Effects of Advanced Oxidation Processes on the Decomposition Properties of Organic Compounds with Different Molecular Structures in Water

摘要

Studies to decompose persistent organic pollutants in wastewater from chemical factories by using Advanced Oxidation Processes (AOPs) have recently been performed. Oxidation reactions involving ozone and ·OH radicals and cleavage caused by UV are the main decomposition reactions that occur in AOPs using ozone and UV. The mechanisms through which organic compounds are decomposed in AOPs are complicated and difficult to understand because various decomposition reactions occur simultaneously. The Total Organic Carbon (TOC) removal efficiencies achieved in several different AOPs were evaluated in this study. The TOC removal efficiencies were different for organic compounds with different chemical structures. The TOC was more effectively removed when aromatic compounds were treated using the O_3-UV-TiO_2 process than when using the other AOPs, and the TOC was removed more effectively by the O_3-UV process than by the UV-TiO_2 process. However, the TOC was removed more effectively when open-chain compounds were treated using the UV-TiO_2 process than using the O_3-UV process, and the UV-TiO_2 and O_3-UV-TiO_2 processes resulted in similar TOC removal efficiencies. Therefore, it is necessary to use the O_3-UV-TiO_2 process to decompose aromatic compounds as quickly as possible. On the other hand, the UV-TiO_2 process degraded the open-chain compounds most effectively, and the O_3-UV-TiO_2 process did not need to decompose open-chain compounds. Moreover, the TOC of aromatic compounds was removed more slowly than that of open-chain compounds. The TOC removal efficiency increased with decreasing the number of carbon atoms in the molecule. The TOC removal efficiencies increased in order of the organic compounds containing methyl groups, aldehyde groups and carboxyl groups. The removal of the TOC when organic compounds were treated using the O_3-UV-TiO_2 process followed pseudo-zero-order kinetics.