Advancement in abiotic humification for green pollution control: A comprehensive review of mechanisms and applications

Compared with conventional mineralization-oriented treatments, humification offers an alternative route for pollutant control by retaining carbon in stabilized macromolecular products, thereby potentially lowering chemical/energy inputs and associated CO2 emissions. Abiotic humification, driven by oxidants, catalysts, and/or physicochemical conditions, is particularly attractive because of its high reaction efficiency and the tunability of product structure and functionality. This review synthesizes recent advances in abiotic humification for green pollution control by integrating macroscopic formation theories (e.g., sugar-amine condensation and polyphenol pathways) with microscopic initiation mechanisms, including radical-mediated, nonradical-mediated, and nucleophilic-addition-mediated reactions. Special attention is given to the transformation of environmentally relevant pollutants, including phenols, amines, and additional compounds that can release phenolic or amino precursors through biological or chemical processes. To assess technological feasibility and environmental sustainability, current progress in catalyst regeneration, product separation/recovery, and potential reuse is summarized, and critical challenges in mechanistic elucidation, product safety evaluation, and practical implementation are highlighted. Overall, this review provides a mechanistically informed framework and methodological guidance for advancing abiotic humification toward low-carbon, efficient, and environmentally responsible wastewater treatment.