Catalysts containing Fe and Mn from dewatered sludge showing enhanced electrocatalytic degradation of triclosan

Abstract

The present work demonstrates a simple one-step pyrolysis method for the synthesis of a catalytic sludge-based carbon (SBC) biochar containing Fe and Mn from dehydrated sludge with added KMnO4 and Fe(II). The electrocatalytic degradation of triclosan (TCS) in water was evaluated using an Fe/Mn-SBC cathode to promote a heterogeneous Fenton-like reaction. The catalyst generated at 500 °C exhibited an abundant porous structure and a relatively high surface area, and produced an electrode with better conductivity and electron diffusion. The presence of metal oxides changed the surface structure defects of this biochar and enhanced its catalytic performance while increasing the electrochemically active surface area by 72.68 mF/cm2 compared with plain SBC. TCS was degraded (91.3%) within 180 min by oxygen species generated in situ on an Fe/Mn-SBC cathode because the activation energy for oxygen reduction was lowered by 4.62 kJ/mol. The degradation of TCS followed pseudo first-order kinetics and was controlled by TCS diffusion and interfacial chemical reactions between adsorbed TCS and the electrode. Possible TCS degradation pathways were devised based on the main intermediates, and 1O2 was found to be more important than •OH radicals. Through toxicity test and prediction, the toxicity of degradation was gradually reduced. This study demonstrates a simple and ecofriendly method for the electrocatalytic degradation of organic pollutants.