Development of a novel Ag-doped TiO2/carrageenan–locust bean gum biocomposite for enhanced adsorptive and photocatalytic elimination of methylene blue

In this work, Ag-doped TiO2 (AT), a natural biopolymer-based matrix composed of carrageenan and locust bean gum (LC), along with their integrated composite (ATLC), were successfully synthesized and assessed for their potential in removing methylene blue dye via both adsorption and photocatalytic degradation. Comprehensive physicochemical characterization techniques were employed to investigate the structural, morphological, and surface features of the materials. Among them, ATLC exhibited the most enhanced characteristics, including a high specific surface area of 410.4 m2 g−1, a point of zero charge near pH 6, and a reduced band gap energy of 2.6 eV, indicating improved light absorption and surface reactivity. In batch adsorption studies, ATLC demonstrated a higher adsorption capacity (413.5 m2 g−1) than the individual components. ATLC demonstrated excellent photocatalytic performance under visible light, achieving a 96% degradation rate of methylene blue within 80 min at 30 °C. This efficiency is attributed to the combined effects of Ag doping and polymer matrix support, which improve charge separation and light utilization. Thermodynamic findings suggest the degradation process is endothermic and non-spontaneous. After six cycles of reuse, ATLC preserved 94.9% of its photocatalytic efficiency and 97.9% of its adsorption capacity, demonstrating good stability and reusability. These results indicate that the ATLC composite is a promising, eco-friendly, and reusable material for the efficient treatment of dye-contaminated wastewater. Graphical abstract