Modification of photocatalyst with enhanced photocatalytic activity for water treatment

Increasing demand and shortage of energy resources and clean water due to the rapid development of industry, population growth, and long-term droughts have become an issue worldwide. As a result, global warming, long-term droughts, and pollution-related diseases are becoming more and more serious. The traditional technologies, such as precipitation, neutralization, sedimentation, filtration, and waste immobilization, cannot prevent the pollution but restrict the waste chemicals only after the pollution emission. Meanwhile, most of these treatments cannot thoroughly degrade the contaminants and may generate toxic secondary pollutants into ecosystem.Heterogeneous photocatalysis as the innovative wastewater technology attracts many attention, because it is able to generate highly reactive transitory species for total degradation of organic compounds, water pathogens, and disinfection by-products. Semiconductors as photocatalysts have demonstrated their efficiency in degrading a wide range of organics into readily biodegradable compounds and eventually mineralized them to innocuous carbon dioxide and water. But, the efficiency of photocatalysis is limited, and hence, it is a crucial issue to modify photocatalyst to enhance photocatalytic activity.In this thesis, first of all, two literature views are conducted. A survey of materials for photocatalysis has been carried out to summarize the properties and the applications of photocatalysts that have been developed in this field. Meanwhile, the strategy for the improvement of photocatalytic activity has been explicitly discussed.Furthermore, all the raw material and chemicals used in this work have been listed as well as a specific experimental process and characterization method has been described. The synthesize methods of different photocatalysts have been depicted step by step. Among these cases, different modification strategies have been used to enhance the efficiency of photocatalyst on degradation of organic compounds (methylene blue or phenol). For each case, photocatalytic experiments have been done to exhibit their photocatalytic activity. The photocatalytic experiments have been designed, and its process has been explained and illustrated in detailed.Moreover, the experimental results have been shown and discussed. All the findings have been demonstrated in detail and discussed case by case. Eventually, the mechanisms on the improvement of photocatalytic activities have been clarified by characterization of samples and analysis of results. As a conclusion, the photocatalytic activities of selected semiconductors have been successfully enhanced via choosing appropriate strategy for the modification of photocatalysts.