Ultraviolet radiation/persulfate/hydrogen peroxide treatment system for the degradation of acid blue 80 dye from a batch flow chemical reactor: effects of operational parameters, mineralization, energy consumption, and kinetic studies

Abstract

This study offers a comprehensive investigation into the efficiency of the degradation of acid blue 80 (AB80) dye by utilizing a system that uses ultraviolet (UV) radiation combined with hydrogen peroxide (H2O2) and persulfate (PS) oxidants (UV/PS/H2O2). The degradation reactions were performed under different PS and H2O2 concentrations, initial AB80 dye concentrations, pH values, UV intensities, and contact times. The results revealed that the UV/H2O2 system provided the best performance at a pH of 5, while the best performance for the UV/PS and UV/PS/H2O2 systems was obtained at a pH of 7. In addition, 15 mmol was found to be the optimum concentration for both oxidants. The efficiency of the combined process of UV/PS/H2O2 was higher than those of the other two processes, UV/PS and UV/H2O2, which was 98.2% for a dye concentration of 25 mg/L. Furthermore, the five-day biochemical oxygen demand/chemical oxygen demand (BOD5/COD) ratios at the beginning and end of the UV/ PS/H2O2 process were 0.19 and 0.52, respectively, indicating the conversion of nonbiodegradable dye molecules to biodegradable compounds. A toxicity test was performed using the bioassay method with Daphnia magna, with a 90% reduction in toxicity was observed for the effluent. The 50% lethal concentration (LC50) was found to be 4.7 mg/L for the dye solution. The results also revealed that the degradation data adhere to pseudo-firstorder kinetics, and the reaction rate constant was higher for the UV/PS/H2O2 system than for the other systems. The rate of mineralization by this process was 0.92. Scavenging studies also showed that both sulfate (SO4-) and hydroxyl (OH) radicals played an important role in the degradation process. The energy consumption in the UV/H2O2, UV/PS, and UV/PS/H2O2 processes was 61, 47.8, and 20.8 kWh/m(3), respectively. In conclusion, UV/PS/H2O2 is an effective and applicable process for the treatment of dyes in wastewater, particularly when the medium is neutral.