Sustainable MgO-biochar nanointerface derived from ziziphus mauritiana for enhanced Congo red photodegradation.

Efficient and sustainable photocatalysts are needed for wastewater treatment due to persistent toxic dyes such as Congo red (CR), which threatens aquatic ecosystems and human health. Herein, a MgO@BC-ZM nanocomposite was synthesized via a green route using Ziziphus mauritiana-derived biochar and evaluated for photocatalytic degradation of CR dye. The novelty of this work lies in the development of a Ziziphus mauritiana-derived MgO-biochar nanointerface, in which biomass-derived biochar acts as a sustainable support to improve MgO dispersion, provide adsorption-active sites, and facilitate interfacial charge transfer for rapid solar-assisted Congo red degradation. Structural and physicochemical analyses confirmed successful formation, with XRD showing cubic MgO, FTIR identifying functional groups, and BET, SEM, AFM, and TEM revealing porous hierarchical morphology. Under optimized conditions (22.0 mg catalyst, 5 ppm CR, pH 7), 98% degradation was achieved within 20 min following pseudo-first-order kinetics. The catalyst retained 51% activity after seven cycles, indicating moderate reusability and stability. Enhanced performance was attributed to MgO-biochar synergy, promoting charge separation and reactive species generation, making the material a promising eco-friendly photocatalyst for wastewater remediation. This study highlights a sustainable approach for efficient dye removal from contaminated water systems while supporting environmentally safer wastewater treatment.