Polymeric vanadium pentoxide gel was formed via the reaction of V2O5 powder with hydrogen peroxide. The polymeric vanadium pentoxide gel was then dispersed in alumina gel. Different vanadium loading composites were coated on alumina support and calcined at 500 degrees C for 1 hr. These composite layers were characterized using TGA, FT-IR, XRD, SEM, and Autosorb. It was found that the lamellar structure of polymerized vanadium pentoxide was retained in the inorganic matrix. Crystalline alumina in gamma phase was formed after calcinations. However, the vanadium-alumina mixed oxides are lack of the well defined PXRD peaks for polycrystalline V2O5. This is possibly because the vanadia species are highly dispersed in the alumina matrix or the vanadia species are dispersed as crystalline which is smaller than 4 nm. In addition, the imbedded polymeric vanadium oxide improved the specific area and average pore diameter of the composite layer.
The synthesis of fatty acid methyl esters (FAME) as a substitute to petroleum diesel was investigated in this study from crude jatropha oil (CJO), a non-edible, low-cost alternative feedstock, using aluminium modified heterogeneous basic oxide (Mg-Zn) catalyst. The transesterification reaction with methanol to methyl esters yielded 94% in 6h with methanol-oil ratio of 11:1, catalyst loading of 8.68 wt.% at 182°C and the properties of CJO fuel produced were determine and found to be comparable to the standards according to ASTM. In the range of experimental parameters investigated, it showed that the catalyst is selective to production of methyl esters from oil with high free fatty acid (FFA) and water content of 7.23% and 3.28%, respectively in a single stage process. Thus, jatropha oil is a promising feedstock for methyl ester production and large scale cultivation will help to reduce the product cost.
Percolation theory has been used with great interest in understanding the design and characterization of dosage forms. In this study, work has been carried out to investigate the behavior of binary mixture tablets containing excipients of similar and different deformation properties. The binary mixture tablets were prepared by direct compression using lactose, polyvinyl chloride (PVC), Eudragit RS 100, and microcrystalline cellulose (MCC). The application of percolation theory on the relationships between compactibility, Pmax, or compression susceptibility (compressibility), gamma, and mixture compositions reveals the presence of percolation thresholds even for mixtures of similar deformation properties. The results showed that all mixture compositions exhibited at least one discreet change in the slope, which was referred to as the percolation threshold. The PVC/Eudragit RS100 mixture compositions showed significant percolation threshold at 80% (w/w) PVC loading. Two percolation thresholds were observed from a series of binary mixtures containing similar plastic deformation materials (PVC/MCC). The percolation thresholds were determined at 20% (w/w) and 80% (w/w) PVC loading. These are areas where one of the components percolates throughout the system and the properties of the tablets are expected to experience a sudden change. Experimental results, however, showed that total disruption of the tablet physical properties at the specified percolation thresholds can be observed for PVC/lactose mixtures at 20-30% (w/w) loading while only minor changes in the tablets' strength for PVC/MCC or PVC/Eudragit RS 100 mixtures were observed.
Ethyl acrylate-methyl methacrylate copolymer (Eudragit NE40D) was evaluated as matrix material for preparing controlled-release tablets of diclofenac sodium. Drug release could be modified in a predictable manner by varying the Eudragit NE40D content, but was pH dependent, being markedly reduced at lower pH. This could be attributed to the low solubility of the drug at these pH values. Thermal treatment of the tablets at 60 degrees C was also found to affect the rate of drug release, which was found to decrease with an increase in the treatment duration, but could be stabilized after 96 hr of treatment. This was also associated with a corresponding increase in the tablet tensile strength. However, treatment of the granules for 5 hr prior to compaction into tablets could shorten the stabilizing time of the drug release to 48 hr and that of the tensile strength to 24 hr. The effect of thermal treatment may be ascribed to better coalescence of the Eudragit particles to form a fine network, resulting in matrix of higher tortuosity and lower porosity.
This in vivo study revealed that porous hydroxyapatite (PHA) and dense hydroxyapatite (DHA) are good implant materials that can accelerate bone healing and resorbed in acceptable time. But there were differences in the mechanism of the resorption of DHA and PHA due to variability in the physical properties and osteogenicity.
The paper discusses the influence of sintering temperature on the microstructure and strength of hydroxyapatite ceramics prepared using the extrusion process. The average pore diameters observed were in the range of approximately 150mm to 300mm whereas the compaction strength was found to be around 120-160 MPa.
The paper presents the effect of sintering temperature on the physical properties of porous hydroxyapatite (HAp In this study, the HAp was prepared using polymeric sponge techniques with different binder concentrations. The sintering process was carried out in air for temperature ranging from 1200 degrees C to 1600 degrees C. Different physical properties namely density and porosity were observed at different sintering temperatures. The HAp prepared with higher PVP binder showed a slightly decreased in apparent density with increasing sintering temperature, while those HAp prepared with lower PVP showed a slightly increase in apparent density with increasing sintering temperature. The total porosity was found to be approximately constant in the whole sintering temperature range. However, closed porosity decreases with increasing sintering temperature for HAp prepared by lower binder concentration. On the other hand, the HAp prepared by higher binder concentrations showed increasing closed porosity with increasing sintering temperature. Other features such as the influence of sintering temperatures on grain and strut would also be presented in this paper.
In the effort to find alternative low cost adsorbent for volatile organic vapors has prompted this research in assessing the effectiveness of activated carbon produced from durian shell in removing toluene vapors. Durian shells were impregnated with different concentrations of H3PO4 followed by carbonization at 500 °C for 20 min under nitrogen atmosphere. The prepared durian shell activated carbon (DSAC) was characterized for its physical and chemical properties. The removal efficiency of toluene by DSAC was performed using different toluene concentrations. Results showed that the highest BET surface area of the produced DSAC was 1404 m2/g. Highest removal efficiency of toluene vapors was achieved by using DSAC impregnated with 30% of acid concentration heated at 500 °C for 20 min heating duration. However, there is insignificant difference between removal efficiency of toluene by DSAC and different toluene concentrations. The toluene adsorption by DSAC was better fitted into Freundlich model.
In this work, the adsorption of malachite green (MG) on rattan sawdust (RSD) was studied at 30 degrees C. The results indicated that RSD can be used as a low-cost adsorbent for the removal of MG dye from aqueous solutions. Equilibrium data were analyzed by two isotherms, namely the Freundlich isotherm and the Langmuir isotherm. The best fit to the data was obtained with the Langmuir isotherm. The monolayer adsorption capacity of RSD was found to be 62.71 mg/g. The adsorption kinetics can be predicted by the pseudo-first-order model. The mechanism of adsorption was also studied. It was found that for a short time period the rate of adsorption is controlled by film diffusion. However, at longer adsorption times, pore-diffusion controls the rate of adsorption. The amount adsorbed on the outer surface was estimated from the time where film-diffusion stops controlling the adsorption rate.
Polyhydroxyalkanoates (PHAs) have attracted the attention of academia and industry because of their plastic-like properties and biodegradability. However, practical applications as a commodity material have not materialized because of their high production cost and unsatisfactory mechanical properties. PHAs are also believed to have high-value applications as an absorbable biomaterial for tissue engineering and drug-delivery devices because of their biocompatibility. However, research in these areas is still in its very early stages. The main problem faced by proponents of PHAs is the lack of a niche area where PHAs will be the most desired material in terms of its function during use rather than because of its eco-friendly virtues after use. Here, we report on the oil-absorbing property of PHA films and its potential applications. By comparing with some of the existing commercial products, the potential application of PHAs as cosmetic oil-blotting films is revealed for the first time. Besides having the ability to rapidly absorb and retain oil, PHA films also have a natural oil-indicator property, showing obvious changes in opacity following oil absorption. Surface analysis revealed that the surface structures such as porosity and smoothness exert great influence on the rapid oil-absorption properties of the PHA films. These newly discovered properties could be exploited to create a niche area for the practical applications of PHAs.
Adsorption isotherm and kinetics of methylene blue on activated carbon prepared from coconut husk were determined from batch tests. The effects of contact time (1-30 h), initial dye concentration (50-500 mg/l) and solution temperature (30-50 degrees C) were investigated. Equilibrium data were fitted to Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The equilibrium data were best represented by Langmuir isotherm model, showing maximum monolayer adsorption capacity of 434.78 mg/g. The kinetic data were fitted to pseudo-first-order, pseudo-second-order and intraparticle diffusion models, and was found to follow closely the pseudo-second-order kinetic model. Thermodynamic parameters such as standard enthalpy (DeltaH degrees), standard entropy (DeltaS degrees) and standard free energy (DeltaG degrees) were evaluated. The adsorption interaction was found to be exothermic in nature. Coconut husk-based activated carbon was shown to be a promising adsorbent for removal of methylene blue from aqueous solutions.
In vitro production of sperm is a desirable idea for fertility preservation in azoospermic men and prepubertal boys suffering from cancer. In this study, a biocompatible porous scaffold based on a triad mixture of silk fibroin (SF), alginate (Alg), and laminin (LM) is developed to facilitate the differentiation of mouse spermatogonia stem cells (SSCs). Following SF extraction, the content is analyzed by SDS-PAGE and stable porous 3D scaffolds are successfully prepared by merely Alg, SF, and a combination of Alg-SF, or Alg-SF-LM through freeze-drying. Then, the biomimetic scaffolds are characterized regarding the structural and biological properties, water absorption capacity, biocompatibility, biodegradability, and mechanical behavior. Neonatal mice testicular cells are seeded on three-dimensional scaffolds and their differentiation efficiency is evaluated using real-time PCR, flow cytometry, immunohistochemistry. Blend matrices showed uniform porous microstructures with interconnected networks, which maintained long-term stability and mechanical properties better than homogenous structures. Molecular analysis of the cells after 21 days of culture showed that the expression of differentiation-related proteins in cells that are developed in composite scaffolds is significantly higher than in other groups. The application of a composite system can lead to the differentiation of SSCs, paving the way for a novel infertility treatment landscape in the future.
Multi-walled carbon nanotubes (MWCNTs) were prepared via chemical vapor deposition (CVD) using a series of different catalysts, derived from FeCoNiAl, CoNiAl and FeNiAl layered double hydroxides (LDHs). Catalyst-active particles were obtained by calcination of LDHs at 800 °C for 5 h. Nitrogen and hexane were used as the carrier gas and carbon source respectively, for preparation of MWCNTs using CVD methods at 800 °C. MWCNTs were allowed to grow for 30 min on the catalyst spread on an alumina boat in a quartz tube. The materials were subsequently characterized through X-ray diffraction, Fourier transform infrared spectroscopy, surface area analysis, field emission scanning electron microscopy and transmission electron microscopy. It was determined that size and yield of MWCNTs varied depending on the type of LDH catalyst precursor that is used during synthesis. MWCNTs obtained using CoNiAl-LDH as the catalyst precursor showed smaller diameter and higher yield compared to FeCoNiAl and FeNiAl LDHs.
This paper studies parameters which affect the pore size diameter of a silicon membrane. Electrochemical etching is performed in characterise the parameter involved in this process. The parameter has been studied is volume ratio of hydrofluoric acid (HF) and ethanol as an electrolyte aqueous for electrochemical etch. This electrolyte aqueous solution has been mixed between HF and ethanol with volume ratio 3:7, 5:5, 7:3 and 9:1. As a result, the higher volume of HF in this electrolyte gives the smallest pore size diameter compared to the lower volume of HF. These samples have been dipped into HF and ethanol electrolyte aqueous with supplied 25 mA/cm2 current density for 20, 30, 40, and 50 minutes. The samples will inspect under Scanning Electron Microscope (SEM) to execute the pore formations on silicon membrane surface.
Powder-based inkjet 3D printing method is one of the most attractive solid free form techniques. It involves a sequential layering process through which 3D porous scaffolds can be directly produced from computer-generated models. 3D printed products' quality are controlled by the optimal build parameters. In this study, Calcium Sulfate based powders were used for porous scaffolds fabrication. The printed scaffolds of 0.8 mm pore size, with different layer thickness and printing orientation, were subjected to the depowdering step. The effects of four layer thicknesses and printing orientations, (parallel to X, Y and Z), on the physical and mechanical properties of printed scaffolds were investigated. It was observed that the compressive strength, toughness and Young's modulus of samples with 0.1125 and 0.125 mm layer thickness were more than others. Furthermore, the results of SEM and μCT analyses showed that samples with 0.1125 mm layer thickness printed in X direction have more dimensional accuracy and significantly close to CAD software based designs with predefined pore size, porosity and pore interconnectivity.
Mesoporous silica materials (MSMs) were synthesized economically using silica (SiO2) as a precursor via a modified alkaline fusion method. The MSM prepared at 500°C (MSM-500) had the highest surface area, pore size, and volume, and the results of isotherms and the kinetics of ibuprofen (IBP) removal indicated that MSM-500 had the highest sorption capacity and fastest removal speed vs. SBA-15 and zeolite. Compared with commercial granular activated carbon (GAC), MSM-500 had a ~100 times higher sorption rate at neutral pH. IBP uptake by MSM-500 was thermodynamically favorable at room temperature, which was interpreted as indicating relatively weak bonding because the entropy (∆adsS, -0.07 J mol(-1) K(-1)) was much smaller. Five times recycling tests revealed that MSM-500 had 83-87% recovery efficiencies and slower uptake speeds due to slight deformation of the outer pore structure. In the IBP delivery test, MSM-500 drug loading was 41%, higher than the reported value of SBA-15 (31%). The in vitro release of IBP was faster, almost 100%, reaching equilibrium within a few hours, indicating its effective loading and unloading characteristics. A cost analysis study revealed that the MSM was ~10-70 times cheaper than any other mesoporous silica material for the removal or delivery of IBP.
Scaffold design from xenogeneic bone has the potential for tissue engineering (TE). However, major difficulties impede this potential, such as the wide range of properties in natural bone. In this study, sintered cortical bones from different parts of a bovine-femur impregnated with biodegradable poly(ethylene glycol) (PEG) binder by liquid phase adsorption were investigated. Flexural mechanical properties of the PEG-treated scaffolds showed that the scaffold is stiffer and stronger at a sintering condition of 1000°C compared with 900°C. In vitro cytotoxicity of the scaffolds evaluated by Alamar Blue assay and microscopic tests on human fibroblast cells is better at 1000°C compared with that at 900°C. Furthermore, in vitro biocompatibility and flexural property of scaffolds derived from different parts of a femur depend on morphology and heat-treatment condition. Therefore, the fabricated scaffolds from the distal and proximal parts at 1000°C are potential candidates for hard and soft TE applications, respectively.
The impact of ionic strength (from 0.003 to 500mM) and salt type (NaCl vs MgCl2) on transport and retention of titanium dioxide (TiO2) nanoparticles (NPs) in saturated limestone porous media was systematically studied. Vertical columns were packed with limestone grains. The NPs were introduced as a pulse suspended in aqueous solutions and breakthrough curves in the column outlet were generated using an ultraviolent-visible spectrometry. Presence of NaCl and MgCl2 in the suspensions were found to have a significant influence on the electrokinetic properties of the NP aggregates and limestone grains. In NaCl and MgCl2 solutions, the deposition rates of the TiO2-NP aggregates were enhanced with the increase in ionic strength, a trend consistent with traditional Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Furthermore, the NP aggregates retention increased in the porous media with ionic strength. The presence of salts also caused a considerable delay in the NPs breakthrough time. MgCl2 as compared to NaCl was found to be more effective agent for the deposition and retention of TiO2-NPs. The experimental results followed closely the general trends predicted by the filtration and DLVO calculations. Overall, it was found that TiO2-NP mobility in the limestone porous media depends on ionic strength and salt type.
Bleached kenaf core pulps (BKC) were hydrolyzed in H2SO4 (0.5M) at different time (0min to 90min) at room temperature. After the hydrolysis process, the viscosity average molecular weight (Mŋ) for BKC sample has reduced from 14.5×10(4) to 2.55×10(4). The hydrolyzed BKC was then dissolved in NaOH:urea:water and in LiOH:urea:water mixed solvent at the ratio of 7:12:81 and 4.6:15:80.4, respectively. The increased in hydrolysis time has decreased Mŋ of cellulose leading to easy dissolution process. Higher porosity and transparency with lower crystallinity index (CrI) of regenerated membrane produced can be achieved as the Mŋ reduced. The properties of membrane were observed through FESEM, UV-vis spectrophotometer and XRD. This study has proven that acid hydrolysis has reduced the Mŋ of cellulose, thus, enhanced the properties of regenerated membrane produced with assisted by alkaline/urea system.