Hollow sea-urchin-shaped carbon-anchored single-atom iron as dual-functional electro-Fenton catalysts for degrading refractory thiamphenicol with fast reaction kinetics in a wide pH range

Abstract

Narrow pH application range and tepid reaction kinetics greatly hinder the efficacy of heterogeneous Fenton and electro-Fenton technologies. Herein, a hollow sea-urchin-shaped carbon-anchored single-atom iron (SAFe@HSC) derived from metal organic framework has been developed as a dual-functional electro-Fenton catalyst for O2 reduction to H2O2 followed by in situ activation to •OH. Benefited by the unique structure and atomically dispersed iron, the electro-Fenton system exhibits fast reaction kinetics in a wide pH range from 3 to 11. For instance, 120.7 mmol gcatalyst−1 (7.5 mol gFe−1) H2O2 and 50.7 mmol gcatalyst−1 (3.1 mol gFe−1) •OH can be detected simultaneously at 60 min (20 mA cm−2 and pH 7). As a result, the mass kinetic constants of refractory thiamphenicol (TAP) degradation are as high as 4506 min−1 gFe−1 (pH 3), 4099 min−1 gFe−1 (pH 5), 4037 min−1 gFe−1 (pH 7), 2974 min−1 gFe−1 (pH 9), and 2595 min−1 gFe−1 (pH 11). The TAP removal efficiency in static flow process achieves nearly 100% within 40 min, showing a high total organic carbon (TOC) removal of 85% in 2 h (pH 7, 20 mA cm−2, C0 = 20 mg L−1, 1.5 mg of catalyst). It is the highest electro-Fenton activity among the reported catalysts for pollutant degradation at pH above 5. Furthermore, the TAP removal keeps 97% and the TOC removal reaches as high as 82.2% in the continuous-flow process (C0 = 20 mg L−1, pH 7, 20 mA cm−2, flow rate = 2 mL min−1). Moreover, only 1.5% Fe is leaked within 6 h. This study develops a highly efficient electro-Fenton catalyst for the treatment of organic wastewater.