Rapid removal of tetrabromobisphenol A by α-Fe2O3-x@Graphene@Montmorillonite catalyst with oxygen vacancies through peroxymonosulfate activation: Role of halogen and α-hydroxyalkyl radicals

Schematic illustration of the activation mechanism and degradation process of TBBPA in α-Fe2O3-x@Graphene@Mt/PMS system. [Display omitted] •α-Fe2O3-x@Graphene@Mt exhibits superior conductivity and abundant oxygen vacancies.•TBBPA can be removed rapidly by α-Fe2O3-x@Graphene@Mt activated PMS.•The formation of halogen radicals contributes to catalytic oxidation of TBBPA.•The formation of alcohol radicals contributes to reductive degradation of TBBPA. We employed hydrolyzed iron-pillared montmorillonite/tetracycline complex (FeOOH-Mt-TC) as precursor to prepare iron oxide@Graphene@Montmorillonite composite (α-Fe2O3-x@Graphene@Mt) through pyrolysis strategy under nitrogen atmosphere. During the pyrolysis process, the involvement of hydrolyzed iron (FeOOH) and TC made the α-Fe2O3-x@Graphene@Mt composite have superior conductivity, higher percent of structural Fe(II) and abundant oxygen vacancies, resulting in highly-efficient degradation of tetrabromobisphenol A (TBBPA) in the presence of PMS. Meanwhile, O2•− played the leading role in the oxidation process when compared with •OH, SO4•− and 1O2. In addition, the released Br− from TBBPA and the addition of alcohol led to the formation of reactive halogen and α-hydroxyalkyl radicals, which contributed to the rapid removal of TBBPA. This study not only provided a novel strategy to prepare excellent iron-based catalysts for PMS activation, but also evaluated the application of reactive halogen and α-hydroxyalkyl radicals in the treatment of halogenated organic pollutants.