Electro-Fenton process at mild pH using Fe(III)-EDDS as soluble catalyst and carbon felt as cathode

The feasibility of destruction of organic pollutants in water at near-neutral pH by homogeneous electro-Fenton (EF) process employing a soluble Fe(III)-EDDS complex as catalyst is demonstrated for the first time. The performance of the Fe(Ill)-EDDS-assisted EF process with carbon-felt or air-diffusion cathodes was evaluated from the degradation of butylated hydroxyanisole (BHA) in sulfate medium. The influence of applied current, pH and Fe(III):EDDS ratio and dosage on BHA decay and mineralization was related to the evolution of H2O2 and iron concentrations. Using Fe(III)-EDDS, up to 50% Fe(II) regeneration was achieved in 10 min, whereas only 23% was transformed using hydrated Fe3+. Almost total removal of BHA was achieved thanks to homogenous Fenton, heterogeneous Fenton with cathodically adsorbed Fe(III), and electrocatalysis. The mineralization partly corresponded to the gradual destruction of EDDS by hydroxyl radical (k(abs) = 5.22 x 10(9) M-1 s(-1)), and involved the formation of 5 oxidation and 6 dimerization or cyclization by-products.