A comparative study of the removal of 3-indolebutyric acid using advanced oxidation processes.

In this study, advanced oxidation technologies, namely Fenton Process (FP), Fenton-Like Process (FLP), ozonation (O3) and O3/H2O2 processes, were applied to synthetic wastewater containing 3-indolebutyric acid (IBA). The effectiveness of each process was investigated at different pH values, Fe(+2), Fe(+3), O3 and H2O2 concentrations with respect to the removal efficiencies for chemical oxygen demand (COD) and total organic carbon (TOC). The best removal efficiencies were seen at pH 3 and 2 mM Fe concentration in both FP and FLP, in which the optimum H2O2 concentrations were 6 mM for FP and 10 mM for FLP. Optimum process conditions were pH 12 for the O3 process, pH 9 for the O3/H2O2 process and 1:1 O3/H2O2 molar ratio. The highest COD removal efficiency was 86 percent, obtained in the O3/H2O2 process and the highest TOC removal efficiency was obtained at 77 percent in the FP.

Advanced oxidation and mineralization of 3-indole butyric acid (IBA) by Fenton and Fenton-like processes.

The degradation and mineralization of 3-indole butyric acid (IBA) in aqueous solution was examined using Fenton and Fenton-like processes. Various operating conditions were evaluated including pH and the concentrations of iron ions (Fe(2+) and Fe(3+)) and hydrogen peroxide (H(2)O(2)). The highest COD removal efficiency was achieved at 0.2 mM/0.6 mM Fe(2+)/H(2)O(2) ratio and 0.2 mM/1.0 mM Fe(3+)/H(2)O(2) ratio at pH 3 for Fenton and Fenton-like processes, respectively. IBA degradation and mineralization exhibited pseudo-first-order kinetics while the depletion of H(2)O(2) and Fe(2+) or Fe(3+) exhibited zero-order kinetics during both processes in all experiments. 97% of IBA degradation proceeded via two distinctive kinetic regimes. The initial phase of the reaction was directly attributable to the Fenton reaction wherein nearly all of the OH radicals were generated. This was followed by a slower degradation phase, which can be thought of as a series of Fenton-like reactions within a Fenton process. In the Fenton-like process, the initial phase lasted longer than in the Fenton process because the generation of OH radicals proceeded at slower rate; however, 98% degradation of IBA was achieved. The mineralization of IBA was 16.2% and 50% for Fenton and Fenton-like processes, respectively. After 24 h, H(2)O(2) was the limiting reagent for further mineralization of IBA intermediates present in the system. The results of the study showed that Fenton Process may be more useful when only removal of IBA is required and mineralization is unnecessary. But if mineralization of IBA is needed, Fenton-like process gains more important than Fenton Process due to its mineralization efficiency.