Enhanced degradation of perfluorooctanoic acid using dielectric barrier discharge with La/Ce-doped TiO2.

A synergistic system of dielectric barrier discharge (DBD) combined with La/Ce-TiO2 was developed to investigate the decomposition performance of the environmentally persistent perfluorooctanoic acid (PFOA). The La/Ce-TiO2 was modified by sol-gel method and characterized by XRD, SEM, and energy dispersive X-ray. The effects of PFOA concentration, applied voltage, initial pH, liquid conductivity, and additives on the removal rate of PFOA were explored. The results showed that the La/Ce-TiO2 exhibited excellent catalytic effects on PFOA degradation in DBD system. When the applied voltage, PFOA concentration, pH value, and solution volume were 75 V, 100 mg/L, 3.63, and 1000 mL, respectively, the removal efficiency of PFOA was up to 97.5% by adding La4Ce1-TiO2 in DBD. The corresponding defluorination ratio, TOC removal, and decomposition yield were 62.2%, 57.3%, and 37 g/kWh, respectively. Furthermore, five main intermediates including CF3(CF2)6H, CF3(CF2)5COOH, CF3(CF2)5COH, CF3(CF2)4COOH, and CF3CF2CF3 were identified with LC-MS, and the degradation pathways of PFOA were proposed. The degradation mechanisms revealed that hydroxyl radicals play a significant role in the degradation of PFOA in the synergistic system.