| Nano semiconductor photocatalytic technology has been widely studied and applied in organic and inorganic pollutants as well as a variety of water pollution in recent years. While, as a major group of aquatic ecosystems, algae is often used as a risk assessment of biological pollution and toxins. So the mechanism effects of nano-TiO2 photocatalysis on Chlamydomonas reinhardtii and Microcystis aeruginosa were studied by using micro-thermal, scanning electron microscopy(SEM), Fourier transform infrared(ATR-FTIR), plasma-atomic emission spectroscopy(ICP-AES) and other kinds of characterization methods to analyze the algal cells, which were degraded in this paper. In addition, the photocatalytic activity of TiO2 and Bi2WO6 for microorganisms was compared by dealing with E. coli. The main contents are as follows:1. At first the P25 TiO2 which was used in the experiments was characterized by XRD and transmission electron microscopy(TEM), and according to microcalorimetry, the individual nano-TiO2 has no effect on the growth of C. reinhardtii. When nano-TiO2 photocatalysis act on C. reinhardtii, the microscopic structure of the cell surface was observed by SEM. And found that photocatalysis with UV irradiation has a larger extent damage than under natural light to the cells. With the increase of photocatalytic time, the cell surface was damaged and sunk. It was also noted that cell surface was surrounded by TiO2 particles, which could present an obstacle to the exchange of substances between the cell and its surrounding environment. The FTIR spectroscopy revealed that in the same time, the destroy degree of the epidermis functional groups was greatest by nano Ti O2 with UV photocatalysis. Especially the peaks of C-C, C-H, C=O and P=O depressed greatly. In addition, we found that nano-TiO2 with UV photocatalysis has little effect on chlorophyll and pigment of algal cells.2. The morphology of M. aeruginosa was changed and even broken when treated by nano-TiO2 with UV photocatalysis, and with the growth of the processing time, the extent of the damage was getting worse. During photocatalytic 12 h, the epidermal polysaccharides, phospholipids, proteins and other molecules, and functional tissue is broken down, followed then the cells are degraded. By ATR-FTIR spectra showed that functional infrared peak of M. aeruginosa cells significantly weaken or even disappear after UV photocatalytic TiO2 treatment. Within 12 h, the active substance(? OH) and other active substances such as(h+, ?OH, ?O2-, HO2?) which were produced by photocatalysis interact to degradate C-C, C-H, C=O, P=O and other groups. With the growth of the photocatalytic time, νa(CH3) and νs(CH2) highlights gradually and then disappeared. This is the change about polysaccharide of LPS and PGNas well as C-H bonds in phospholipid molecules tail, which further explanation of extracellular polysaccharides and phospholipid molecules photocatalytic peroxide is very sensitive. According to the dynamic analysis of the infrared peaks, the damage on the cell groups under nano-TiO2 photocatalysis with different time periods was different. ICP-AES determination showed that M. aeruginosa lost the function of the cell membrane selective permeability after treated by nano-TiO2 with UV light, and fluorescence polarization indicated that with the growth of processing time, mobility was getting worse.3. This experiment synthesized the orthogonal Bi2WO6 nanomaterials by hydrothermal method, and found it was orthogonal-type crystals by analyzing the XRD spectrum. After observed and studied by scanning electron microscopy and FTIR analysis, nanometer semiconductor Bi2WO6 has less good effect on E. coli than TiO2 photocatalysis when under UV irradiation. |
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