Green synthesis of tea residue-derived cellulose flocculants: High-efficiency performance and mechanistic insights

To achieve high-value utilization of tea waste and develop environmentally friendly flocculants, this study used tea waste cellulose, chitosan, sodium alginate, and itaconic acid as raw materials. Under acidic conditions, a novel green multi-component bioflocculant, C₂A₂, was synthesized using a synergistic strategy combining microwave-assisted graft copolymerization and cross-linking. Characterization by X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) indicates that C₂A₂ possesses both a polysaccharide backbone and itaconic acid-modified features, and incorporates multifunctional groups such as carboxyl, hydroxyl, and amino groups, thereby enhancing its hydrophilicity, charge-neutralizing capacity, and complexation properties. The results of the flocculation experiments indicate that C₂A₂ exhibits excellent treatment performance for kaolin suspensions, with a maximum flocculation rate of 96.68%. Optimal results were achieved at a dosage of 0.6 g/L, and the compound maintained good stability within a pH range of 4-10, with minimal influence from monovalent and divalent inorganic ions. At the same time, C₂A₂ also demonstrated high removal efficiency for simulated dye wastewater, indicating good application potential. Mechanistic analysis indicates that C₂A₂ promotes particle aggregation primarily through the synergistic effects of charge neutralization and polymer cross-linking, with multifunctional interactions further enhancing the floc structure. In summary, as a renewable, stable, and environmentally friendly biological flocculant, C₂A₂ holds promising prospects for application in the field of water treatment.