Multi-scale research on coal chemical wastewater treatment: Pollutant molecules, technologies, and process integration

The coal chemical industry serves as an indispensable element in the fabric of the global energy system. However, the wastewater generated from its production processes exhibits high chemical oxygen demand, high toxicity, and poor biodegradability, posing severe challenges to the ecological sustainability of the coal chemical industry. This review systematically summarizes recent advances in treatment technologies for coal chemical wastewater (CCW) through a “pollutant molecules–technology–process integration” framework analyzed from micro-to macro-scale perspectives. It begins by delineating the complex chemical composition of CCW and identifying key toxic substances, thereby clarifying the current challenges in treatment processes and establishing a micro-scale foundation for technological development. The review then highlights solvent extraction, grounded in intermolecular interactions, as a core method for recovering phenolic compounds. This is followed by an in-depth analysis of the performance and mechanisms of biological treatment and advanced oxidation processes (AOPs) for the deep removal of refractory organic pollutants. Finally, from a macro-scale perspective, the integration of pretreatment, biological treatment, and AOPs into systematic frameworks is discussed. A thorough understanding of the molecular characteristics of pollutants is crucial for developing efficient treatment technologies. Moreover, system-level integration via process intensification and technological synergy is considered essential for achieving efficient purification and resource recovery from CCW.