The chain length and isomeric effects of monohydric alcohols on the flotation of magnesite and dolomite by sodium oleate

Abstract

To improve the flotation efficiency while decreasing costs, mixed reagents composed of sodium oleate (NaOL) and monohydric alcohols were used as collectors for the flotation of magnesite and dolomite respectively. Single mineral flotation followed by measurements of surface tension and FTIR spectra were conducted to investigate the carbon chain length and isomeric effects of alcohols on the flotation and adsorption behavior of NaOL. Compared to NaOL alone, the mixed reagents of NaOL and monohydric alcohols, including butanol, isobutanol, octanol, and isooctanol, improved the recoveries of magnesite and dolomite. Additionally the recoveries increased as the carbon chains of the alcohols lengthened. The recoveries were enhanced in the case of mixed reagents consisting of NaOL and isomeric alcohols compared with those of the reagents composed of NaOL and the corresponding normal alcohols. The coadsorption of NaOL and monohydric alcohols on mineral surfaces could be verified by FTIR spectra. Alcohols could reduce the surface tension of NaOL solutions. Furthermore, the adsorption configurations of the NaOL alone and mixed reagents on the mineral surfaces were further investigated by DFT calculations. The bond population between the O atoms of NaOL and metal atoms of minerals increased with the lengthening carbon chains of the alcohols. When isomeric alcohols were added, the interaction intensities between NaOL and minerals were higher than those with corresponding normal alcohols. Hydrogen bonds formed between NaOL and monohydric alcohols, contributing to the dense hydrophobic layer on mineral surfaces. Additional hydrogen bonding between monohydric alcohols and mineral surfaces could also be observed when alcohols with long carbon chains were added. Finally, the flotation of magnesite and dolomite by NaOL were both enhanced by monohydric alcohols, especially those with long carbon chains and isomeric structures.