Decrease in hydrophilicity and inhibition moisture re-adsorption of lignite using binary surfactant mixtures with different hydrophilic head-groups

Abstract

Effect of binary surfactant mixtures on hydrophobic modification and moisture re-adsorption inhibition of lignite are investigated, along with that of dodecyltrimethylammonium bromide (DTAB), sodium dodecyl sulfonate (SDS) and dodecyl nonaethoxyl ether (C12(EO)9). Decrease in hydrophilicity of lignite is measured by determination of wetting heat and moisture re-adsorption rate of lignite before and after adsorbing surfactant. The differences in hydrophilicity change of lignite by using single and binary surfactant mixtures are discussed to disclose the synergistic or antagonism effect on hydrophobic modification of lignite. The experimental results show that, with adsorption of both single and binary mixtures of surfactants, lignite surface become hydrophobic. Compared to single component, DTAB-C12(EO)9 and DTAB-SDS display a higher efficiency on the hydrophilicity reduction and moisture re-absorption inhibition of lignite, while C12(EO)9-SDS does not. The calculated results indicate that there exists intermolecular synergism in the mixtures of DTAB-C12(EO)9 and DTAB-SDS, with forming synergetic aggregates “co-surfactant” DTAB-C12(EO)9 and DTAB-SDS, and C12(EO)9-SDS acts no synergism. These experimental results correspond to the calculation results of the properties of surfactant solution. Therefore, the solution properties of binary surfactant mixtures may provide a theoretical guiding in binary surfactant selection for reducing the hydrophilicity of lignite.