Investigation into the Exothermic Laws of Degradation for o-Phenylenediamine-Containing Wastewater by the Fenton Reaction

Abstract

This study investigates the exothermic laws involved when Fenton’s reagent is employed in the degradation of organic substances to achieve positive energy in wastewater treatment. It analyzes the effects of Fenton’s reagent concentration, target pollutant (o-phenylenediamine) concentration, initial reaction temperature, and reaction time to evaluate the observed temperature elevation and its exothermic law for o-phenylenediamine degradation by Fenton’s reagent. It was found that the Fenton oxidation process is accompanied by a rapid temperature elevation of the solution, which was mainly influenced by the concentration of added hydrogen peroxide and the concentration of the target pollutant. More specifically, when [H2O2] is 0.15 mol·L−1, [Fe2+] is 10 mmol·L−1, and the reaction time is 30 min, the degradation efficiency of o-phenylenediamine (200 mL and 0.04 mol·L−1) was 95.87%, and the temperature increased by 9.2°C. It was also found that the heat produced during o-phenylenediamine degradation by Fenton’s reagent mainly originated from the exothermic reaction between the OH• radicals (and other reactive oxygen species) and o-phenylenediamine (and its intermediate product), in addition to the exothermic production of OH• free radicals and the consumption of other active groups.