Selective Removal of Methylene Blue Using Cellulose-Based Imprinted Polymers from Agro-Waste

Methylene blue (MB), a common cationic dye, poses environmental and health risks due to its persistence in industrial effluents. In this study, cellulose-based molecularly imprinted polymer (MIP) was synthesized from oil bean (<i>Pentaclethra macrophylla</i>) seed shell waste, using MB as a template. Non-imprinted polymer (NIP) was prepared as control. The materials were characterized by FTIR, SEM, and XRD, which confirmed successful polymerization and the presence of template-specific binding cavities in MIP. Batch adsorption experiments assessed the effects of pH, contact time, adsorbent dosage, initial dye concentration, and temperature. The adsorption kinetics followed a pseudo-second-order model, while equilibrium data were best fitted to the Freundlich isotherm, indicating heterogeneous surface binding. The maximum adsorption capacity of the MIP was 14.93 mg g<sup>-1</sup>, compared with 10.26 mg g<sup>-1</sup> for the NIP. Thermodynamic analysis showed the process was spontaneous and exothermic. Selectivity studies demonstrated strong molecular recognition of MB, with an imprinting factor of 3.37 and selectivity factors of 3.25 (MB/indigo carmine) and 2.89 (MB/fuchsin basic). These findings highlight that agro-waste valorization into functional MIPs provides an efficient and low-cost adsorbent with enhanced affinity and selectivity for dye removal. The study contributes to sustainable wastewater management by combining molecular imprinting with biomass utilization, thereby supporting circular economy goals. Future work should investigate regeneration, scale-up, and application in continuous-flow systems for practical deployment.