The adsorption affinity of N-doped biochar plays a crucial role in peroxydisulfate activation and bisphenol A oxidative degradation

Metal-free biochar to activate persulfate and degrade organic contaminants has attracted great attention in advanced oxidation processes, while the role of biochar adsorption in the activation and oxidative decomposition process still needed to be further clarified. In this study, nitrogen-doped porous biochar derived from a waste litchi branch was prepared as a peroxydisulfate (PDS) activator for bisphenol A (BPA) degradation, in which the regulation behavior of biochar adsorption was evaluated on the basis of phase distribution and PDS activation mechanism. N-doped biochar obtained at 800 degrees C with urea and sodium bicarbonate added presented a high specific surface area (821 m(2)/g), abundant nanopores, and a graphitic structure, and showed the best adsorption capacity and catalytic activity toward BPA. At a dosage of 0.15 g/L NBC-800, 95% BPA can be completely degraded within 60 min 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 center dot(-) and center dot OH and nonradical pathways including O-1(2) originated from C = O and surface electron-transfer mechanisms were involved in BPA decomposition. The experiments and activation mechanisms all confirmed that BPA adsorption on the NBC-800 surface was an extremely crucial step for BPA oxidative degradation.

Automated summary

Metal-free biochar has been widely studied as an activator for the degradation of organic contaminants. In this study, nitrogen-doped porous biochar derived from waste litchi branches was used as a peroxydisulfate activator for the degradation of bisphenol A. The results showed that the biochar had excellent adsorption capacity and catalytic activity towards BPA. The study also revealed the active species and reaction mechanism involved in the oxidative decomposition of BPA, confirming that BPA adsorption is a crucial step in the process.