Showing papers on "Mesoporous silicate published in 2017"

Fly ash-derived MCM-41 as a low-cost silica support for polyethyleneimine in post-combustion CO2 capture

Abstract: The mesoporous silicate molecular sieve, MCM-41, has been synthesized from pulverized coal fly ash (PFA), where the silicate filtrate used is a by-product from hydrothermal zeolite production. Rice husk ash was also used for comparison but fusion with sodium hydroxide was used to prepare the silicate filtrate, along similar lines to earlier reports of using PFA as a precursor for MCM-41 synthesis. The MCM-41 samples are chemically and mineralogically similar to a commercially available sample, but with higher pore volumes dominated by mesopores (0.92–1.13 cf. 0.88 cm3 g−1). After polyethyleneimine (PEI) impregnation for CO2 capture, the ash derived MCM-41 samples displayed higher uptakes than the commercial sample with the maximum achievable PEI loading of 60 Wt.% PEI (dry basis) before particle agglomeration occurs, approximately 13 compared to 11 Wt.%, respectively, the latter being comparable to earlier reports in the literature. The PFA sample that displays the fastest kinetics to achieve 90% of the equilibrium uptake had the largest mesopore volume of 1.13 cm3 g−1. Given the PFA-derived MCM-41 uses a waste silicate solution for hydrothermal preparation and no prior preparation is needed, production costs are estimated to be considerable lower where silicate solutions need to be prepared by base treatment, even if ash is used, as for the RHA derived MCM-41 used here.

Composite Biomaterials Based on Sol-Gel Mesoporous Silicate Glasses: A Review.

Abstract: Bioactive glasses are able to bond to bone and stimulate the growth of new tissue while dissolving over time, which makes them ideal materials for regenerative medicine. The advent of mesoporous glasses, which are typically synthesized via sol-gel routes, allowed researchers to develop a broad and versatile class of novel biomaterials that combine superior bone regenerative potential (compared to traditional melt-derived glasses) with the ability of incorporating drugs and various biomolecules for targeted therapy in situ. Mesoporous glass particles can be directly embedded as a bioactive phase within a non-porous (e.g., microspheres), porous (3D scaffolds) or injectable matrix, or be processed to manufacture a surface coating on inorganic or organic (macro)porous substrates, thereby obtaining hierarchical structures with multiscale porosity. This review provides a picture of composite systems and coatings based on mesoporous glasses and highlights the challenges for the future, including the great potential of inorganic-organic hybrid sol-gel biomaterials.

From illite/smectite clay to mesoporous silicate adsorbent for efficient removal of chlortetracycline from water

Abstract: A series of mesoporous silicate adsorbents with superior adsorption performance for hazardous chlortetracycline (CTC) were sucessfully prepared via a facile one-pot hydrothermal reaction using low-cost illite/smectite (IS) clay, sodium silicate and magnesium sulfate as the starting materials. In this process, IS clay was "teared up" and then "rebuilt" as new porous silicate adsorbent with high specific surface area of 363.52m2/g (about 8.7 folds higher than that of IS clay) and very negative Zeta potential (-34.5mV). The inert SiOSi (Mg, Al) bonds in crystal framework of IS were broken to form Si(Al) O- groups with good adsorption activity, which greatly increased the adsorption sites served for holding much CTC molecules. Systematic evaluation on adsorption properties reveals the optimal silicate adsorbent can adsorb 408.81mg/g of CTC (only 159.7mg/g for raw IS clay) and remove 99.3% (only 46.5% for raw IS clay) of CTC from 100mg/L initial solution (pH3.51; adsorption temperature 30°C; adsorbent dosage, 3g/L). The adsorption behaviors of CTC onto the adsorbent follows the Langmuir isotherm model, Temkin equation and pseudo second-order kinetic model. The mesopore adsorption, electrostatic attraction and chemical association mainly contribute to the enhanced adsorption properties. As a whole, the high-efficient silicate adsorbent could be candidates to remove CTC from the wastewater with high amounts of CTC.

Synthesis of conductive polymer-coated mesoporous MCM-41 for textile dye removal from aqueous media

Abstract: In this paper, we aimed to evaluate Acid Blue 62 removal from aqueous media, using mesoporous silicate MCM-41, loaded with polypyrrole (PPy) and polyaniline (PAni) composites. PPy/MCM-41 nanocomposite showed higher performance than PAni/MCM-41 due to its smaller molecule size. For characterizing the synthesized composites, different methods were applied. The Langmuir model showed the greatest agreement with the experimental findings (q m, 55.55 mg g−1). The kinetic study also confirmed the compatibility between the pseudo-second-order model and adsorption. Moreover, we measured Gibbs free energy changes (ΔG o) and enthalpy changes (ΔH o). Considering the negative ΔG o and positive ΔH o, AB62 adsorption on PPy/MCM-41 nanocomposite can be considered a spontaneous, endothermic reaction.

A novel mesoporous silicate material (MS) preparation from dolomite and enhancing methylene blue removal by electronic induction

Abstract: In this investigation, a novel mesoporous silicate material (MS) was successfully synthesized from dolomite and applied for removal of hazardous dye Methylene Blue (MB). Properties of the material were characterized by XRD, FT-IR, BET, SEM-EDS, TEM, and TG-DSC. During the adsorption process, conditions like contact time, dye concentration, temperature and pH were studied to investigate the adsorption characteristics of the material. The adsorption capacity for MB could reach 111.65 mg/g. Thermodynamic and kinetic studies were also carried out in this paper. Moreover, a relative reasonable adsorption mechanism was revealed by XPS analysis. The results showed that the electronic induction between calcium and magnesium ions is advantageous to enhance the MB adsorption.

Preparation, characterization and catalytic performance of mesoporous silicates derived from natural diatomite: Comparative studies

Abstract: This paper aims at preparation of disordered mesoporous silicates from the diatomite ore as a natural resource of silica. Studying the morphological, chemical and textural properties of the prepared silicate samples was evaluated by field-emission scanning electron microscope (FE-SEM) combined with energy dispersive spectroscopy (EDS), high-resolution transmission electron microscope (HR-TEM), X-ray diffraction (XRD) and nitrogen adsorption isotherms at −196 °C. Catalytic oxidation studies were performed for methylene blue dye (MB) in presence of H2O2. Effects of different parameters like catalyst dose, pH, temperature, and initial concentrations of MB dye solution were investigated. Nanospherical and mesoporous silicates were formed without and with addition of cetyltrimethylammonium bromide (CTAB) surfactant, respectively. The obtained results in catalytic oxidation of MB dye are mainly related to the changes in surface area and mesopore size distributions as well as the significant effect of Fe (III) ions. The most effective catalytic oxidation studies were attained with catalyst dose (2 g/L), pH (4), temperature (50 °C) and initial dye concentration of MB dye (25 mg/L). A sharp decomposition proceeded during the first hour of the reaction. The obtained mesoporous silicate containing well-dispersed iron species as catalyst with the highest surface area and the lowest mesopore diameter showed excellent catalytic activity toward the removal of MB dye.

Kinetic modelling of cytochrome c adsorption on SBA-15

Abstract: The adsorption capacity of mesoporous silicate (MPS) materials as an adsorbent for protein adsorption from the aqueous phase and the mechanism of the adsorption processes by comparative analyses of the applicability of five kinetic transfer models, pseudo-first-order model, pseudo-second-order model, Elovich kinetic model, Bangham's equation model, and intraparticle diffusion model, were investigated. A mixture of tetraethyl orthosilicate (TEOS) and triblock copolymer as a template was stirred, hydrothermally treated to form the mesoporous SBA-15 structure, and heat-treated at 550°C to form the MPS material, SBA-15. The synthesized SBA-15 was immersed in a phosphate buffered saline (PBS) solution containing cytochrome c for 2, 48, and 120 hours at 4°C. The TEM observations of proteins on/in mesoporous SBA-15 revealed the protein behaviors. The holes of the MPS materials were observed to overlap those of the stained proteins for the first 2 hours of immersion. The stained proteins were observed between primary particles and partly inside the mesoporous channels in the MPS material when it had been immersed for 48 hours. For MPS when it had been immersed for 120 hours, stained proteins were observed in almost all meso-scale channels of MPS. The time profiles for adsorption of proteins can be described well by Bangham's equation model and the intraparticle diffusion model. The Bangham's equation model is based on the assumption that pore diffusion was the only rate controlling step during adsorption, whose contribution to the overall mechanism of cytochrome c adsorption on SBA-15 should not be neglected. The kinetic curves obtained from the experiment for cytochrome c adsorption on SBA-15 could show the three steps: the initial rapid increase of the adsorbed amount of cytochrome c, the second gradual increase, and the final equilibrium stage. These three adsorption steps can be interpreted well by the multi-linearity of the intraparticle diffusion model, proving the significant role of intraparticle diffusion as one of the rate controlling mechanisms.

Caffeine loading into micro- and nanoparticles of mesoporous silicate materials: in vitro release kinetics

Abstract: Caffeine was loaded into microparticles and nanoparticles of MCM-41 and MCM-48 to study its release into simulated body fluid at pH 7.4 and 37°C. The silicate systems were characterized by X-Rar Diffraction (XRD), scanning electron microscopy, and nitrogen adsorption/desorption isotherms. Loading of caffeine was confirmed by thermal gravimetric analysis and FTIR and the loading capacity was determined by high performance liquid chromatography (HPLC). The loading capacities for the microparticles are higher than that for the nanoparticles for both silicate systems, with the highest (56.8%) for the microparticles of MCM-48. However, for each system, the release from nanoparticle is faster than from microparticles. For all systems, diffusion is the major dissolution mechanism.

Hydroconversion of rapeseed oil to hydrocarbons in the presence of MFI/MCM-41 micro–mesoporous materials synthesized by the hydrothermal microwave method

Abstract: Catalysts containing an MFI zeolite and an MFI/MCM-41 composite synthesized by the hydrothermal microwave method have been first studied in rapeseed oil hydroconversion. Catalysts provide the production of valuable petrochemicals, namely, high-octane components of motor fuels and С2–С4 olefins. Synthesized MFI zeolite mostly catalyzed the formation of aromatic hydrocarbons (ArH); incorporation of this zeolite into the matrix of mesoporous silicate MCM-41 leads to a decrease in the ArH content in the liquid hydrocarbon products owing to an increase in the yield of liquid aliphatic hydrocarbons. Promotion of the MFI zeolite synthesized by the hydrothermal microwave method with zinc ions leads to the formation of a catalyst providing the formation of liquid products consisting of ArH.

Depolymerization of lignin using metal incorporated mesoporous silicate catalysts

Abstract: Provided is a process for depolymerizing lignin, the process comprising exposing a liquid feed comprising lignin and a solvent to a metal-incorporated solid mesoporous silicate catalyst under conditions sufficient to depolymerize the lignin to produce one or more aromatic monomers.

Mesoporous Ag2O-MnO2 catalyst, preparation method thereof and application of catalyst

Abstract: The invention provides a mesoporous Ag2O-MnO2 catalyst, a preparation method thereof and an application of the catalyst. The method includes the steps: (1) mesoporous manganese dioxide preparation: taking mesoporous silicate materials as template agents, performing soaking by the aid of manganese nitrate solution, removing impregnation liquid, performing drying and calcination to obtain precursors, and removing the template agents to obtain mesoporous manganese dioxide; (2) silver oxide loading: loading the silver oxide on the mesoporous manganese dioxide acquired in the step (1) to obtain a mesoporous manganese dioxide catalyst loaded the silver oxide. The catalyst is used for removing formaldehyde, and the cost of the catalyst is low as compared with a Pt loaded catalyst with high cost.

Protein Adsorption on Spark Plasma Sintered Mesoporous Silicate Compacts

Abstract: The preparation of mesoporous silica compact through spark plasma sintering (SPS) and adsorption / desorption of protein onto SPS mesoporous silica (MPS) compact is reported. MPS powders, prepared using triblock copolymer, PEO20PPO70PEO20, were compacted in carbon die and heated at 400 or 500 °C for 5 min under uniaxial pressure. The products are referred to as MPS-400 and MPS-500, respectively. The MPS sinters keep the mesoporous configuration, but the mode diameter of MPS-400 was smaller than that of MPS powders and MPS-500. The adsorbed amounts of protein on MPS-400 was higher than that on MPS-500, while the pore diameter, BET surface area, pore volume of MPS-400 are less than those of MPS-500. The interstices in MPS-500 are narrower than that in MPS-400, which may restrict the protein to penetrate through the narrow channels to reach the mesopores of MPS. The quantity of adsorbed amount of protein on MPS sinters does not depend on mesopore configuration but on the macropore configuration of the MPS sinters.

Adsorbent for sulfur dioxide

Abstract: FIELD: chemistry.SUBSTANCE: adsorbent comprises a carrier - MCM-41 mesoporous silicate with a specific surface area of about 1300 m/G and an active ingredient - sodium carbonate in an amount of 20-30 wt % of the total adsorbent weight.EFFECT: obtaining a product with improved sorption characteristics.2 ex

Adsorbent for hydrogen sulfide

Abstract: FIELD: chemistry.SUBSTANCE: adsorbent comprises a carrier - mesoporous silicate MCM-41 with a specific surface area of 1300 m/G, where sodium hydroxide is deposited. The amount of deposited sodium hydroxide is 20-30 wt % of the total adsorbent weight.EFFECT: product with improved sorption characteristics is obtained.2 ex