The mineralization ability of a chloride-resistant γ-Cu2(OH)3Cl Fenton catalyst: effects of the cation type, salt concentration and organic pollutants

Abstract

A chloride-resistant heterogeneous Fenton catalyst γ-Cu₂(OH)₃Cl is used to mineralize phenol and other aromatic organics (bisphenol A, salicylic acid and aniline) in saline solutions with different salts (MgCl₂, CaCl₂, NaCl and KCl) and concentrations (1000–15 000 mg L⁻¹). The effects of the cation type, salt concentration and organic pollutants on the mineralization activity were investigated. The mineralization activity of γ-Cu₂(OH)₃Cl is improved in saline solutions due to the enhanced electron transfer from H₂O₂ to the catalyst induced by chloride. The cation type has little influence on such electron transfer but significantly affects the zeta potential of γ-Cu₂(OH)₃Cl in saline solutions. The order of zeta potential is consistent with that of the activity: MgCl₂ > CaCl₂ > NaCl > KCl, because of the less aggregated catalyst particles and the more favorable adsorption of reactants on the positively charged catalyst surface. The inverse order of the zeta potential with the classic theory is ascribed to the covalent bonding between hydroxyls in γ-Cu₂(OH)₃Cl and Ca²⁺ or Mg²⁺, the strong ion pairing between divalent cations and chloride, and the highly hydrated cations. With the increased salt concentration, the mineralization activity increases followed by decreasing and reaching a plateau, because the promotion of chloride may reach saturation at a low chloride concentration whereas the further increase of chloride causes a significantly reduced zeta potential. The mineralization of bisphenol A shows the greatest enhancement in saline solutions, due to its salting-out effect.