A study on the adsorptive removal of chromium ( <scp>VI</scp> ) using zerovalent iron nanoparticles prepared from <scp> <i>Aegle marmelos</i> </scp> fruit shell: Kinetic and isotherm insights

Abstract This study explores a green and sustainable approach for the synthesis of zero‐valent iron nanoparticles using the fruit shell extract of Aegle marmelos (Bael) and their application in the adsorptive removal of chromium (VI) from aqueous systems. The biosynthesized nanoparticles were characterized using XRD and SEM techniques, confirming their porous morphology and predominantly zero‐valent state. Batch adsorption experiments were conducted to evaluate the influence of key parameters such as pH, contact time, adsorbent dosage, and initial chromium (VI) concentration on removal efficiency. Optimal adsorption (∼89%) was achieved at pH 4.0, with a dose of 0.3 g/100 mL and 40 min of contact time. Pseudo‐second‐order kinetic model with R 2 value as 0.93 was the dominant mechanism, suggesting chemisorption. Equilibrium data fit well to the Langmuir isotherm ( R 2 = 0.917), indicating monolayer adsorption with a highest possible capacity ( q m ) of 24.32 mg/g. The process's spontaneous, exothermic, and entropy‐driven nature was validated by thermodynamic characteristics. The dual role of the Bael shell derived zerovalent iron nanoparticles in reducing chromium (VI) to chromium (III) and facilitating its adsorption highlights the potential of this biosorbent for effective and eco‐friendly remediation of chromium‐contaminated water.