Biomass-derived carbon quantum dots in wastewater treatment: Synthesis, sensing, and degradation

Effective wastewater treatment is critical for environmental protection and resource recovery. Carbon quantum dots (CQDs), notably biomass-derived carbon quantum dots (BCQDs), have emerged as promising nanomaterials owing to their favorable physicochemical properties and environmental sustainability. This review examines BCQD formation from carbohydrate, protein, and lignin precursors. The molecular oxidation, radical-mediated oxidation, and physical shearing pathways are discussed with the key cross-linking reactions that drive nanodot growth. The existing separation techniques based on different parameters are systematically classified with emphasized advantages or disadvantages. The role of BCQDs in the whole process of wastewater treatment is summarized, and the detection and removal mechanisms and patterns were clarified. Especially, radioactive ion detection, photocatalytic degradation of complex pollutants such as heavy metals and plastic, membrane treatment, and antibacterial in wastewater are covered. New ideas and insights for the future applications of BCQDs in wastewater management are expanded.