Tea waste derived activated carbon as a multifunctional photoactive material for visible light dye degradation with optical dielectric and electrochemical investigation

Abstract The development of sustainable, metal-free photocatalysts from biomass waste is highly desirable for green energy and environmental remediation applications. In this work, a tea-waste-derived activated carbon was synthesized through controlled carbonization and chemical activation and evaluated as a multifunctional photoactive material for the visible-light-driven degradation of organic dyes. Comprehensive structural, surface, optical, dielectric, and electrochemical characterizations revealed a hierarchically porous carbon framework enriched with oxygen-containing functional groups, a narrow optical band gap (~ 1.54 eV), favorable dielectric response, prolonged charge carrier relaxation time, and efficient charge transport behavior. These intrinsic properties enable effective light harvesting, enhanced charge separation, and suppressed recombination, allowing the activated carbon to function beyond its conventional role as a passive adsorbent. The photocatalytic performance was investigated toward methyl orange, methylene blue, and rhodamine B under visible-light irradiation, achieving high degradation efficiencies of ~ 91% for methylene blue and ~ 93% for rhodamine B, with significantly faster pseudo-first-order kinetics compared to methyl orange. Reactive species trapping experiments and band structure estimation based on the Mulliken electronegativity approach revealed that the degradation mechanism is dominated by electron-driven oxygen reduction pathways, with hydroxyl radicals as the primary oxidative species. The activated carbon also exhibited good reusability and stability over multiple photocatalytic cycles. This study establishes clear structure–property–performance relationships for biomass-derived activated carbon and demonstrates its potential as a sustainable, low-cost, and metal-free photocatalyst for clean water applications. The findings provide new insights into carbon-driven photocatalysis and support the valorization of biomass waste for green energy and clean environment technologies.