Removal of heavy metals by iron reductants and cobalamin in anaerobic environment / Jalina Kassim

This study highlights the removal of Cr and Zn by iron reductant with the present of Cobalamin under various experimental condition that is significant in the engineered or natural anaerobic environment. New findings on the role of enzymatic compound that significantly contribute to the removal of heavy metals in anaerobic environment was also reported. SEM analyses verify that particles size of synthesized nZVI and nFe304 were in the range of 25-70 nm (< 100 nm). Iron (Fe) is reported as dominant composition in both nZVI (73.87%) and nFe304 (58.88%). Batch experiments were carried out to elucidate the removal kinetics of Cr and Zn by nZVI and Co for the effects of metal concentration, pH, nZVI amount and Co concentration. From the effects of metals concentration, both Cr and Zn attained highest removal under nZVI-Co suspension at 0.5ppm having removal kinetic, A=1.0560 min"\ R^=0.9981for Cr and A=1.4409 min"\ R^=0.9996 for Zn. Effects of pH reveal highest removal of Cr was obtained under nZVI-Co suspension at pH 7 and pH 9 for Zn under nZVI-Co suspension. From the effects of different nZVI amount, both Cr and Zn removal increases with the increase of nZVI amount in the system having removal kinetic, k =1.1462 min"\ R2=0.9975 for Cr and removal kinetic, k= 1.5035 min"\ R2=0.9997 for Zn. From the effects of Co concentration, highest removal of Cr and Zinc was best achieved in nZVI-Co suspension having Co concentration of 1.5 mM where removal kinetic, k =1.0324 min-1 min"\ R^=0.9965 was attained for Cr and removal kinetic, k =1.1950 min"\ R^=0.9963 for Zn. Second sets of batch experiment were carried out to elucidate the removal kinetics of Cr and Zn by nFe304 and Co under different effects of metal concentration, pH, nFe304 amount and Co concentration. Effects of metal concentration reveal, highest Cr and Zn removal was obtained under nFe304-Co suspension having metal concentration of 0.5ppm with removal kinetic, k=lA2l5 min" \ R2=0.9978 for Cr and removal kinetic, k= 0.3162 min"\ R^= 0.9996 for Zn. Effects of pH reveal both Cr and Zn shows highest removal at pH 9 under nFe304-Co having removal kinetic, A: =0.8741 min"\ R^ 0.9963 for Cr and removal kinetic, A=1.3553 min" \ R^=0.9976 for Zn. The effects of different nFe304 amount towards the removal of Cr and Zn shows highest removal was obtained under nFe304-Co suspension having nZVI amount of 0.15g of nFe304 with removal kinetic, A=1.2916 min"\ R^=0.9944for Cr and removal kinetic, A=1.4437 min"\ R^=0.9954 for Zn. Effects of Co concentration reveal, highest Cr and Zn removal was obtained under nFe304-Co suspension having Co=1.5mM with removal kinetic, A:=0.7869 min"\ R^=0.9965 for Cr and removal kinetic, k =1.0942 min^ R^ =0.9930 for Zn. All of the removal kinetics, k of Cr and Zn removal fit the pseudo-first-order rate law having R^>0.95. Results strongly imply that the presents of Co is significant in enhancing removal of Cr and Zn by iron reductant.