Jeffrey Shi

Adsorptive Removal of Copper Ions from Aqueous Solution Using Cross-linked Magnetic Chitosan Beads

The performance of cross-linked magnetic chitosan, coated with magnetic fluids and cross-linked with epichlorohydrin, was investigated for the adsorption of copper (II) from aqueous solutions. Infrared spectra of chitosan before and after modification showed that the coating and cross-linking are effective. Experiments were performed at different pH of solution and contact time, and appropriate conditions for the adsorption of Cu(II) were determined. Experimental equilibrium data were correlated with Langmuir and Freundlich isotherms for determination of the adsorption potential. The results showed that the Langmuir isotherm was better compared with the Freundlich isotherm, and the uptake of Cu(II) was 78.13 mg·g−1. The kinetics of adsorption corresponded with the first-order Langergren rate equation, and Langergren rate constants were determined.

A novel calcium looping absorbent incorporated with polymorphic spacers for hydrogen production and CO2 capture

High temperature looping cycles can be used to produce hydrogen or capture CO2 from power stations, though sintering of absorbents is frequently a problem, reducing reactivity. In this work we develop materials, in which the crystal structure and volume of polymorphic materials change with temperature, as active spacers to reduce sintering.

A Comparative Study on the Inhibitory Effects of Different Parts and Chemical Constituents of Pomegranate on α-Amylase and α-Glucosidase

Pomegranate has been documented for the management of diabetes in Unani and Chinese medicine. This study compared the effects of the extracts of different pomegranate parts, including juice, peels, seeds and flowers, on carbohydrate digestive enzymes (α‐amylase and α‐glucosidase) in vitro. The methanolic flower extract inhibited α‐amylase and α‐glucosidase, while the methanolic peel extract inhibited α‐glucosidase selectively. The most active flower extract was subjected to water‐ethyl acetate partition. The ethyl acetate fraction was more potent than the water fraction in inhibiting both enzymes. Gallic acid and ellagic acid also showed selective inhibition against α‐glucosidase, and their presence in the ethyl acetate fraction was confirmed by HPLC‐DAD and HPLC‐HESI‐MS. Our findings suggest that the inhibition of carbohydrate digestive enzymes and their phenolic content may contribute to the anti‐hyperglycaemic effects of pomegranate flower and peel, and support their claims in diabetes. Copyright

High-flux ceramic membranes with a nanomesh of metal oxide nanofibers

Traditional ceramic separation membranes, which are fabricated by applying colloidal suspensions of metal hydroxides to porous supports, tend to suffer from pinholes and cracks that seriously affect their quality. Other intrinsic problems for these membranes include dramatic losses of flux when the pore sizes are reduced to enhance selectivity and dead-end pores that make no contribution to filtration. In this work, we propose a new strategy for addressing these problems by constructing a hierarchically structured separation layer on a porous substrate using large titanate nanofibers and smaller boehmite nanofibers. The nanofibers are able to divide large voids into smaller ones without forming dead-end pores and with the minimum reduction of the total void volume. The separation layer of nanofibers has a porosity of over 70% of its volume, whereas the separation layer in conventional ceramic membranes has a porosity below 36% and inevitably includes dead-end pores that make no contribution to the flux. This radical change in membrane texture greatly enhances membrane performance. The resulting membranes were able to filter out 95.3% of 60-nm particles from a 0.01 wt % latex while maintaining a relatively high flux of between 800 and 1000 L/m2.h, under a low driving pressure (20 kPa). Such flow rates are orders of magnitude greater than those of conventional membranes with equal selectivity. Moreover, the flux was stable at approximately 800 L/m2.h with a selectivity of more than 95%, even after six repeated runs of filtration and calcination. Use of different supports, either porous glass or porous alumina, had no substantial effect on the performance of the membranes; thus, it is possible to construct the membranes from a variety of supports without compromising functionality. The Darcy equation satisfactorily describes the correlation between the filtration flux and the structural parameters of the new membranes. The assembly of nanofiber meshes to combine high flux with excellent selectivity is an exciting new direction in membrane fabrication.

Thermal-crosslinked porous chitosan scaffolds for soft tissue engineering applications

The aim of this study was to demonstrate the feasibility of using a steam autoclave process for sterilization and simultaneously thermal-crosslinking of lyophilized chitosan scaffolds. This process is of great interest in biomaterial development due to its simplicity and low toxicity. The steam autoclave process had no significant effect on the average pore diameter (~70 μm) and overall porosity (>80%) of the resultant chitosan scaffolds, while the sterilized scaffolds possessed more homogenous pore size distribution. The sterilized chitosan scaffolds exhibited an enhanced compressive modulus (109.8 kPa) and comparable equilibrium swelling ratio (23.3). The resultant chitosan scaffolds could be used directly for in vitro cell culture without extra sterilization. The data of in vitro studies demonstrated that the scaffolds facilitated cell attachment and proliferation, indicating great potential for soft tissue engineering applications.

One‐Step Room‐Temperature Synthesis of [Al]MCM‐41 Materials for the Catalytic Conversion of Phenylglyoxal to Ethylmandelate

Mesoporous [Al]MCM‐41 materials with nSi/nAl ratios of 15 to 50 suitable for the direct catalytic conversion of phenylglyoxal to ethylmandelate have been successfully synthesized at room temperature within 1 h. The surface areas and pore sizes of the obtained [Al]MCM‐41 materials are in the ranges of 1005–1246 m2 g−1 and 3.44–3.99 nm, respectively, for the different nSi/nAl ratios. For all [Al]MCM‐41 catalysts, most of the Al species were tetrahedrally coordinated with Si in the next coordination sphere of atoms. 1H and 13C magic‐angle spinning NMR spectroscopic investigations indicated that the acid strength of the SiOH groups on these [Al]MCM‐41 catalysts and the density of these surface sites are enhanced with increasing Al content in the synthesis gels. These surface sites with enhanced acid strength were found to be catalytically active sites for phenylglyoxal conversion. The [Al]MCM‐41 material with nSi/nAl=15 showed the highest phenylglyoxal conversion (93.4 %) and selectivity to ethylmandelate (96.9 %), whereas the [Al]MCM‐41 material with nSi/nAl=50 reached the highest turnover frequency (TOF=99.3 h−1). This is a much better catalytic performance than that of a dealuminated zeolite Y (TOF=1.7 h−1) used as a reference catalyst, which is explained by lower reactant transport limitations in mesoporous materials than that in the microporous zeolite.

A COMPARISON OF DIFFERENT TECHNIQUES FOR WATER-BASED EXTRACTION OF PECTIN FROM ORANGE PEELS

The extraction of pectin from orange peels has been studied using microwave and conventional extraction, with operating conditions including different extraction periods, different solvent pHs, and different types of solvent systems. The extracted pectin from orange peels was initially precipitated with concentrated ethanol and was quantified by the carbazole assay. For microwave extraction, the greatest total amount of pectin yield was found to be 5.27% on a dry basis for 15 minutes of extraction, although the greatest amount of material per unit time (%/min) was obtained after 5 minutes. This amount was the same as that extracted using Soxhlet extraction for three hours. The 15-minute microwave extraction period was further investigated at pH values of 1.5, 2.0, 5.5, and 10.0. The greatest amount of pectin was extracted from orange peels at the most strongly acidic condition of pH 1.5. The effect of a solvent system containing ethanol and EDTA (ethylenediamine tetraacetic acid) with a 15-minute extraction period and a pH of 1.5 was studied, giving approximately double the amount of pectin extracted using distilled water.

Microbiologically Induced Corrosion of Concrete and Protective Coatings in Gravity Sewers

Abstract Microbiologically induced corrosion of concrete (MICC) and its protective coatings has a high economic impact on sewer maintenance and rehabilitation. A better understanding of the micro-organisms and the biogenic acids that are generated in the sewer is essential in controlling the corrosion of concrete pipes and protective coatings. The role of succession of micro-organisms growth in the corrosion of concrete and protective coatings was evaluated in this study. Examination of various sewer pipe materials exhibiting various extents of degradation, including concrete, cement based and epoxy based coating revealed the presence of both organic and biogenic sulphuric acids. This reflects the activity of fungi and the thiobacilli strains. Organism growth and metabolism were strongly related to the substrate pH. Fungi were found to grow and metabolise organic acids at pH from 2.0–8.0. Whilst the thiobacilli strains grew and generated sulphuric acids at pH below 3.0. The successive growth of the organisms provides an important bearing in developing improved strategies to better manage sewers.

Influence of support acidity on the performance of size-confined Pt nanoparticles in the chemoselective hydrogenation of acetophenone

Size-confined Pt nanoparticles of about 1.5 nm have been introduced into [Al]MCM-41 supports with similar acid strength but various population densities of acid sites by means of wet impregnation. The Pt nanoparticles covered preferentially the surface Bronsted acid sites (BAS) of the supports or were located near acid sites rather than on the bigger free space between acid sites even at a very low acid density (6 BAS per 1000 nm2). The free BAS around the Pt particles did not interact with Pt atoms and the electronic properties of the Pt nanoparticles as probed by DRIFTS combined with CO adsorption were similar for Pt/[Al]MCM-41 with and without nearby free BAS. Ionic effects were generated by the Pt-covered acid sites, whereas the population of BAS did not contribute significantly to the ionic effects induced on the Pt nanoparticles. The coverage of BAS of similar strength by platinum nanoparticles led to similar chemoselectivity and product distribution in acetophenone (Aph) hydrogenation, though the density of BAS on the supports increased by more than 11 times. However, increasing the number of BAS on the supports significantly changed the hydrogenation rate. TOFs continuously increased from 125 h−1 up to 534 h−1, when the population of free BAS increased from 18.2 BAS per 1000 nm2 to 39.9 BAS per 1000 nm2. When the free BAS density was further increased to 70.4 BAS per 1000 nm2, the TOF then dropped to 176 h−1. The hydrogenation pathway is similar for both monofunctional (Pt covering all BAS) and bifunctional catalysts (Pt with free BAS), and the reaction was initiated on the Pt surface. This finding indicates that proper tuning of the population density of acid sites on the support can significantly improve the catalytic performance of the supported metal catalysts while keeping similar product selectivities.

A bioceramic with enhanced osteogenic properties to regulate the function of osteoblastic and osteocalastic cells for bone tissue regeneration

Bioceramics for regenerative medicine applications should have the ability to promote adhesion, proliferation and differentiation of osteoblast and osteoclast cells. Osteogenic properties of the material are essential for rapid bone regeneration and new bone formation. The aim of this study was to develop a silicate-based ceramic, gehlenite (GLN, Ca2Al2SiO7), and characterise its physiochemical, biocompatibility and osteogenic properties. A pure GLN powder was synthesised by a facile reactive sintering method and compacted to disc-shaped specimens. The sintering behaviour and degradation of the GLN discs in various buffer solutions were fully characterised. The cytotoxicity of GLN was evaluated by direct and indirect methods. In the indirect method, primary human osteoblast cells (HOBs) were exposed to diluted extracts (100, 50, 25, 12.5 and 6.25 mg ml(-1)) of fine GLN particles in culture medium. The results showed that the extracts did not cause any cytotoxic effect on the HOBs with the number of cells increasing significantly from day 1 to day 7. GLN-supported HOB attachment and proliferation, and significantly enhanced osteogenic gene expression levels (Runx2, osteocalcin, osteopontin and bone sialoprotein) were compared with biphasic calcium phosphate groups (BCP, a mixture of hydroxyapatite (60wt.%) and β-tricalcium phosphate(40wt.%)). We also demonstrated that in addition to supporting HOB attachment and proliferation, GLN promoted the formation of tartrate-acid resistance phosphatase (TRAP) positive multinucleated osteoclastic cells (OCs) derived from mouse bone marrow cells. Results also demonstrated the ability of GLN to support the polarisation of OCs, a prerequisite for their functional resorptive activity which is mainly influenced by the composition and degradability of biomaterials. Overall, the developed GLN is a prospective candidate to be used in bone regeneration applications due its effective osteogenic properties and biocompatibility.