Effect of surfactant ionic character on adsorption and wettability control of bituminous coal surfaces

To examine the impact of various ionic surfactants on the surface wetting properties of low-rank coals, three typical ionic surfactants , dodecyl hydroxy sulfobetaine (DHSB), dodecyl trimethyl ammonium bromide (DTAB) and sodium dodecylbenzene sulfonate (SDBS), were selected for the bituminous wettability study using Hongliulin coal in Yulin as the research object. Employing a model of coal chemical structure as proposed by Hatcher, along with molecular simulation techniques, contact angle, adsorption, and X-ray photoelectron spectroscopy are carried out to determine the wetting effects of various surfactants on bituminous. Based on a comprehensive analysis integrating empirical observations with simulated outcomes, The adsorption configurations of different ionic surfactants on coal are different. The adsorption of the cationic surfactant DTAB on coal is a double-layer adsorption, The adsorption behavior of the anionic surfactant SDBS and amphoteric surfactant DHSB onto coal exhibits monolayer adsorption properties. The presence of a greater number hydrophilic groups in the surfactant results in a greater modulation of the bituminous coal surface's wettability . This study offers novel concepts for the screening of suitable surfactants that exhibit enhanced wettability on low-rank coal surfaces. Furthermore, it provides theoretical substantiation for the role of surfactants in the regulation of wettability in coal surfaces.