Porous Silicate Materials Research Articles

Mesoporous zinc silicate bio-composite: Preparation, characterization and in vitro evaluation

Abstract Zinc silicate composites bring together the unique properties of silica and zinc giving rise to a material that possesses biocompatibility, bioactivity, antibacterial activity, ability to stimulate osteogenesis and differentiation. Recently, owing to such exceptional features, zinc silicate based biocomposites have found application as a biomaterial. In this study, we report a novel one-pot method to engineer porous nanostructured mesoporous zinc silicate material (mZS). The synthesized rod-like particles with pores of size 2–3 nm had a surface area of 292.065 m2/g and were found to be pure and amorphous in nature. The material exhibited antibacterial activity against Gram positive Staphylococcus aureus where Minimum Inhibitory Concentration (MIC) of mZS was found to be around 0.15 mg/mL and Minimum Bactericidal Concentration (MBC) was around 0.9 mg/mL. It was found to be biocompatible towards mouse mesenchymal stem cells (C3H10T1/2) and human osteoblastic cells (MG-63). The synthesized material was stable even after 32 days and exhibited only minor structural changes due to dissolution when biodegradability studies were done in PBS. In addition, the ability of the material to carry small molecules was assessed using a water soluble cationic dye, Methylene Blue. The adsorption capacity of mZS for methylene blue dye was found to be around 47.28 ± 0.57 μg/mg of particle. The results indicated that synthesized mZS can efficiently load small molecules and possesses properties like antibacterial activity and biocompatibility, thus, might prove to be a promising biomaterial as bone fillers, bioactive coatings and bone cements.

Impact of polyacrylamide adsorption on flow through porous siliceous materials: State of the art, discussion and industrial concern

HypothesisAdsorption of high molar mass polymers impacts flow in porous media. In the industrially crucial case of acrylamide-based polymers in porous silicates, the very occurrence of adsorption is still debated. Thus, the present work aimed at establishing a clear correlation between adsorption of acrylamide-based polymers and injectivity loss in porous silica. ExperimentsA review of the literature revealed apparent discrepancies regarding the affinity of acrylamide-based polymers for siliceous materials having ostensibly the same chemical composition. Through a deeper analysis of the reported literature and new experimental measurements on well-defined polymers and surfaces, we investigated the relation between the silica surface properties and the acrylamide-based polymer adsorption. Our observations were confronted with water injection experiments in porous media of different surface compositions previously put in contact with polymers. FindingsThe polymer affinity towards the silica surface depended on the density of hydroxyl groups at the surface of the oxide, its thermal treatment, storage condition and purity. This demonstrated that the impact of adsorption on acrylamide-based polymer flow within porous silicates heavily depends on the silicate surface composition and must be carefully evaluated. In view of the continually expanding use of acrylamide-based polymers, notably in enhanced oil recovery, such considerations provide interesting insights into the effect of adsorption on their flow into porous materials.

Preparation and characterization of a porous silicate material using a CO2-storage material for CO2 adsorption

A porous silicon material (PSM) was successfully prepared by using a CO2-storage material (CO2SM) as raw material, in which Na2SiO3 was used as a silicon source and the CO2SM was used as an acid source. The effects of CO2SM dosage, particle size, post-treatment temperature, and post-treatment time on CO2 adsorption capability was systemically evaluated, and the optimum condition was confirmed by response surface experiments as follows: 10 g CO2SM dosage, 50 mL 0.5 M Na2SiO3, 40–160 mesh, the post-treatment temperature of 80 °C, and the post-treatment time of 36 h with the maximum adsorption capacity of 9.74 mg CO2/g adsorbent for 8% CO2/N2 at 25 °C. Based the optimum condition, SiO32− extraction from coal gangue was used as the silicon source to prepare the PSM with the maximum adsorption capacity of 9.02 mg CO2/g adsorbent for 8% CO2/N2 at 25 °C. Next, PSM was impregnated with ethanediamine (EDA), after that the CO2 adsorption capacity increased to 17.14 mg CO2/g adsorbent. In addition, the optimum PSM was characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and N2 adsorption-desorption isotherms. Although the resulting materials showed a low adsorption capacity, its silicon source was inexpensive, which was of significance in the rational utilization of coal gangue.

CO2 Capture on a Novel Porous Silicate Material from Coal Gangue: Equilibrium, Kinetic, and Thermodynamic Studies

The adsorption of CO2 on a novel porous silicate material (PSM) from coal gangue at T = (288.15, 303.15, and 318.15) K was thoroughly characterized, and the experimental results showed that the adsorption capacity increased with the increasing pressures. Furthermore, the isotherm data were well fitted to Double–Langmuir model, and the adsorption process was found to be exothermic in nature with a decrease in entropy. Meanwhile, thermodynamic results also showed that the adsorption occurred via a spontaneous and enthalpy driven process and controlled by physisorption. In addition, the adsorption performance was still stable after 10 times adsorption—desorption cycles, which indicated that the PSM had a positive regeneration performance.

Preparation and characterization of a porous silicate material from silica fume

A porous silicate material derived from silica fume was successfully prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR) spectroscopy, Thermogravimetry and Differential thermal gravity (TG-DTG), N2 adsorption and desorption isotherms, and scanning electron microscopy (SEM). Raw silica fume was analyzed by XRD, FT-IR and SEM. The analysis results of silica fume indicated that SiO2 in silica fume is mainly determined as amorphous state, and that the particles of raw silica fume exhibited characteristic spherical structure with a diameter of from 50 nm to 200 nm. The preparation of the porous silicate material involved two steps. The first step was the extraction of the SiO 3 2− leachate from raw silica fume. The maximum value of SiO 3 2− extraction yield was obtained under the following conditions: reaction temperature of 120 °C, reaction time of 120 min, NaOH concentration of 15%, and alkali to SiO2 molar ratio of 2. The second step was the preparation of the porous silicate material though the reaction of SiO 3 2− leachate and Ca(OH)2 suspension liquid. The optimum preparation conditions were as follows: preparation temperature of 90 °C, preparation time of 1.5 h, Si/Ca molar ratio of 1 : 1, and stirring rate of 100 r/min. The BET surface area and pore size of the porous silicate material were 220.7 m2·g−1 and 8.55 cm3/g, respectively. The porous silicate material presented an amorphous and unordered structure. The spectroscopic results indicated that the porous silicate material was mainly composed of Si, Ca, O, C, and Na, in the form of Ca2+, SiO 3 2− , CO 3 2− and Na+ ions, respectively, which agreed with the XRD, TG-DSC, and FT-IR data. The N2 adsorption-desorption isotherm mode indicates that the porous silicate material belonged to a typical mesoporous material. The porous silicate material presented efficiency for the removal of formaldehyde: it showed a formaldehyde adsorption capacity of 8.01 mg/g for 140 min at 25 °C.

Применение пористых силикатных материалов различного строения для ацеталирования фурфурола и 5-гидроксиметилфурфурола метанолом

Применение пористых силикатных материалов различного строения для ацеталирования фурфурола и 5-гидроксиметилфурфурола метанолом

Design of TiO<sub>2</sub>-loaded Porous Siliceous Materials and Application to Photocatalytic Environmental Purification

Design of TiO<sub>2</sub>-loaded Porous Siliceous Materials and Application to Photocatalytic Environmental Purification

Rational Design and Fabrication of Porous Calcium-Magnesium Silicate Constructs That Enhance Angiogenesis and Improve Orbital Implantation.

Tissue integration of orbital implants, following orbital enucleation treatment, represents a challenge for rapid fibrovascularization, long-time stability, anti-infection, and even induction of vascule regeneration. The objective of this study was to develop porous calcium-magnesium silicate materials, with good stability, bioactivity, and antibacterial potential as new orbital fillers. Three-dimensional (3D) diopside scaffolds (low dissolvability) were fabricated by direct ceramic ink writing assembly and then followed by one-step sintering at 1150 °C for 3 h. The pore wall of the scaffold was modified by another calcium-magnesium silicate, such as bredigite or akermanite, which dissolves quickly but shows greater angiogenic potential. These two Ca-Mg-silicates can be coated onto the pore strut, and the coating layers were observed to slowly dissolve in Tris buffer. The vascularization-favorable Cu ions, which had been doped into the bredigite or akermanite coating, could also be measured in the immersion medium. A primary angiogenic test in a panniculus carnosus muscle model in rabbit indicated that the Cu-doped bredigite and akermanite coatings were significantly beneficial for the neovascularization in the early stages. These results suggest that the diopside-based porous materials modified with functional coatings hold great potential for application in orbital reconstruction.

Preparation and characterization of a novel porous silicate material from coal gangue

A novel porous silicate material (PSM) derived from coal gangue was successfully prepared and characterized by N2 adsorption–desorption isotherms, thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction measurements. The preparation procedure involved two steps: (1) SiO32− leaching from coal gangue by both activation and chemical approaches, and (2) preparation of the PSM by reaction of the leachate with Ca(OH)2. It was found that the maximum SiO32− leaching yield was achieved at calcination temperature of 1000 °C, reaction temperature of 106 °C for 2 h, NaOH concentration of 25%, and the ratio of coal gangue to alkali of 0.5:1. The PSM was then easily prepared from the SiO32− leaching at 98 °C for 2 h with a Ca/Si ratio of 1.2:1 and the pH value of 12.70. The spectroscopic results showed that the PSM was mainly composed C, Ca, O, Si and Na, in the form of Ca2+, Na+, SiO32−, and CO32− ions. Some adsorbed water and/or surface water was observed. The adsorption behavior revealed that the CO2 adsorbed amount on PSM was 36.69 mg g−1 at 293.15 k and ambient pressure with a pure CO2 flow rate of 120 mL min−1 during 90 min.

Effect of Pore Structure on CO₂ Adsorption Characteristics of Aminopolymer Impregnated MCM-36.

The CO2 adsorption characteristics of a pillared 2-dimensional porous silicate material impregnated with amine containing polymers have been investigated. It was determined that the introduction of amine polymer deteriorates the CO2 capture kinetics of the MCM-36 supported amine adsorbents compared to that of the bare material, due to the fact that with the addition of a higher loading of amine polymer the diffusion of CO2 through the 2-dimensional interlayer mesoporous channels of MCM-36 becomes greatly hindered. This pore blocking sets an upper limit to the CO2 capture performance of the polymer impregnated MCM-36 and greatly reduces the utility of using this sort of amine-solid adsorbent for carbon capture. Interestingly, these results suggest that for 2-D channel solid supports there is an optimal amine loading which is not likely to be equal to the maximum loading, and which can be determined and utilized to obtain the maximum improvement over the original materials. The study performed in this work for the MCM-36 material could therefore be applied to other porous supports to determine these optimum loadings and be used to more easily compare and contrast the alterations to capture characteristics which occur upon amine loading for a wide range of materials. It is believed this will make it more straightforward to determine which solid supports hold the promise for greatly improved capture characteristics upon amine loading and allow the field to more quickly determine avenues for fruitful development. These results also suggest the need for a new sort of support structure for amine loaded solids, one which can allow us to decouple amine loading from increasing diffusion resistance so that high amine efficiency can be maintained throughout the range of increased amine loadings.

Model for the interpretation of nuclear magnetic resonance relaxometry of hydrated porous silicate materials.

Nuclear magnetic resonance (NMR) relaxation experimentation is an effective technique for probing the dynamics of proton spins in porous media, but interpretation requires the application of appropriate spin-diffusion models. Molecular dynamics (MD) simulations of porous silicate-based systems containing a quasi-two-dimensional water-filled pore are presented. The MD simulations suggest that the residency time of the water on the pore surface is in the range 0.03-12 ns, typically 2-5 orders of magnitude less than values determined from fits to experimental NMR measurements using the established surface-layer (SL) diffusion models of Korb and co-workers [Phys. Rev. E 56, 1934 (1997)]. Instead, MD identifies four distinct water layers in a tobermorite-based pore containing surface Ca2+ ions. Three highly structured water layers exist within 1 nm of the surface and the central region of the pore contains a homogeneous region of bulklike water. These regions are referred to as layer 1 and 2 (L1, L2), transition layer (TL), and bulk (B), respectively. Guided by the MD simulations, a two-layer (2L) spin-diffusion NMR relaxation model is proposed comprising two two-dimensional layers of slow- and fast-moving water associated with L2 and layers TL+B, respectively. The 2L model provides an improved fit to NMR relaxation times obtained from cementitious material compared to the SL model, yields diffusion correlation times in the range 18-75 ns and 28-40 ps in good agreement with MD, and resolves the surface residency time discrepancy. The 2L model, coupled with NMR relaxation experimentation, provides a simple yet powerful method of characterizing the dynamical properties of proton-bearing porous silicate-based systems such as porous glasses, cementitious materials, and oil-bearing rocks.

Comparison of mesoporous silicate supports for the immobilisation and activity of cytochrome c and lipase

The activity and stability of Candida antartica lipase B (CALB) and cytochrome c immobilised onto SBA-15 and a porous spherical silicate material (PPS) were examined. The materials possess similar pore diameters but have different morphologies, pore volumes and surface areas. CALB exhibited higher catalytic activity and stability on SBA-15 when compared to PPS, while cytochrome c showed similar catalytic activity on both materials. The activity of CALB immobilised on SBA-15 was retained (95%) after 7 uses, while CALB immobilised on PPS retained only 43% activity. Such changes can be mainly ascribed to the different physical properties (pore volume, surface area and pore shape) of the supports.

Nano‐Layered Inorganic‐Organic Hybrid Materials for the Controlled Delivery of Antimicrobials

SummaryAn essential oil (EO) blend has been identified that provides a broad spectrum potent antimicrobial effect. Adsorption of the EO onto porous silicate materials (Rockwood Additives: Laponite® B, Laponite® RD and Fulcat® 800) and has been analysed and it was found that Laponite® RD organically modified with dihydrogenated tallow dimethyl ammonium chloride (2HT2M) at 50% cation exchange capacity gave the highest levels of adsorption. The Laponite® RD 2HT2M with EO blend adsorbed has been added to polymer materials to produce an antimicrobial polymer. The adsorption of the EO onto the Laponite® RD was done to achieve controlled release of the EO to prolong the antimicrobial effect within the polymer.Addition of the EO loaded substrates into silicone elastomer has resulted in successfully conferring a high level of antimicrobial activity to the polymer.

Effect of oil content in paraffin on waterproofing properties of paraffin emulsions

We demonstrate that a paraffin emulsion can be used as a waterproofing agent for porous silicate materials. We establish that the water-repellant properties of the indicated material are affected both by the paraffin and by the oil contained in the paraffin. We study the effect of the oil content in the paraffin on the waterproofing properties of the emulsion and the water-repellant properties of the porous silicate material.

Lightweight geopolymer made of highly porous siliceous materials with various Na2O/Al2O3 and SiO2/Al2O3 ratios

The syntheses of lightweight geopolymeric materials from highly porous siliceous materials viz. diatomaceous earth (DE) and rice husk ash (RHA) with high starting SiO2/Al2O3 ratios of 13.0–33.5 and Na2O/Al2O3 ratios of 0.66–3.0 were studied. The effects of fineness and calcination temperature of DE, concentrations of NaOH and KOH, DE to RHA ratio; curing temperature and time on the mechanical properties and microstructures of the geopolymer pastes were investigated. The results indicated that the optimum calcination temperature of DE was 800 °C. Increasing fineness of DE and starting Na2O/Al2O3 ratio resulted in an increase in compressive strength of geopolymer paste. Geopolymer pastes activated with NaOH gave higher compressive strengths than those with KOH. The optimum curing temperature and time were 75 °C and 5 days. The lightweight geopolymer material with mean bulk density of 0.88 g/cm3 and compressive strength of 15 kg/cm2 was obtained. Incorporation of 40% RHA to increase starting SiO2/Al2O3 and Na2O/Al2O3 ratios to 22.5 and 1.7 and enhanced the compressive strength of geopolymer paste to 24 kg/cm2 with only a marginal increase of bulk density to 1.01 g/cm3. However, the geopolymer materials with high Na2O/Al2O3 (>1.5) were not stable in water submersion.

Single-walled carbon nanotubes shell decorating porous silicate materials: A general platform for studying the interaction of carbon nanotubes with photoactive molecules

Single-walled carbon nanotubes (SWCNTs) have been deposited onto the external surface of porous silicate materials by deposition from a solution of individualized, protonated SWCNTs in chlorosulfonic acid. It is demonstrated that the deposited SWCNTs can be deprotonated on the silicate surface, yielding a microporous or mesoporous material with individual or small bundles of SWCNTs. These carbon nanotubes present all the spectral characteristics of pristine SWCNTs, including van Hove transitions, Raman and NIR photoluminescence. Furthermore, it is shown that these materials can be used as scaffolds to study the interaction of SWCNTs with photoactive molecules loaded in the cavities of the porous silicate materials. As a proof-of-concept, we showed that the photoluminescence of tris(2,2′-bipyridine)ruthenium(II) can be quenched by protonated SWCNTs in the nearby surface decreasing its lifetime by nearly two orders of magnitude. This represents a novel application for these materials, especially considering the large amount of different molecules that can be immobilized in the internal cavities of these porous silicates.

Adsorption Potential Distributions for Silicas and Organosilicas

Adsorption potential distributions (APDs) were calculated from nitrogen adsorption isotherms for macroporous silicas, and for disordered and ordered mesoporous silicas without and with organic groups attached to the surface. It was shown that the APDs for porous silicas and organosilicas differ significantly from those obtained for carbonaceous materials, especially in the range of high adsorption potentials which correspond to low relative pressures. Although the high adsorption potential portions of APDs for porous siliceous materials are less informative than those for carbons, they are still useful for monitoring the changes in the surface properties due to the attachment of various organic groups.

Magic number silicon dioxide‐based clusters: Laser ablation‐mass spectrometric and density functional theory studies

The magic number silica clusters [(SiO(2))(n)O(2)H(3)](-) with n = 4 and 8 have been observed in the XeCl excimer laser (308 nm) ablation of various porous siliceous materials. The structural origin of the magic number clusters has been studied by the density functional theoretical calculation at the B3LYP/6-31G** level, with a genetic algorithm as a supplementary tool for global structure searching. The DFT results of the first magic number cluster are parallel to the corresponding Hartree-Fock results previously reported with only small differences in the structural parameters. Theoretical calculation predicts that the first magic number cluster (SiO(2))(4)O(2)H(4) and its anion [(SiO(2))(4)O(2)H(3)](-) will most probably take pseudotetrahedral cage-like structures. To study the structural properties of the second magic number cluster, geometries of the bare cluster (SiO(2))(8), the neutral complex cluster (SiO(2))(8)O(2)H(4), and the anionic cluster [(SiO(2))(8)O(2)H(3)](-) are fully optimized at the B3LYP/6-31G** level, and the corresponding vibrational frequencies are calculated. The DFT calculations predict that the ground state of the bare silica octamer (SiO(2))(8) has a linear chain structure, whereas the second magic number complex cluster (SiO(2))(8)O(2)H(4) and its anion [(SiO(2))(8)O(2)H(3)](-) are most probably a mixture of cubic cage-like structural isomers with an O atom inside the cage and several quasi-bicage isomers with high intercage interactions. The stabilization of these structures can also be attributed to the active participation of the group of atoms 2O and 4H (3H for the anion) in chemical bonding during cluster formation. Our theoretical calculation gives preliminary structural interpretation of the presence of the first and second magic number clusters and the absence of higher magic numbers.

Dependence of the electrical conductivity and the low-frequency dielectric constant upon pressure in porous media containing a small quantity of humidity

The interaction between the matrix of a porous material and a small quantity of a liquid located in its porous space induces intense polarisation phenomena and enhances the charge transport. The temperature dependence of the corresponding relaxation time was reported recently by employing the high-resolution thermally stimulated depolarisation current spectroscopy. The present work includes d.c. conductivity and a.c. capacitance measurements under pressure up to 0.3 GPa in two porous silicate materials: sandstone with 0.26 wt.% and pelite with 0.07 wt.%. The water was adsorbed from the atmospheric humidity. Electrical impedance measurements are used to monitor the effects of confining pressure on the matrix–liquid interaction. Positive activation volumes are computed from the observed variations in the d.c. conductivity of the samples with pressure. The pressure derivatives of the dielectric constant at 10 4 Hz were also obtained. The effect of pressure on the effective relaxation time that determines the humidity-related polarisation processes was estimated.

Magic Numbers in Silicon Dioxide-Based Clusters

The generation of magic number silica clusters [(SiO2)nO2H3]- with n = 4 and 8 by XeCl laser (308 nm) ablation of porous siliceous materials is reported. The production of magic cluster [(SiO2)4O2H3]- can be enhanced by sample selection and experimental optimization so that it becomes the most prominent species in silica clusters. To study the structure of the magic cluster [(SiO2)4O2H3]-, we performed structural optimization for the neutral bare cluster (SiO2)4, the neutral complex cluster (SiO2)4O2H4, and the anionic cluster [(SiO2)4O2H3]- at the HF/6-31G** level. It was found that the ground state of the bare silica tetramer has a linear chain structure whereas a pseudotetrahedral cage-like structural isomer of S4 symmetry is most stable for the complex cluster (SiO2)4O2H4. The stabilization of the three-dimensional (3D) structure can be attributed to the active participation of the O2H4 group in chemical bonding during cluster formation. Our theoretical calculation and bonding analysis indicate that t...