The Impact of Organic Constituents in Coal Chemical Wastewater on Additive Adsorption at the Coal Surface: Experimental Investigation and Molecular Dynamics Simulation

Direct preparation of coal–water slurry using coal chemical wastewater represents an economical and feasible approach for wastewater resource utilization. Unlike clean water, however, the complex organic components in wastewater may exert adverse effects on slurry properties. To explore the mechanism underlying the influence of organic components in coal chemical wastewater on the adsorption characteristics of additives onto coal surfaces, address the issue of slurry property variations arising from slurry preparation with different wastewaters, and verify the technical and economic feasibility of wastewater-based coal–water slurry preparation, this study integrated isothermal adsorption experiments with molecular dynamics (MD) simulations. With deionized water as the control group, the study systematically analyzed the effects of four typical organic pollutants, namely, quinoline, phenol, acetic acid, and 5-hydroxymethylfurfural (5-HMF), on the “coal-additive” adsorption system, while comparing the economic performance of preparation strategies in the context of coal–water slurry production lines. The results demonstrated that the Langmuir model (with a fitting deviation of < 6%) and Δ G 0 ads (all negative values) confirmed the spontaneous nature of the adsorption process. The order of additive adsorption capacity and system interaction energy was determined as quinoline > deionized water > acetic acid > phenol > 5-HMF, where quinoline promoted adsorption whereas the other three components exhibited inhibitory effects. MD simulations revealed that the interaction between coal and additives in deionized water was primarily dominated by van der Waals forces. Organic components reduced electrostatic repulsion but caused a more significant weakening of van der Waals forces, and monolayer adsorption was identified as the optimal microscopic configuration for additives to exert their functional effects—this conclusion was consistent with analyses of adsorption configuration, molecular density distribution, and mobility. Economic analysis indicated that when comparing the two strategies of “adjusting additive dosage” and “ozone oxidation pretreatment,” and taking into account the environmental benefits of wastewater treatment, coal–water slurry preparation using coal chemical wastewater could achieve significant positive benefits under appropriate strategies compared with the conventional method, thereby realizing a win-win scenario for both wastewater treatment and economic gains. This study clarifies the regulatory mechanism of organic components in wastewater on additive adsorption from both macro- and micro-dimensional perspectives, confirms the technical and economic feasibility of coal chemical wastewater-based coal–water slurry preparation, and provides crucial support for advancing the coordinated development of industrial wastewater resource utilization and clean production.