Surface modified silver/magnetite nanocomposite activating hydrogen peroxide for efficient degradation of chlorophenols

Abstract

The mixed-valent magnetite (Fe₃O₄) played a critical role in H₂O₂-based Fenton-like system for the removal of chlorophenols, but high activity and cycle stability of the Fe₃O₄-based catalysts are still a huge challenge. Herein, a series of surface hydroxyl- and carboxyl-modified Ag⁰/Fe₃O₄ nanocomposite catalysts were prepared and used to activate H₂O₂ for degradation chlorophenols pollutants. Under the optimized condition, nearly 100% degradation ratio were achieved within 2-30 min for 2,4-dichlorophenol, 2,3-dichlorophenol, 3,4-dichlorophenol, 2,4,6-trichlorophenol, p-nitrophenol, and 98% degradation ratio for 2,5-dichlorophenol, 2,6-dichlorophenol and 3,5-dichlorophenol,. Moreover, wide pH applicability was obtained for the Ag⁰/Fe₃O₄-H₂O₂ system, where 95% degradation ratio of 2,4-dichlorophenol was still obtained at pH 6.0. The excellent activity of Ag⁰/Fe₃O₄ catalyst can be ascribed to the incorporation of Ag⁰ nanoparticles that accelerated the Fe(III)/Fe(II) transformation with the assistance of surface hydroxyl and carboxyl groups. Detailed mechanism study indicated a pseudo-second-order kinetic model, where the oxidative degradation and reductive degradation pathways coexisted in the system. The surface-modified Ag⁰/Fe₃O₄-H₂O₂ provide a practical catalyst system for the removal of phenol contaminants with high reaction rate, wide pH adaptability, and validity for a series of chlorophenols.

Keywords: Ag(0)/Fe(3)O(4) nanocomposite; Catalytic activation; Chlorophenols; Degradation; Surface hydroxyl and carboxy groups.