Silica aerogels synthesized with butyl-4-methylpyridinium tetrafluoroborate

The supercritical drying effects were investigated, on a series of samples synthesized with: tetramethoxysilane and methyltrimethoxysilane, used as precursors, and butyl-4- methylpyridinium tetrafluoroborate (BMPyBF4) ionic liquid (IL), as gelation catalyst. These results show that the IL addition has a significant impact on the structure of the aerogel as a function of used nIL/nSi molar ratio

Catalytic properties of cesium salts of 12-molybdophosphoric acid supported on SBA-15 mesoporous silica

The Cs salt of molybdophosphoric acid CS2.5H0.5PM012O40 (CsHPM) was supported on SBA15 in the concentration of 20, 30 and 40 wt. % loadings. The structure and texture of these CsHPM/SBA-15 composites were studied by XRD, FT-IR and micro-Raman spectroscopy, BET and pore size distribution, SEM-EDS. Thermal stability was investigated by thermo gravimetric analysis (TGA), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The dehydration of ethanol was used to probe the catalytic properties of the CsHPM samples incorporated on the silica matrix. The main reaction products obtained on acid (dehydration) catalytic centres were ethylene and diethyl ether, and respectively acetaldehyde which was obtained on redox (dehydrogenation) catalytic centres

Studies on the physico-chemical properties of lanthanum manganite prepared by different synthesis methods

Perovskite LaMnO3 and related materials are technologically important for many possible applications due to their unique physical and chemical properties. It is well known that the properties of the materials depend on their synthesis processes, as have been already shown in the literature for a large class of materials [1, 2]. In this work, lanthanum manganite perovskite type materials prepared by ultrasonically method with immersed sonotrode in the reaction medium and sol-gel method, followed by heat treatment at 600°C, 6 h are reported. The asprepared samples were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), surface area analysis (BET), scanning / transmission electron microscopy (SEM /HRTEM/EDX), and FT-IR spectroscopy. X-ray diffraction indicates that the synthesized materials are well crystallized, with perovskite structure and without any secondary phases

Novel asymmetric benzylidenecyclohexanone photochromic compound as food dye with antioxidant properties

Nature has always been the provider of compounds with unique properties and amazing application within or outside the living organisms [1]. Color is certainly one of the natural features that have always fascinated researchers from almost all fields of knowledge and compounds with such properties have been isolated from raw materials or have been designed and synthesized based thereon [2]. Flavylium derivatives are natural or synthetic compounds responsible for certain color of fruits and flowers and are able to turn from yellow to red and blue depending on the pH of the media [3]. They are also studied for their photochromic behavior when excited with different wavelengths and their network of chemical transformation has been the subject of many research papers [4,5]. We have focused lately on the synthesis of xanthylium derivatives [6], compounds similar in behavior with flavylium ones with symmetrical and asymmetrical substituents on the aromatic rings. The photochromic behavior of the new asymmetric benzylidene cyclohexanone derivative 4-(p-hydroxybenzylidene)-6-hydroxy-1,2,3,4-tetrahydroxanthylium chloride (HTX)in aqueous solution at different pH values was studied using UV-Vis, NMR and fluorescence spectroscopy. In strong acid environment HTX exhibits purple color and a broad absorption band at about 516 nm, corresponding to the presence of the xanthylium cation, while in basic conditions the solutions are red, with an absorption band at about 596 nm. At pH ranging from 9 to 12 HTX is bluish and suffers spontaneous transformations between species involved in the network of chemical reactions. HTX shows good fluorescence behavior at all pH values. HTX has a good antioxidant character of 55.15% determined by DPPH method. The features described above and its curcumin origin would highly recommend it for application in the field of food colorants

Ordered Mesoporous Silica Prepared in Different Solvent Conditions: Application for Cu(II) and Pb(II) Adsorption

In this work, the synthesis of ordered mesoporous silica of MCM-41 type was investigated aimed at improving its morphology by varying the synthesis conditions in a one-pot process, employing different temperatures and solvent conditions. 2-methoxyethanol was used as co-solvent to ethanol. The co-solvent ratio and the synthesis temperature were varied. The pore morphology of the materials was characterized by nitrogen porosimetry and small angle neutron scattering (SANS), and the particle morphology by transmission electron microscopy (TEM) and ultra-small angle neutron scattering (USANS). The thermal behavior was investigated by simultaneous thermogravimetry-differential scanning calorimetry (TG-DSC) measurements. The SANS and N(2) sorption results demonstrated that a well-ordered mesoporous structure was obtained at all conditions in the synthesis at room temperature. Addition of methoxyethanol led to an increase of the pore wall thickness. Simultaneously, an increase of methoxyethanol content led to lowering of the mean particle size from 300 to 230 nm, according to the ultra-small angle scattering data. The ordered porosity and high specific surfaces make these materials suitable for applications such as adsorbents in environmental remediation. Batch adsorption measurements of metal ion removal from aqueous solutions of Cu(II) and Pb(II) showed that the materials exhibit dominantly monolayer surface adsorption characteristics. The adsorption capacities were 9.7 mg/g for Cu(II) and 18.8 mg/g for Pb(II) at pH 5, making these materials competitive in performance to various composite materials

Synthesis and Characterization of Amorphous SiO₂−Fe_xO_y Materials Starting from Iron Sulfate for Preliminary Studies of CO₂ Adsorption

The goal of this work is to investigate the effectiveness of amorphous SiO2−FexOy loaded by functionalization with Ce(SO4)2, Li2SO4, and 3-aminopropyltriethoxysilane (APTES) for CO2 adsorption. Silica and iron-based materials are gaining popularity due to their wide range of applications, such as catalysis, photocatalysis, imaging, etc.; however, there are very few studies regarding the adsorption of CO2 with the aforementioned materials. In our study, we proposed to test their ability in this direction by adding cerium sulfate and lithium sulfate. Three base materials were obtained and characterized using XRD, FTIR, RAMAN, TG, SEM, and BET followed by their functionalization with amino groups by using of the APTES precursor. The SEM images indicate an increase in size, forming clusters from 100 nm for base materials to 500 nm for functionalized materials. The results indicate a maximum CO2 adsorption of 1.58 mmol/g material for the SiO2−FexOy−Li−APTES sample

Selenite Removal from Aqueous Solution Using Silica–Iron Oxide Nanocomposite Adsorbents

In recent years, during industrial development, the expanding discharge of harmful metallic ions from different industrial wastes (such as arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, or zinc) into different water bodies has caused serious concern, with one of the problematic elements being represented by selenium (Se) ions. Selenium represents an essential microelement for human life and plays a vital role in human metabolism. In the human body, this element acts as a powerful antioxidant, being able to reduce the risk of the development of some cancers. Selenium is distributed in the environment in the form of selenate (SeO42–) and selenite (SeO32–), which are the result of natural/anthropogenic activities. Experimental data proved that both forms present some toxicity. In this context, in the last decade, only several studies regarding selenium’s removal from aqueous solutions have been conducted. Therefore, in the present study, we aim to use the sol–gel synthesis method to prepare a nanocomposite adsorbent material starting from sodium fluoride, silica, and iron oxide matrices (SiO2/Fe(acac)3/NaF), and to further test it for selenite adsorption. After preparation, the adsorbent material was characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The mechanism associated with the selenium adsorption process has been established based on kinetic, thermodynamic, and equilibrium studies. Pseudo second order is the kinetic model that best describes the obtained experimental data. Also, from the intraparticle diffusion study, it was observed that with increasing temperature the value of the diffusion constant, Kdiff, also increases. Sips isotherm was found to best describe the experimental data obtained, the maximum adsorption capacity being ~6.00 mg Se(IV) per g of adsorbent material. From a thermodynamic point of view, parameters such as ΔG0, ΔH0, and ΔS0 were evaluated, proving that the process studied is a physical one