Abstract
This paper provides a comparative study of different photochemical oxidation processes and a detailed characterization of the by-products of diesel oil degradation performed using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS). Diesel degradation was conducted in a photolytic reactor using UV, H2O2, UV/H2O2, O3 or O3/UV. The best conditions for each process were obtained applying multivariate analysis and the experimental results indicated that the O3/UV process was the most feasible for the treatment of wastewater containing diesel fuel, with a degradation percentage of > 90%. Almost complete degradation of the aromatics was achieved. Phenolic compounds were identified as by-products of the diesel samples treated with the UV, H2O2, O3 and O3/UV processes. Besides the phenolic compounds, other by-products identified included carboxylic acids and ethers in the UV/peroxide treatment, ethers in the UV irradiation treatment and ketones in the ozone treatment.
Highlights
Petroleum pollutants and their derivatives are discharged daily into the environment as a consequence of several processes, such as the extraction, exploration and transportation of these products.[1]
Photooxidation has been extensively applied in petroleum degradation. 2,7-10 Advanced oxidation processes are based on the enhanced formation of hydroxyl radicals,[11] which are highly reactive and able to react with practically all classes of organic compounds,[12] resulting in complete mineralization of these compounds or their conversion into less aggressive products.[11]
The objective of this study was to investigate the application of five photochemical oxidation processes: direct photolysis (UV), peroxide (H2O2), UV/H2O2, ozonation (O3) and O3/UV for the treatment of waters contaminated by diesel oil and to obtain a detailed characterization of the by-products of diesel oil degradation
Summary
Petroleum pollutants and their derivatives are discharged daily into the environment as a consequence of several processes, such as the extraction, exploration and transportation of these products.[1]. 2,7-10 Advanced oxidation processes are based on the enhanced formation of hydroxyl radicals,[11] which are highly reactive and able to react with practically all classes of organic compounds,[12] resulting in complete mineralization of these compounds or their conversion into less aggressive products.[11] Hydrogen peroxide, for example, is a strong oxidant usually applied, among other purposes, to reduce the levels of pollutants present in wastewater. The use of H2O2 becomes more effective when it acts in conjunction with energy sources capable of dissociating it to generate hydroxyl radicals.[3] Ozone is widely used as an oxidant and disinfectant in water treatment. The O3/UV process is more complex than the previously described technique, since hydroxyl radicals are produced through different reaction pathways.[14,15]
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