Showing papers in "Journal of Porous Materials in 2013"

Effects of ultrasound on the synthesis of zeolites: a review

Abstract: In this review, effects of ultrasound on the synthesis of different zeolites are studied. Ultrasound has been applied in crystallization because of its significant influences on the induction periods and nucleation. The effects of ultrasound assisted aging process for different zeolites compared with the effects of static aging, in some cases with microwave assisted aging, stirring aging and synthesis without any aging. Application of ultrasound can influence the size and morphology of the crystals, crystallization time and the crystallinity of the zeolites. The observations indicate that application of ultrasound can shorten the crystallization time. Application of ultrasound also improves crystallinity of the synthesized zeolites. Moreover, use of ultrasound assisted aging leads to altered morphologies and size of the particles.

Potassium geopolymer foams made with silica fume pore forming agent for thermal insulation

Abstract: Porous potassium based geopolymers with a mutli-scale porosity were synthesized. Silica fume is introduced as an additive to the geopolymer formulation. The free silicon contained inside this silica fume is oxidized in alkaline solution, releasing molecular hydrogen which generates the porosity. Previous work has shown how the porosity can be controlled with temperature, repeated temperature cycles and the mass introduced. Using this protocol, homogeneous foams were made and then studied with scanning electron microscopy. In particular the foam expansion has been followed with time in relation to the microstructure. The thermal conductivity values of the foams were evaluated using a fluxmeter method. The effective thermal conductivities are comprised between 0.12 and 0.35 W m−1 K−1 for apparent densities ranging from 0.40 to 0.85 g cm−3. The corresponding calculated pore volume fractions are in the range of 65–85%. The interest of this material is that it combines the advantages of low bulk density and insulating properties with the characteristics of a geopolymer skeleton. Literature reports a very good fire and acid/base resistance, a low cost of production and the possibility of recycling industrial waste in the form of silica fume.

Titanium foam made with saccharose as a space holder

Abstract: In this work we show a very promising method of titanium foam preparation with saccharose crystals (table sugar) as a space holder particles. The mixture of Ti and sugar particles was compacted to form a green compacts. In the next step the saccharose crystals were dissolved in the water, leaving open spaces surrounded by metallic scaffold. The sintering of the scaffold leads to foam with typical morphology and porosity. We found that 1:1 Ti/sugar ratio leads to porosities of about 72 % with pore diameter of about 0.8–1.0 mm, when we used 0.8–1.0 mm diameter sugar crystals. The foams morphology was investigated by SEM, porosity and internal structure was investigated using computed tomography and the structure was shown using XRD. The foam morphology pointed theirs potential applications in medical as well as catalyst devices.

Development of ciprofloxacin hydrochloride loaded poly(ethylene glycol)/chitosan scaffold as wound dressing

Abstract: A novel ciprofloxacin hydrochloride loaded chitosan/poly(ethylene glycol) (PEG) composite scaffold was developed for wound dressing application PEG incorporation in chitosan scaffold showed enhanced loading up to 54 % and increased cumulative release of the drug up to 35 % as compared to pure chitosan scaffold (20 %) The drug loading and control release of the drug has been explained by the morphological features and drug–polymer/polymer–polymer interactions revealed by SEM, FTIR and DSC Bacterial growth inhibition evaluation using Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus confirmed the efficacy of released drug from the scaffolds (pure and PEG mixed chitosan) Swelling study, bacterial penetration, moisture vapour transmission rate, haematocompatibility and biodegradation profile supported the suitability of scaffold used as wound dressing materials In-vivo study on mice finally validated the controlled rate of drug release showing the effectiveness of PEG incorporation into the scaffold for quicker and regulated wound healing

Activated carbon derived from macadamia nut shells: an effective adsorbent for phenol removal

Abstract: In this study, activated carbon based on the waste macadamia nut shells (MAC) was investigated for potential use as an adsorbent for phenol removal. The pseudo second-order kinetic model best described the adsorption process. The extent of the phenol adsorption was affected by the pH solution and the adsorbent dosage. Equilibrium data fitted well to the Langmuir model with a maximum adsorption capacity of 341 mg g−1. The calculated thermodynamic parameters suggested that the phenol adsorption onto MAC was physisorptive, spontaneous and exothermic in nature. Phenol desorption from loaded adsorbent was achieved by using 0.1 mol L−1 NaOH, ethanol (100 %) and deionized water.

Porous mullite ceramics derived from coal fly ash using a freeze-gel casting/polymer sponge technique

Abstract: The objective of this study was to prepare highly porous mullite ceramics with relatively large-sized pores and improved compressive strength using a freeze/gel casting route combined with polymer sponge for recycling of coal fly ash into high value-added ceramics. In this work, a tertiary-butyl alcohol /coal fly ash slurry system with an appropriate addition of Al2O3 was used. A reticulated structure with large pore size of 220–300 μm, which formed on burnout of polyurethane was obtained; then, the skeletons consisted mainly of more dense crystalline phases together with a few fine pores ( 3.7 (~4 μm in diameter) seen to have grown within the silicate melts existed. The compressive strength of the sintered porous materials increased in the reverse order of the degree of porosity, i.e. low porosity gave a high compressive strength. The porous materials with an average porosity of 61.6 %, sintered at 1600 °C with 70 wt.% solid loading showed the maximum average compressive strength (~45 MPa).

Crystal formation and size control of zeolitic imidazolate frameworks with mixed imidazolate linkers

Abstract: The effect of synthesis parameters, such as batch composition and synthesis temperature, on the formation and crystal size of zeolitic imidazolate frameworks (ZIFs) using mixed linkers, imidazole (Im) and benzimidazole (bIm), were studied by X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM). ZIF-7 and ZIF-62 were identified as the main phases and a phase diagram relating the batch composition and the final product was constructed based on XRPD and SEM. The range of batch composition giving rise to ZIF-7 and ZIF-62 was identified from the phase diagram. Changes of crystal size and morphology of ZIF-7 and ZIF-62 in terms of batch composition and synthesis temperature were studied by SEM and different trends were observed for the two ZIFs. Thermogravimetric analysis (TGA) and in situ XRPD showed that ZIF-62 possesses a similar high thermal stability as ZIF-7.

Characteristics and evaluation of synthetic 13X zeolite from Yunnan’s natural halloysite

Abstract: High purity microporous 13X zeolitic materials with octahedral microstructure were successfully synthesized by using Yunnan’s natural halloysite as silica and aluminum sources through hydrothermal method in alkaline media. The effects of various factors such as the molar ratio of SiO2/Al2O3, alkalinity, crystallization time and crystallization temperature were investigated. In addition, the characteristics of its structure and porosity were studied. The optimum synthesis conditions were SiO2/Al2O3 molar ratio of 4.3, NaOH solution concentration of 2 mol/L, aging time at room temperature 12 h and crystallization temperature of 100 °C/8 h. The optimum 13X zeolitic materials were fully characterized by chemical analysis, X-ray diffraction, field emission scanning electron microscopy, thermogravimetry and N2 adsorption–desorption. The as-synthesized 13X zeolitic products exhibited high thermal stability and Langmuir surface area of up to 726 m2/g, value much higher than elsewhere reported.

Synthesis and characterization of modified ZSM-5 nanozeolite and their applications in adsorption of Acridine Orange dye from aqueous solution

Abstract: In this research, a novel method was reported for the synthesis of ZSM-5 nanozeolite. The ZSM-5 nanozeolite was modified by transition metals such as nickel, copper and iron. These nanozeolites were characterized using X-ray diffraction, scanning electronic microscopy, Fourier transform infrared and Energy-dispersive X-ray techniques. The synthesized Fe-ZSM-5 nanozeolite has been smaller average particle size than the other nanozeolites. Adsorption behavior of Acridine Orange (AO) onto nanozeolites has been studied in an aqueous medium using UV–VIS technique. The modified nanozeolites have more adsorption efficiency compared to the unmodified ZSM-5 nanozeolite for AO removal. Also, Fe-ZSM-5 nanozeolite was shown higher adsorption efficiency of AO than the other synthesized nanozeolites. Adsorption isotherms were fitted with the Langmuir, Freundlich and D–R models. The kinetic data were investigated using pseudo-first order and pseudo-second order models. The adsorption kinetics of AO on Fe-ZSM-5 nanozeolitewell matched with pseudo-second order kinetic model.

Adsorption and diffusion properties of xylene isomers and ethylbenzene in metal–organic framework MIL-53(Al)

Abstract: Adsorption and diffusion behaviour of C8 aromatic isomers, including para-xylene (PX), ortho-xylene (OX), meta-xylene (MX), and ethylbenzene (EB), in metal–organic framework Mil-53(Al) has been systematically investigated by using intelligent gravimetric analyzer, thermogravimetric analysis and molecular simulation respectively The results indicate that adsorptions of xylene isomers and ethylbenzene molecules in Mil-53(Al) at 303 K present type-I isotherms The deviation from normal Langmuir model of the isotherms at higher temperature can be, however, found because of the breathing effect of Mil-53(Al) framework In order to well understand the selective adsorption process of above adsorbates, the diffusion behaviour has been determined and the diffusion coefficient is in the order: OX > PX > MX > EB The adsorption thermodynamics have been determined by the isotherms at different temperature A sharp increase of the heat of sorption Q st suggests that a strong interaction between sorbates molecules and between sorbates and the framework appears as the increase of the loading Two desorption peaks in DTG curves suggests that two sorption locations exist in Mil-53(Al) to C8 alkylaromatics The molecular simulation results have been used to successfully explain the experimental phenomena and to well understand the underlying adsorption and diffusion features of the systems

Synthesis of mesoporous LTA zeolites with large BET areas

Abstract: Mesoporous LTA zeolites were successfully synthesized by performing a direct hydrothermal synthesis using tetraethylorthosilicate (TEOS) and an organosilane surfactant as the silicon source and the mesopore-generating agent, respectively. The as-synthesized materials were characterized using a complementary combination of X-ray diffraction, nitrogen adsorption–desorption measurements, scanning electron microscopy, and transmission electron microscopy. The characteristics of the samples are comparable with the materials synthesized with sodium metasilicate nonahydrate as the silicon source. The influence of the adding amount of the amphiphilic organosilane [3-(trimethoxysilyl)propyl]-tetradecyl-dimethylammonium chloride on the mesoporous and microporous properties of the samples were investigated. Our results indicate that the materials synthesized with TEOS possess a mesoporous-microporous hierarchical structure. Moreover, the synthesized materials have a large Brunauer–Emmett–Teller area of up to 244 m2/g and present consistent mesopore diameter distributions centered at approximately 4.6 nm. The results of thermogravimetric analysis prove that more amphiphilic surfactant molecules bond to the LTA zeolite framework surface synthesized using TEOS.

SEM–EDX and XRD characterization of zeolite NaA, synthesized from rice husk and aluminium scrap by different procedures for preparation of the initial hydrogel

Abstract: A number of investigations have demonstrated that zeolite NaA could be synthesized using Si, extracted from rice husk ash; however, experiments on direct extraction of Si from rice husk (RH) are scarce. The main objective of the present study was to explore the possibility to synthesize high-quality zeolite NaA from RH and waste aluminium cans (as a source of Al), applying different procedures for the preparation of initial hydrogel and a unified procedure for crystallization of zeolite NaA. Products were characterized by SEM–EDX and XRD analyses. The investigation demonstrated that Si could be extracted directly from RH, avoiding the process of RH burning. Practically complete dissolution of Si from RH was achieved by alkali treatment (with 10 % NaOH for 7 h) at boiling temperature and atmospheric pressure, i.e. using refluxing system instead of autoclave for the preparation of Si-gel. Zeolite NaA samples synthesized from such Si-gels were pure, highly crystalline and white. Furthermore, it was found that the direct dissolution of Al in Si-gel did not affect the quality of the final product. Although this investigation was not focused on the mechanism of zeolite NaA crystallization, the results obtained indicated clearly that the history of Si-gel preparation played an important role in the nucleation and growth of zeolite NaA crystals and influenced their yield, size, and shape. Therefore, the optimization of Si-gel preparation procedure has to be considered as essential not only for the economy of the synthesis of NaA from RH, but also for the quality of the final product.

Synthesis and performance of microporous inorganic membranes for CO2 separation: a review

Abstract: Removal of CO2 by membrane technologies is one promising approach as compared to other CO2 capture technologies due to advantages such as simpler operation, higher reliability, lower capital and operating cost, higher energy efficiency, and a cleaner process. In the field of CO2 gas separation, inorganic membranes have been attracting a lot of attention. Three classes of microporous membrane family, i.e. microporous silica membranes, microporous carbon membranes and zeolite membranes, have been widely studied due to their potential in separating CO2 gas molecules, contributed by their distribution of selective micropores which are almost identical to the required molecular sizes for diffusing CO2 gas. This paper review various methods to fabricate the above three types of microporous membranes, at the same time, looking at other researchers employing these methods to fabricate microporous membranes for CO2 separation.

Preparation and characterization of porous crosslinked microspheres of new aromatic methacrylates

Abstract: The aim of this work was to prepare a new group of aromatic methacrylate monomers, utilise them in preparation of porous microspheres and study the influence of their chemical structure on the textural properties of porous methacrylate microspheres. Polymeric microspheres were prepared by suspension-emulsion polymerisation of four aromatic monomers: methacryloiloxybenzene, 1,2-dimethacryloiloxybenzene, 1,3-dimethacryloiloxybenzene and 1,4-dimethacryloiloxybenzene with another crosslinking agent—trimethylolpropane trimethacrylate. Mass median diameters of obtained beads are in the range 22–35 μm. The polymerisation reactions were carried out in the presence of a pore forming diluent. The influence of the diluent system on the porous structure of microspheres was studied in detail. To determine the textural properties of the studied microspheres, nitrogen adsorption–desorption and inverse sized exclusion chromatography measurements were used. Specific surface area of the obtained microspheres achieves value from 185 to 510 m2/g. Since obtained polymeric materials can be used as chromatographic packings for HPLC their porous structure in a swollen state was investigated. Significant differences in the porous structure parameters for dry and swollen microspheres were observed.

Oxidative dehydrogenation of n-butane over bimetallic mesoporous and microporous zeolites with CO2 as mild oxidant

Abstract: Oxidative dehydrogenation of n-butane was tested using carbon dioxide as a mild oxidant over bimetallic Cr–V supported catalysts (MCM-41, ZSM-5, MCM-22 and mesoZSM-5). The textural properties of the catalysts were measured by means of XRD, N2 adsorption, SEM-EDX, Raman, H2-TPR, pyridine FT-IR, NH3 and CO2-TPD techniques. The metal content of Cr and V was maintained around 1.2 and 2.8 wt% for the catalytic test in packed bed reactor at different temperatures (525–600 °C) for 180 min. 1.2Cr2.8 V/MCM-41 and 1.2Cr2.8 V/ZSM-5 exhibited maximum conversion of 14 and 13.1 %, respectively at 10 min and 600 °C. Significantly, high butenes selectivity was observed over MCM-41 (86.27 %) than ZSM-5 support (58.1 %). The mesoporosity in ZSM-5 had a negative impact on conversion level (7.1 %) but improved the butenes selectivity slightly. 1.2Cr2.8 V/M-22 showed the highest cracking ability leading to overall reduced butenes selectivity (57.9 %). The study shows that over all catalysts, n-butane conversion is independent of CO2 conversion. 1.2Cr2.8 V/M-22 showed highest CO2 conversion in the range 2.35–2.2 % between 525 and 550 °C. The apparent activation energies of dehydrogenation and cracking reaction over the four catalysts were evaluated. The ratio of conversion to coke weight per cent over the four catalysts are observed in the following order: 1.2Cr2.8 V/M-41 > 1.2Cr2.8 V/Z-5 > 1.2Cr2.8 V/mesoZ-5 > 1.2Cr2.8 V/M-22.

Fabrication of highly ordered porous anodic alumina membrane with ultra-large pore intervals in ethylene glycol-modified citric acid solution

Abstract: Fabrication of anodic alumina membrane with ultra-large pore intervals is still a challenge because it is difficult to maintain stable anodization without breakdown or burning of the alumina due to the corrosive acid attack at high electric fields. A novel strategy is proposed that the undesired burning phenomena of the alumina can be avoided at relatively high voltage anodization in ethylene glycol-modified citric acid solution at room temperature, and an ultra-large pore interval up to 1,800 nm was achieved at 700 V. A large pore of 800 nm was readily obtained by chemical etching of the alumina pore wall in 5.0 wt% H3PO4 solution.

Efficient removal of Congo red by magnetically separable mesoporous TiO2 modified with γ-Fe2O3

Abstract: Magnetically separable mesoporous TiO2 modified with γ-Fe2O3 was prepared and characterized by X–ray diffraction, N2 adsorption–desorption measurements, scanning electron microscopy, UV–vis absorption and magnetic measurements The adsorptive removal of Congo red using the binary system was performed under various experimental conditions to examine the effects of contact time, solution pH, and initial concentration of Congo red The results show that the removal abilities and separability of mesoporous TiO2 adsorbent for Congo red can be significantly improved by modification with γ-Fe2O3 The adsorption of Congo red on the γ-Fe2O3–TiO2 reaches the maximum percentage removal of ca 97 % within 60 min, showing that most of Congo red can be removed in a short time When the pH of solution is varied from 34 to 103, the percentage removal of Congo red decreases from ca 97 to ca 15 %, showing that the adsorption is strongly dependent on solution pH The adsorption kinetics of Congo red fit well with pseudo-second-order kinetic model, and the equilibrium data is best described by Langmuir adsorption model The maximum adsorption capacity of the γ-Fe2O3–TiO2 for Congo red is estimated to be 1250 mg/g

Improvement of catalytic efficiency of chloroperoxidase by its covalent immobilization on SBA-15 for azo dye oxidation

Abstract: Chloroperoxidase from the fungus Caldariomyces fumago was covalently immobilized on SBA-15 mesoporous material and assayed for the enzymatic oxidation of four azo dyes. All dyes were oxidized by the free and the immobilized enzyme to different extent. Acid Blue 120 and Direct Blue 85 dyes were decolorized almost completely. The catalytic efficiency, k cat/K M, of the immobilized enzyme was 27, 2.9, 137 and 28 times higher than the free enzyme for Basic Blue 41, Disperse Blue 85, Acid Blue 120 and Direct Black 22 oxidation, respectively. The immobilized enzyme displayed improved thermostability and a similar pH profile compared to the free enzyme. The immobilized chloroperoxidase showed excellent storage stability and maintained 100 % catalytic activity after 90 days at both 4 and 25 °C.

Synthesis and single-crystal structure of lead oxide nanoclusters in zeolite Y, |Pb15.52+(Pb4O4(Pb16/192+Pb3/194+)4)4.75|[Si117Al75O384]-FAU

Abstract: A single crystal of excessively Pb2+-exchanged zeolite Y (|Pb 15.5 2+ (Pb4O4(Pb 16/19 2+ Pb 3/19 4+ )4)4.75|[Si117Al75O384]-FAU) was prepared by exchange of Na–Y (|Na75|[Si117Al75O384]-FAU, Si/Al = 1.56) with an aqueous stream 0.05 M Pb(C2H3O2)2 at 294 K, followed by vacuum dehydration at 1 × 10−6 Torr and 693 K. Its structure was determined at 100 K, by X-ray diffraction techniques in the cubic space group Fd $$ \overline{3} $$ m and was refined to the final error indices R 1/wR 2 = 0.0639/0.1323. About 53.5 Pbn+ ions per unit cell occupy three different equipoints; 26 are at site I′, 19 are at site II, and the remaining 8.5 are at another site II. Three Pb4+ ions at some of the positions must have higher oxidation states due to elevated dehydration temperature; Pb(IIa) is supposed to coexist with Pb2+ and Pb4+ ions assuming the charge balance of the zeolite framework. A distorted Pb4O4 cube, alternating Pb2+ at Pb(I′) and O2− at O(5), coordinates with four Pb2+ and/or Pb4+ ions through its oxygen atoms to give a [Pb 4 2+ O 4 2− (Pb 16/19 2+ Pb 3/19 4+ )4]176/19+ cluster in 4.75 of eight sodalite cavities per unit cell in zeolite Y.

Production, mechanical properties and in vitro biocompatibility of highly aligned porous poly(ε-caprolactone) (PCL)/hydroxyapatite (HA) scaffolds

Abstract: We produced highly aligned porous poly(e-caprolactone) (PCL)/hydroxyapatite (HA) scaffolds by unidirectionally freezing PCL/HA solutions with various HA contents (0, 5, 10 and 20 wt% in relation to the PCL polymer) and evaluated their mechanical properties and in vitro biocompatibility to examine their potential applications in bone tissue engineering. All the prepared scaffolds had a highly aligned porous structure, in which the HA particles were uniformly dispersed in the PCL walls. The elastic modulus of the PCL/HA scaffolds significantly increased from 0.12 ± 0.02 to 2.65 ± 0.05 MPa with increasing initial HA content from 0 to 20 wt%, whereas the pore size decreased from 9.2 ± 0.7 to 4.2 ± 0.8 μm. In addition, the PCL/HA scaffolds showed considerably enhanced in vitro cellular responses that were assessed in terms of cell attachment, proliferation and osteoblastic differentiation.

Grafting of lignin onto nanostructured silica SBA-15: preparation and characterization

Abstract: The slow decline in oil reserves with mounting oil prices is pushing industry to find more sustainable sources for industrial manufacturing. Lignin is the second most abundant natural renewable biopolymer that is underutilized and has many functional groups (–OH, phenolics) that make the biopolymer a convenient substrate for materials manufacturing by the industry. The present study thus describes grafting of lignin onto nanostructured silica SBA-15 (Santa Barbara amorphous 15) by first silylating lignin with triethoxychlorosilane followed by treatment of silylated lignin with SBA-15. The resulting nanocomposite denoted as LIG–SBA-15-G was then characterized by powder X-ray diffraction, infra-red (FTIR), 31P nuclear magnetic resonance (31P NMR), N2 adsorption (BET), scanning and transmission electron micrographs (SEM and TEM) and thermogravimetric analysis (TGA). X-ray data showed that LIG–SBA-15-G exhibited hexagonal structure closely similar to that observed for the SBA-15 host. FTIR of LIG–SBA-15-G showed characteristic absorption bands from lignin and attenuated Si–OH band due to its conversion to Si–O–Si ether bonds. Whereas, 31P NMR revealed that the majority of hydroxyl groups in lignin were replaced by Si–O–LIG ether bonds in LIG–SBA-15-G. SEM images of LIG–SBA-15-G displayed little changes in the macroscopic structure as compared to SBA-15. TEM images showed some disordered area in LIG–SBA-15-G and the grafted lignin appeared as black film on the silica surface. Using BET analysis the surface area of LIG–SBA-15-G was found to be 560 m2 g−1. Finally, TGA showed that LIG–SBA-15-G was more thermally stable than lignin and contained 13 % w/w lignin. Understanding the physicochemical and structural properties of the resulting lignin-nanosilica hybrid material should help engineer a robust and sustainable biomaterial suitable for various application, e.g. removal of contaminants from contaminated water.

Synthesis of a ZSM-5(core)/SAPO-5(shell) composite and its application in FCC

Abstract: A core/shell structure composite was synthesized via a new method of pre-coating one raw material. The composite was characterized by X-ray diffraction, SEM, TEM and N2 isothermal adsorption–desorption and Py-FTIR. In addition, the catalytic performance of the composite in cracking of heavy oil for producing olefin was also investigated. The characterization results show that the composite with a core/shell structure had smaller particle size, uniform SAPO-5 shell, and fewer acid sites than ZSM-5, accelerating the transport of reactant and product molecules between different zeolites. Consequently, the light olefins on the composites had high specific selectivity.

A simple thermogravimetric method for the evaluation of the degree of fly ash conversion into zeolite material

Abstract: The thermogravimetry was used for the evaluation of degree of conversion of fly ash into zeolite material alongside the CEC and XRD methods being currently proposed for this purpose. The present work proposes the calculation of the thermogravimetric fly ash-to-zeolite conversion factor, CFTGA, based on the comparison of the mass loss of the commercial zeolite (standard) occurred during dehydration with that of the fly ash-derived zeolite. This mass loss is characteristic of a specific zeolite type, and the corresponding zeolite water content in the sample of zeolites indicates their degree of crystallinity and zeolite phase content. The use of the TGA method for the indirect determination of the fly ash-to-zeolite conversion factor would be preferable owing to its “speed” compared to other methods proposed for this purpose, as well as the capability to use a consistent procedure. Because of its short CFTGA determination procedure, the thermogravimetric method can be used for the control and determination of the quality of fly ash-derived zeolite in an industrial plant.

Trapping of biological macromolecules in the three-dimensional mesocage pore cavities of monolith adsorbents

Abstract: Gene technology is experiencing remarkable progress, and proteins are becoming crucial in the field of disease diagnosis and treatment. Adsorption of biomolecules on the surface of inorganic materials is an important technique for diagnostic assays and gene applications. In this study, highly ordered mesocage cubic Pm3n aluminumsilica monoliths were fabricated by the one-pot direct-templating of a microemulsion of the liquid crystalline phases of a Brij 56 surfactant. Mesocage cubic Pm3n aluminosilica monoliths with well-defined mesostructures offer high adsorption and loading capacity of proteins from an aqueous solution. Three-dimensional monoliths characterized by spherical pore cavities can potentially perform efficient adsorption and trapping of insulin, cytochrome C, lysozyme, myoglobin, β-lactoglobin proteins. A wide variety of characterization techniques such as SAXS, SEM, TEM, the Brunauer–Emmett–Teller method for nitrogen adsorption and surface area measurements, and TEM were used. The adsorption of proteins as well as the kinetic and thermodynamic characteristics of adsorption was studied, and adsorption isotherms were described by the Langmuir equation. Our findings indicated that monolayer coverage of proteins formed on mesoporous adsorbent surfaces during immobilization and uptake assays. Adsorption efficiency of proteins was attained after a number of reuse cycles, which indicates the presence of mesoporous adsorbents of biomolecules. Integration of mesoporous adsorbents may be feasible in various scientific fields such as nanobioscience, material science, artificial implantation, protein purification, biosensors, drug delivery systems, and molecular biology/biotechnology.

Sol–gel preparation of PTMS modified hydrophobic and transparent silica coatings

Abstract: Wettability of solid surfaces is an important property, which depends on both the surface chemistry and surface roughness. The present paper describes the room temperature synthesis of dip coated water repellent silica coatings on glass substrates using phenyltrimethoxysilane (PTMS) as a co-precursor with two-step sol–gel process. Silica sol was prepared by keeping the molar ratio of tetraethylorthosilicate precursor, methanol solvent, acidic water (0.001 M oxalic acid) and basic water (12 M NH4OH) constant at 1:11.03:0.17:0.58 respectively, throughout the experiments and the PTMS weight percentage was varied from 0 to 15 %. It was found that with an increase in wt% of PTMS, the roughness and hydrophobicity of the films increased. However, the optical transmission decreased from 93 to 82 % in the visible range. The hydrophobic silica films retained their hydrophobicity up to a temperature of 386 °C and above this temperature the films became hydrophilic. The hydrophobic silica thin films were characterized by taking into consideration the surface roughness studies, Fourier transform infrared spectroscopy, percentage of optical transmission, scanning electron microscopy, thermogravimetric–differential thermal analysis and contact angle measurements.

Highly selective oxidation of alcohols catalyzed by Cu(II)-Schiff base-SBA-15 with hydrogen peroxide in water

Abstract: An efficient catalyst for selective oxidation of alcohols was prepared by grafting the Cu(II) Schiff base complex onto the channels of mesoporous silica material SBA-15. The characterizations illustrated that the functionalized SBA-15 maintained the primary hexagonally ordered mesoporous structure, and the Cu(II) Schiff base complexes were bonded inside the mesoporous channels of SBA-15. The selective oxidation of benzyl alcohol was carried out in water phase with hydrogen peroxide. The C6H5CH2OH conversion could reach 98.5 % with 100 % of the selectivity to C6H5CHO under the optimum conditions. The catalyst could also react well on the selective oxidation of other primary alcohols.

High-surface-area SBA-15–SO3H with enhanced catalytic activity by the addition of poly(ethylene glycol)

Abstract: The influence of poly(ethylene glycol) (PEG) and synthesis temperature in the synthesis of SBA-15–SO3H was investigated to evaluate the catalytic activity in the esterification of propionic acid with methanol. The catalysts were characterized by means of surface and structure analyses; X-ray diffraction, FT-IR, scanning electron microscopy, Thermo-gravimetric and N2 adsorption/desorption techniques. It was found that, by the addition of PEG, the surface area and porosity of SBA-15–SO3H increased, while the structure and size of mesopores remained unchanged. Nitrogen sorption measurements indicate that PEG introduces additional pores into the pore walls of SBA-15–SO3H. Thus, a simple way of improving the porosity of mesoporous SBA-15–SO3H was presented that could enhance transport of substrates through the porous system and allow the generation of stable mesoporous replicas, important for catalytic applications and also beneficial for replication and nanocasting purposes.

Density and porosity of bentonites

Abstract: The calculation and measurement of the densities of smectites proved that calculation can lead to accurate values if the smectite d001-value, water content, molar mass of one formula unit, interlayer composition, and layer charge density are considered. The density measurement was supposed to be affected by accommodation of some He in micropores. The specific surface area determined by the common N2 adsorption is largely affected by micropores which in turn was used as proxy for microporosity. The investigated materials show a wide range of microporosities (5–65 % of the total porosity up to 50 μm). Micropores are supposed to result from the imperfect stacking of single TOT layers resulting in the quasi crystalline overlap region but they also result from partial access of the interlayer at the edges. Unfortunately, both types of microporosity could not be distinguished quantitatively. For measurement of the microporosity both N2 and CO2 adsorption were found to be suitable. The mesoporosity of bentonites also covers a significant range. One particularly mesoporous material was identified both by N2 adsorption and mercury intrusion. SEM investigation suggests the fibrous microstructure to be responsible for the extraordinary mesoporosity. For the characterization of the mesoporosity, N2 adsorption showed best resolution. The macroporosity may be classified according to the type of aggregates observable by SEM. The typical rose like arrangement of smectites results in 1 μm macropores and relict structures of the volcanic glass particles result in larger pores. The third type of macropore simply results from the relative arrangement of aggregates.

Hybrid MCM-41 grafted by a general microwave-assisted procedure: a characterization study

Abstract: Hybrid materials obtained through a Microwave-assisted grafting of organic functional groups on mesoporous silica (MCM-41 type) have been characterized by X-ray powder diffraction, TG-DSC, N2 adsorption, solid state 13C- and 29Si-NMR, TEM and SEM. The studied grafting procedure is effective in the preparation of hybrid organosilicas under solvent-free conditions. Microwaves allows an ultra-fast and clean functionalization of the mesoporous materials and the method has been applied to produce a wide series of functional materials. The hybrid materials maintain the original mesoporous structure when the loading of linked organic groups does not exceed 10 %. In this cases, the slight pore volume reduction is linearly correlated to the organic amount in the product. If functional groups able to interact among them through hydrogen bond are used, hybrid materials exhibit high Organic/SiO2 ratios and low pore volumes due to the formation of a network occluding the pores, where functional groups of free organosilane molecules interacts with the functional groups of molecules linked to the matrix. NMR data confirm that the network is composed by organosilane molecules linked or not to the framework. Acid washing is able to labilize hydrogen bond and open the network. In the case of bulky but chemically inert functionalising agents the network is not produced.

Effect of the thermal treatment on microstructure and physical properties of low-density and high transparency silica aerogels via acetonitrile supercritical drying

Abstract: In this paper, we reported the experimental results about the effect of the thermal treatment on microstructure and physical properties of low-density and high transparent silica aerogels. From our results, with tetramethyl orthosilicate as precursor and via acetonitrile supercritical drying process, silica aerogel monolith was obtained possessing the properties as low-density (0.018 g/cm3), high surface area (923 m2/g), high optical transparency (87.9 %, 800 nm). It should be noted that high transparency of silica aerogel can be maintained up to 600 °C (91.5 %, 800 nm). The mechanical properties of silica aerogel decreased with increasing heat treated temperature to 600 °C, and silica aerogels still maintained crack-free monoliths completely and possessed high homogeneous density even after 600 °C thermal treatment. Furthermore, thermal conductivity of the monoliths at desired temperatures was analyzed by the transient plane heat source method. When the temperature flowed from 25 to 600 °C, thermal conductivity coefficients of silica aerogels changed from 0.021 to 0.065 W (m K)−1, revealed an excellent heat insulation effect in high-temperature area. Currently, the specific process developed for low-density aerogels affected by thermal treatment has not been reported in previous literature.