Heterogeneous and homogeneous Fenton processes using activated carbon for the removal of the herbicide amitrole from water

Abstract

The study objective was to investigate the removal of amitrole (AMT) by oxidation using the decomposition of hydrogen peroxide in heterogeneous and homogeneous Fenton reactions. For this purpose, an activated carbon cloth was used to prepare supported iron catalysts with different iron salts (sulfate, acetate and nitrate) and iron metal loadings. Homogeneous Fenton reactions were carried out by using iron sulfate or acetate in the absence or presence of the activated carbon cloth. In the heterogeneous Fenton reaction, the amounts of TOC (total organic carbon) and AMT removed depended on the iron metal loading and the Fe/H2O2 molar ratio; iron leaching was very low. The highest AMT degradation (∼90%) was achieved with the homogeneous Fenton reaction using FeSO4 in the presence of the activated carbon cloth, which may be due to a synergic effect between activated carbon and iron salt; with this procedure, ∼60% of the TOC was removed. The synergic effect was not observed when iron acetate was used as homogeneous catalyst. The presence of sulfate ions favored the oxidation of AMT to urazole. Nitrate and ammonium ions were observed but at negligible concentrations.