Progress in the removal of pharmaceutical compounds from aqueous solution using layered double hydroxides as adsorbents: A review

Emerging contaminants and, among them, pharmaceutical compounds, have a significant impact on water ecosystems. Layered Double Hydroxides (LDH), being easy to synthesize and cheap materials, have recently gained attention as adsorbents in aqueous solutions. This work describes the latest research performed in the adsorption capacity of LDH towards both antibiotics and Non-Steroidal Anti-Inflammatory Drugs (NSAID) describing and analyzing the synthesis conditions (Me2+:Me3+ molar ratio, calcination temperature, choice of metals for the memory effect), kinetics and isotherm models used, use of support (more practical in a 3D over a 2D form), temperature effect and several techniques for the recovery of the adsorbents. LDH exhibited great performance and potential as clean adsorbents for these emerging contaminant

Saline slag waste as an aluminum source for the synthesis of Zn–Al–Fe–Ti layered double-hydroxides as catalysts for the photodegradation of emerging contaminants

In this work, aluminum extracted from saline slag waste is valorized to create a layered double-hydroxide series containing zinc and various proportions of aluminum/titanium. Materials were synthesized by the co-precipitation method with an Me2+/Me3+ molar ratio of 3:1 and tested for the removal of diclofenac and salicylic acid from water under UV radiation. The incorporation of 5 wt% iron by wet impregnation is evaluated. In addition, another series of zinc, aluminum/iron materials with and without 5 wt% impregnated titanium are tested as catalysts for comparison. Structural characterization and comparison of the two series was performed by powder X-ray diffraction (PXRD), nitrogen adsorption at 77 K, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) measurements. The uncalcinated samples had a typical hydrotalcite structure with a high crystallinity; the presence of ZnO, ZnFe2O4 or Fe3O4 was found after calcination. The specific surface areas of the dried samples ranged from 78 to 199 m2/g, being highest for Zn6Al0.5Ti1.5. Overall, the results showed that the ZnAlTi series were more effective catalysts than ZnAlFe for photodegradation of the emerging contaminants diclofenac and salicylic acid, under UV light at 298 K, considering two concentrations of the organic molecules (5 and 50 μmol/dm3

Synthesis and CO2 adsorption properties of hydrotalcite-like compounds prepared from aluminum saline slag wastes

[EN]This study describes the synthesis of hydrotalcite-like materials by the co-precipitation method using aluminum extracted from saline slags wastes. Saline slags were chemically treated with 2 mol/dm3 aqueous solutions of NaOH for 2 h using a reflux system. The aluminum aqueous solutions were used as precursors with cobalt, magnesium and nickel nitrates, and Na2CO3, to obtain hydrotalcite-like materials with two mole M2+/Al3+ ratios, 2:1 and 4:1. The resulting solids were characterized by X-ray diffraction, termogravimetric analyses, nitrogen adsorption at −196 °C and scanning electron microscopy. After thermal treatment at 200 °C, the CO2 adsorption at 50, 100 and 200 °C was evaluated under dry conditions. The results showed a remarkable sorption capacity of 5.26 mmol/g at a pressure of 80 kPa and at a temperature of 50 °C for the MgAl-2:1 sample, with sorption capacities considerably higher than those reported in the literature for hydrotalcites under similar conditions. The Henry’s law constants were obtained directly from the adsorption isotherms at low pressures and the values found are between 0.01 and 4.20 mmol/kPa·g. The isosteric heats of CO2 adsorption found, using the Clausius-Clapeyron equation, were in the range of 5.2 to 16.8 kJ/mol.The authors are grateful for financial support from the Spanish Ministry of Economy, Industry and Competitiveness (AEI/MINECO), and the European Regional Development Fund (ERDF

A review on characterization of pillared clays by specific techniques

[EN]The use of specific characterization techniques, namely Thermal Analysis, Near Infrared Spectroscopy, Ultraviolet–Visible Spectroscopy, Electron Paramagnetic Resonance, Mössbauer Spectroscopy and Neutron Scattering, in the characterization of pillared clays is reviewed. Special emphasis is placed in the information provided by each of these techniques in the characterization of pillared clays

Microfluidic model of monocyte extravasation reveals the role of hemodynamics and subendothelial matrix mechanics in regulating endothelial integrity

Extravasation of circulating cells is an essential process that governs tissue inflammation and the body's response to pathogenic infection. To initiate anti-inflammatory and phagocytic functions within tissues, immune cells must cross the vascular endothelial barrier from the vessel lumen to the subluminal extracellular matrix. In this work, we present a microfluidic approach that enables the recreation of a three-dimensional, perfused endothelial vessel formed by human endothelial cells embedded within a collagen-rich matrix. Monocytes are introduced into the vessel perfusate, and we investigate the role of luminal flow and collagen concentration on extravasation. In vessels conditioned with the flow, increased monocyte adhesion to the vascular wall was observed, though fewer monocytes extravasated to the collagen hydrogel. Our results suggest that the lower rates of extravasation are due to the increased vessel integrity and reduced permeability of the endothelial monolayer. We further demonstrate that vascular permeability is a function of collagen hydrogel mass concentration, with increased collagen concentrations leading to elevated vascular permeability and increased extravasation. Collectively, our results demonstrate that extravasation of monocytes is highly regulated by the structural integrity of the endothelial monolayer. The microfluidic approach developed here allows for the dissection of the relative contributions of these cues to further understand the key governing processes that regulate circulating cell extravasation and inflammation

Structural, textural and acidic properties of Cu-, Fe- and Cr-doped Ti-pillared montmorillonites

Montmorillonite has been treated with Ti-based solutions, alone or doped with Cu2 +, Fe3 + or Cr3 + cations, yielding new intercalated solids, which have been calcined at various temperatures to test the stability of the so-formed pillars. The solids calcined at 500 °C were fully characterized by chemical analysis, X-ray diffraction, FT-IR spectroscopy, thermal analyses, nitrogen adsorption and acidity evaluation. The evolution of the specific surface area, porosity and acidic properties is discussed, analysing the effect of pillaring and doping procedures on these propertie

Effect of dopants on the structure of titanium oxide used as a photocatalyst for the removal of emergent contaminants

Photocatalysts composed of titanium dioxide modified with B, F, N and P have been synthesized, characterized and applied to the degradation of caffeine, diclofenac, ibuprofen and salicylic acid. The modified TiO2 samples were prepared by the sol–gel technique starting from titanium(IV) isopropoxide and using H3BO3, NH4F, N(C2H5OH)3 and H3PO4 as precursors of the modifiers, with the content varying between 0 and 5 wt%. Structural characterization was based on nitrogen physisorption at −196 °C, powder X-ray diffraction (PXRD), simultaneous thermogravimetric/differential thermal analysis (TG/DTA) and X-ray photoelectron spectroscopy (XPS). The structural properties of the modified TiO2 solids were significantly different depending on the nature and amount of modifiers and the calcination temperature. TiO2 in the anatase phase was obtained in all cases and was stable upon calcination at 400 °C. The photocatalytic degradation of caffeine, diclofenac, ibuprofen and salicylic acid by modified TiO2 was investigated under ultraviolet irradiation at 25 °C. The photocatalytic degradation behavior followed the order: caffeine > diclofenac = ibuprofen > salicylic acid. B-doped TiO2 was the most efficient catalyst in the degradation of these selected emerging contaminants

Synthesis and characterization of organosaponites. Thermal behavior of their poly(vinyl chloride) nanocomposites

[EN]The aim of this work was to synthesize and characterize the structural properties of the materials resulting from the combination of a synthetic saponitewith several organicmolecules, namely, Arquad 2HT-75, octadecylamine, 3-aminopropyltriethoxysilane, trimethyloctadecylammonium bromide and tetraethoxysilane, or combinations of them, and with or without the addition of HCl during synthesis. The ratios organic molecule/saponite and HCl/organic molecule were considered as synthesis variables. Structural characterization was based on X-ray diffraction (XRD), simultaneous thermogravimetric/differential thermal analysis (TG/DTA) and infrared spectroscopy (FTIR). The chemical composition of the materials was determined through X-ray fluorescence (XRF) and atomic absorption spectroscopy (AAS), and theirmorphologywas analyzed through scanning electron microscopy (SEM). The values obtained for the basal spacings were a function of the type and amount of the organic molecule. Otherwise, HCl did not significantly influence the basal spacing, but it had the capacity to significantly modify the morphology and the chemical composition of the samples. From the results found, the solids modified with tetraethoxysilane and 3-aminopropyltriethoxysilane were selected to incorporate various titaniumprecursors. These neworgano-modified saponiteswere used in the formulation of PVC nanocomposites and their thermal behavior was evaluated at two temperatures (70 and 180 °C).This work was funded by the Spanish Ministry of Science and Innovation (MICINN) and the European Regional Development Fund (FEDER)IPT-420000-2010-01

Spin splitting and precession in quantum dots with spin-orbit coupling: the role of spatial deformation

Extending a previous work on spin precession in GaAs/AlGaAs quantum dots with spin-orbit coupling, we study the role of deformation in the external confinement. Small elliptical deformations are enough to alter the precessional characteristics at low magnetic fields. We obtain approximate expressions for the modified $g$ factor including weak Rashba and Dresselhaus spin-orbit terms. For more intense couplings numerical calculations are performed. We also study the influence of the magnetic field orientation on the spin splitting and the related anisotropy of the $g$ factor. Using realistic spin-orbit strengths our model calculations can reproduce the experimental spin-splittings reported by Hanson et al. (cond-mat/0303139) for a one-electron dot. For dots containing more electrons, Coulomb interaction effects are estimated within the local-spin-density approximation, showing that many features of the non-iteracting system are qualitatively preserved.Comment: 7 pages, 7 figure

Studies on combining ability in tomato (Solanum lycopersicum L.)

ArticleThe present study was done seven elite tomato lines (Solamun lycopersicum L.) of determinate and indeterminate growth with good yield potential and good combining ability, using diallel fashion without reciprocals to produce 21 F1s. General combining ability (GCA) and Specific combining ability (SCA) analysis were conducted, with Diallel-SAS, assessing six yield and component traits. Results showed highly significant differences (p ≤ 0.01) among genotypes, as well as in GCA and SCA effects in all the characteristics that was assessed, with the exception of Days to First Cut. The results revealed that variance contribution to the yield attributed to the crossings had more non-additive effects (SCA) than additive effects (GCA). Furthermore, Line D4 had the greatest effect on yield in terms of GCA, as well in AFW (Average Fruit Weight), NFP (Number of Fruits per Plant) and PD (Polar Diameter) followed by D3 and K3. These lines can be used as donor parent in future tomato-breeding program. Hybrids K3×D4, R1×Y53, D3×IR13 and F3×Y53 had the highest level of SCA, with average yields of 93 t ha-1. These potential hybrids could be exploited at commercial level after critical testing