19The use of soluble bio-based organic substances (SBO) obtained from urban wastes to 20 expand the pH region where the photo-Fenton process can be applied has been
Highlights
40The effect of operational variables on the photo-Fenton process has been studied.
41Surface response methodology has been applied for this purpose.
In this work, analysis of excitation-emission-matrices (EEM) has been employed to gain further insight into the characterization of humic like substances (HLS) obtained from urban wastes (soluble bio-organic substances, SBOs). In particular, complexation of these substances with iron and changes along a photo-Fenton process have been studied. Recorded EEMs were decomposed by using parallel factor analysis (PARAFAC). Three fluorescent components were identified by PARAFAC modeling of the entire set of SBO solutions studied. The EEM peak locations (λ/λ) of these components were 310-330 nm/400-420 nm (C1), 340-360 nm/450-500 nm (C2), and 285 nm/335-380 nm (C3). Slight variations of the maximum position of each component with the solution pH were observed. The interaction of SBO with Fe(iii) was characterized by determining the stability constants of the components with Fe(iii) at different pH values, which were in the order of magnitude of the ones reported for humic substances and reached their highest values at pH = 5. Photochemical experiments employing SBO and Fe(iii), with and without HO, showed pH-dependent trends for the evolution of the modeled components, which exhibited a strong correlation with the efficiency reported for the photo-Fenton processes in the presence of SBO at different pH values.
A methodology combining experimental design methodology, liquid chromatography, excitation emission matrixes (EEM) and bioassays has been applied to study the performance of O3 and O3/UVA-vis in the treatment of a mixture of eight phenolic pollutants. An experimental design methodology based on Doehlert matrixes was employed to determine the effect of pH (between 3 and 12), ozone dosage (02-1.0 g/h) and initial concentration of the pollutants (1-6 mg/L each). The following conclusions were obtained: a) acidic pH and low O3 dosage resulted in an inefficient process, b) increasing pH and O3 amount produced an enhancement of the reaction, and c) 2 interaction of basic pH and high amounts of ozone decreased the efficiency of the process. The combination of O3/UVA-vis was able to enhance ozonation in those experimental regions were this reagent was less efficient, namely low pH and low ozone dosages. The application of EEM-PARAFAC showed four components, corresponding to the parent pollutants and three different groups of reaction product and its evolution with time. Bioassys indicated important detoxification (from 100% to less than 30% after 1 min of treatment with initial pollutant concentration of 6 mg/L, pH = 9 and ozone dosage of 0.8 g/h) according to the studied methods (D. magna and P. subcapitata). Also estrogenic activity and dioxin-like behavior were significantly decreased.
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