Understanding the adsorption behaviors of naphthalene sulfonate formaldehyde in coal water slurry

Naphthalene sulfonate formaldehyde (NSF) has been widely used as a dispersant for coal water slurry (CWS) preparation. However, the adsorption behaviors of NSF on different components were scarcely discussed due to the complex nature of coal. In this study, the adsorption kinetics and isotherms of NSF on the particle surfaces of carbonaceous matter, kaolinite, quartz, pyrite were investigated, along with X-ray photoelectron spectroscopy (XPS) and contact angle meter were conducted to clarify the adsorption mechanism of NSF on each particle surface. The adsorption measurements showed that the saturated adsorption capacities of NSF on the surfaces of kaolinite, pyrite and carbonaceous matter were much higher than that of quartz. Further single-layer adsorption occurred for the NSF adsorbed by all particles except quartz, where multi-layer adsorption was observed. The XPS and contact angle results showed that the interaction between the hydrophobic tail of NSF and carbonaceous matter is mainly attributed to hydrophobic force, concurrently the combination of the hydrophilic groups in NSF with Al elements of kaolinite and Fe elements of pyrite. The findings are significant to elucidate the adsorption mechanism of dispersants on the coal-water interface and proposed a reference for dispersants utilization based on different coal components.