Effect of [C12mim][Cl]-NaCl compound solutions on pore structure and wetting characteristics of bituminous coal based on Pearson correlation coefficient

Abstract

Water injection technology is a compelling technical measure to improve the water content of coal seams and reduce dust generation during mining. At present, the methods to enhance the wetting effect in the research progress are limited to increasing the dosage of a single wetting agent and using a variety of anionic and cationic wetting agents in large doses. More research is needed on the synergistic enhancement of the wetting effect by inorganic salts and ionic liquids. Aiming at this problem, this paper studies the influence of the combination of NaCl and surface active ionic liquid [C12mim][Cl] on the wetting effect and pore structure of bituminous coal. The influence of composite solution and ratio change on coal pore structure and wetting characteristics is studied based on Pearson correlation coefficient, combined with the experimental results of nitrogen adsorption at low temperature, scanning electron microscope and wetting characterization. The results show that bituminous coal exhibits different sizes of hysteresis rings after [C12mim][Cl] and NaCl treatments. With the change in composite ratio, the pore connectivity of coal samples is improved, and the surface roughness of modified bituminous coal is affected by the shift in composite ratio. With the enhancement of the wetting effect, the pore depth increases. On the other hand, adding 0.6 mol/L NaCl makes the composite solution reach a critical micelle concentration, which could synergistically enhance the surface activity and wetting effect of [C12mim][Cl] solution. There is a negative correlation between the volume of bituminous coal macropores and the contact angle, which indicates that the optimal solution ratio can be determined by analyzing the bituminous coal macropore volume change.