Synthesis of γ-Cu2(OH)3Cl/LDH composites as Fenton catalysts to mineralize aniline: successive mineralization by hydroxyl and superoxide radicals

Abstract

A series of composites were synthesized through in situ fabrication of γ-Cu₂(OH)₃Cl and CuNiAl layered double hydroxide (LDH) and used as Fenton catalysts to mineralize aniline. They exhibit higher activity and efficiency than the two pure phases. The optimal composite can mineralize 95.1% aniline under circumneutral pH and exhibits good stability. HO˙ dominates the mineralization over γ-Cu₂(OH)₃Cl, whereas both HO˙ and O₂˙⁻ are responsible for mineralization over the composite and LDH. Cu⁺ and oxygen vacancies (OVs) are related to HO˙ and O₂˙⁻ generation, respectively. The in situ fabrication of two phases with similar layered structures and Cu-oxo octahedra may provoke structural disorder, leading to more OVs and thereby O₂˙⁻. HO˙ and O₂˙⁻ play different roles in aniline mineralization. HO˙ prefers to initially degrade aniline into carboxylic acids but is less reactive in further mineralizing carboxylic acids owing to the electrophilicity of HO˙, whereas O₂˙⁻ prefers to further mineralize carboxylic acids considering its strong nucleophilicity. Aniline mineralization occurs via denitrification and deamination routes. The γ-Cu₂(OH)₃Cl/LDH composite could combine favorable characteristics of both phases, offering more HO˙ and O₂˙⁻ to allow for the successive mineralization of refractory organic pollutants.