Thesis (Ph.D.)--Chulalongkorn University, 2008

Chemical compounds with aromatic amine group such as 2,6-dimethylaniline and aniline are widely used in dyestuff, rubber, pesticide and pharmaceutical industries. Both are considered toxic and carcinogenic, and therefore, the industry wastewater that are contaminated with these chemicals need to be treated prior to discharge into the environment. This research aimed to study the degradation of 2,6-dimethylaniline and aniline by Fenton technologies which are the processes that have the potential to rapidly degrade toxic and organic compounds. The Fenton processes applied were: (1) Fenton process; (2) electro-Fenton process using IrO2/RuO₂ coated titanium metal as anode and stainless steel cathode; and (3) photoelectro-Fenton process using UVA as light source. The effects of parameters such as initial pH, initial ferrous ion concentration, initial hydrogen peroxide concentration, electricity application and UVA lamps irradiation were also determined in this study. Results showed that the photoelectro-Fenton process had the highest degradation efficiency compared to Fenton and electro-Fenton processes. In the photoelectro-Fenton process, 100% removal of 2,6-dimethylaniline and 48% COD removal were achieved in 1 hour (initial pH = 3, initial Fe2+ concentration = 1 mM, initial H2O₂ concentration = 1 mM, electric current = 2 A and UVA, 4 lamps), and 100% removal of aniline and 84% COD removal were achieved in 40 minutes (initial pH = 2, initial Fe2+ concentration = 0.25 mM, initial H2O₂ concentration = 10 mM, electric current 2 A and UVA, 4 lamps). The kinetics of 2,6-dimethylaniline and aniline degradation by Fenton processes were also determined. The oxidation reactions of both chemicals were found to follow the second-order reaction rate. The photoelectro-Fenton process provided highest value of initial degradation rate of 2,6-dimethylaniline and aniline which were determined to be 0.0584 mM/min and 0.0739 mM/min, respectively. The rate constants of aniline degradation by Fenton, electro-Fenton and photoelectro-Fenton processes were higher than the rate constants of 2,6-dimethylaniline degradation. The degradation pathways for 2,6-dimethylaniline and aniline were also proposed in this study.