Removal of 17β-Estradiol Using Persulfate Synergistically Activated Using Heat and Ultraviolet Light

Abstract

Among all female sex hormones, 17β-estradiol (E2) has been most often detected in discharge water from animal farms. The objectives of this study were to evaluate the performance of UV/heat-activated persulfate to degrade E2 and the technical feasibility to use this system for treating real wastewater. As an individual persulfate (PS) homogeneous activator, UV-activated PS removed E2 better than using low heat (40 °C) and solar irradiation to activate PS. When both UV and heat (25–65 °C) were used to activate PS, the Arrhenius equation represented well the observed rate constant, with activation energy of 118.07 kJ mol−1. Inorganic ion concentrations increased the degradation rate. These ions included Cl− (3500 mg L−1), which increased rates by 18.1%, HCO3− (250 mg L−1) by 4.6%, and NO3− (5 mg L−1) by 7.9%. However, lesser impacts on degradation kinetics were observed at higher concentrations for all constituents due to SO4·− scavenging by the formed radicals such as Cl2·−, Cl·, HCO3·, CO3·−, and NO3·. The E2 degradation observed rate constant (kobs) was highest at pH 3. Although both synthetic wastewater and real wastewater showed inhibitory effects due to UV blocking from turbidity and the existence of the –COOH and –OH functional groups that acted as radical scavengers, E2 degradation was still observed. The overall results provided proof-of-concept that UV/heat-activated PS can be applied to treat E2 in wastewater containing a high organic content and can minimize the chemical and operating costs, as solar irradiation provides the heating source.