Study on Surface Activity of Inorganic Salts on [C₁₂MIm]Cl and Wetting Characteristics of Compound Modified Bituminous Coal

Abstract

The technical problem of the difficult wetting of coal bed water injection urgently needs to be solved, and the wetting of surfactants on the coal body is mainly affected by the concentration. In recent years, research related to surface-active ionic liquids (SAILs) with long-chain alkyl groups has attracted much attention. Salt can enhance the wetting effect of surfactants, but there are few studies on the effect of inorganic salts on the surface activity of [C 12 MIm]Cl and the effect of compound wetting bituminous coal. In this paper, NaCl was selected to be complexed with [C 12 MIm]Cl, and the trends of key functional groups and surface activity changes during coal wetting were quantitatively characterized from a microscopic point of view by functional group and wetting characterization analysis. The results showed that under the treatment of 0.6 mol/L of NaCl + 10 mmol/L of the [C 12 MIm]Cl compound, the surface tension was reduced by 7 N m/m and the minimum contact angle by 15.5°. In the modified coal, the peak area of the �CH 2 group is reduced by 29%, the peak area of the −CH 3 group is increased by 24%, the peak area of the OH•••N group is reduced by 14%, and the wetting effect is enhanced. However, the high concentration of NaCl in the composite solution will weaken the wetting effect on bituminous coal. The research results provide theoretical support for coal seam composite wetting by water injection.