Synergistic effect of particle size,shear rate and driving-force during microfiltration of fruit juices: Toward a relevant choice of pretreatments and filtration conditions

With an objective to recommend relevant operating conditions for fruit juice microfiltration, the combined effect of particle size, shear rate and driving-force on fouling was studied. The filterability of three orange juices with different granulometry was estimated at pilot scale under different shear rates and driving forces (flux or TMP, in immersed and side-stream membrane configuration respectively). In flux-driven filtrations, fluxes to avoid an intense fouling were identified (below 5–10 L.h⁻¹.m⁻² for studied juices) and the role of juice granulometry on fouling highlighted. In TMP-driven filtrations, whatever the juice granulometry, steady-state fluxes were TMP-independent but shear rate dependent (around 10 and 30 L.h⁻¹.m⁻², for 4500 s⁻¹ and 15500 s^-1 respectively). The results demonstrated that, whatever their granulometry, juice filterability was higher in low shear rate flux-driven filtrations, than in high shear rate TMP-driven ones, which relativizes the relevance of crossflow filtration.     

Preparation of biomimetic three-dimensional gelatin/montmorillonite–chitosan scaffold for tissue engineering

A novel gelatin/montmorillonite–chitosan (Gel/MMT–CS) nanocomposite scaffold was prepared via the intercalation process and the freeze-drying technique, using the ice particulates as the porogen materials. Properties including pore structure, water adsorption content, in vitro degradation and tensile strength were investigated. It was demonstrated that the introduced intercalation structure endowed the Gel/MMT–CS scaffold with good mechanical properties and a controllable degradation rate. Scanning of the electron microscope images revealed that the scaffold obtained was highly porous and suitable for the implanted cells to adhere and grow. The mitochondrial activity assay provided good evidences of cells viability on the Gel/MMT–CS membranes, giving an indication of possible application as a matrix for tissue engineering.     

Immobilization of mushroom polyphenol oxidase on poly(allyl glycidyl ether-co-ethylene glycol dimethacrylate) macroporous beaded copolymers

Functional, macroporous, beaded copolymers containing epoxy groups were synthesized for immobilization of polyphenol oxidase (PPO) from edible mushroom (Agaricus bisporus). The effect of incorporation of two different sets of monomers such as glycidyl methacrylate (GMA) and allyl glycidyl ether (AGE) and the effect of cross-linking agent ethylene glycol dimethacrylate (EGDM) with varying cross-link densities on binding and expression of mushroom PPO activity were studied. The effect of porogen viz. cyclohexanol and hexanol on PPO immobilization was studied. AGE copolymers with hexanol as a porogen were found to give higher binding and expression of PPO activity than GE polymers. Cross-linking of amino groups of enzyme with 5% glutaraldehyde for 6 h gave a stable binding of PPO on AGE-75(Hex) polymer with storage half-life of approximately 25 days. Under optimum conditions, AGE-75(Hex) polymer gave 70.3% of activity yield while percent retention of PPO activity was found to be 83.5%. Immobilized PPO showed a broader pH, higher temperature and excellent storage stability.     

Improved Dyeing with Redox Systems: IV—dyeing of nylon-6 with disperse dyes

The dyeing of nylon-6 fabric with Terasil Red 2GL (CI Disperse Red 72), in the absence and presence of redox systems based on ammonium persulphate [(NH₄)₂S₂O₈] as oxidant and potassium pyrosulphite (K₂S₂O₅), glucose (C₆H₁₂O₆) or thiourea (CH₄N₂S) as reductant, was studied. It was found that for a given set of dyeing conditions the colour strength, expressed as K/S, follows the order

Increasing the (NH₄)₂S₂O₈ concentration (0.00–0.03 m ) as well as the duration (15–60 min) and temperature (65–95° C) of the dyeing process caused significant enhancement in the colour strength and dye fixation. It is postulated that the presence of (NH₄)₂S₂O₈ alters the mode of dye interaction. In the presence of the oxidant component, i.e. (NH₄)₂S₂O₈ , attachment of the disperse dye to the nylon-6 substrate seems to involve covalent bonding in addition to the usual hydrogen bond. This is indicated by the significant colour strength remaining after DMF extraction for dyeings obtained using different disperse dyes and in the presence of (NH₄)₂S₂O₈. A free-radical mechanism for the covalent bond formation between nylon-6 and the disperse dyes is tentatively suggested.     

Facile solid-state synthesis of Ag/graphene oxide nanocomposites as highly active and stable catalyst for the reduction of 4-nitrophenol

A facile solid-state synthetic route was used to fabricate graphene oxide (GO) decorated with Ag nanoparticles. Ag/GO nanocomposites were prepared by reducing silver acetate with ascorbic acid in the presence of GO at ambient conditions. The characterization results showed that Ag nanoparticles with an average diameter of ~ 50 nm were well dispersed on the surface of GO nanosheets. Moreover, an application of the obtained Ag/GO nanocomposites as a catalyst in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol by NaBH₄ was demonstrated. The Ag/GO nanocomposites exhibited high activity and stability for the catalytic reduction of 4-NP.     

Carbon nanotube/boehmite-derived alumina ceramics obtained by hydrothermal synthesis and spark plasma sintering (SPS)

Preparation, structure and properties of hydrothermally treated carbon nanotube/boehmite (CNT/γ-AlOOH) and densification with spark plasma sintering of Al₂O₃ and CNT/Al₂O₃ nanocomposites were investigated. Hydrothermal synthesis was employed to produce CNT/boehmite from an aluminum acetate (Al(OH)(C₂H₃O₂)₂) and multiwall-CNTs mixture (200 °C/2 h.). TEM observations revealed that the size of the cubic shape boehmite particles lies around 40 nm and the presence of the interaction between surface functionalized CNTs and boehmite particles acts to form ‘nanocomposite particles’. Al₂O₃ and CNT/Al₂O₃ compact bodies were formed by means of spark plasma sintering (SPS) at 1600 °C for 5 min using an applied pressure of 50MPa resulting in the formation of stable α-Al₂O₃ phase and CNT–alumina compacts with nearly full density. It was also found that CNTs tend to locate along the alumina grain boundaries and therefore inhibit the grain coarsening and cause inter-granular fracture mode. The DC conductivity measurements reveal that the DC conductivity of CNT/Al₂O₃ is 10^?4 S/m which indicate that there is a 4 orders of magnitude increase in conductivity compared to monolithic Al₂O₃. The results of the microhardness tests indicate a slight increase in hardness for CNT/Al₂O₃ (28.35 GPa for Al₂O₃ and 28.57 GPa for CNT/Al₂O₃).     

Perspectives on supercritical fluid processing of fats and oils

Over the past two decades, fats and oils processing using supercritical carbon dioxide (SC-CO₂) has developed from focusing only on extraction to fractionation of complex lipid mixtures, conducting reactions in supercritical fluid media and particle formation techniques for the delivery of bioactive lipid components. Extraction of specialty oils and column fractionation of deodorizer distillates to concentrate tocopherols have reached commercial scale. Even though significant progress has been made in fundamental aspects, many challenges lie ahead to better understand the phase behavior and solubility of multicomponent lipid mixtures in SC-CO₂ and to generate the much needed fundamental data, including transport properties, density and interfacial tension. Considering the increasing consumer demand for “natural” products and stricter government regulations on the use of organic solvents like hexane, the future of SC-CO₂ processing of lipids is bright. Based on the know-how accumulated, integrated processes can be developed, targeting ingredients for both food and non-food industrial applications, which would fit well into a larger biorefinery approach.     

Molecular dynamics study on nanotube-resonators with mass migration applicable to both frequency-tuner and data-storage-media

We investigated the cantilevered carbon-nanotube-resonator including electromigratively movable nanoparticle via classical molecular dynamics simulations and continuum model. The change of the effective mass value, which was closely correlated with the position change of the encapsulated nanoparticle, could be regressed by a power function, the resonance frequency of the carbon-nanotube-resonator could be tuned by controlling the nanoparticle’s position, and the possible frequency-shift-ranges then reached 18–85%. The suggested device could be served as a data-storage-media for electromechanical nonvolatile-memory as well as a frequency-tuner.     

A new and direct preparation method of iron-based bimodal catalyst and its application in Fischer–Tropsch synthesis

A bimodal iron-based catalyst was prepared by a new one-step impregnation method. The active components were used as the “brick” to directly build the small pores inside the large pores of support, which was quite different from the previous bimodal catalysts that were prepared once more on a bimodal support. Comparing with the unimodal catalysts and conventional co-precipitated catalyst, the prepared bimodal catalyst exhibited excellent activity in Fischer–Tropsch synthesis due to the improved active metal dispersion and fastened diffusion efficiency. This preparation method is much simpler than the previous methods and can be extended to prepare various bimodal catalysts with different chemical compositions.     

Effects of sulfate ions and slightly acidic pH conditions on Cr(VI) adsorption onto silica gelatin composite

The feasibility of utilizing CTAB–silica gelatin composite (C-SGC) to remove hexavalent chromium from aqueous solutions under different conditions was investigated. Removal of chromate was assessed through evaluation of the adsorption kinetics of chromate ions on the composite under equilibrium conditions in the presence of sulfate ions and at a slightly acidic pH condition (pH 5.8). Adsorption competition tests in the presence of sulfate ions showed that Cr(VI) was still effectively adsorbed from aqueous solution regardless of the presence of the competing anions. In fact, the adsorption kinetics performed at different initial chromate concentrations were unaffected by the presence of 100 mg L^?1 sulfate ions (pH 7.5). The equilibrium adsorption data were fitted by Freundlich adsorption isotherms which confirmed that the adsorption efficiency of chromium on the CTAB–silica gelatin composite was unchanged in the presence of sulfate ions. Further, the adsorption process was shown to be pH dependent and more efficient at slightly acidic pH (5.8). These findings demonstrated a high specificity of the CTAB–silica gelatin composite for chromium, and highlight the possibility of using this matrix for efficient removal of chromium from industrial wastewater without the need to eliminate contaminant sulfate ions.