Performance assessment of zero‐valent iron nanoparticles for <scp>C</scp> r ( <scp>VI</scp> ) removal in a continuous flow fixed‐bed column system

Abstract The efficacy of green‐synthesized zero‐valent iron nanoparticles (ZVI‐NPs) obtained from Aegle marmelos leaf extract in the removal of chromium (VI) from aqueous solutions under continuous fixed‐bed column system is investigated in this study. An environmentally friendly method was used to synthesize the ZVI‐NPs, and scanning electron microscopy (SEM), zeta potential, and particle size distribution investigations were used to characterize them. The nanoparticles were synthesized of about 55 nm, demonstrating spherical morphology. Zeta potential of −27.89 mV and limited size distribution (40–70 nm) indicated great stability and uniformity. To study the breakthrough behaviour, the effect of different parameters such as bed height (2–6 cm), flow rate (2–8 mL min −1 ), and influent Cr (VI) concentration (5–15 mg L −1 ) were performed for the column system. Bed height of 6 cm, flow rate of 2 mL min −1 , and initial Cr (VI) concentration of 5 mg L −1 showed best results with maximum adsorption capacity of 12.22 mg/g and removal efficiency of 93.33%. Adams–Bohart, Thomas, and Yoon–Nelson models were studied to describe the column dynamics and adsorption mechanism. The Thomas model had the best fit with R 2 value between 0.89 and 0.98. In the regeneration studies, 79.25% of the initial adsorption capacity of the ZVI‐NPs bed was maintained in the first cycle, and subsequently dropped to 50.7% after three cycles. These results demonstrate that Aegle marmelos derived ZVI‐NPs are stable, sustainable, and effective adsorbents for Cr (VI) removal in continuous flow system, providing a scalable and environmentally beneficial substitute for the treatment of industrial wastewater.