Studies On Photodegradation Of Organic Pollutants Induced By Algae In Aqueous Solutions

Various chemicals exist in natural water. These chemicals along with their transformed substances can affect the health of human bodies. For this reason, the transformation of chemicals in natural water is always a focus among the environmental issues for researchers. The photochemical process in natural water bodies is an important way for organic pollutants to transform. This paper firstly gives a complete comprehensive illustration to the photochemical process in natural water bodies and how algae contribute to protect water environment. Then in the following chapters, we focused on four experimentations: the photodegradation of anilines induced by Chlorella vulgaris, the photodegradation of 17α-ethynylestradiol (EE2) and 17p-estradiol (E2) induced by three algae-Microcytis aeruginasa kutz, Chlorella vulgaris and Anabaena cylindrica, and microalgal bioassays as a test of photodegradation efficiency of 17(3- estradiol.(1) Exposed to high-pressure Hg-lamp(HPML, 250w, λ≥365nm ), the algae all can induce the photodegradation of three organic pollutants. As the concentration of Chlorella vulgaris is 2.0 × 10¹⁰cells/L and the initial concentration of aniline is 1mg/L, the rate of anilines photodegradation could reach to 37%. When anilines concentration is between 0.4-2mg/L, anilines photodegradation rates increase with increasing anilines initial concentrations, and the photodegradation reaction obeys the law of pseudo first-order reaction. For Chlorella vulgaris, Anabaena cylindrica and Microcytis aeruginasa kutz, as the concentrations are 1.1 × 10¹⁰cells/L, 1.8× 10¹⁰cells/L, 2.8× 10¹⁰cells/L respectively, and the initial concentration of EE2 is 8mg/L, EE2 photodegradation are very obvious, and their photodegradation rates are 18.9%, 17.6%, 20.3% respectively. When EE2 concentration is between 4-16mg/L, EE2 photodegradation rates increase with increasing anilines initial concentrations, and the photodegradation reaction obeys the law of pseudo first-order reaction; For Chlorella vulgaris, Anabaena cylindrica and Microcytis aeruginasa kutz, as the concentrations are 4.0 × 10¹⁰ cells/L, 2.5 × 10⁹ cells/L, 1.5 × 10¹⁰ cells/L respectively, and the initial concentration of E2 is 8mg/L, E2 photodegradation are very obvious, and their photodegradation rates are 37.0%, 21.0%, 16.0% respectively. When E2 concentration is between 4-16mg/L, E2 photodegradation rates increase with increasing anilines initial concentrations, and the photodegradation reaction obeys the law of pseudo first-order reaction.And the concentration of algae can influence the photodegradation rates of three organic pollutants. When the Chlorella vulgaris concentration is between 5.5 X 10 cells/L-2.0 X 1010cells/L and the initial concentration of anilines is 1 mg/L, the photodegradation rate increases with increasing the algae concentration; For Chlorella vulgaris, Anabaena cylindrica and Microcytis aeruginasa kutz, as the concentrations are between 2.75 X 109cells/L- 2.20X1010cells/L, 7.00X 108cells/L- 8.40X 109cells/L, 2.20X 109cells/L-1.60 X 1010cells/L respectively, and the initial concentration of EE2 is 8mg/L, the photodegradation rates increase with increasing the algae concentrations; For Chlorella vulgaris, Anabaena cylindrica and Microcytis aeruginasa kutz, as the concentrations are between2.0 X 109cells/L- 4.0 X 1010cells/L, 7.5 X 108cells/L- 4.5 X 109cells/L, 1.5 X 109cells/L- 2.3 X 1010cells/L respectively, and the initial concentration of E2 is 8mg/L, the photodegradation rates increase with increasing the algae concentrations. Because more higher are algae concentrations, more active oxygens are produced. So the rates of three organic pollutants photodegradation increased accordingly.Moreover, for the same initial concentration of three organic pollutants and the same concentration of algae, using 125w, 250w HPML to irradiate the pollutants solutions respectively, we analyzed the rate of photodegradation one by one. And we find the 250w HPML is more in favor of the photodegradation of organic pollutants. Because the bigger luminous flux benefits this photodegradation system.(2) Using benzene as scavenger to produce 1- phenol, the photo-generation of ? OH in the algae complex systems is investigated. The generation of ? OH is the direct cause of the pollutants photodegradation.(3) To examine the photo-induced algal degradation acts of organic pollutants, we use uv-vis spectrum and HPLC to analyze the anilines photodegradation fore-and-aft solutions with catalyzing of Chlorella vulgaris; and we find anilines photodegradation opened benzene ring; using IR to analyze the photodegradation products of EE2 with catalyzing of Anabaena cylindrical, we also find EE2 photodegradation opened benzene ring, and produced the substance with C = O structure; using HPLC to analyze the E2 photodegradation fore-and-aft solutions with catalyzing of Chlorella vulgaris, we find when E2 solutions with algae was illuminated, the acid products increased while E2 concentration decreased, and weak polarity substances produced by algae solutions illuminated by HMPL kept the same concentration , so which showed Chlorella vulgaris induced the photodegradation of E2.(4) Using microalgal bioassay to test the photodegradation fore-and-aft solutions of17p-estradiol, we made sure that when the initial concentration of E2 is 8mg/L, the photodegradation inducing by algae can decrease the biological toxicity of 17p-estradiol, but the photodegradation process need be optimized.