Fast oxidation of the neonicotinoid pesticides listed in the EU Decision 2018/840 from aqueous solutions

Neonicotinoid pesticides family is nowadays identified as the most important type of insecticides in the world. Their consequent widespread occurrence in the environment represents not only a well-known risk for bees but also a significant negative impact in aquatic ecosystems. In this work, the capability of catalytic wet peroxide oxidation (CWPO) (Fe3O4-R400/H2O2) as a low-cost and environmentally-friendly system for the treatment of the neonicotinoid pesticides listed in the EU Watch List (Decision 2018/840) (acetamiprid (ACT), clothianidin (CLT), imidacloprid (IMD), thiacloprid (THC) and thiamethoxam (THM)) has been investigated. Remarkably, complete elimination of the pollutants (1000 g L-1)and the aromatic by-products was reached in 20 min reaction time operating at 25 °C, 1 atm, and pH0 = 5,, with the stoichiometric H2O2 amount (~4 – 5 mg L-1) and 1 g L-1 catalyst load. The reactivity order of the insecticides decreased as follows: THC>IMD>THM>CLT>ACT, being the pseudo-first order rate constant values within the range of 0.26 – 0.61 min-1. Notably, high mineralization yields were obtained (>50%) being the final effluents non-toxic. As example, the oxidation pathway of ACT was proposed. Finally, the catalytic system was tested in real surface waterThis research has been founded by the CTM2016-76454-R project (Spanish MINECO) and by the S2013/MAE-2716 project (CM). M. Munoz thanks the postdoctoral Ramón y Cajal contract (RYC-2016-20648) to the Spanish MINEC

Triclosan breakdown by Fenton-like oxidation

Fenton-like oxidation has proved to be highly efficient for the removal of triclosan, a highly toxic emerging water pollutant. From 10mg/L starting aqueous solutions complete conversion of triclosan was achieved in less than 1h at 25°C and around 20min at 50°C with 1mg/L Fe3+ and H2O2 at the theoretical stoichiometric amount (25mg/L). From the evolution of byproducts a reaction pathway has been proposed according to which oxidation of triclosan gives rise to several aromatic intermediates (mainly, p-hydroquinone of triclosan and 2,4-dichlorophenol) which evolve to short-chain organic acids. These compounds are mineralized except oxalic acid. A dramatic decrease of ecotoxicity was achieved in a relatively short time (more than 95% in 15min at 35°C). The evolution of ecotoxicity is intimately related to the disappearance of triclosan, much more toxic than the aromatic oxidation intermediates. This disappearance was successfully described by a simple pseudo-first order rate equation with an apparent activation energy value close to 27kJ/mol. The apparent rate constant at 25°C was several orders of magnitude higher than the reported in the literature for other chlorophenolic compounds indicating a higher susceptibility of triclosan to OH radical attackThis research has been supported by the Spanish MICINN through the project CTQ2008-03988 and by the CM through the project S-2009/AMB-158

Preparation of magnetite-based catalysts and their application in heterogeneous Fenton oxidation - A review

This study presents a critical review on the application of magnetite-based catalysts to industrial wastewater decontamination by heterogeneous Fenton oxidation. The use of magnetic materials in this field started only around 2008 and continues growing increasingly year by year. The potential of these materials derives from their higher ability for degradation of recalcitrant pollutants compared to the conventional iron-supported catalysts due to the presence of both Fe(II) and Fe(III) species. In addition, their magnetic properties allow their easy, fast and inexpensive separation from the reaction medium. The magnetic materials applied up to now can be classified in three general groups: magnetic natural minerals, in-situ-produced magnetic materials and ferromagnetic nanoparticles. A survey of the catalysts investigated so far is presented paying attention to their nature and competitive features in terms of activity and durabilityThis research has been supported by the Spanish MICINN through the project CTQ2013-4196-R and by the CM through the project S2013/MAE-271

Electronic-momentum distribution in deformed sodium clusters

4 págs.; 3 figs.; 1 tab.We present results for electronic momentum distribution n(k) of deformed sodium clusters in the framework of the Kohn-Sham formalism. We discuss properties of both spheroidal clusters and fission configurations. For spheroidal clusters we have analyzed properties of total and single-particle electronic momentum distribution. The results show that deformation has more of an effect on the latter, and that the total quadrupole moment in k space can be used to search the minimum-energy configuration. With regard to fission configurations, we present the behavior of total quadrupole moment for different fission pathways. ©1998 American Physical SocietyThis work has been supported by DGICYT ~Spain!, Grant Nos. PB95-0492 and PB95-0123.Peer Reviewe

Catalytic hydrodechlorination as polishing step in drinking water treatment for the removal of chlorinated micropollutants

This Accepted Manuscript will be available for reuse under a CC BY-NC-ND license after 24 months of embargo periodThe presence of micropollutants in fresh waters represents an important challenge for drinking water treatment plants (DWTPs). In particular, the chlorinated ones are especially harmful given their high toxicity and strong bioaccumulation potential. The aim of this work is to evaluate the feasibility of catalytic hydrodechlorination (HDC) for the removal of a representative group of chlorinated micropollutants commonly found in the source waters of DWTPs: the antibiotic chloramphenicol (CAP), the anti-inflammatory diclofenac (DCF), the antibacterial agent triclosan (TCL) and the antidepressant sertraline (SRT). The complete degradation of the isolated micropollutants (3 mg L−1) was achieved in 1 h reaction time using a Pd/Al2O3 catalyst load of 0.25 g L−1 and a H2 flow rate of 50 N mL min−1. The experimental data were properly described by a pseudo-first order kinetic equation, obtaining degradation rate constants in the range of 0.32–1.56 L gcat−1 min−1 and activation energy values within 42–52 kJ mol−1. In all cases, the final reaction products were chlorine-free compounds and thus, HDC effluents were non-toxic (<0.1 TU). Remarkably, the catalyst showed a suitable stability upon five consecutive applications. The versatility of the process was demonstrated in the treatment of the micropollutants mixture in different aqueous matrices (mineral, surface and tap waters). Strikingly, the removal rate was not affected by the presence of co-existing substances, being the micropollutants completely removed in 15 min with 1 g L−1 catalyst concentration. Finally, the potential of HDC for the removal of trihalomethanes, by-products formed along the oxidation step by chlorination in DWTPs, was also demonstratedThis research has been supported by the Spanish MINECO thorough the project CTM2016-76454-R and by the CM through the project P2018/EMT-4341. J. Nieto-Sandoval thanks the Spanish MINECO for the FPI predoctoral grant (BES-2017- 081346). M. Munoz thanks the Spanish MINECO for the Ramón y Cajal postdoctoral contract (RYC-2016-20648

Choked flow in water/CO2 solutions on air-independent propulsion systems

We develop a simplified model of choked flow in pipes for CO2-water solutions as an important step in the modelling of a whole hydraulic system with the intention of eliminating the carbon dioxide generated in air-independent submarine propulsion. The model is based on an approximate fitting of the homogeneous isentropic solution upstream of a valve (or any other area restriction), for given fluid conditions at the entrance. The relative maximum choking back-pressure is computed as a function of area restriction ratio. Although the procedure is generic for gas solutions, numeric values for the non-dimensional parameters in the analysis are developed only for choking in the case of carbon dioxide solutions up to the pure-water limit

Adsorption of micropollutants onto realistic microplastics: role of microplastic nature, size, age, and NOM fouling

This work aims at evaluating the role of nature, size, age, and natural organic matter (NOM) fouling of realistic microplastics (MPs) on the adsorption of two persistent micropollutants (diclofenac (DCF) and metronidazole (MNZ)). For such goal, four representative polymer types (polystyrene (PS), polyethylene terephthalate (PET), polypropylene (PP) and high-density polyethylene (HDPE)) were tested. MPs were obtained by cryogenic milling of different commercial materials (disposable bottles, containers, and trays), and fully characterized (optical microscopic and SEM images, FTIR, elemental analysis, water contact angle and pHslurry). The micropollutants hydrophobicity determined to a high extent their removal yield from water. Regardless of the MP's nature, the adsorption capacity for DCF was considerably higher than the achieved for MNZ, which can be related to its stronger hydrophobic properties and aromatic character. In fact, aromatic MPs (PS and PET) showed the highest adsorption capacity values with DCF (~100 μg g−1). The MP size also played a key role on its adsorption capacity, which was found to increase with decreasing the particle size (20–1000 μm). MPs aging (simulated by Fenton oxidation) led also to substantial changes on their sorption behavior. Oxidized MPs exhibited acidic surface properties which led to a strong decrease on the adsorption of the hydrophobic micropollutant (DCF) but to an increase with the hydrophilic one (MNZ). NOM fouling (WWTP effluent, river water, humic acid solution) led to a dramatic decrease on the MPs sorption capacity due to sorption sites blocking. Finally, the increase of pH or salinity of the aqueous medium increased the micropollutants desorptionThis research has been supported by the Autonoma University of Madrid and Community of Madrid through the project SI1-PJI-2019-00006, and by the Spanish MINECO through the project PID2019-105079RB-I00. Muñoz and J. Nieto-Sandoval thank the Spanish MINECO for the Ramón y Cajal postdoctoral contract (RYC-2016-20648) and the FPI predoctoral grant (BES-2017-081346), respectively. D. Ortiz thanks the Spanish MIU for the FPU predoctoral grant (FPU19/04816

Application of intensified Fenton oxidation to the treatment of hospital wastewater: Kinetics, ecotoxicity and disinfection

Fenton oxidation has proved to be effective for the treatment of a real hospital wastewater. The intensification of the process viz. the improvement on the efficiency of H2O2consumption, by increasing the temperature, is necessary to operate in a single step and avoid high reaction times and the need of large H2O2 and iron concentrations. This approach would allow taking advantage of the heat energy contained in the laundry stream since the washing process is performed at high temperature to assure disinfectionof the hospital textiles. In this work, temperatures within the range of 50-90 °C have been tested, which allowed an effective oxidation of the real wastewater ([COD]0 = 365 mg L-1, [Phenols]0 = 8.4 mg L-1, [total coliforms]0 = 4.16 × 106 MPN/100 mL, 5 toxicity units) with the stoichiometric amount of H2O2 (1000 mg L-1) and a relatively low iron concentration (25 mg L-1 Fe3+). Operating at 90 °C, complete disappearance of phenolic compounds and 70% and 50% reduction of COD and TOC were achieved in 1 h reaction time. Time evolution of those global parameters were appropriately fitted to pseudo-first and second order kinetic equations, providing a useful approach for design purposes. The main by-products were short-chain organic acids (oxalic and formic), being the final effluents non-toxic. Disinfection of the hospital wastewater was also achieved at all the operating temperatures tested, as confirmed by the absence of coliformsThis research has been supported by the CM through the project S2013/MAE-2716 and by the Spanish MINECO through the project CTQ2013-41963-R. M. Munoz thanks the Spanish MINECO for a Juan de la Cierva-Incorporación postdoctoral contract (IJCI-2014-19427