Mineralization of dinitrotoluenes in industrial wastewater by electro-activated persulfate oxidation

• The sulfate radicals are main oxidants responsible for the degradation of DNTs.
• The cathodic reduction of persulfate anions leads to formation of sulfate radicals.
• A synergistic effect is found by cooperating electrolysis and persulfate oxidation.
• Electrogenerated hydrogen peroxide makes some contribution for abatement of DNTs.

Decomposition of dinitrotoluenes (DNTs) in wastewater was conducted using electrolysis coupled with persulfate oxidation, wherein a synergistic effect was found. Experiments under batch-wise mode were performed to investigate the influence of various operation variables on the electrolytic behavior, such as electrode potential, electrolytic temperature, nitrogen/oxygen dosage, acidity of wastewater and persulfate anion concentration. It is remarkable that the dinitrotoluene pollutants could be nearly completely eliminated by means of electro-activated persulfate oxidation, in which sulfate radicals offer as principal oxidizing agents, of which amounts are significantly enhanced via injection of nitrogen gas. Additionally, electrogenerated hydrogen peroxide derived from cathodic reduction of oxygen, furnished mainly by anodic oxidation of water, would make minor contribution for elimination of DNTs. It is believed that the electro-activated persulfate process is potentially applied to deal with wastewater from toluene nitration processes.