Humic-like substances from urban waste as auxiliaries for photo-Fenton treatment: a fluorescence EEM-PARAFAC study

Abstract

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.

Photophysical and Photochemical Properties of Naturally Occurring normelinonine F and Melinonine F Alkaloids and Structurally Related N(2)‐ and/or N(9)‐methyl‐β‐carboline Derivatives

“…Multivariate analysis techniques are increasingly used to obtain quantitative information from spectrofluorometric data. Parallel factor analysis (PARAFAC), the most widely used technique, is able to retrieve the information contained in complex sets of excitation–emission matrices (EEMs) into independent factors, for both quantitative and qualitative analyses . PARAFAC is a generalization of principal components analysis (PCA) and has been frequently applied for the analysis of sets of EEMs arranged in three‐way arrays ( X ).…”

Humic like substances for the treatment of scarcely soluble pollutants by mild photo-Fenton process

“…Two of these components, with emission maxima at 344 nm and 350 nm, were also observed for TBZ solutions free of BOS and may be ascribed to the acidic (F1) and neutral (F3) forms of TBZ, respectively. Other two factors (whose emission maxima are at 444 and 532 nm) could be assigned to SBO (F4 and F5), according to previous studies performed with these substances (García Ballesteros et al (2017)). Interestingly, a fifth factor (F2) was found, whose emission maximum was close to 360 nm; this component can solely be observed for solutions where both TBZ and SBO were present, and hence it should be assigned to an interaction TBZ-SBO.…”

“…5, with only a slight loss of efficiency which could be considered as acceptable (Gomis et al (2015a)). Interestingly, recent fluorescence measurements have demonstrated the high ability of SBO to complex iron at an optimum pH of 5 (García Ballesteros et al (2017)). In addition to this, SBO have been described to have surface active properties (Negueroles et al (2017)).…”

Innovative depollution treatment using multi-valent iron species: from fundamental study to application in municipal wastewater

“…These results can be explained by the non-selective reactivity of AA which does not react exclusively with iron species in the treated wastewater, while EDDS is rather selective in the formation of Fe(III) complexes. In addition, the organic matter present in wastewater probably has a complexation/stabilization effect on aqueous iron (Garcia Ballesteros et al 2017). Therefore, the EDDSenhanced ferrate-mediated heterogeneous photo-Fenton treatment is considered as the most viable for municipal WW treatment in our experimental conditions.…”