Photonanocatalytic Conversion of Rice Straw to Sorbitol Using MnZnFe₂O₄: A Green Chemistry Approach for Sustainable Biomass Valorization
Rice straw valorization through green-chemistry-based photocatalysis offers a cleaner and safer alternative to conventional high-pressure hydrogenation for sorbitol production. This study develops and optimizes a MnZnFe₂O₄ photonanocatalytic process under UV irradiation to convert cellulose into sorbitol. Three key process variables—catalyst mass (0.5–1.0 g), UV energy (60–125 J/s), and exposure time (30–60 min)—were evaluated and optimized using Response Surface Methodology, Genetic Algorithm, and Particle Swarm Optimization. The optimum operating conditions were achieved at 1.0 g catalyst, 125 J/s UV energy, and 60 min exposure, producing a sorbitol yield of 55%, product mass of 6.244 g, and economic output of Rp 3,401, with model accuracy exceeding 95% (R² = 0.998). The enhanced catalytic performance is attributed to the MnZnFe₂O₄ spinel ferrite structure, which improves electron–hole separation and photocatalytic activation under UV light. Product characterization (SEM, FTIR, XRD, TGA) confirmed structural and functional consistency with standard sorbitol. Overall, MnZnFe₂O₄ photonanocatalysis demonstrates feasibility as a low-emission conversion pathway, supporting agricultural waste utilization and reducing the environmental burden of rice straw disposal. These outcomes indicate strong alignment with green chemistry principles and highlight the potential for scalable, sustainable sorbitol production.