Inserting EO groups to improve the performance of fatty acid collectors: Flotation and adsorption study performed with calcite, dolomite, and quartz

Abstract

• EO groups improves dispersibility and ion tolerance of AECNa. • Optimal performance is obtained when 3 EO groups inserted. • Ca ions cannot activate quartz with AECNa. • Electrostatic interaction between EO groups and ions improves ion tolerance. Flotation using a fatty acid collector is always restricted by ions, temperature, and other factors in production. In this study, sodium fatty alcohol polyoxyethylene ether carboxylate with 3, 5, and 7 EO repeating units (AEC 3 Na, AEC 5 Na, and AEC 7 Na, respectively) were synthesized to improve the performance of fatty acids. The flotation performance and adsorption mechanism for calcium species (including calcite, dolomite, and quartz activated by calcium ions) were investigated, and the methods used include flotation tests, surface tension tests, contact angle measurements, X-ray photoelectron spectroscopy (XPS) measurements, and density functional theory (DFT) calculations. The flotation results show that the optimum amount of the AECNa series was lower than that of sodium oleate (NaOL), and the collecting ability decreased gradually with the increase in the number of EO repeating units. Additionally, the EO group has an anti-activation effect on the fatty acid collector, and AECNa will not collect quartz activated by Ca 2+ ions. AEC 3 Na with 3 EO repeating groups has advantages such as better capture ability and dispersibility, and is a promising collector in the replacement of fatty acids. The mechanism analysis shows that AECNa collectors still adsorb by forming chemical bond between carboxyl groups and calcium sites on calcite and dolomite surfaces. The EO groups significantly improved the surface activity and dispersibility of fatty acids. Meanwhile, multiple ether bonds in the EO groups can attract ions electrostatically, weakening the effect of ions on the polar group of collectors and thereby leading to the anti-activation effect.