Treatment of concentrated brine water in modern coal chemical industry by reverse osmosis: advantages and technical challenges

With the rapid development of the modern coal chemical industry, high water consumption and wastewater treatment have become major constraints on its green and sustainable development. Reverse osmosis concentrate generated during advanced treatment and reuse of coal chemical wastewater is characterized by high salinity and high concentrations of organic matter. At present, zero liquid discharge (ZLD) processes based mainly on high-pressure reverse osmosis concentration and evaporation crystallization have become the mainstream approach for the volume reduction and resource recovery of such wastewater. However, the presence of a high concentration of organic contaminations can lead to membrane pollution, evaporator corrosion, high saline rate, and low whiteness of crystallized salt. These challenges result in the “zero discharge” technology facing issues such as high cost and poor stability. To address these industry challenges, this review introduces the sources and composition of the concentrated brine from coal chemical reverse osmosis were introduced, the advantages and technical challenges of centralized treatment were analyzed, and the key to achieving “zero discharge” technology by efficient removal of organic contaminants in high-salt environments was proposed. In terms of removing organic contamination, the research progress on membrane separation, adsorption, and advanced oxidation methods used for separating or degrading organic matter in coal chemical reverse osmosis concentrated brine was reviewed. Then, the advantages and urgent technical problems associated with loose nanofiltration in separating organic contaminations from inorganic salts as well as activated carbon-based catalyst coupling adsorption and ozone catalytic oxidation in degrading organic contaminations were discussed. Meanwhile, a potential technical route integrating membrane separation, adsorption, and advanced oxidation is proposed. This review aims to provide a theoretical basis and technical reference for the efficient treatment of reverse osmosis concentrate from coal chemical wastewater and the resource recovery of crystallized salts, while supporting the development of coal chemical wastewater treatment systems toward minimal- or even zero-waste discharge.