Perchlorate Removal Using a Minimized Dosage of Electrodeposited Zero-Valent Iron

This study attempted to develop an effective alternative to remove perchlorate (ClO4-) in water by using electrodeposited zero-valent iron (Fe-0) as an electron donor. Zero-valent iron was prepared on a titanium sheet as substrate through cathodic electrodeposition of ferrous ions in the presence of organic matter. It was observed that the freshly prepared Fe-0 was nearly free of oxides, whereas after reductive removal of ClO4-, a mixture of iron oxides (gamma-Fe2O3/Fe3O4) in a crystalline hexagonal plate shape was formed. The reaction rates of ClO4- removal relied on the dosages of Fe-0. At pH 6.5, 80.9% of 1mM ClO4- was removed in 336h using 10mM Fe-0. This value of electrodeposited Fe-0 dosage for sustaining the effective removal of ClO4- was at least 90x smaller than the Fe-0 dosages previously reported. The accumulation of chloride ion, which was the only detected product containing chlorine, was detrimental to further reaction. The reduction reaction was faster at neutral pH than at acidic or basic pH. In addition, increasing the temperature and introducing Pd into the electrodeposited Fe-0 to form Pd/Fe-0 improved the removal efficiency of ClO4-.