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Microcystins, a group of hepatotoxin produced by cyanobacteria in eutrophic freshwater, have proven unreliable to be removed by conven-tional treatments. In this study, the photocatalytic degradation experiments of Microcystin-LR were conducted using nano-TiO2 thin film, prepared by sol- gel and dip-coating method, with low UVA intensity irradiation. Analysis results from SPE (solid-phase extraction) combined with HPLC method showed that Microcystin-LR whose initial concentration (μg/L) around that occurs naturally was easily to be re-moved by photocatalytic system. The degradation efficiency of toxin was influenced by the pH condi-tions, initial concentration and UV intensity. The maximum initial rate of photocatalytic degradation occurred at pH 4 and over 95% of 20 μg/L Micro-cystin-LR was decomposed within 120 min under 400μW/cm2 UV illumination. The kinetic equations and parameters revealed that degradation reaction of trace level MC-LR, which was depicted by Langmuir- Hinshelwood kinetics model, was in accordance with pseudo first order kinetics process in appearance well. Under the condition of pH=6.7, irradiation inten-sity=400 μW/cm2 and initial concentration=20 μg/L, the corresponding pseudo-first-order rate constant k and half-life were determined to be 0.0157 min?1 and 44 min, respectively. During the range of 200―1000 μW/cm2, the degradation rate increases with incident intensity to the 0.82 power and the corresponding apparent quantum yield (Φapp) was found to be 5.19× 10-8 g/J approximately.
Microcystins, a group of hepatotoxin produced by cyanobacteria in eutrophic freshwater, have proven unreliable to be removed by convenional measures. In this study, the photocatalytic degradation experiments of Microcystin-LR were conducted using nano-TiO2 thin film, prepared by sol- gel and dip-coating method, with low UVA intensity irradiation. Analysis results from SPE (solid-phase extraction) combined with HPLC method showed that Microcystin-LR whose initial concentration (μg / L) around that occurs naturally occurs easily to be re- The degradation efficiency of toxin was influenced by the pH condi-tions, initial concentration and UV intensity. The maximum initial rate of photocatalytic degradation occurred at pH 4 and over 95% of 20 μg / L Micro-cystin-LR was decomposed within 120 min under 400 μW / cm2 UV illumination. The kinetic equations and parameters revealed that degradation reaction of trace level MC-LR, which was depicted by Langmuir-Hinshelwo Under the condition of pH = 6.7, irradiation inten-sity = 400 μW / cm2 and initial concentration = 20 μg / L, the corresponding pseudo-first-order rate constant k and half-life were determined to be 0.0157 min-1 and 44 min, respectively. During the range of 200-1000 μW / cm2, the degradation rate increases with the incident intensity to the 0.82 power and the corresponding apparent quantum yield Φapp) was found to be 5.19 × 10-8 g / J approximately.