Design and evaluation of a novel dispersant with “surface-to-surface” adsorption function for preparing low-rank coal water slurry

Abstract

It is important to improve the performance of low-rank coal water slurry (CWS) for the development of coal gasification. In this study, to prepare high-quality Shenhua coal water slurry, a novel GON-APEG dispersant with “surface-to-surface” adsorption function was designed and synthesized by grafting the allyl polyoxyethylene ether (APEG) onto the edge of graphite oxide nanosheet (GON) through esterification and emulsion polymerization. The influences of GON-APEG on the properties of CWS, the adsorption isotherm of GON-APEG, and the surface properties of coal were studied, and compared with GON, sodium lignosulphonate (SL), and polycarboxylate (PC) dispersants. The GON-APEG was superior to other dispersants in viscosity-reducing and stabilizing ability. Under the optimum dosage of 0.3 wt%, the maximum coal content of CWS with GON-APEG was 64.5 wt%. All the CWSs with different dispersants belonged to typical yield pseudoplastic fluid. Meanwhile, the adsorption isotherms of four dispersants had a good correlation with the Langmuir model, and the saturated adsorption capacity of GON-APEG was greater than SL and PC dispersants. The GON-APEG decreased the contact angle of water on the coal surface and increased the absolute value of Zeta potential of coal to the greatest extent. The excellent performance of GON-APEG in CWS was due to its strong interaction with coal derived from “surface-to-surface” adsorption mode, which was beneficial to regulate the surface properties of coal. In sum, this study provides a new idea for improving the properties of Shenhua coal water slurry and developing the efficient dispersants in other fields.