Current trends in the use of zero-valent iron (Fe0) for degradation of pharmaceuticals present in different water matrices

This work evaluates the Fenton process in the removal of eight pharmaceuticals (gemfibrozil, nimesulide, furosemide, paracetamol, propranolol, dipyrone, fluoxetine, and diazepam), present at an initial concentration of 500 μg L−1 for each compound, from three different water matrixes (distilled water, simulated wastewater, and hospital wastewater). The Fenton process conditions (iron and hydrogen peroxide concentrations, and pH) were optimized for the distilled water matrix by Doehlert design associated with response surface methodology. These corresponded to initial Fe2+ and hydrogen peroxide concentrations of 12.5 and 533 mg L−1, respectively, and pH 5.0. Mineralization rates and pharmaceutical degradation were monitored for all water matrixes and different experimental conditions employed. Unique iron addition, using low (12.5 mg L−1) and increased concentrations (37.5 mg L−1) were evaluated. These preliminary results motivated the study of the Fenton process employing successive iron additions and using an excess of hydrogen peroxide in the reaction medium. Multiple iron addition favored higher oxidation of the initial contaminants. Finally, the most persistent transformation products generated during the Fenton process were identified by liquid chromatography coupled with quadrupole-time of flight mass spectrometry (UHPLC-QTOF MS) using a purpose-built database that allowed monitoring 97 transformation products in a single injection. In this study, 12 transformation products (TPs) were tentatively identified employing this purpose-built database. Most TPs generated were classified as of high toxicity (Cramer rules) and showed ready biodegradability (START biodegradability).

Pharmaceutical removal from different water matrixes by Fenton process at near-neutral pH: Doehlert design and transformation products identification by UHPLC-QTOF MS using a purpose-built database

Oxidation of geosmin and 2-methylisoborneol by the photo-Fenton process: Kinetics, degradation intermediates, and the removal of microcystin-LR and trihalomethane from Nak-Dong River water, South Korea

The degradation of roxithromycin (ROX) by hydroxyl radical (·OH) generated by UV/H2O2 was systematically investigated in terms of degradation kinetics, effects of water chemistry parameters, oxidation products, as well as toxicity evaluation. The degradation of ROX by UV/H2O2 with varying light irradiation intensity, initial ROX concentration, and H2O2 concentration in pure water and wastewater all followed pseudo-first-order kinetics. The second-order rate constant for reaction between ROX and ·OH is 5.68 ± 0.34 × 109/M/s. The degradation rate of ROX increased with the pH; for instance, the apparent degradation rates were 0.0162 and 0.0309/min for pH 4 and pH 9, respectively. The presence of natural organic matter (NOM) at its concentrations up to 10 mg C/L did not significantly affect the removal of ROX. NO3− and NO2− anions inhibited the degradation of ROX due to the consumption of ·OH in reactions with these ions. Fe3+, Cu2+, and Mg2+ cations inhibited the degradation of ROX, probably because of the formation of ROX-metal chelates. A total of ten degradation products were tentatively identified by HPLC/LTQ-Orbitrap XL MS, which mainly derived from the attack on the oxygen linking the lactone ring and the cladinose moiety, tertiary amine and oxime side chain moiety by ·OH. The toxicity evaluation revealed that UV/H2O2 treatment of ROX induced the toxicity to bioluminescent bacteria increased.

Degradation of typical macrolide antibiotic roxithromycin by hydroxyl radical: kinetics, products, and toxicity assessment.

In this work, the degradation of a mixture of nine pharmaceuticals was performed in near environmental concentrations (500 µg L−1) using hospital wastewater as the matrix and employing as a coupling strategy solar photo-Fenton (SPF) treatment followed by adsorption. Different SPF approaches were studied. The best condition chosen for the degradation of the pharmaceuticals by SPF was that which used an initial concentration of H2O2 of 100 mg L−1 and multiple additions of Fe2+ of 5 mg L−1 at times of t = 0, 5, and 10 min in hospital wastewater. Degradation of 80% was obtained for Fluconazole, whereas the degradation of other pharmaceuticals achieved 99% of primary elimination. Consequently, 38 Transformation Products (TPs) were generated by the SPF process. The combination of SPF with the adsorption process using avocado seed activated carbon (ASAC) as sorbent was used to prevent TPs reaching the aqueous environment. For this reason, the SPF process was stopped after 15 min; and within this time, the largest number of TPs (28 TPs) was observed. A volume of 20 mL of hospital wastewater (HWW) previously treated by SPF was combined with 14 mg ASAC, for 15 min of contact time. This coupling removed 30 of the 36 compounds (remaining pharmaceuticals and TPs), with an open-chain and highly polar TPs having a 50% and 60% removal for FLT TP2 and FLT TP3, respectively. With respect to compounds that present aromatic rings, these presented a 98–100% removal rate in the coupled processes, with π–π interactions as the main interaction mechanisms with ASAC.

Combination of tertiary solar photo-Fenton and adsorption processes in the treatment of hospital wastewater: The removal of pharmaceuticals and their transformation products

The occurrence of taste and odor in drinking water is the most common cause of consumer complaints. In this study, the effect of water matrix constituents (i.e. TOC, alkalinity, and ) on the removal of geosmin/2-MIB with UV/H2O2 treatment was assessed. Experiments were carried out with a collimated beam apparatus equipped with a low and a medium-pressure (MP) UV lamp, with UV doses ranging from 300 to 1,200 mJ/cm2 with and without the addition of 4 mg/L H2O2. Results showed that the removal efficiency of geosmin/2-MIB with low pressure UV/H2O2 was inversely proportional to both the concentration of TOC and alkalinity in the synthetic water, as both parameters acted as scavengers of OH radicals. In the case of geosmin, the addition of 0.8 mg C/L of fulvic acid decreased the removal efficiency by 30%. The application of MPUV/H2O2 to water containing resulted in formation of which is also a OH radical scavenger. The presence of scavengers, in particular natural organic matter, causes significant incr...

Removal of taste and odor causing compounds by UV/H2O2 treatment: effect of the organic and inorganic water matrix

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Removal of taste and odor causing compounds by UV/H2O2 treatment: effect of the organic and inorganic water matrix