Investigation of oxidation and mineralization of 1-naphthaleneacetic acid using Fenton processes

Abstract

In this study, the degradation and mineralization of 1-naphthaleneacetic acid (NAA) in aqueous solution was examined using Fenton processes. Various operating conditions were evaluated including pH and the concentrations of iron ions (Fe2+ and Fe3+) and hydrogen peroxide (H2O2). The highest COD removal efficiency was achieved at 0.5 mM:2 mM Fe2+:H2O2 ratio and 0.5 mM:2 mM Fe3+:H2O2 ratio at pH 3 for Fenton process (FP) and Fenton-like process (FLP), respectively. NAA degradation and mineralization exhibited pseudo-first-order kinetics while the depletion of H2O2 and Fe2+ or Fe3+ exhibited zero order kinetics during both processes in all experiments. 100% of NAA degradation proceeded via two distinctive kinetic regimes. The initial phase of the reaction was directly attributable to the Fenton reaction where in nearly all of the OH center dot were generated. This was followed by a slower degradation phase, which can be thought of as a series of Fenton-like reactions within a FP. In the FP, the initial phase lasted longer than in the FLP because the generation of OH center dot proceeded at slower rate; however, 100% degradation of NAA was achieved. The mineralization of NAA was 31% and 39% for FP and FLP, respectively. After 24 h, H2O2 was the limiting reagent for further mineralization of NAA intermediates present in the system.