Sustainable valorization of jamun seed waste into activated carbon for enhanced performance adsorption: characterization and application in removal of cationic dyes from aqueous solutions

This study investigates the potential of Jamun Seed Activated Carbon (JSAC) derived from agricultural waste as an efficient adsorbent for the Crystal Violet (CV) and Malachite Green (MG). There is two distinct preparation routes: chemical activation and thermal (physical) activation. Thermal activation at 700 °C achieved the highest surface area (773 m²/g), outperforming chemical activation with H₃PO₄ (404 m²/g). Characterization using FTIR, BET, SEM, and zeta potential (-36.36 mV) confirmed high colloidal stability and the presence of active oxygen-containing functional groups (-OH and -COOH). Batch experiments achieved 98-99% removal with maximum adsorption capacities of approximately 3.233 mg/g for both dyes. Optimal parameters included contact times of 40-50 min, a dosage of 0.9 - 1.2 g, and temperatures of 35-45 °C. The Hill model provided the best fit for MG and the Redlich-Peterson model provided the best fit for CV. The pseudo-first-order model demonstrated the highest correlation coefficient for MG whereas the Elovich model was the best fit for CV, suggesting a chemisorption mechanism on a heterogeneous surface. The thermodynamic parameters show that the adsorption process is spontaneous and endothermic. Scale-up simulations further showed that JSAC can effectively treat large volumes of dye-contaminated water with practical adsorbent mass requirements.