Fenton and Photofenton Oxidation of Aniline Derivatives in Water

Abstract

Aniline derivatives are dye intermediates with wide applications. Disposal of untreated effluent containing these derivatives is detrimental to the receiving water bodies. Hence, new and improved treatment methods are being investigated to effectively degrade and remove these harmful compounds from industrial effluents before disposal. In the present study, oxidation of some of the selected aniline derivatives viz. 2-Nitroaniline (2-NA), 3-Nitroanailine (3-NA), 4-Nitroaniline (4- NA), 2-Methoxyanailine (2-MA) and 4-Methoxyanailine (4-MA) using Fenton and photo-Fenton oxidation methods were carried out. Fenton's and Photo-Fenton oxidation process seems to be a simple and cost-effective method for degradation of organic compounds in effluents. However, iron is found to increase the cost of treatment. Hence, iron extracted from the laterite soil (LS) was evaluated as a catalyst in the above treatment techniques. Optimization of pH, hydrogen peroxide concentration and iron concentration was carried out for different initial concentrations of 2-NA, 3-NA, 4-NA, 2-MA and 4-MA in water using FeSO4 and iron extracted from laterite (LS) as a catalyst. The optimum pH obtained was 2.5 & 3 for the selected compounds. The optimum hydrogen peroxide concentration obtained was in the range of 3.5 mM – 5 mM and iron concentration of 0.05 mM for the maximum removal efficiencies at 0.5 mM of initial concentration. The corresponding Hydrogen Peroxide/Iron (H/F) ratio was in the range of 70-108 for Fenton’s oxidation process for the varied initial concentration of aniline derivatives in the range of 0.5 mM - 2.5 mM. The removal efficiency observed was 4-NA>2-NA>3-NA and 4- MA>2-MA. Removal efficiencies obtained for Photo-Fenton oxidation were 4-6% higher than the Fenton process. Kinetic studies were carried out for the initial concentration of 0.5 mM for both Fenton & Photo-Fenton oxidation processes using FeSO4 and iron extracted from laterite as sources of iron. It was found that kinetic rate constant was higher for Photo-Fenton oxidation process compare to the Fenton oxidation process. During Fenton and Photo-Fenton studies for a mixture of aniline derivatives, maximum removal efficiencies obtained were 92.3%, 86.2%, 94.7%, 98.1% and 89.7% respectively for 2-NA, 3-NA, 4-NA, 2-MA & 4-MA. Maximum removal efficiency was obtained for Photo-Fenton technique using FeSO4.