Removal of toxic metal Hexavalent Chromium [cr(vi)] from aqueous solution using starch – stabilized nanoscale zerovalent iron as adsorbent: Equilibrium and kinetics

Groundwater remediation by nanoparticles has received increasing interests in recent years. The present work was conducted to investigate the feasibility of using new class of stabilized zerovalent iron (ZVI) nanoparticles for In situ reductive immobilization of Cr(VI) in water. The nanoparticles were prepared by chemical reduction method using Ferrous sulfate heptahydrate (FeSO₄.7H₂O) with sodium borohydride (NaBH₄) as a reducer. This sample was subjected to XRD for the determination of crystallinity and average particle size. The size of the particle is 12.4 nm. The morphology of the nanoparticles was observed using SEM. Batch experiments reported that the synthesized starch stabilized zerovalent iron nanoparticles were able to rapidly reduce Cr(VI) in aqueous solution. The extend of Cr(VI) reduction was increased with increasing concentration of iron nanoparticles (0.1 g/L – 0.4 g/L) and inversely with initial Cr(VI) concentration (10 mg/L – 25 mg/L) as well as with decreasing pH (3 – 10). The equilibrium data obtained from the experimental results were then fitted to the Freundlich and Langmuir isotherm models. Kinetic models were examined with pseudo first order rate reaction. The Correlation coefficient between experimental parameters and time shows that there is a strong positive correlation for Cr(VI) reduction. This study indicates that the zerovalent iron nanoparticles, especially those which were starch-stabilized can yield a high removal efficiency in the reduction of Cr(VI) contaminated groundwater.