Hydrothermal conversion of tea waste into a sustainable catalyst for rapid methylene blue degradation and antimicrobial water treatment

Abstract Water pollution remains a significant environmental challenge in the contemporary era, largely attributed to the widespread use of synthetic dyes in textile industries and the discharge of pathogens such as Escherichia coli ( E. coli ) into nearby water bodies. These organic and microbial contaminants pose various health risks, including but not limited to carcinogenic threats, reproductive issues, skin allergies, and other potential health hazards. Addressing this issues, recent efforts have focused on leveraging waste management strategies and geochemical water pollution control approaches, particularly through the photodegradation process, to eliminate different types of contamination from wastewater. This study employed a green synthesis method to produce tea waste hydrochar (TWH) through a hydrothermal process at 180˚C for 10 h. Characterization of the TWH involved techniques such as XRD (X-ray Diffraction), SEM (scanning electron microscopy), and FTIR (Fourier-Transform Infrared Spectroscopy). Subsequently, the synthesized TWH was utilized to eliminate dye-based contamination from both pure (Milli Q water) and river-based water under UV light irradiation. The experimental findings revealed remarkable photodegradation efficiency, as methylene blue (MB) dye achieved 90% degradation in pure water and 75% degradation in river-based water within 3 h under UV light irradiation. Moreover, the TWH exhibited excellent antibacterial action in removing E. coli bacteria from river water achieved 99.64% removal efficiency under UV light irradiation. These results confirm TWH offers dual-functionality, cost-effective and greener approach for wastewater treatment, particularly in the organic contaminants degradation and antimicrobial activities, and help to achieve the Sustainable Development Goals (SDG 6: Clean water and sanitation) of the United Nations.