Fe(VI)-assisted photocatalytic degradating of microcystin-LR using titanium dioxide

Microcystin cyanobacterial hepatotoxins represent an increasingly severe global health hazard. This study focused on enhancing photocatalytic degradation of microcystin-LR (MCLR) following the addition of ferrate as the indirect electron acceptors to the process. The degradation rate of MCLR by ferrate or the photocatalysis only was 54 and 63%, respectively. However, when relatively low ferrate dose (0.08 mmol/L) was added to the photocatalytic process, a significant enhancement in the photocatalytic rate was observed and the efficiency can be increased to 100%. Compared the effect of Fe(III) and Fe(VI) on the photocatalysis rate, the process of Fe(VI)-assisted photocatalytic degradation of MCLR apparently existed the synergistic effect and the photocatalysis rate constant k of Fe(VI)/UV/TiO2 process was higher than Fe(III)/UV/TiO2 by 2.5 times and than UV/TiO2 by 4.4 times, but an overdose of ferrate will retard the rate due to the short circuiting reactions between Fe3+ and Fe2+ and the lower absorption of UV light. As expected, pH had a remarkable influence on the reaction rate of detoxification of microcystin-LR and pH 6 was beneficial to the photocatalytic process.