Effective removal of anionic and cationic dyes by kaolinite and TiO2/kaolinite composites

The present study investigated the removal of methylene blue (MB) and orange II (OII) dyes from synthetic wastewater by means of adsorption and photocatalysis using natural kaolins. For MB adsorption, the raw kaolinite-rich samples showed the greatest adsorption capacity, with rapid uptake (90% after 20 min). The experimental results were fitted better using the Langmuir isotherm model parameters compared to the Freundlich model, suggesting that the adsorption corresponds to monolayer coverage of MB molecules over the kaolinite surface. For OII, neither the Langmuir nor the Freundlich model gave reliable results, because the adsorption of anionic dye molecules by the clayey particles is not favoured. Mixtures of kaolinite/Degussa TiO2 were also prepared, and their photocatalytic properties under UV-light exposure were investigated. Decolourization of MB solutions was observed, even in a mixture with low TiO2 content. This is related to the combined effect of adsorption and photocatalysis and, unlike the pure clay samples, the efficiency of such mixtures against OII was only slightly weaker (80-94%). For TiO2-impregnated clays, with the kaolinite layers separated by sol-gel TiO2 particles, the MB removal was slow and effective only after >24 h due to the complexity of the bonding of MB molecules. On the other hand, the removal performance against OII solutions was very efficient (nearly 100%) within only 2 h. This excellent performance was attributed to morphological changes in clay particles

Carbon-modified titanium oxide materials for photocatalytic water and air decontamination

Titanium oxide-based materials with different physical and chemical features were synthetized aiming at removing organic pollutants from both water and air media. The materials were produced employing two different heating methodologies (thermal, T and hydrothermal, H) at distinct temperatures resulting in porous materials. These materials were also modified with either graphene oxide (GO) or carbon nanotubes (CNT), using an in-situ approach. All materials were tested as photocatalysts using ultra-violet (UV), visible (Vis) and solar radiation. Rhodamine B (RhB) and benzene were used as representative pollutants in water and air, respectively. The addition of carbon to the catalysts improved the removal of both pollutants. In the case of the photocatalytic degradation of rhodamine B, under both UV and Vis light, it was found that, the materials containing carbon nanostructures allowed the highest degradation degree, while the photosensitisation phenomenon became negligible. The best catalyst is the one containing CNT (2.98 wt% of C) and thermally treated at 300 °C (T300_CNT). This material showed higher degradation ability than the commercial TiO2 nanopowder Degussa P25 (P25) under Vis light. Regarding benzene removal, the samples thermally treated at 300 °C and modified with CNT and GO (T300_CNT and T300_GO, respectively) outperformed Degussa P25. The former material was successfully reused in the photocatalytic degradation of benzene over 6 consecutive cycles.publishe

Chitosan-hydroxyapatite composites made from sustainable sources: a morphology and antibacterial study

Chitosan (Cs) and hydroxyapatite (HA) 3D scaffolds/composites were prepared with a sustainable process, as HA was obtained using CaCO3 derived from cork, a natural material used as a template agent. The HA@Cs composites were prepared with HA in situ formation in a Cs solution, with a dissolution-precipitation mechanism. Different reaction times were considered, with time of 72 h leading to the best materials (sample CsHA_72). X-ray Diffraction (XRD) analysis confirmed HA formation. The analysis of Cs unit cell parameters showed that, for the unmodified Cs, the cell had larger dimensions and a higher degree of distortion than previously reported in literature; HA incorporation in the CsHA_72 composite led to a further increase in the cell dimensions. The morphology of the scaffolds was studied with Scanning Electron Microscopy (SEM) and a high level of porosity was observed; a statistical comparison was performed between the unmodified Cs and CsHA_72 to determine the pore size, structure, and distribution. This analysis, the first of this kind for this type of composites, showed smaller and more circular pores for the CsHA_72 composite (average diameter of 70 μm vs. 88 μm for unmodified Cs). The overall level of porosity, however, did not change (>77%); likewise, the Young modulus was not affected by HA incorporation (about 11 kPa). Antibacterial tests, performed on Escherichia coli and Staphylococcus aureus, showed that HA presence did not significantly reduce the antimicrobial properties; the composites were particularly effective towards S. aureus, as a >90% the bacterial population reduction was observed for an incubation time of 2 h. HA@Cs also showed excellent biocompatibility and good cell proliferation. The properties of these 3D scaffolds make them suitable for application as biomaterials.info:eu-repo/semantics/publishedVersio

Asociación entre urticaria crónica y cándida

Ningun

Synergistic effects of zirconium- and aluminum co-doping on the thermoelectric performance of zinc oxide

This work aims to explore zirconium as a possible dopant to promote thermoelectric performance in bulk ZnO-based materials, both within the single-doping concept and on simultaneous co-doping with aluminum. At 1100–1223 K mixed-doped samples demonstrated around ∼2.3 times increase in ZT as compared to single-doped materials, reaching ∼0.12. The simultaneous presence of aluminum and zirconium imposes a synergistic effect on electrical properties provided by their mutual effects on the solubility in ZnO crystal lattice, while also allowing a moderate decrease of the thermal conductivity due to phonon scattering effects. At 1173 K the power factor of mixed-doped Zn0.994Al0.003Zr0.003O was 2.2–2.5 times higher than for single-doped materials. Stability tests of the prepared materials under prospective operation conditions indicated that the gradual increase in both resistivity and Seebeck coefficient in mixed-doped compositions with time may partially compensate each other to maintain a relatively high power factorpublishe

Synthesis and characterization of Sn‑doped TiO2 flm for antibacterial applications

Simple sol–gel method has been exploited to deposit Sn-doped TiO2 thin flms on glass substrates. The resultant coatings were characterized by X-ray difraction (XRD), UV–visible techniques (UV–Vis), Fourier transform infrared spectroscopy (FTIR), and photoluminescence analysis (PL). The XRD pattern reveals an increase in crystallite size of the prepared samples with the increasing doping concentration. A decrease in doping concentrating resulted in the decrease in bandgap values. The diferent chemical bonds on these flms were identifed from their FTIR spectra. The photoluminescence analysis shows an increase in the emission peak intensity with increasing dopant concentration, and this can be attributed to the efect created due to surface states. The prepared samples were tested as antibacterial agent toward both Gram-positive and Gram-negative bacteria like S.aureus (Staphylococcus aureus) and E.coli (Escherichia coli), respectively. The size of the inhibition zones indicates that the sample shows maximum inhibitory property toward E.coli when compared to S.aureus

Dielectrical Properties of CeO2 Nanoparticles at Different Temperatures

A template-free precipitation method was used as a simple and low cost method for preparation of CeO2 nanoparticles. The structure and morphology of the prepared nanoparticle samples were studied in detail using X-ray diffraction, Raman spectroscopy and Scanning Electron Microscopy (SEM) measurements. The whole powder pattern modelling (WPPM) method was applied on XRD data to accurately measure the crystalline domain size and their size distribution. The average crystalline domain diameter was found to be 5.2 nm, with a very narrow size distribution. UV-visible absorbance spectrum was used to calculate the optical energy band gap of the prepared CeO2 nanoparticles. The FT-IR spectrum of prepared CeO2 nanoparticles showed absorption bands at 400 cm(-1) to 450 cm(-1) regime, which correspond to CeO2 stretching vibration. The dielectric constant (er) and dielectric loss (tan delta) values of sintered CeO2 compact consolidated from prepared nanoparticles were measured at different temperatures in the range from 298 K (room temperature) to 623 K, and at different frequencies from 1 kHz to 1 MHz

Creación de un logo para el trabajo en las colonias: La Revolucionaria, Lomas del Pedregal y Balcones del Cuatro

En este proyecto se recopiló información sobre las colonias La Revolucionaria, Pedregales y Balcones del Cuatro con el objetivo de crearles una identidad a través de materiales gráficos. Con esto se pretende dotar a estas comunidades de una identidad y abonar a la integración social