Ionizing radiation based advanced oxidation process for reactive orange 122 dye degradation and kinetics studies

Abstract

Abstract In the current study, the degradation of reactive orange 122 (RO 122) dye was carried out under UV and gamma irradiation in presence of H2O2. The effect of variables such as UV exposure time, gamma-ray absorbed dose, initial concentration of dye and oxidant dose were investigated. The removal of 64.10, 58.84 and 55.46 (%) was observed for 50, 100 and 150 (mg/L) dye concentrations, respectively using UV radiation time of 150 (min). The degradation was enhanced to 80.39, 69.95 and 67.01 (%) when UV radiation was employed in the presence of H2O2 (0.5 mL/L) for above concentrations respectively. The degradation was further improved to 97, 92.54 and 81.32 (%) using 5 kGy absorbed dose along with H2O2 (0.5 mL/L). The reduction in chemical oxygen demand (COD) was 77, 64 and 57 (%) using UV/H2O2 (0.5 mL/L), while 63, 56 and 53 (%) in case of gamma/H2O2 for aforementioned concentrations. The removal efficiency (G-value), dose constants (k), dose indispensable for 50, 90 and 99 (%) degradation (D 0.5, D 0.90, and D 0.99) after the treatment with gamma radiation were determined. The G-value was noted as 0.46–0.0711 for 50–150 mg/L dye concentration for gamma irradiated samples which improved to 0.57–0.1204 for above mentioned concentrations in presence of H2O2. The FTIR analysis showed that all the peaks were disappeared using gamma/H2O2 at 5 kGy absorbed dose except a minor peak of −CO stretching. The degradation mechanism of dye followed pseudo-first-order kinetics. A significant decrease in peak area was observed by the HPLC analysis after treating the dye samples with gamma/H2O2 (0.5 mL/L) at absorbed dose of 5 kGy which has proven the process efficiency for dye degradation.