Activation of persulfate by EDTA-2K-derived nitrogen-doped porous carbons for organic contaminant removal: Radical and non-radical pathways

Nitrogen-doped porous carbons prepared from ethylenediaminetetraacetic acid dipotassium salt (EDTA-2K) were employed in combination with sodium persulfate (PS) for the catalytic removal of sulfamethoxazole (SMX). Almost complete removal (99.5%) of SMX was obtained with the optimum carbon prepared at 800 degrees C (NC800), which was attributed to its high surface area, good electrical conductivity, rich defects as well as doped carbonyl and nitrogen groups. The reaction mechanism was proposed to be a combination of both radical and non-radical pathways. (OH)-O-center dot, SO4 center dot-, O-2(center dot-) and O-1(2) as reactive oxidative species were involved in the reaction process based on quenching tests and electron spin resonance (ESR) measurements, while the non-radical pathway between PS and SMX with the assistance of NC800 also made a significant contribution as indicated from PS decomposition tests and linear sweep voltammetry (LSV) analysis. Adsorption played an important role in the reaction process, and this point was emphasized when interpreting the effects of quenchers and pH values. For potential practical applications of the NC800/PS system, experiments concerning catalyst stability, the catalytic removal of three other organic contaminants and SMX removal in real water matrices were also conducted.Y