A new approach to 4-chlorophenol dechlorination on monometallic copper compared to its Cu/Fe bimetallic system

摘要

In this work, with very different mechanism from Cu/Fe bimetallic system, monometallic Cu-0 showed an unusually high reductive dechlorination reactivity for 4-chlorophenol (4-CP) in aqueous media. The Cu/Fe bimetallic system showed a typical indirect hydrogenation dechlorination with the main product of phenol, while the monometallic Cu-0 showed a direct electron reduction with the main, product of cyclohexanone. Cu-0 exhibited higher dechlorination activity. The aim of this work was to explore the reasons for the mechanism. Based on our experiments; the high degradation efficiency of monometallic Cu-0 should result from the conjugation between electron orbits of Cu-0 and large pi bond of the benzene ring of 4-CP. With this mechanism, phenol was also efficiently transformed to cyclohexanone by monometallic Cu-0. Although aliphatic chlorinated organic compounds are less chemically stable than aromatic chlorinated organics, Cu-0 cannot degrade aliphatic chlorinated organics, such as monochloroacetic acid (MCA) and dichloroacetic acid (DCA). Because no conjugation is existed between them. The conjugation reaction also depends on the purity of the copper surface, a clean, reactive surface of the metal was found to be very important. That is the reason of anions such as AcO-, SO42- inhibited the degradation. (C) 2016 Elsevier B.V. All rights reserved.