Research On Toxigenicity Characteristics Of Microcystics Aeruginosa And Visible Light Photocatalysis Degradation By Mn-TiO₂

The toxins produced from cyanobacteria blooms have become a serious threaten to public health and the safety of drinking water. Researches of the rule of toxins producing and effective detoxication methods has been highly concerned. In this study, we choose Microcystics aeruginosa as the typical toxin-producing algae for multiplication culturing and analyzing the regulatity of the relationship between concentration of intracellular, extracellular MC-LR and characteristics pigments upon the different periods of Microcystics aeruginosa growth process. Besides, nanoscale Mn-TiO₂ photocatalyst were prepared and characterized by SEM, XRD, UV-vis and XPS. Then the best visible light catalytic properites were screened by the effect of degradation and mineralization complex organic. Finally, Mn-TiO₂ were studied in visible light on MC-LR degradation efficiency and in-depth oxidation ?mineralization? degree.Results showed that, the growth of M. aeruginosa accorded with the "S" Logistic model growth curve under the condition of 2500 lux,25?, at light to dark rate of 12:12. The intracellular MC-LR concentration was up to a maximum of 2.837 mg/L in the late logarithmic phase of M. aeruginosa. The dissolution of extracellular MC-LR showed a slight increase trend, rising from 0.640 mg/L to 1.211 mg/L. The results of Pearson's analysis showed that intracellular MC-LR was extremely correlated with Chl-a ?R2=0.8640? and extracelluar MC-LR was correlated with PC strongly ?R2=0.9576?. In addition, PC content kept a significantly correlated to the density of algae ?R2=0.9634?. The producing of MC-LR by M. aeruginosa had obvious dynamic change and closely related to the pigment content. As a result, it was necessary to use visible light photocatalysis technology to reduce the pollution of MC-LR resulting by blue algae bloom.The different calcined temperature and Mn doped amount of Mn-TiO₂ nano photocatalyst were prepared by sol-gel method. The result of materials characterization and visible light degradation experiment showed that, the anatase crystal type of Mn-TiO₂ with a significant visible light response was presented mostly in all samples and particle size distribution was betweenl 1.03?13.96nm and the particles dispersion was better than TiO₂, Mn element was successful incorporation of TiO₂ lattice and existed in Mn3+, Mn-TiO₂ presented the best visible light catalytic activity under 400? calcined temperature. The MC-LR degradation was up to 98.93% after visible illumination of 12h under the condition of initial concentration 0.1mg/L, catalyst dosage 0.2g/L of 10%Mn-TiO₂, but with mineralization only 50.87%. The photocatalytic degradation reaction of MC-LR by Mn-TiO₂ followed pseudo first order L-H kinetics equation basically, the degradation rate and the mineralization reaction rate was 0.0475/h and 0.1320/h respectively.