Nalinrut Masomboon

Chemical oxidation of 2,6-dimethylaniline in the fenton process.

2,6-Dimethylaniline degradation by Fenton process has been studied in depth for the purpose of learning more about the reactions involved in the oxidation of 2,6-dimethylaniline under various reaction conditions. The effect of reaction conditions including the initial pH value, and the dosages of ferrous ions and hydrogen peroxide on 2,6-dimethylaniline and COD removal were investigated. 2,6-Dimethylaniline removal efficiency of 70% was achieved under optimal reaction conditions of pH value of 2, dosage of 2 mM of ferrous ion, and 20 mM of hydrogen peroxide after 3 h. A series of intermediates were identified, corresponding to ring compounds and short-chain organic acids. The intermediates were 2,6-dimethylphenol, 2,6-dimethylnitrobenzene, 2,6-dimethylbenzoquinone, 3-hexanone, maleic acid, acetic acid, formic acid, and oxalic acid. An oxidation pathway of the target organic was also proposed in this study.

Chemical oxidation of 2,6-dimethylaniline by electrochemically generated Fenton's reagent.

Oxidation of 2,6-dimethylaniline by electro-Fenton process in acidic solution at pH 2 was investigated. The effects of pH, Fe(2+), H(2)O(2) and current density were assessed to determine the optimum operating parameters. The oxidation efficiency of 2,6-dimethylaniline was determined by the reduction of 2,6-dimethylaniline, COD and TOC in the solutions. Results reveal that 1 mM of 2,6-dimethylaniline can be completely degraded in 4 h with 1 mM of Fe(2+) and 20 mM of H(2)O(2) and current density of 15.89 A m(-2) at pH 2. The highest COD and TOC removal were observed when 120 mM of hydrogen peroxide was applied. Consequently, the electro-Fenton process is a reliable alternative in the degradation of 2,6-dimethylaniline. 2,6-dimethylphenol, 2,6-dimethylnitrobenzene, 2,6-dimethylbenzoquinone, 3-hexanone, lactic acid, oxalic acid, acetic acid, maleic acid and formic acid were detected during the degradation of 1 mM of 2,6-dimethylaniline solution by electro-Fenton method. A reaction pathway that includes these products is proposed for 2,6-dimethylaniline degradation.

Kinetics of 2,6-dimethylaniline oxidation by various Fenton processes.

The kinetics of 2,6-dimethylaniline degradation by Fenton process, electro-Fenton process and photoelectro-Fenton process was investigated. This study attempted to eliminate the potential interferences from intermediates by making a kinetics comparison of Fenton, electro-Fenton and photoelectro-Fenton methods through use initial rate techniques during the first 10 min of the reaction. Exactly how the initial concentration of 2,6-dimethylaniline, ferrous ions and hydrogen peroxide affects 2,6-dimethylaniline degradation was also examined. Experimental results indicate that the 2,6-dimethylaniline degradation in the photoelectro-Fenton process is superior to the ordinary Fenton and electro-Fenton processes. Additionally, for 100% removal of 1mM 2,6-dimethylaniline, the supplementation of 1mM of ferrous ion, 20mM of hydrogen peroxide, current density at 15.89 A m(-2) and 12 UVA lamps at pH 2 was necessary. The overall rate equations for 2,6-dimethylaniline degradation by Fenton, electro-Fenton and photoelectro-Fenton processes were proposed as well.

Effect of carrier composition on 2,6‐dimethylaniline degradation in aqueous solution by fluidized‐bed Fenton process

The fluidized‐bed Fenton process is an alternative process that decreases iron sludge from the Fenton reaction by using carriers to crystallize iron on to the surface of the carrier. In this study, the target compound is 2,6‐dimethylaniline, which is a carcinogen and difficult to degrade. This study examined the effect of different carriers on the degradation of 2,6‐dimethylaniline by a fluidized‐bed Fenton process. The six carriers were alumina dioxide (Al2O3), silica dioxide (SiO2), and black, white, brown and coloured gravels. The results revealed that differences in the composition of elements and the structures of each carrier have different effects on the oxidation of 2,6‐dimethylaniline. The carriers containing Ca were not suitable for use in the fluidized‐bed Fenton process. In contrast, Al2O3 and SiO2 were more efficient at removing 2,6‐dimethylaniline, and the pH value was almost stable. Moreover, 2,6‐dimethylanililne removal efficiency of Al2O3 was higher compared with the other carriers. Therefore, in this study, Al2O3 was an optimum carrier for the oxidation of 2,6‐dimethylaniline.

Application of Fenton Processes for Degradation of Aniline

Fenton process is one of advanced oxidation processes (AOPs) which are considered as alternative methods for treatment of non-biodegradable and toxic organic compounds. Fenton process has been widely used in the treatment of persistent organic compounds in water. In general, the mechanism of Fenton reaction included the formation of hydroxyl free radicals, which has E◦ of 2.8 V, that can oxidize and mineralize almost all the organic carbons to CO2 and H2O (Glaze et al., 1987), by the interaction of hydrogen peroxide with ferrous ions (Walling C., 1975). The Fenton’s reagent is generally occurred in acidic medium between pH 2 -4 (Rodriguez et al., 2003). The advantage of Fenton process is the complete destruction of contaminants to harmless compounds, for instance, carbon dioxide and water (Neyen E. et al., 2003). However, its application has been limited due to the generation of the excess amount of ferric hydroxide sludge that requires additional separation process and disposal (Chang P.H., 2004). Therefore, electro-Fenton (EF) process is developed for minimizing the disadvantages of conventional Fenton process. In the electro-Fenton method, the Fenton’s regent was utilized to produce hydroxyl radical in the electrolytic cell, and ferrous ion was regenerated via the reduction of ferric ion on the cathode (Zhang et al., 2007). The regenerated ferrous ion will react with hydrogen peroxide and produce more hydroxyl radicals that can destroy the target compounds. However, the electro-Fenton reaction still faces several obstacles that must be overcome first such as the formation of ferric hydroxide sludge. Therefore, the new method which can promote the ferrous ion regeneration was focused in this part of experiment. The efficiency of pollutant removal and the reduction of ferric hydroxide sludge can be improved by using UVradiation. The photoelectro-Fenton process involves the additional irradiation of the solution with UVA light. Due to the generation of additional hydroxyl radical from the regeneration of ferrous ion and the reaction of hydrogen peroxide that reacted with UV light, so-called photoelectro-Fenton process (Brillas et al., 2000). Under UV-vis irradiation, the overall