| Summary: | 碩士 === 國立臺灣大學 === 生物環境系統工程學研究所 === 107 === Degradation of pollutants in the environment has become an issue through the development of industry nowadays. Phenol, a widely used aromatic organic compound, is a hazardous substance due to its corrosiveness and reproductive toxicity. The incomplete degradation of phenol results in the formation of toxic phenolic intermediates such as catechol and hydroquinone. For the reason, the degradation and mineralization of phenol containing phenolic compounds is a critical concern when disposal with sewage discharge. Fenton process is one of the mostly-used AOP (advanced oxidation processes) when it comes to wastewater treatment due to its simplicity and low cost. However, the effects of the existence of humic acid (HA) in the treatment should be considered when wastewater treatment is conducted in real aquatic water environment. Furthermore, seasons in Taiwan causes the variation in temperature of the water body, which ranges from 20℃ to 30℃, and even reaches a higher level if containing the discharge of industrial wastewater. Therefore, discussion of temperature impact and HA coexistent on wastewater treatment of phenol by Fenton process should be an essential issue.
The objective of this study is to obtain the degradation and mineralization efficiency in Fenton wastewater treatment of low concentration phenol. This study applies Fenton process to the degradation of phenol and its phenolic intermediates at different conditions of temperature and humic acid concentrations. Beside the residual phenol and phenolic compounds concentration, TOC, ORP, hydroxyl radicals and COD were measured to compare the degradation efficiency under different experimental conditions.
In regard with the results, the impact caused by temperature variation or humic acid coexistence on low concentration phenol with sub-stoichiometric Fenton reagent (Fe2+: H2O2=0.1 mM: 0.5 mM) is not as apparent, but more TOC mineralization was observed. The enhancement of the mineralization rate by the coexistence of humic acid could reach 40.3% removal at room temperature of 20℃ rather than at higher temperature as the rate <30% due to the hinder effect produced by the humic acid and instability of the processes over 50℃. The constant value k of TOC mineralization at 60℃ with humic acid is 9.73×10^-4 M^-1min^-1 and is slower than that without humic acid as 5.41×10^-3 M^-1min^-1. The k of 20℃ with humic acid process is 2.11×10^-3 M^-1min^-1 and is 1.60×10^-3 M^-1min^-1 in the process without humic acid. The presence of humic acid in Fenton process resulted in more complicated mechanisms such as providing electrons, competing for oxidants and sorption. Therefore, the hinder effect on the mineralization of phenol by Fenton process at higher temperature is enhanced. According to the results in this study, an effective Fenton treatment with sub-stoichiometric Fenton reagent for low concentration phenol degradation should be applied at ambient temperature as 20℃ rather than higher temperature in the real water body.
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