Sulfonamides (SAs) are common antibiotics for human and animals and frequently detected in water. Among SAs, sulfachloropyridazine (SCP), sulfamethoxazole (SMX), sulfadimethoxine (SDX) and sulfamethazine (SMT) are most commonly detected in water. In this study, electro-Fenton reaction was applied to treat SAs in water. Electro-Fenton can utilize cathodic reduction to produce H2O2. In addition, pyrite was used iron catalyst to enhance degradation of four SAs during electro-Fenton process. Electro-Fenton experiments were conducted using mixture of 20 mg/L of SCP, SMX, SDX and SMT in 500 mL of 0.05 M Na2SO4 at pH 3. Pt plate was used as anode and carbon nanotube (CNT)/teflon/carbon felt electrode was used as cathode, and O2 was injected at 0.5 L/min. By binding CNT and carbon felt, H2O2 production of the cathode increased up to 20.6 mg/L/hr/cm2. SAs were analyzed using HPLC. Table 1 shows the removal rate constants of 4 SAs after 1 hour of electro-Fenton reactions at various conditions. Compared to Fe2SO4, pyrite was acted as the efficient catalyst and showed the greater removal. It was found that 0.2 A was the optimal current. At 0.1 A, H2O2 generation was not sufficient for Fenton reaction. At high current, Fe(II) ion was oxidized on the anode. For pyrite concentration, 2 g/L of pyrite showed the greatest removal of SAs. Higher dosage of pyrite resulted into the excessive Fe(II) ion consuming OH radical. Four SAs did not show significant difference in removal efficiencies due to structure similarity. At optimal conditions, 43.0~49.0 % of SAs was removed in 1 hour. Energy consumption and electric energy per order (EEO) were calculated as 0.0037 kWh and 25.7 kWh m-3 order-1, respectively. Our results imply that pyrite was oxidized by O2 and Fe(II) ion was released to generate OH radical by Fenton reaction, resulting in effective oxidization of four SAs by OH radicals.

Degradation of sulfonamide antibiotics by electro-Fenton with heterogeneous iron catalysts

2019 Spring National Meeting

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