Removal Of Microcystin-LR From Drinking Water By Fenton Reagent

The increasing eulrophication of fresh waters many of which include drinking water reservoirs by human activity has increased the occurrence and intensity of cyanobacterial blooms and approximately 50% of them are known to occur toxin. These toxins can cause potent hepatotoxicity and tumor-promoting activity to animal and human through inhibition of proteinphosphatases 1 and 2A. The potential for these toxins to impact adversely on human health requires that these toxins be removed from water supplies prior to use.Many strategies for the removal of cyanobacterial toxins from water have been investigated, but their efficacy are limited. Recent studies has been shown that the use of Advanced Oxidation Technologies (AOTs) such as photocatalysis for the degradation and removal of highly toxic microcystin-LR effectively in water purification because hydroxyl radicals are generated on the surface of semiconductor. The hydroxyl radical is believed to a strong oxidant in destruct organic pollutants in drinking water.This study focused on catalytic hydrogen peroxide oxidation to destructing microcystin-LR following the addition of ferrous as catalyst to the process. The treatment of Fe + and H2O2 gives rise to HO- radicals, which can initiate radical chain reactions and accelerate degradation of MCLR by chain propagation. The effects of H2O2 dosage, Fe + dosage, reaction time and pH on removal of Microcystin-LR were investigated. The toxin was easily decomposed by oxidation with Fenton reaction, and the removal efficiency depended on the H2O2 dosage, Fe2+/H2O2 mol ratio, pH and contact time. Under the condition pH=2-3, [H2O2] = 0.24mol/L, [Fe2+]/[H2O2]=l:12, and 45 min, the efficiency of removal MCLR could be reached above 98%.In addition the dynamics of MCLR degraded by Fenton reaction was also investigated in this paper. The results proved that the oxidation of MCLR by Fenton's reagent is in conformity with the first-order dynamics model and this macro-dynamic model was in a good agreement with experimental results, thus confirming theproposed reaction mechanism.Simultaneously the mechanism of Fenton to removal MCLR was studied indirectly by determining Fe(phen)32+ spectrophotometry which indicated the apparent productivity of hydroxyl radicals in Fenton reaction and directly by analyzing the treated cyanobacterial extracts through high-performance liquid chromatograph at 238 nni wavelength. The results showed that the removal tendency of MCLR was in agreement with the formation of -OH during the Fenton process and the HPLC suggested that MCLR was destroyed to CO2 and H2O2 through the formation of stable intermediate. So Fenlon treatment may be an effective and practical method for the removal of cyanobacterial peptide toxins from eutrophic water.