Theoretical-experimental study of the advanced oxidative process using peracetic acid and solar radiation: Removal efficiency and thermodynamic elucidation of radical formation processes

Advanced Oxidative Processes (AOPs) are efficient methods of treating industrial effluents specially to dyes, and therefore, there is great interest in the development of new methods that can contribute to the degradation of complex contaminants. In this work, peracetic acid (PAA) photolysed by solar radiation was used for the degradation of the methylene blue dye and the following factors were evaluated: PAA concentration, pH, temperature, dose of solar radiation and isolated action of the PAA constituents. The results obtained demonstrated that the concentration of 28.6 mmol L-1 of PAA showed dye degradation efficiency of 77.5% in the assay without radiation and reached 98.5% with a solar radiation with a dose of 61905.95 Wminm- 2. Through theoretical calculations it was possible to determine the values of bond dissociation enthalpy (BDE) which showed that the formation of the hydroxyl radical by PAA requires less energy (46.42 kcal mol-1). Higher energies are required for H2O2 (50.12 kcal mol-1) and acetic acid (109.68 kcal mol- 1). Thus, the formation of the hydroxyl radical in the presence of PAA occurs more easily and there is the increase in temperature which was not observed for isolated reagents H2O2 and acetic acid.