Effects of sulfation on the flotation capacity of oleic acid in the dolomite and fluorapatite system: A combined experimental and DFT study

Abstract

Dolomite cannot be efficiently separated from fluorapatite (FA) by oleic acid in an acidic slurry, due to the poor collecting ability of oleic acid. In this work, sulfation was used to improve the flotation performance of oleic acid. Flotation tests showed that the sulfating collector exhibited stronger flotation ability for dolomite. However, the H2SO4-treated FA could not be floated by the sulfating collector. The solubility of the sulfating collector at pH 4.5 was higher than that of HOL at the same pH. Thus, more sulfating molecules and anions were generated in the collector solution, which accounted for the high flotation efficiency of the sulfating reagent. The sulfating collector molecule and anion could adsorb on the H2SO4-treated dolomite surface. Moreover, the reaction of the sulfating collector anions with the dolomite surface generated alkyl Mg/Ca salts.Furthermore, DFT calculations were employed to evaluate the interactions of the sulfating reagent with the H2SO4-treated dolomite surface. The sulfation produced two isomers. The most stable isomer, i.e., 10-sulfooxy stearic acid (SOA), was used in the calculations. The SOA anion could vertically or paralelly adsorb onto the dolomite. The parallel structure was more stable, where the COO− and OSO3− groups of SOA anion bonded with two metal atoms on the dolomite surface. These findings suggest that the sulfation collector is suitable for the reverse flotation of collophane.