Enhanced degradation of triclosan in heterogeneous E-Fenton process with MOF-derived hierarchical Mn/Fe@PC modified cathode

Abstract

Mn/Fe@porous carbon (PC) was successfully fabricated through a simple carbonization of Mn-doped MIL-53(Fe) precursor and used as cathode modification in hydroxyl radical (OH) based heterogeneous electro-Fenton (hetero-EF) process for triclosan (TCS) degradation. With co-doping of bimetal (Mn and Fe) in porous carbon, Mn/Fe@PC could markedly enhance the electrocatalysis with low oxygen reduction potential, high electrochemical active area and low resistance. Mn/Fe@PC modified cathode showed high electrocatalytic activity, great stability and low energy consumption (1.92 kWh m−1 and 0.63 kWh log−1 m−3) for TCS degradation over a wide pH range. The complete TCS degradation within 120 min and a 56.9 ± 2.0% TOC removal within 240 min were achieved under the condition of current 40 mA and initial pH 3. Based on the CV curves, the more negative reductive peak of Fe and Mn revealed the kinetically beneficial regeneration of FeII/MnII/III in Mn/Fe@PC. The electron transfer between FeII/III and MnII/III/IV, together with the direct regeneration of FeII/MnII/III on the cathode, could markedly promote the utilization of H2O2, eventually leading to facilitating TCS degradation. According to the GC–MS intermediates, the possible TCS degradation pathway was deduced, including hydroxylation and dehalogenation attacked by OH. Furthermore, the TCS degradation experiments were also performed in different water matrix including river water, tap water and municipal sewage, indicating the feasibility of the TCS degradation in actual waters with Mn/Fe@PC-CP cathode in hetero-EF process. The toxicity analysis indicated that the hetero-EF process could achieve the TCS degradation and toxicity reducing.