Effective degradation of phenol via Fenton reaction over CuNiFe layered double hydroxides.

A series of CuNiFe layered double hydroxides (LDHs) with various Cu/Ni molar ratios were synthesized as catalysts for Fenton degradation of phenol. It is found that Cu, Cu, Ni, Ni and Fe are present on LDHs, owing to an electron transfer from Ni to Cu via metal-oxo-metal bridges. At lower Cu/Ni ratios, the highly dispersed MO octahedra and the electron donation effect of Ni facilitate such electron transfer and thus increase the percentage of Cu. The catalytic activity increases with the decrease in Cu/Ni ratio. The most active CuNiFe LDH can mineralize 98.9% phenol at ambient pH and less excessive HO dosage ( [Formula: see text] /M = 37). Even at the HO dosage close to the theoretical value, around 90% phenol can be mineralized. The structure-activity correlation indicates Cu which can readily react with HO to produce hydroxyl radicals may dominate the reaction. The regeneration of Cu could be achieved by the electron transfer between Cu and Ni in LDHs. Moreover, Fe can also act as Fenton-like active sites. The special structure of CuNiFe LDHs could offer surface-enriched and easily regenerated Cu species, leading to the complete mineralization of phenol and the efficient use of HO.