Tea-residue-derived carbon nanomaterials for adsorption-degradation coupling: mechanistic insights into pollutant removal and sustainability challenges.

Low-cost adsorption materials derived from waste tea powder (WTPs) have been extensively studied for contaminant removal. However, these materials face limitations such as adsorption site saturation, secondary waste generation, and lack of contaminant removal. Most work in the literature has concentrated on the adsorption efficiency rather than on the catalytic transformation mechanism. Little work has focused on potential applications of WTPs as environmental remediation materials. This review addresses these gaps by examining the transformation of WTPs into multifunctional carbon nanomaterials (CNM) that integrate adsorption and catalytic degradation mechanisms to overcome these limitations. The review highlights the enhanced properties of heteroatom-doped (N, P, S) and defect engineered WTP-derived CNMs, which enable effective activation of peroxymonosulfate (PMS) and peroxydisulfate (PDS) oxidants, facilitating both radical and non-radical pathways for contaminant degradation. In addition, the development of hierarchical porosity and surface functionalization facilitates a capture-degrade mechanism, circumventing the adsorption bottleneck associated with traditional materials. The review describes how WTP-CNMs can be reused in soil systems to help immobilize pollutants, stimulate microbial activity, and advance sustainable remediation, thereby promoting a circular waste-to-resource approach. By linking traditional adsorption-based remediation materials with catalytic-active NMs derived from waste, this review provides design approaches for large-scale and sustainable environmental remediation. Overall, integration of catalytic function with tea-residue-derived NMs represents a viable path for large-scale sustainable environmental remediation.