Advanced Oxidation of Trace Organics in Water by Hydrogen Peroxide Solar Photolysis

Abstract

Solar-UV/H2O2 advanced oxidation for destruction of trace organics was investigated under a variety of operating conditions in homogeneous, laboratory-scale batch reactor experiments. Fluorescein and p-cresol were selected as representative targets in the experiments. Half times for degradation of p-cresol ranged between 500 min with 2 mM H2O2 and 20 min with 50 mM H2O2 during high-solar irradiance experiments (around noon on July 15th). A kinetic model, previously developed for monochromatic light, was adapted for use with solar UV irradiance, using (i) calculated ground-level solar spectral irradiance for the date and time of the experiments and (ii) wavelength-dependent light attenuation in the reaction mixture. The model accurately represents experimental data without adjustable parameters. Model output included the time-dependent pH arising from complete mineralization of the targets. Observed radical scavenging effects were correctly predicted by the kinetic model. Contaminant transformation was also measured in a municipal secondary wastewater effluent matrix. Here, 2-D fluorescence spectroscopy was used as a measure of the time-dependent bulk organic characteristics in treated wastewater. Results indicated that solar-UV/H2O2 advanced oxidation is capable of eliminating or drastically reducing the concentrations of organic constituents that remain in conventionally treated municipal wastewater effluent.