Sustainable TiO₂/Diospyros texana seed-derived activated carbon composites for rapid photodegradation of oxytetracycline and amoxicillin under visible light

Background: The widespread occurrence of antibiotics in aquatic environments has emerged as a serious environmental concern due to their persistence, bioaccumulation, and role in promoting antimicrobial resistance. Conventional treatment methods are often inadequate for complete antibiotic removal. Thus, developing multifunctional, sustainable materials capable of both adsorption and degradation is essential for effective water treatment. Results: This study introduces a novel titanium dioxide (TiO₂)/activated carbon (AC) composite synthesized from Diospyros texana seed biomass for efficient removal of oxytetracycline (OTC) and amoxycillin (AMX). The optimized 10 wt% TiO₂/AC composite, prepared via an impregnation method, exhibited enhanced visible-light photocatalytic activity and adsorption capacity. Structural characterization confirmed well-dispersed TiO₂ nanoparticles within the macroporous AC framework, promoting effective light harvesting, charge separation, and contaminant binding. The composite demonstrated thermal stability and a point of zero charge of 7.8, facilitating pH-dependent interactions with AMX and OTC. Under optimal conditions (pH 3 for AMX, pH 7 for OTC, 0.1 g/L composite), the system achieved rapid removal (> 90%), equilibrium within 3 min for AMX and 5 min for OTC. Performance remained stable for over 180 min and showed no significant decline even after five reuse cycles. However, increasing TiO₂ beyond 10% reduced efficiency due to pore blockage and loss of active surface area. Conclusion: The synergistic integration of bio-derived AC and TiO₂ yields a cost-effective material for efficient antibiotic removal from water. Overall, this study offers a scalable strategy for wastewater remediation, addressing critical environmental challenges posed by pharmaceutical contaminants through rapid degradation within minutes.