Effect and mechanism of coal desulfurization using a surfactant-assisted NaClO-NaOH system

This study employed both experimental and theoretical approaches to explore the desulfurization effects and mechanisms of surfactants in the NaClO-NaOH system. The effects of five different surfactants on the coal desulfurization rate, wettability, electrostatic potential, and chemical bonding were analyzed. The results revealed that all five surfactants enhanced the coal desulfurization rate and significantly improved its wettability. However, wettability alone was not the sole determinant of desulfurization effectiveness. For individual surfactants, improved wettability correlated with a greater desulfurization effect. Electrostatic potential analysis showed that oxygen-containing functional groups in the surfactants had high electron density, which attracted weakly electrophilic chlorine and carbon atoms. This interaction increased the reactivity of ClO⁻ with compounds such as benzenethiol or dibenzothiophene, making these regions preferential sites for reaction. A higher number of oxygen-containing functional groups in a surfactant was associated with better desulfurization performance. Among the surfactants, AEC-9Na was the most effective due to its high content of oxygen functional groups. Furthermore, surfactants were found to influence the bond lengths of Cl-O, S-H, and S-C to varying degrees. These findings provide insights into the microscopic mechanisms of surfactant-assisted coal oxidation desulfurization and offer guidance for improving reaction efficiency.