Comparison of ultraviolet and heat-activated peroxymonosulfate processes for effective removal of natural organic matter: The case of humic acid

Abstract

In this study, humic acid (HA) removal using ultraviolet-activated peroxymonosulfate (UV/PMS) and heat-activated peroxymonosulfate (heat/PMS) processes was investigated. Under optimum conditions (UV/PMS: PMS dose 1.5 mM, 24 W UV power, pH 5, initial HA concentration 20 mg/L; heat/PMS: PMS dose 1 mM, T 80 degrees C, pH 3, initial HA concentration 20 mg/L), HA removal of 66.8% and 89.1% was achieved by UV/PMS and heat/ PMS, respectively. These optimized conditions were then applied to real wastewater (nanofiltration (NF) concentrate of leachate). In experimental studies with NF concentrate, the UV/PMS and heat/PMS processes achieved removal efficiencies of 80.6% and 42.2%, respectively. The chloride effect was evaluated in synthetic wastewater to simulate the NF concentrate. With the addition of 50 and 150 mM chloride, HA removal decreased from 66.8% to 40.7% and 38.5%, respectively, for heat/PMS, while it decreased from 89.1% to 78.3% and 77.6%, respectively, for UV/PMS. Quenching studies showed that hydroxyl radicals, singlet oxygen, and sulfate radicals contributed at rates of 42.5%, 30.4%, and 24.3%, respectively, in heat/PMS. In UV/PMS, hydroxyl radicals, singlet oxygen, and sulfate radicals contributed at rates of 79.5%, 11.4%, and 4.55%, respectively. UV/ PMS and heat/PMS required 93.5 kWh/m3 and 63.9 kWh/m3, respectively. Overall, UV/PMS demonstrated superior HA removal performance.