Kinetic Modeling of Toxicity Evolution during Phenol Oxidation

Abstract

A previously proposed lumped pseudokinetic model has been improved and applied to analyze the literature toxicity evolution data for phenol oxidation using different abatement technologies, such as electrochemical (EC) treatment, photocatalysis (PC), Fenton’s reagent (FR), and catalytic wet oxidation (CWO). It has been considered that phenol, P, reacts to a lumped intermediate species I, and the latter reacts to a lumped species D. In this serial scheme, P→r1I→r2D, all species can contribute to the toxicity of the aqueous sample. The literature toxicity data found for the oxidation of phenol were analyzed by this model considering first-order kinetics for both reactions in the serial scheme. The ratios of effective nominal concentrations, EC50(P)/EC50(I) and EC50(P)/EC50(D), were calculated from the fitting procedure. Values higher than unity were obtained in some cases, indicating that compounds more toxic than the parent pollutant are produced. Also, the pseudokinetic constants for the first and second reactions in the scheme were estimated. The lumping proposed adequately explains the literature data analyzed.