Removal of cyanobacterial microcystin-LR by ferrate oxidation-coagulation

In this study, the effect of a multiple function reagent-ferrate on the removal of microcystins-LR (MCLR) from freeze-dried Planktothrix sp. was investigated. The toxin was easily decomposed by oxidation with ferrate, and the removal efficiency depended on the dosage of ferrate, pH, and contact time. Simultaneously the reduction product Fe(OH)3 after ferrate oxidation could flocculate the organic compounds so that 50% TOC removal of the extract was reached. The low residual iron reflected the excellent results of coagulation and could meet the standard of drinking water. Analysis of the treated cyanobacterial extracts by high-performance liquid chromatograph, monitoring absorbance at 210 and 238 nm, suggested that the heptapeptide ring of MCLR and its Adda group had been opened or modified, respectively. So ferrate treatment may be an effective and practical method for the removal of cyanobacterial peptide toxins from eutrophic waters, especially which hold high total organic carbon. (C) 2002 Elsevier Science Ltd. All rights reserved.