Abstract
There is significant environmental concern about chlorinated organic compounds (COCs) in wastewater, surface water, and groundwater due to their low biodegradability and high persistence. In this work, 1,2,4-trichlorobenzene (124-TCB) was selected as a model compound to study its abatement using wet peroxide oxidation at neutral pH with goethite as a heterogeneous catalyst, which was enhanced with visible monochromatic light-emitting diode (LED) light (470 nm). A systematic study of the main operating variables (oxidant and catalyst concentration and irradiance) was accomplished to investigate their influence in the abatement of 124-TCB in water. The reaction was carried out in a well-mixed reactor of glass irradiated by a visible LED light. The hydrogen peroxide concentration was tested from 0 to 18 mM, the goethite concentration within the range 0.1–1.0 g·L−1 and the irradiance from 0.10 to 0.24 W·cm−2 at neutral pH. It was found that this oxidation method is a very efficient technique to abate 124-TCB, reaching a pollutant conversion of 0.9 when using 0.1 g·L−1 of goethite, 18 mM of H2O2, and 0.24 of W·cm−2. Moreover, the system performance was evaluated using the photonic efficiency (ratio of the moles of 124-TCB abated and the moles of photons arriving at the reactor window). The maximum photonic efficiencies were obtained using the lowest lamp powers and moderate to high catalyst loads.
Highlights
The presence of chlorinated organic compounds (COCs) in wastewater, surface water, and groundwater is a significant environmental issue
It was proved that goethite intensified by VIS light-emitting diode (LED) light is an effective system for the catalytic wet peroxide oxidation (CWPO) of 124-TCB
This contaminant was selected as a model compound of COC that are commonly found as pollutants in the aqueous phase
Summary
The presence of chlorinated organic compounds (COCs) in wastewater, surface water, and groundwater is a significant environmental issue. Framework Directive (Directive 2000/60/EC), several COCs have been added in the last two decades to the list of substances to be monitored, encouraging limiting their production and use This list comprises pollutants as 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,2dichlorobenzene, 1,2-dichloroethane, 1,4-dichlorobenzene, 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, carbon tetrachloride, chlorine, chlorobenzene, pentachlorobenzene, chloroform, dichloromethane, dioxins and furans, hexachlorobenzene, hexachlorobutadiene, hexachlorocyclohexane, pentachlorophenol, tetrachloroethylene, trichlorobenzene, trichloroethylene, and vinyl chloride [1]. Due to their extensive use as wood preservatives, pesticide precursors, solvents, hydraulic fluids, dielectric oil, dyes, and other materials [2,3,4,5,6,7], these COCs still pose a risk for the water quality.
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