Reactivity and Molecular Transformation of Dissolved Organic Matter during the Treatment of Coal Gasification Wastewater

The coal gasification process generates a large amount of toxic and highly concentrated industrial wastewater, posing significant challenges for its efficient treatment due to the presence of dissolved organic matter (DOM). This paper employs high-resolution tandem mass spectrometry to delineate the molecular composition and structure characterization of coal gasification wastewater (CGW) DOM, as well as the reaction activity in the treatment processes. The results showed that the CGW DOM is predominantly composed of oxygenated and nitrogenous compounds, with treatment inducing a shift toward saturation and highly oxidized states of polyphenols and polycyclic aromatic compounds. In comparison to oxygen- and sulfur-containing compounds, nitrogen-containing compounds posed a greater challenge for degradation, particularly those that exist in the form of nitrogen heterocycle rings. Furthermore, indene ring-based oxygen-containing compounds exhibited lower removal efficiencies than their benzene ring-based counterparts during the treatment. The molecular composition of the effluent from advanced oxidation processes is mainly characterized by the prevalence of simple naphthenic rings, indenes, nitrogen heterocycle rings, etc., in conjunction with multiple hydroxyl and carboxyl functional groups. These observations are crucial for the comprehensive understanding of pollutant transformation mechanisms, facilitating accurate and effective wastewater pollutant treatment implementation and contributing to energy conservation and consumption reduction.