Fluorescence spectroscopic characterization of DOM fractions isolated from a filtered river water after ozonation and catalytic ozonation

Abstract

Fluorescence spectra were applied to investigate the structural changes of four dominant dissolved natural organic matter (DOM) fractions of a filtered river water before and after ozonation and catalytic ozonation. The ozonation and catalytic ozonation with synthetic goethite (FeOOH) and cerium dioxide (CeO 2 ) were carried out under normal conditions, i.e. pH 7, reaction time of 10 min, and ozone/DOC ratio of about 1. The fluorescence spectra were recorded at both excitation-emission matrix (EEM) and synchronous scanning modes. EEM results reveal that ozonation of these DOM fractions causes a significant decrease of the aromaticity of humic-like structures and an increase of electron withdrawing groups, e.g., carboxylic groups. The catalysts can further improve the destruction of the humic-like structures in catalytic ozonation. Synchronous spectra reveal that ozonation of hydrophobic acid and hydrophilic acid (HIA) yields a significant amount of by-products with low aromaticity and low molecular weight. Catalytic ozonation enhances substantially the formation of these by-products from HIA and improves the destruction of highly polycyclic aromatic structures for all examined DOM fractions.

Fate of natural organic matter at a full-scale Drinking Water Treatment Plant in Greece

“…Various studies revealed that the fluorescence upon oxidation depends on the nature of NOM and ozone dosage. Similarly to our results, Zhang et al (2008) also reported a reduction of the intensity at λ 280, 380, and 460 nm in river water during oxidative processes indicative of significant destruction of aromatic structures associated with generation of carbohydrates. Rodríguez et al (2014b) reported that humic acids presented an increase in fluorescence at low to moderate dosage of ozone, whereas fulvic acids showed a reduction in fluorescence regardless the ozone applied.…”

“…The third peak at λ em ∼330 nm, which has the highest intensity, represents more complex structures, such as substituted aromatic rings and compounds of higher MW. At λ em ∼465 nm, a shoulder peak, which corresponds to high MW humic materials and aromatic structures with high degree of conjugation, can be seen (Chen et al 2003;Duarte et al 2003;Fu et al 2007;Peuravuori et al 2002;Santos et al 2010;Sierra et al 2005;Zhang et al 2008). Raw water exhibited different fluorescence intensities during different sampling campaigns (Fig.…”

“…The wavelength offset of 18 nm was found optimal for the NOM SFS spectra in our study in comparison to the other tested Δλ values (Δλ=18, 20, 44, 50, 66, 80, and 120 nm). Other investigators also reported that Δλ=18 nm provides the optimum resolution of the synchronous spectra (Peuravuori et al 2002;Rodríguez et al 2014a, b;Zhang et al 2008).…”

Environmental pH and ionic strength influence the electron-transfer capacity of dissolved organic matter

“…The positions, shifts, and intensities of the fluorescence peaks provide information not only on conformational changes but also on intramolecular and intermolecular interactions (Mobed et al 1996;Chen et al 2003a;Zhang et al 2008). As shown in Fig.…”

Feasibility Assessment of Spectroscopic Methods in Characterising Leachate Dissolved Organic Matter

“…The intensities of Zone 3 and 4 (270 -280 nm excitation) fluorophores (tyrosine-like and tryptophan-like compounds respectively) was also found to decrease during 30 days of aerobic biodegradation. This reduction can be attributed to the breakdown of proteineous materials by aeration (Zhang et al, 2008). Fig.…”