Removal of propham from water by using electro-Fenton technology: kinetics and mechanism

The removal of a carbamate herbicide, propham, from aqueous solution has been carried out by the electro-Fenton process. Hydroxyl radical, a strong oxidizing agent, was generated catalytically and used for the oxidation of propham aqueous solutions. The degradation kinetics of propham evidenced a pseudo-first order degradation. The absolute rate constant of second order reaction kinetics between propham and ()OH was determined as (2.2+/-0.10)x10(9)m(-1)s(-1). The mineralization of propham was followed by the organic carbon (TOC) removal. The optimal Fe(3+) concentration was found as 0.5mM at 300mA. The 94% of initial TOC of 0.25mM propham solution was removed in 8h at the optimal conditions by using the cathode area to solution volume ratio of 3.33dm(-1). The maximum mineralization current efficiency values were obtained at 60mA in the presence of 0.5mM Fe(3+). During the electro-Fenton treatment, several degradation products were formed. These intermediates were identified by using high performance liquid chromatography, liquid chromatography-mass spectrometry, gas chromatography-mass spectrometry and ion chromatography analysis. The identified by-products allowed proposing a pathway for the propham mineralization.