| During recent years, organophosphorus pesticides (OPs) have been extensively used in modern agriculture due to their high efficiency for insect elimination and low cost. However, the emissions and residues of OPs can lead to contamination of environment, resulting in a significant threat to human health. Thus, there is an increasing need to develop a novel treatment and detection method for OPs. With the development of nanotechnology, it has been applied to the treatment and detection of OPs. This thesis mainly focuses on the synthesis of some TiO2-based semiconductor nanocomposites, including Fe3O4@SiO2@TiO2core-shell nanocomposites and rGO/TiO2/CdS nanocomposites. Techniques such as powder X-ray diffraction (XRD), transmission electron micrographs (TEM), scanning electron micrographs (SEM) and high resolution transmission electron micrographs (HRTEM) were used to characterize the as-prepared. The as-prepared nanocomposites are applied to the treatment and detection of OPs. The main results can be summarized as follows:1. Synthesis of magnetic sonophotocatalyst and its enhanced biodegradability of organophosphate pesticideTaking into consideration that organophosphate pesticide wastewaters have poor biodegradability, a magnetic sonophotocatalyst Fe3O4@SiO2@TiO2is developed in this paper. The as-prepared nanoparticles (NPs) were characterized using different techniques, such as XRD and TEM. The radial sonophotocatalytic activity of Fe3O4@SiO2@TiO2nanocomposite was investigated, in which commercial dichlorvos (DDVP) was chosen as an object. The degradation efficiency was evaluated in terms of chemical oxygen demand (COD) and enhancement of biodegradability. The effect of different factors, such as reaction time, pH, the added amount of catalyst on CODq-removal efficiency were investigated. The average CODcr removal efficiency reached63.13%after240min in12L sonophotocatalytic reactor (Fe3O4@SiO2@TiO20.2g L-1, pH7.3). The synergistic effect occurs in the combined sonolysis and photocatalysis which is proved by the significant improvement in CODcr removal efficiency compared with that of solo photocatalysis. Under this experimental condition, the BOD5/CODcr ratio rose from0.131to0.411, showing a remarkable improvement in biodegradability. These results showed that sonophotocatalysis may be applied as pre-treatment of pesticide wastewater, and then for biological treatment. The synthesized magnetic naocompostite had good photocatalytic performance and stability, as when it was used for the fifth time, the CODcr removal efficiency was still about62.38%.2. Synthesis of rGO/TiO2/CdS nanocomposite electrode and its photoelectrochemical determination for parathion-methylA novel light "on-off" photoelectrochemical (PEC) sensing for the determination of OPs was developed based on rGO/TiO2/CdS nano-photoactive material. The rGO/TiO2and rGO/TiO2/CdS nanocomposites were prepared by solvothermal method and electrochemical deposition technique, respectively. The morphologies and structures of the as-prepared nanocomposites were extensively investigated by SEM and XRD. In alkaline condition, p-nitrophenol as the hydrolysate of parathion-methyl could be obtained by a simple hydrolyzation process. The photocurrent intensity was enhanced towards the increased in the concentration of the hydrolysate of parathion-methyl. Under optimal conditions, The rGO/TiO2/CdS modified ITO electrode showed good PEC behavior toward the hydrolysate of parathion-methyl. The proposed PEC method could detect parathion-methyl ranging from0.05to10nmol L"1with a detection limit of0.02nmol L-1(S/N=3). Thus, the semiconductor nanocomposites could serve as a novel photoactive material for PEC sensing. Figure19table6reference99... |
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