The Adsorption Affinity of N-Doped Biochar Might Play a Crucial Role in Peroxydisulfate Activation and Bisphenol a Oxidative Degradation

Abstract

Metal-free biochar as an efficient catalyst to activate persulfate (PS) and degrade organic contaminants has attracted great attention in advanced oxidation processes (AOPs), while, the role of biochar adsorption in the activation and oxidative decomposition process is important and still needed to be further clarified. In this study, nitrogen doped porous biochar derived from waste litchi branch was prepared as peroxydisulfate (PDS) activator for bisphenol A (BPA) degradation, in which the regulation behavior of biochar adsorption was evaluated on the base of phase distribution and PDS activation mechanism. Biochar obtained at 800 ℃ with N-doped and sodium carbonate added presented high specific surface area (821 m 2 /g), abundant nanopores and graphitic structure, and showed the best adsorption capacity and catalytic activity towards BPA. At the dosage of 0.15 g/L 800CN, 95% BPA can be completely degraded within 60 minutes with an apparent rate constant (k obs ) of 0.0483 min -1 . The identified active sites and reactive oxygen species as well as electrochemical tests suggested that both free radicals O 2 • - and •OH and non-radical pathways including 1 O 2 originated from C=O and surface electron transfer mechanisms were involved in BPA decomposition. In this study, the phase distribution analysis, reaction kinetics, biochar reuse experiments and activation mechanisms all confirmed that BPA adsorption on 800CN surface was an extreme crucial step for BPA oxidative degradation . This work not only presented an effective metal-free PDS activator, but also enables the deep insights into the regulation behavior of biochar adsorption on organics oxidative degradation.