Kinetics study on the oxidation of chlorophenols by permanganate

Abstract

A B S T R A C TThe kinetics of the oxidation of chlorophenols (CPs) by potassium permanganate was studied in the present study, along with the changes in oxidant dosage, pH, temperature, and real water matrices. The reactions between permanganate and three kinds of CPs, i.e. 4-chlorophenol (4-MCP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP), are second order overall and first-order with respect to each reactant. The degradation rates of the CPs increase with increasing permanganate dosage or temperature. pH plays an important role during permanganate oxidation. With the increase in pH from 4.0 to 10.0, the reaction rates of 4-MCP and 2,4-DCP decrease first and then increase, and finally decrease rapidly when pH > pK a , while the rates of 2,4,6-TCP decrease continuously. The degradation rates of the CPs are obviously higher in real water than in pure water. The reaction rate follows the order of 2,4,6-TCP > 2,4-DCP > 4-MCP under acidic conditions, and follows the reverse order under alkaline conditions in both pure water and real water.

Neutral Phenolic Contaminants Are Not Necessarily More Resistant to Permanganate Oxidation Than Their Dissociated Counterparts: Importance of Proton-Coupled Electron Transfer

“…By considering the change in the PCET mechanism with pH, eq can fit well the parabolic pH-dependent rate constants for the oxidation of phenols documented in the literature, ,,− as shown in Figure S6. Moreover, the goodness of fit [e.g., phenol, 3-chlorophenol (3-CP), 4-chlorophenol (4-CP), and pentachlorophenol (PCP)] in the present model (PCET model) is better than that in the acid–base speciation model and the proton-mediated model (Figure ).…”