A Rational Analysis on Key Parameters Ruling Zerovalent Iron-Based Treatment Trains: Towards the Separation of Reductive from Oxidative Phases.

The development of treatment trains for pollutant degradation employing zerovalent iron has been attracting a lot of interest in the last few years. This approach consists of pre-treatment only with zerovalent iron, followed by a Fenton oxidation taking advantage of the iron ions released in the first step. In this work, the advantages/disadvantages of this strategy were studied employing commercial zerovalent iron microparticles (mZVI). The effect of the initial amount of mZVI, H2O2, pH, conductivity, anions and dissolved oxygen were analysed using p-nitrobenzoic acid (PNBA) as model pollutant. 83% reduction of PNBA 6 µM into p-aminobenzoic acid (PABA) was achieved in natural water at an initial pH 3.0 and 1.4 g/L of mZVI, under aerobic conditions, in 2 h. An evaluation of the convenience of removing mZVI after the reductive phase before the Fenton oxidation was investigated together with mZVI reusability. The Fenton step against the more reactive PABA required 50 mg/L of H2O2 to achieve more than 96% removal in 15 min at pH 7.5 (final pH from the reductive step). At least one complete reuse cycle (reduction/oxidation) was achieved with the separated mZVI. This approach might be interesting to treat wastewater containing pollutants initially resistant to hydroxyl radicals.

Olive mill wastewater reuse to enable solar photo-Fenton-like processes for the elimination of priority substances in municipal wastewater treatment plant effluents.

Olive mill wastewater (OMW) appears as an interesting and innovative natural alternative to synthetic chelating agents of iron in solar photo-Fenton processes at circumneutral pH due to its high polyphenol content, valorizing wastewater typically found in sunny countries. The aim of this work was the reuse of OMW for the elimination of other recalcitrant microcontaminants: terbutryn, chlorfenvinphos, diclofenac, and pentachlorophenol. Highly diluted OMW (1:1500) was employed to keep the iron in solution at circumneutral pH. Eighty percent degradation of microcontaminants was achieved, although the reaction rate was slow compared with conventional photo-Fenton process, due to Fe-polyphenol complex instability at neutral pH. At pH around 4 (considerable superior to the photo-Fenton optimal pH 2.8), Fe-polyphenol complex stability was promoted: solar UV energy required was 25 times lower to reach the objective of 80% microcontaminants degradation, which was attained in a single step, without coupling with other processes. Operating photo-Fenton at slightly acidic pH was proposed for the first time for possible reuse of treated wastewater in crop irrigation, requiring minimum pH adjustment by simply mixing it with natural wastewater. Graphical abstract.

Headspace solid-phase microextraction coupled to gas chromatography-tandem mass spectrometry for the determination of haloanisoles in sparkling (cava and cider) and non-sparkling (wine) alcoholic beverages.

A highly sensitive analytical method was developed to determine 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA), 2,4,6-tribromoanisole (TBA) and 2,3,4,5,6-pentachloroanisole (PCA) in sparkling alcoholic beverages. The method was based on the use of headspace solid-phase microextraction (HS-SPME) using a polydimethylsiloxane (PDMS) fibre. It was coupled to gas chromatography-triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS) for the detection and quantification of the target haloanisoles. The method was fully automated and no sample preparation was needed. The method was validated for alcoholic beverages. The influence of CO2 on the extraction efficiency was also evaluated for the studied sparkling drinks (cava and cider). All the calibration curves showed good linearity (R2 > 0.98) within the tested range (1-50 ng l-1). Recoveries were evaluated at three different levels (1, 5 and 50 ng l-1) and were always between 71% and 119%. Precision was expressed as relative standard deviation (RSD), and was evaluated as intra- and inter-day precisions, with values ≤ 22% in both cases. Limits of quantitation (LOQs) were ≤ 0.91 ng l-1, which are below the sensory threshold levels for such compounds in humans. The validated method was applied to commercial samples, 10 cavas and 10 ciders, but it was also used for the analysis of nine red wines and four white wines, demonstrating the further applicability of the proposed method to non-sparkling beverages. TCA was detected in most samples at up to 0.45 ng l-1.

Determination of polycyclic aromatic hydrocarbons in soy isoflavone nutraceutical products by gas chromatography coupled to triple quadrupole tandem mass spectrometry.

Thirteen polycyclic aromatic hydrocarbons have been determined in soy-based nutraceutical products. First, an optimization of extraction procedure was performed, and a solid-liquid extraction assisted by sonication and a dilute and shoot procedure were compared, selecting the dilute and shoot approach for the extraction of target compounds, utilizing a mixture of acetone/n-hexane (1:1 v/v) as extractant solvent. After this, a clean-up step was needed bearing in mind the complexity of these matrices. Dispersive solid-phase extraction, using a mixture of C18 and Zr-Sep+ (25 mg/mL each) was used. The separation was achieved by gas chromatography and detection with triple quadrupole tandem mass spectrometry. For quantification purposes, matrix-matched calibration was used. The validation was applied at three concentration levels (20, 100 and 250 µg/kg), obtaining recoveries between 70 and 120% and precision values equal to or lower than 23%. Limits of detection and quantification were below 8 and 20 µg/kg, respectively. The method was applied in 11 samples, detecting five polycyclic aromatic hydrocarbons at concentrations ranging from 4.1 to 18.5 µg/kg.