Synthesis of noble metal-decorated NH2-MIL-125 titanium MOF for the photocatalytic degradation of acetaminophen under solar irradiation

This work reports the solvothermal synthesis of a titanium-based metal organic framework (NH2-MIL-125(Ti)) and the further deposition of palladium, platinum and silver nanoparticles on its framework, with the aim to obtain visible light-driven photocatalysts. The structure of the NH2-MIL-125 was not affected by the incorporation of the metal nanoparticles, while the textural properties changed depending on the metal used. All M/NH2-MIL-125 (M = Pd, Pt, Ag) synthesized materials showed enhanced light absorption in the visible region due to the effect of the metal nanoparticles, which were mainly in reduced state as confirmed by XPS analyses. The metal nanoparticles were between 1.8 and 3.8 nm in size depending of the metal. They were responsible for the reduction in the recombination process, as suggested by photoluminescence measurements. The photocatalytic performance of M/NH2-MIL-125 was tested for the degradation of acetaminophen (ACE) under simulated solar irradiation. Pt/NH2-MIL-125 achieved the highest conversion rate (rate constant of 0.0165 min−1), with complete conversion of the contaminant in less than three hours. Scavengers studies confirmed that O.-2[rad]− radicals play a main role in the degradation process, followed by .OH radicals. The catalytic stability of Pt/NH2-MIL-125 was confirmed upon three successive reaction cycles. Different water matrices were tested to understand the effect of common inorganic ions, being the presence of bicarbonates the most detrimental to the performance of the photocatalytic processThis research was funded by the State Research Agency (PID2019-106186RB-I00/AEI/10.13039/501100011033). V. Muelas-Ramos thanks to MCIU for BES-2017-082613 gran

Equilibrium, kinetics and breakthrough curves of acetaminophen adsorption onto activated carbons from microwave-assisted FeCl3-activation of lignin

Activated carbons have been prepared by chemical activation of lignin with FeCl3 using microwave (MW) heating. The use of MW significantly reduced the activation time compared to conventional heating. Microwave power, impregnation ratio (R: mass ratio of FeCl3 to lignin precursor) and MW holding time have been studied as variables affecting the development of porous texture. The optimum conditions were found at 800 W, R = 5 and 30 min MW heating time. Under those conditions an essentially microporous activated carbon was obtained, with BET surface area higher than 1150 m2·g−1 and acidic surface, whose pH at the point of zero charge was 4.2. This activated carbon was tested for the adsorption of acetaminophen, as model emerging contaminant, from aqueous phase. The adsorption isotherms, obtained at 20, 40 and 60 °C, fitted well to Redlich–Peterson model. The maximum acetaminophen adsorption reached about 300 mg·g−1 at 60 °C. Values of 35.5 kJ·mol−1 and 238.3 J·mol−1·K−1 were obtained for the enthalpy and entropy of adsorption, respectively. Those positive values are indicative of an endothermic process and increased randomness at the solid/solution interface upon adsorption. The adsorption kinetics was better described by pseudo-second order driving force model. Breakthrough curves were also obtained at different adsorption temperatures, flow rates and acetaminophen inlet concentrations. They fitted well to a logistic-type equation representative of the Bohart-Adams, Thomas and Yoon-Nelson models. Adsorbent regeneration with hot water (80 °C) revealed easy and complete desorption thus providing a promising view of the potential application of this activated carbonThe authors acknowledge the financial support from the State Research Agency (PID2019-106186RB-I00/AEI/10.13039/501100011033, Spain). M. Penas-Garzón thanks Spanish MECD for FPU16/00576 gran

A Light Calibration System for the ProtoDUNE-DP Detector

A LED-based fiber calibration system for the ProtoDUNE-Dual Phase (DP) photon detection system (PDS) has been designed and validated. ProtoDUNE-DP is a 6x6x6 m3 liquid argon time-projection-chamber currently being installed at the Neutrino Platform at CERN. The PDS is based on 36 8-inch photomultiplier tubes (PMTs) and will allow triggering on cosmic rays. The system serves as prototype for the PDS of the final DUNE DP far detector in which the PDS also has the function to allow the 3D event reconstruction on non-beam physics. For this purpose an equalized PMT response is desirable to allow using the same threshold definition for all PMT groups, simplifying the determination of the trigger efficiency. The light calibration system described in this paper is developed to provide this and to monitor the PMT performance in-situ.Comment: 15 pages, 5 figure

The structural and electronic properties of nanostructured Ce1–x–yZrxTbyO2 ternary oxides: Unusual concentration of Tb3+ and metal_oxygen_metal interactions

10 pages, 12 figures, 1 table.Ceria-based ternary oxides are widely used in many areas of chemistry, physics, and materials science. Synchrotron-based time-resolved x-ray diffraction, x-ray absorption near-edge spectroscopy (XANES), Raman spectroscopy, and density-functional calculations were used to study the structural and electronic properties of Ce–Zr–Tb oxide nanoparticles. The nanoparticles were synthesized following a novel microemulsion method and had sizes in the range of 4–7 nm. The Ce1–x–yZrxTbyO2 ternary systems exhibit a complex behavior that cannot be predicted as a simple extrapolation of the properties of Ce1–xZrxO2, Ce1–xTbxO2, or the individual oxides (CeO2, ZrO2, and TbO2). The doping of ceria with Zr and Tb induces a decrease in the unit cell, but there are large positive deviations with respect to the cell parameters predicted by Vegard's rule for ideal solid solutions. The presence of Zr and Tb generates strain in the ceria lattice through the creation of crystal imperfections and O vacancies. The O K-edge and Tb LIII-edge XANES spectra for the Ce1–x–yZrxTbyO2 nanoparticles point to the existence of distinctive electronic properties. In Ce1–x–yZrxTbyO2 there is an unexpected high concentration of Tb3+, which is not seen in TbO2 or Ce1–xTbxO2 and enhances the chemical reactivity of the ternary oxide. Tb_O_Zr interactions produce a stabilization of the Tb(4f,5d) states that is responsible for the high concentration of Tb3+ cations. The behavior of Ce1–x–yZrxTbyO2 illustrates how important can be metal_oxygen_metal interactions for determining the structural, electronic, and chemical properties of a ternary oxide.The research carried out at the Chemistry Department of Brookhaven National Laboratory was financed through Contract No. DE-AC02-98CH10886 with the US Department of Energy (Division of Chemical Sciences). The NSLS is supported by the Divisions of Materials and Chemical Sciences of DOE. Work at the “Instituto de Catálisis y Petroleoquímica (CSIC)” was done with financial support from CICYT (Project No. MAT2000-1467).Peer reviewe

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

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

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