Surfactant-Modified Asphaltene and Graphite Surfaces to Enhance CH4 and CO2 Adsorption

Through molecular simulation, the adsorption of CO2 and CH4 on asphaltene and graphite surfaces in the presence of three surfactant types: cationic (dodecyl trimethylammonium bromide, DTAB), anionic (sodium dodecyl sulfate, SDS), and amphoteric (betaine) were investigated. Simulations revealed that an increasing surfactant concentration enhanced gas adsorption, indicated by additional peaks in gas density profiles. In particular, asphaltene surfaces showed significant improvements in gas adsorption capacity with surfactants, increasing the CO2 adsorption from 37 to 80% when surfactants were present. An analysis of surfactant structures on surfaces highlighted distinct arrangements and interactions with gases, influencing adsorption mechanisms depending on the gas characteristics and surface properties. The relevant interactions between surfactant polar and nonpolar groups with gases were described, finding that the electrostatic forces of CO2 lead to a preference for adsorption on the polar group of the surfactant. At the same time, CH4 prefers the nonpolar group. The mechanism of new molecular aggregate formation on solid surfaces was established during gas adsorption with the formation of surfactant bilayers being described. These findings underscore the potential of surfactants to augment the gas adsorption capacity, offering insights into optimizing adsorption systems for practical applications. Further research in this area promises innovative solutions for addressing greenhouse gas emissions and advancing environmental sustainability.