcite clusters, but only weak hydrogen bonds and other electrostatic interactions, as expected. The adsorption mechanism is confirmed to be the electrostatic interaction between the positively charged HDDA molecules and the negatively charged scheelite. We believe that this research can provide some guidance for the development of novel cryogenic collectors.