Highly Efficient Continuous-Flow Electro-Fenton Treatment of Antibiotic Wastewater Using a Double-Cathode System
Haifang Tang, Zuoyan Zhu, Qian Shang, Yanhong Tang, Danyu Zhang, Yi Du, Meijun Liu, Kai Yin, Chengbin Liu
Abstract
A simple, efficient, and environmentally friendly electro-Fenton (EF) process is highly demanded for EF practical application. Herein, a highly practical double-cathode EF system has been developed: (1) KOH-activated graphite felt (AGF) for H2O2 production and (2) FeOCl-modified carbon cloth (FeOCl/CC) for H2O2 activation. The H2O2 production at the AGF cathode reaches 3.4 mmol/L in 60 min (pH 3, −0.6 V vs Ag/AgCl), and the FeOCl/CC cathode shows an excellent H2O2 activation performance where the removal percentage of tetracycline (TC, a rising refractory organic pollutant) reaches 98.2% in 5 min ([H2O2] = 1.0 mmol/L, C0 = 10.0 mg/L, pH 3, and −0.8 V vs Ag/AgCl). The double-cathode EF system is proved by TC degradation. The removal percentage of TC achieves 96% in 20 min and total organic carbon (TOC) removal percentage reaches 92% in 2 h (C0 = 10.0 mg/L, pH 5, and −0.6 V vs Ag/AgCl) in a static system. Furthermore, the system is highly effective in a wide pH range from 3 to 7. Significantly, in the continuous-flow system, the TC degradation percentage reaches 95% within 1.5 h, the mineralization reaches 88% within 4 h (C0 = 10.0 mg/L, v = 4 mL/min, pH 5, and −0.6 V vs Ag/AgCl), and the performance remains highly stable even after prolonging for 15 h. The system has a high oxidative flux (1510 mg/(min m2)) and low energy consumption (45 kWh/(kg TOC)). Encouragingly, such a small-scale reactor (V = 100 mL, 4 mL/min) can treat 5.76 L of TC wastewater in one day. The toxicity of TC solution is remarkably reduced after EF treatment. This study would advance the practical application of an EF treatment process.