Research On The Oxidation Efficiency And Products Of Microcystins In Water By KmnO₄ / Cl₂

The enhancement of eutrophication in superficial freshwater bodies had increased of blooms of toxic cyanobacteria(blue-green algae)which had drawn attention of environmentalists worldwide.Bloom of microcystis is the most harmful,and produced microcystins which is hepatotoxic peptides and tumor-promoting agent and abundant in surface water.The analysis of microcystins is classified as uncommon item and of 1μg/L limitation in the standard of life and drinking water (GB5749-2006). In this thesis,the removal of MC-LR in aeruginosa cell lysis products by potassium permanganate and chlorine were researched systematically,and the the oxidation kinetics and mechanism of MC-LR acting with potassium permanganate and chlorine were studied too.The degradation of MC-LR in aeruginosa cell lysis products by potassium permanganate and chlorine was investigated in order to study the removal. The effects of the initial concentration of MC-LR, the concentration of oxidant, temperature and pH value on degradation of MC-LR by potassium permanganate or chlorine were studied. The removal of MC-LR was shown to be proportional to the concentration of oxidant and temperature. The initial concentration of MC-LR has little effect on removal rate. The removal of MC-LR decreases with the pH changes from acidity to alkaline.Through the comparison of degradation properties of MC-LR by potassium pennanganate and chlorine under different conditions,it was found that the MC-LR degradation proeesses of three oxidants complied with pseud-first-order kinetics mode as ln(Ct/C0)=-kt reaction rate had nothing to do with initial coneentration of MC-LR,while influenced greatly by oxidant initial concentration that were direct ratio to chlorine and KMnO4. Increase temperature did well to aceelerating degradation. PH had greatinfluence on the degradation of MC-LR by chlorine and decrease of pH accelerated degradation.The analysis of the molecular weight and texture of degradation products discovered that mechanism of MC-LR degradation by two oxidants were different. KMnO4 could oxidize MC-LR to dihydroxyl-MC-LR directly,and under the condition of excessive KMnO4,it could further oxidize to dicarbonyl-MC-LR;While active chiorine could take place additive reaction with MC-LR to generate chlorohydrin-MC-LR,and the halogen in the chlorohydrin may then undergo a nucleophilic substitution reaction with the solvent to form dihydroxyl-microcystin,and under the condition of excessive Cl2, it could further oxidize to dicarbonyl-MC-LR.