Effect of different types of surfactants adsorption characteristics on the wettability of coking coal dust

To investigate the effect of different types of surfactants adsorption characteristics on the wettability of coking coal dust, Guoyang coking coal and three different surfactants - dodecyl dimethyl benzyl ammonium chloride (DDBAC), sodium alcohol ether sulphate (AES), coconut diethanolamide (CDEA) - were used. Firstly, the amount of surfactant adsorbed on coal dust were determined using spectrophotometry. Secondly, the contact angles of surfactants on coal tablets was determined. Subsequently, the relationship between the amount of surfactant adsorbed on the coal dust surface and the contact angle was analysed. Finally, the influence mechanism of the amount of the surfactant adsorbed on the coking coal dust surface on wettability was discussed. The experimental results suggest that the adsorption isotherm of cationic surfactant DDBAC on the coal dust surface is bilayer LS-type, while the adsorption isotherm of anionic surfactant AES and non-ionic surfactant CDEA are L-type and S-type, respectively. Additionally, when the concentration of the solution was 0.05%, the amount of AES adsorbed on the coking coal dust surface was estimated to be 64.9 mgg−1, which was 4.19-fold higher than DDBAC (i.e. to 15.5 mgg−1) and 2.2-fold higher than CDEA (i.e. to 29.5 mgg−1), nearly reaching adsorption saturation. The R2 of the amount of DDBAC, AES, and CDEA adsorbed on the coal dust surface affecting the contact angle was 0.9944, 0.99238, and 0.9923, respectively. The adsorption amount of anionic surfactant AES on the coal dust surface at 0.05% is 64.9 mgg−1, and the adsorption isotherm of surfactant on the coal dust surface is L-type, which is more conducive to enhancing the wettability of coking coal dust. Thus, the amount and adsorption isotherm form of the surfactant adsorbed on the coal dust surface are critical factors affecting the coal dust wettability, which provides a theoretical basis for the reasonable selection of surfactants to improve the coal dust suppression efficiency.