Oxidation of 4-chlorophenol in a heterogeneous zero valent iron/H 2O 2 Fenton-like system: Kinetic, pathway and effect factors

Abstract

In the present study, degradation of 4-chlorophenol (4CP) in a heterogeneous zero valent iron (ZVI)/H 2O 2 system was investigated. Initial pH was proven to have significant effect on the degradation and lower pH brought faster degradation rate. When initial pH was 4, two-stage first-order degradation kinetic of 4CP could be applied very well in all experiments. The two-stage kinetic is composed of an initial slow degradation stage (first-stage) and a followed rapid degradation stage (second-stage), where kinetic constant ( k obs) of the latter stage was one magnitude larger than that of the former stage. In order to investigate mechanism and degradation pathways, variation of H 2O 2 decomposition, iron transformation and intermediates were studied. As a result, a scheme of 4CP degradation pathways in ZVI/H 2O 2 system was proposed and two pathways—4CC pathway (attacking by hydroxyl radical ( OH)) and ortho-parachlorophenolperoxyl radicals (ClPP ) pathway (participating by O 2) were expected to happen in the system. Both pathways would finally lead to the production of low molecule aliphatic organic acid.