Removal of clomazone herbicide from a synthetic effluent by electrocoagulation.

Abstract

The aim of this work was to investigate the kinetics of removal of clomazone herbicide from an aqueous solution by electrocoagulation. The experiments were performed in a cylindrical batch reactor with six aluminum electrodes in monopolar mode, arranged in series and connected to a digital DC power. The aqueous solution (tap water + clomazone) with initial pH close to 7.9 was always treated at ambient temperature (≈20 °C) and atmospheric pressure for 5,400 s. For a confidence level of 95% the rate constant of electrocoagulation and the efficiency of removal of clomazone at equilibrium were 2.1 × 10(-3) ± 0.5 × 10(-3) s(-1) and 97.7 ± 2.2%, respectively. The final chemical oxygen demand was 88% lower than that measured initially, while turbidity and apparent color were totally removed from the synthetic solution at a rate close to that of formation of aluminum hydroxides. Some reaction intermediates, such as benzonitrile-2-chloro and 2-chloro-hex-2,4-diene-1,6-dioic-acid determined by gas chromatography mass spectrometry (GC-MS) analysis, explain the ratio of equilibrium to initial total organic carbon approximately between 0.6 and 0.8 at a probability of 95%.