Adsorption of sodium oleate on coal surface with different oxidation degrees and its effect on flotation

Abstract

As traditional hydrocarbon oils cannot interact effectively with oxidized coal surface, this paper studied the effect of sodium oleate (NaOL) on the flotation of coal with different oxidation degrees. X-ray photoelectron spectroscopy, ultraviolet spectrophotometer, contact angle and zeta potential results confirmed the effective adsorption of NaOL on oxidized coal surface. For 8 h oxidized coal, its contact angle increased from 65.8° to 75.7° and zeta potential decreased from −80.8 mV to -82.1 mV after the adsorption of NaOL. The NaOL mainly reacted with the oxygen-containing functional groups on oxidized coal surface by hydrogen bonding, thus the surface hydrophobicity and floatability of oxidized coal were significantly improved. The flotation yield of clean coal using NaOL as collector was higher than that using kerosene. With the combined usage of sodium hexametaphosphate (SHMP) and NaOL in oxidized coal flotation, the ash content of clean coal was significantly reduced to an acceptable quality.