Study on the effect and mechanism of surfactant synergistic with potassium formate on inhibiting coal spontaneous combustion

In order to increase the specific surface area and reactivity sites of potassium formate and thereby enhance its ability to inhibit coal spontaneous combustion, three surfactants, namely SLS, SDBS, and CTAB, were selected to modify potassium formate in this paper. The pore structure and specific surface area of the modified samples were characterized by BET specific surface area analysis to evaluate the modification effect of surfactants. A variety of analytical techniques, such as programmed temperature oxidation, TG-DTG-DSC, FTIR, contact Angle test, and SEM, were adopted to systematically study the variation laws of modified potassium formate in terms of flame retardancy. The research results show that surfactants enhance the interaction between potassium formate and coal. The CO2 release of the coal samples inhibited by the three surfactants compounded with potassium formate was all higher than that of potassium formate. Among them, the CTAB-modified potassium formate performed the best. The critical temperature of K-CTAB-RC is 30 °C later than that of K-RC. The CO2 release at the critical temperature is 1.45 times that of K-RC. In addition, when the dosage of CTAB in modified potassium formate is 1 mmol, the flame retardant performance is the best. The CO2 release of K-CTAB-RC is 1.07 and 1.33 times that of K-CTAB-RC-0.5 and K- CTAB-RC-1.5, respectively. FTIR indicates that the flame retardant mechanism involves the elimination of hydroxyl radicals. The introduction of CTAB promotes the increase of the specific surface area of potassium formate, generating more reactive sites, which react with the active groups in coal to produce CO2. The generated CO2 gas rapidly diffuses into the pores and fissures of the coal, reducing the oxygen concentration. These findings provide new ideas for the development of high-performance coal-based flame retardants.