Transformation characteristics of refractory pollutants in plugboard wastewater by an optimal electrocoagulation and electro-Fenton process

The treatment of the plugboard wastewater was performed by an optimal electrocoagulation and electro-Fenton. The organic components with suspended fractions accounting for 30% COD were preferably removed via electrocoagulation at initial 5 min. In contrast, the removal efficiency was increased to 76% with the addition of H2O2. The electrogenerated Fe2+ reacts with H2O2 and leads to the generation of OH, which is responsible for the higher COD removal. However, overdosage H2O2 will consume OH generated in the electro-Fenton process and lead to the low COD removal. The COD removal efficiency decreased with the increased pH. The concentration of Fe2+ ions was dependent on the solution pH, H2O2 dosage and current density. The changes of organic characteristics in coagulation and oxidation process were differenced and evaluated using gel permeation chromatography, fluorescence excitation–emission scans and Fourier transform infrared spectroscopy. The fraction of the wastewater with aromatic structure and large molecular weight was decomposed into aliphatic structure and small molecular weight fraction in the electro-Fenton process.

► Characteristics of pollutants in coagulation and Fenton removal were differenced.
► Pollutants removal by coagulation was preferred than by Fenton in initial time.
► An optimal ratio of Fe2+ to H2O2 was important.