Large scale development of a light-enhanced fenton reaction by optimal experimental design

Photochemical advanced oxidation processes (AOP) for the treatment of waste waters containing biocidal or non-biodegradable organic compounds rely mainly on the production of a potent oxidizing agent, the hydroxyl radical. The Fenton's reagent, a mixture of hydrogen peroxide and ferrous ion, represents one possible source of hydroxyl radicals and it has been shown recently that degradation rates may be significantly enhanced by UV/visible irradiation. In this context, we have investigated the feasibility of a large scale application of the light-enhanced Fenton reaction to the treatment of a highly contaminated industrial waste water containing toxic aromatic amines (dimethyl anilines or xylidines) as the main pollutants. Following preliminary laboratory tests performed on the model compounds, 2,4- and 3.4-xylidines (200 mg/L, 2 L), experimentation on the industrial waste water at a large scale level (3000 mgC/L, 500 L) has been carried out using the experimental design methodology for the simulation and the evaluation of the effects of the two critical factors, hydrogen peroxide and ferrous ion concentrations. The light-enhanced Fenton reaction has been proven to be a most effective treatment process under acidic conditions and might be an alternative to adsorption of xylidines on activated carbon as used at present.