Treatment of high strength hexamine-containing wastewater by Electro-Fenton method

A novel Electro-Fenton (EF-Fere) method, applied H2O2 and electrogenerated ferrous ion, was investigated for treating the hexamine-containing wastewat er. The performance of Fe2+ generation in the electrolytic system was first evaluated, including the factors of the cathode material, initial pH, init ial ferric concentration (Fe-i), and current density. When initial pH excee ded 2.5, the current efficiency dramatically decreased, which was due to th e formation of Fe(OH)(3). Between 3000 and 10,000 mg/l of Fe-i, the initial current efficiency of Fe2+ generation was almost constant (85-87%), which dropped sharply to 39% at 1000 mg/l. In EF-Fere experiments, the COD remova l efficiency attained above 94% after 5 h of reaction. The relationship bet ween the temperature, dissolved oxygen, and COD was discussed. The changes in hexamine and its oxidation intermediates (methanol, formaldahyde, format e, ammonium and nitrate) during the reaction were also investigated. Three additional experiments using H2O2/Fe2+, H2O2/Fe3+, and direct electrolysis were also conducted to treat the hexamine-containing wastewater for compari son. The results showed that the EF-Fere method was the most efficient. (C) 1998 Elsevier Science Ltd. All rights reserved.