UiO-66-based metal organic frameworks for the photodegradation of acetaminophen under simulated solar irradiation

This work reports the solvothermal synthesis of UiO-66-based MOFs with three different ligands and its application to the breakdown of aqueous acetaminophen under simulated sunlight. This pharmaceutical is a representative contaminant of emerging concern that enters water bodies mainly through wastewater treatment plant discharges. The synthesis approach of the MOFs was fitted using a zirconium alkoxide as metal cluster precursor and 2-aminoterephthalic and 2,5-dihydroxyterephthalic acids as ligands to prepare UiO-66-NH2 and UiO-66-(OH)2 MOFs, respectively. These new MOFs have enhanced visible light harvesting and narrower band gap than the UiO-66. Among all, UiO-66-NH2 yielded the highest removal of acetaminophen under simulated solar irradiation in batch test. The activity and stability of UiO-66-NH2 were demonstrated for the first time in a continuous flow test, where stable performance was observed upon 30 h on stream. The degradation pathway of acetaminophen was elucidated based on coupling, ring-opening, and oxidation reactions. DFT calculation confirmed that the indirect semiconductor behavior of UiO-66-NH2 upon light excitation occurred through ligand-ligand charge transfer. Overall, promising UiO-66-based MOFs photocatalysts were obtained for effective degradation of acetaminophen with the assistance of solar lightThis research was funded by the National State Research Agency of Spain (project number: PID2019-106186RB-I00/AEI/10.13039/501100011033). Yilan Wang acknowledges the support from the China Scholarship Council (CSC No. 201908610198). We also thank to Prof. Shi Ye for his help with density functional theory calculatio

Metronidazole photodegradation under solar light with UiO-66-NH2 photocatalyst: Mechanisms, pathway, and toxicity assessment

Metronidazole is a nitroimidazole antibiotic that is increasingly detected in aquatic bodies. Therefore, there is an urgent need to research methodologies to remove this and other antibiotics. One of the alternatives is the application of solar photocatalysis, which requires the use of an efficient photocatalyst. In this work, UiO-66-NH2 was synthesized by a facile solvothermal method and evaluated for the degradation of metronidazole under simulated solar light. The effects of catalyst dosage, initial pH, and metronidazole concentration were discussed, establishing the best operation conditions. In addition, the stability and reproducibility of UiO-66-NH2 activity were also verified. The quenching reaction showed that holes and superoxide radicals coexisted as the main active species, being responsible for the metronidazole degradation. The pathway of metronidazole photodegradation was proposed by means of density functional theory calculations and LC/ESI-MS analysis. It is noteworthy that this study detected for the first time C6H11N3O4, C4H6N2O3, and C4H8N2O4 as metronidazole photodegradation byproducts. ECOSAR toxicity analysis showed that all byproducts were less toxic than the original metronidazole, supporting the potential feasibility of this method for treating water polluted with this antibioticThis work was supported by the National State Research Agency of Spain (project number: PID2019–106186RB-I00/AEI/10.13039/ 501100011033). Yilan Wang acknowledges the financial support provided by China Scholarship Council (CSC No. 201908610198). The authors sincerely acknowledged support from the external services of the Autonomous University of Madrid (SIdI

Solar photocatalytic degradation of parabens using UiO-66-NH2

The photocatalytic degradation of methylparaben was investigated under simulated solar light using a synthesised metal–organic framework (UiO-66-NH2). For that purpose, the pollutant was spiked in different water matrices: distilled water, water from Lima River (Northwestern Portugal), and urban wastewater. Complete removal of the methylparaben in distilled water was achieved in 1 h reaction. In natural water matrices, the photocatalytic performance decreased to 70% removal after 3 h reaction, owing to the physical–chemical properties of the water samples. The UiO-66-NH2 photocatalyst revealed high stability under the continuous mode, reaching a steady state in 5 h, from which the removal percentage was kept constant for 25 h. The photocatalytic degradation of methylparaben gave five main reaction byproducts and four short-chain carboxylic acids, identified by LC/ESI-MS and UHPLC analyses, respectively. The mechanism of degradation was investigated by using selective scavengers. Photogenerated holes and superoxide radicals were found as the main species responsible for the degradation of methylparaben. The abatement of other parabens (as ethyl- and propylparaben) was also evaluated, being the conversion influenced by the length of the alkyl side chain. The results of this study give a comprehensive sight into the effective photocatalytic remediation of parabens using UiO-66-NH2Authors acknowledge Spanish State Research Agency (PID2019- 106186RBI00/AEI/10.13039/501100011033). M. Peñas-Garzón is indebted to Spanish MECD (FPU16/00576 grant) and MICIU (EST19/ 00068). M.J.S. thanks to Project POCI-01-0145-FEDER-030674 (MicroPhotOGen, PTDC/NAN-MAT/30674/2017) funded by ERDF through COMPETE2020 - Programa Operacional Competitividade e Internacionalizaçao (POCI) – and by national funds through FCT - Fundaçao para a Ciência e a Tecnologia. We would like to thank the scientific collaboration financially supported by: Base-UIDB/50020/ 2020 and Programmatic-UIDP/50020/2020 Funding of Associate Laboratory LSRE-LCM - funded by national funds through FCT/MCTES (PIDDAC). Authors thank the Research Support Services of the Universidad Autónoma de Madrid (SIdI), University of Extremadura (SAIUEx), University of Málaga (SCAI) and Universidad Complutense of Madrid (CAI

Degradation of diclofenac in water under LED irradiation using combined g-C3N4/NH2-MIL-125 photocatalysts

This study reports the photocatalytic degradation of diclofenac by hybrid materials prepared by combination of graphitic carbon nitride (g-C3N4) and titanium-metal organic framework (NH2-MIL-125), in different mass proportions (MOF:C3N4 of 25:75, 50:50 and 75:25). The hybrid materials were fully characterized, and their properties compared to those of the individual components, whose presence was confirmed by XRD. The porous structure was the result of the highly microporous character of the MOF and the non-porous one of g-C3N4. The band gap values were very close to that of MOF component. Photoluminescence measurements suggested an increase on the recombination rate associated to the presence of g-C3N4. Photodegradation tests of diclofenac (10 mg·L-1) were performed under UV LED irradiation at 384 nm. The hybrid materials showed higher photocatalytic activity than the individual components, suggesting the occurrence of some synergistic effect. The photocatalyst with a MOF:g-C3N4 ratio of 50:50 yielded the highest conversion rate, allowing complete disappearance of diclofenac in 2 h. Experiments with scavengers showed that superoxide radicals and holes played a major role in the photocatalytic process photodegradation, being that of hydroxyl radicals less significant. From the identification of by-products species, a degradation pathway was proposed for the degradation of diclofenac under the experimental operating conditionsThis work was financially supported by Associate Laboratory LSRELCM - UID/EQU/50020/2020 - funded by national funds through FCT/ MCTES (PIDDAC) and by project POCI-01-0145-FEDER-030674, financed by the ERDF through COMPETE2020 and POCI – and by national funds through FCT (Portugal). This research was also funded by Spanish Ministry of Economy and Competitiveness (project CTQ2016-78576-R, FEDER funds) and the State Research Agency (PID2019- 106186RB-I00/AEI/10.13039/501100011033) (Spain). V. MuelasRamos thanks to MCIU for BES-2017-082613 grant. Authors thank the TEM images from the Centro Nacional de Microscopía Electronica ´ (Spain). Authors would like to acknowledge the use of Servicio General de Apoyo a la Investigacion-SAI ´ for EDX mapping images, Universidad de Zaragoza (Spain) and the Research Support Service of XPS data from University of Málaga (Spain

Adsorption of emerging pollutants on lignin-based activated carbon: Analysis of adsorption mechanism via characterization, kinetics and equilibrium studies

Lignin has been employed as a precursor to synthesize activated carbons with the aim of lignin-biomass revalorization. The properties of these activated carbons were compared, and the best adsorbent was employed to remove two emerging pollutants from water, acetaminophen and acetamiprid. The adsorption mechanisms of pharmaceutical and pesticide compounds were analyzed, modeled and interpreted via statistical physics models. In particular, adsorption kinetics and isotherms of acetaminophen and acetamiprid at temperatures between 20 and 60 ◦C were quantified experimentally. Equilibrium data were fitted to different statistical physics-based isotherm models to establish the corresponding adsorption mechanism. A double layer adsorption model with one type of functional group was the best to correlate and explain the removal of these organic molecules. Steric parameters for the adsorption of these organic compounds were also calculated thus determining that their adsorption was multi-molecular. At tested operating conditions, acetaminophen adsorption was endothermic, while acetamiprid removal was exothermic. Physical adsorption forces were expected to be responsible for the removal of both compounds. This study reports new insights on the adsorption mechanisms of relevant emerging pollutants commonly found in water worldwid

Performances of multi-gap timing RPCs for relativistic ions in the range Z=1-6

We present the performance of Multi-gap timing RPCs under irradiation by fully stripped relativistic ions (gamma*beta=2.7, Z=1-6). A time resolution of 80 ps at high efficiency has been obtained by just using standard `off the shelf' 4-gap timing RPCs from the new HADES ToF wall. The resolution worsened to 100 ps for ~ 1 kHz/cm2 proton flux and for ~ 100 Hz/cm2 Carbon flux. The chambers were operated at a standard field of E=100 kV/cm and showed a high stability during the experiment, supporting the fact that RPCs are a convenient choice when accommodating a very broad range of ionizing particles is needed. The data provides insight in the region of very highly ionizing particles (up to x 36 mips) and can be used to constrain the existing avalanche and Space-Charge models far from the usual `mip valley'. The implications of these results for the general case of detection based on secondary processes (n, gamma) resulting in highly ionizing particles with characteristic energy distributions will be discussed, together with the nature of the time-charge correlation curve.Comment: 31 pages, 19 figures, submitted to JINS

An upper limit on hypertriton production in collisions of Ar(1.76 AGeV)+KCl

A high-statistic data sample of Ar(1.76 AGeV)+KCl events recorded with HADES is used to search for a hypertriton signal. An upper production limit per centrality-triggered event of $1.04$ x $10^{-3}$ on the $3\sigma$ level is derived. Comparing this value with the number of successfully reconstructed $\Lambda$ hyperons allows to determine an upper limit on the ratio $N_{_{\Lambda}^3H}/N_{\Lambda}$, which is confronted with statistical and coalescence-type model calculations

Inclusive pion and eta production in p+Nb collisions at 3.5 GeV beam energy

Data on inclusive pion and eta production measured with the dielectron spectrometer HADES in the reaction p+93Nb at a kinetic beam energy of 3.5 GeV are presented. Our results, obtained with the photon conversion method, supplement the rather sparse information on neutral meson production in proton-nucleus reactions existing for this bombarding energy regime. The reconstructed e+e-e+e- transverse-momentum and rapidity distributions are confronted with transport model calculations, which account fairly well for both pi0 and eta production.Comment: 12 pages, 9 figures, submitted to Physical Review

Searching a Dark Photon with HADES

We present a search for the e+e- decay of a hypothetical dark photon, also names U vector boson, in inclusive dielectron spectra measured by HADES in the p (3.5 GeV) + p, Nb reactions, as well as the Ar (1.756 GeV/u) + KCl reaction. An upper limit on the kinetic mixing parameter squared epsilon^{2} at 90% CL has been obtained for the mass range M(U) = 0.02 - 0.55 GeV/c2 and is compared with the present world data set. For masses 0.03 - 0.1 GeV/c^2, the limit has been lowered with respect to previous results, allowing now to exclude a large part of the parameter region favoured by the muon g-2 anomaly. Furthermore, an improved upper limit on the branching ratio of 2.3 * 10^{-6} has been set on the helicity-suppressed direct decay of the eta meson, eta-> e+e-, at 90% CL