Non-radical process of the removal of bisphenol A via the activation of peroxymonosulfate by nitrogen and iron–copper co-doped biochar: the origination of singlet oxygen and the important role of oxygen vacancies

Abstract

In this study, nitrogen and iron–copper co-doped biochar was prepared and utilized to remove bisphenol A (BPA) from an aqueous solution via the activation of peroxymonosulfate (PMS) over a wide pH range. It was found that the entire degradation system was dominated by a complete non-radical process, where singlet oxygen played a major role and Cu(III) played a minor role, and oxygen vacancies and surface catalytic metals were the active sites responsible for their generation. Furthermore, it is PMS that originated singlet oxygen rather than dissolved oxygen or lattice oxygen. XRD, XPS and EPR analyses revealed that the introduction of nitrogen in the biochar composite promoted ferroferric oxide crystal growth and the formation of oxygen vacancies. The quantitative structure–activity relationship (QSAR) model indicated that the degradation rate of phenolic compounds in this catalytic system was related to the minimum value of charge on their carbon atom (q(C)_n), which also revealed that through the oxidation process, singlet oxygen could easily attack partially negatively charged carbon atoms in phenolic compounds.