Fabrication of porous poly(L-lactide) (PLLA) scaffolds for tissue engineering using liquid–liquid phase separation and freeze extraction

PLLA scaffolds were successfully fabricated using liquid–liquid phase separation with freeze extraction techniques. The effects of different processing conditions, such as method of cooling (direct quenching and pre-quenching), freezing temperature (−80°C and −196°C) and polymer concentration (3, 5 and 7 wt%) were investigated in relations to the scaffold morphology. SEM micrographs of scaffolds showed interconnected porous network with pore size ranging from 20 to 60 μm. The scaffolds had porosity values ranging from 80 to 90%. Changes to the interconnected network, porosity and pore size were observed when the method of cooling and polymer concentration was changed. Direct quenching to −80°C gave a more porous interconnected microstructure with uniform pore size compared to samples prepared using pre-quenching method. Larger pores were observed for samples quenched at −80°C compared to −196°C. Scaffolds prepared using direct quenching to −196°C had higher elastic modulus and compressive stress compared to those quenched to −80°C. The compressive elastic modulus ranged from 4 to 7 MPa and compressive stress at 10% strain was from 0.13 to 0.18 MPa.     

Two novel calixarene functionalized iron oxide magnetite nanoparticles as a platform for magnetic separation in the liquid–liquid/solid–liquid extraction of oxyanions

This article focuses on the syntheses of 25,27-bis[3-(N-ethylsulfonic acid)aminopropxy]-26,28-dihydroxy-5,11,17,23-tetra-tert-butyl-calix[4]arene (3) and 25,27-bis[3-(N-ethyl-dihydrogen phosphate)aminopropxy]-26,28-dihydroxy-5,11,17,23-tetra-tert-butyl-calix[4]arene (4) as well as their immobilization onto [3-(2,3-epoxypropoxy)-propyl]-trimethoxysilane-modified Fe₃O₄ magnetite nanoparticles, and the extraction abilities of four new extractants which were characterized by a combination of FTIR, ¹H NMR, elemental analyses, transmission electron microscopy (TEM) and thermogravimetric analyses (TGA) involving electrostatic and hydrogen bonding interactions between the calixarene and oxide anions such as arsenate and dichromate anions. The extraction results indicate that these new calixarene derivatives having high extraction capabilities would be used as effective extractants for the removal of the dichromate/arsenate ions from water.     

Speciation, stability, and reactions of Np(III–VII) in aqueous solutions

Published data on the structure of Np ions in acid and alkali solutions, on hydrolysis of Np ions and their complexation with anions and cations, on their redox reactions with water and with each other (disproportionation, reproportionation), and on the effect of anions on this process are analyzed. Possible directions of research in chemistry of Np ions are outlined.     

Effect of alkaline and acidic solutions on the tensile properties of glass–polyester pipes

The influence of liquids on the state of stresses and tensile strengths in the longitudinal and circumferential direction of glass–polyester pipes is the subject of this paper. The pipes were manufactured in Corporation “Poliester” Priboj, and had a definite structure and known fabrication process. These analyses are of great importance for the use of glass–polyester pipes in the chemical industry.     

Copper(II) ion removal from aqueous solutions using biosorption technology: thermodynamic and SEM–EDX studies

The present study uses biosorption technology to remove copper(II) ions from aqueous solutions. Mature leaves of neem (Azadirachta indica) were developed into powder form of size 32–45 μm and used as the biosorbent, while copper(II) ion solutions were prepared to be used as adsorbates. Parameters varied include copper(II) ion concentration and adsorption temperature. The neem leaf powder (NLP) dosage which was kept constant at 1.0 g L^?1 and pH was between 5 and 6. Adsorption occurred at a high rate initially and reached equilibrium after 50 min. Adsorption seemed to be more favourable at higher temperatures. Optimal temperature was found to be 333 K, with a high adsorption capacity of 146.30 mg g^?1. Thermodynamic studies showed that the system is spontaneous and endothermic in nature, based on the parameters of Gibbs free energy (?G°), biosorption enthalpy (?H°) and biosorption entropy (?S°) obtained, which gave values of ?2.74, 26.70 and 0.07 kJ mol^?1 K^?1, respectively. The adsorption mechanism was found to be predominantly chemisorption. SEM and EDX results show that copper(II) ions were adsorbed on the micropores of NLP. Results indicate that NLP is a suitable biosorbent for removing copper(II) ions from solutions.     

Liquid–liquid equilibrium (LLE) study for six-component transesterification system

Transesterification of oils/triglycerides (TGs) with alcohol in the presence of catalyst has been the most commonly used process to produce biodiesel. Major limiting factors of conventional biodiesel transesterification process are phase separation and product purification. Precise and correct knowledge of the phase equilibrium behaviour is crucial for future industrial biodiesel reaction, separation and purification processes. For this purpose, it is important to consider the phase equilibrium behaviour in order to thoroughly understand the entire transesterification system for biodiesel production, which consists of six components. This work is to discuss on the liquid–liquid equilibrium (LLE) data of six-component system which involves TG, palm biodiesel (FAME), methanol (MeOH), glycerine (GLY), diglyceride (DG) and monoglyceride (MG). The phase equilibrium data of this system were determined experimentally through transesterification of crude palm oil (CPO). The experimental LLE data have been transposed into a pseudo-ternary diagram as TG–DG–MG + MeOH–GLY + FAME for better visualisation and understanding of the six-component system. Results showed that the transesterification of TG to FAME has formed a two-phase system where CPO-rich phase and MeOH-rich phase co-existed during the reaction. Due to immiscibility of CPO and MeOH, as well as the miscibility of FAME and MeOH, the LLE data suggested that at specific reaction operating condition, the reacted product (FAME) could be continuously removed by separating the MeOH phase from the CPO phase. This favours the forward transesterification reaction and eventually enhances the reaction efficiency to produce an oil-free FAME.     

Discrepancies in barrier heights obtained from current–voltage (IV) and capacitance–voltage (CV) of Au/PNoMPhPPy/n-GaAs structures in wide range of temperature

Journal of Materials Science: Materials in Electronics - Au/n-GaAs device was fabricated with an organic PNoMPhPPy thin polymer interfacial layer whose bandgap (Eg) was found as 2.95 eV...     

Investigation of sorbents synthesised by mechanical–chemical reaction for sorption of As(III) and As(V) from aqueous medium

Efficiency of Fe₂O₃ and mixture of Fe₂O₃ and MnO₂ nanoparticles synthesised by mechanical–chemical reaction for inorganic As(III) and As(V) sorption was examined. Sorbents (Fe₂O₃ and mixture Fe₂O₃:MnO₂ = 3:1) synthesised by mechanical–chemical treatment in planetary ball mile with different milling times were tested by batch experiments. Experimental data were fitted both to Freundlich and Langmuir adsorption models. Efficiency of sorption was in good correlation with the time of milling in case of pure oxide. There were small differences in sorption between As(III) and As(V). In the case of mixture of oxides results were different. The best results were obtained by 30 min of milling. With prolonged milling, the sorption decreased to 3 h and after that increased again. These results were explained by phase transition. Sorption kinetics, influence of pH and the presence of other anions were examined for mixture of oxides with highest sorption capacity. The bioavailability of sorbed arsen was tested using modified Tessier procedure.     

Influence of temperature on Pu(IV) extraction from nitric acid solutions into 30% TBP,considered within the framework of A.M. Rozen’s model and of a new (multireaction) model

Published and newly obtained data on the influence of temperature on the extraction of Pu(IV) from nitric acid solutions into 30% TBP are analyzed. The analysis shows that both A.M. Rozen’s model and the new (multireaction) model insufficiently accurately describe the influence of temperature on the Pu(IV) extraction at HNO₃ concentrations in the aqueous phase of 1 M and lower, where Pu(IV) can undergo partial hydrolysis, and at HNO₃ concentrations of 4 M and higher. Changes are made in the system of equilibrium constants in both models.     

Active control of supercooling degree using surfactant (In system with solid–liquid interface)

Supercooling reduces the COP of ice formation systems. So, control of supercooling dissolution is useful and would bring numerous benefits. In a previous report, the authors conducted an experiment to control supercooling dissolution in a mixture with a hydrophilic surfactant and water in a glass test tube which had the liquid–gas(air) interface, and it was possible to actively control average supercooling degree by varying the surfactant concentrations. The average supercooling degrees' tendencies below and over a critical micelle concentration, calculated based on the variation in surface tensions, were quite different. However, since the critical micelle concentration is a physical quantity concerned only with liquid–gas interface, it is essential to investigate phenomena in a system with a solid–liquid interface. So, in a syringe with a system having only a solid–liquid interface, possibility of active control of average supercooling degree by variation in surfactant concentrations is investigated.     

Fabrication and characterization of porous poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide) scaffolds using solid–liquid phase separation

Freeze-extraction, which involves phase separation principle, gave highly porous scaffolds without the time and energy consuming freeze-drying process. The presented method eliminates the problem of formation of surface skin observed in freeze-drying methods. The effects of different freezing temperature (−80 and −24°C), medium (dry ice/ethanol bath and freezer) and polymer concentrations (1, 3, and 5 wt.%) on the scaffold properties were investigated in connection with the porous morphology and physicomechanical characteristics of the final scaffolds. The FESEM micrographs showed porous PLLA scaffolds with ladder-like architecture. The size of the longitudinal pores was in the range of 20–40 μm and the scaffolds had high porosity values ranging from 90% to 98%. Variation in porosity, mechanical resistance, and degree of regularity in the spatial organization of pores were observed when polymer concentration was changed. More open scaffold architecture with enhanced pore interconnectivity was achieved when a dry ice/ethanol bath of −80°C was used. Polymer concentration played an important role in fabricating highly porous scaffolds, with ladder-like architecture only appearing at polymer concentrations of above 3 wt.%. With the freeze-extraction method used here, highly porous and interconnected poly(l-lactide) scaffolds were successfully fabricated, holding great potential for tissue engineering applications.     

Synthesis of fullerene nanowhiskers using the liquid–liquid interfacial precipitation method and their mechanical,electrical and superconducting properties

Abstract

Fullerene nanowhiskers (FNWs) are thin crystalline fibers composed of fullerene molecules, including C₆₀, C₇₀, endohedral, or functionalized fullerenes. FNWs display n-type semiconducting behavior and are used in a diverse range of applications, including field-effect transistors, solar cells, chemical sensors, and photocatalysts. Alkali metal-doped C₆₀ (fullerene) nanowhiskers (C₆₀NWs) exhibit superconducting behavior. Potassium-doped C₆₀NWs have realized the highest superconducting volume fraction of the alkali metal-doped C₆₀ crystals and display a high critical current density (J_c) under a high magnetic field of 50 kOe. The growth control of FNWs is important for their success in practical applications. This paper reviews recent FNWs research focusing on their mechanical, electrical and superconducting properties and growth mechanisms in the liquid–liquid interfacial precipitation method.     

Continuous separation of Fe–Al–Zn dross phase from hot dip galvanised melt using alternating magnetic field

Abstract

Experiments to continuously separate Fe–Al–Zn dross phase from hot dip galvanising zinc melt were conducted on a laboratory scale apparatus by using high frequency alternating magnetic field. Effects of processing time (t) on separation efficiency were investigated. The experimental results show that using the electromagnetic repulsive force resulting from the electrical conductivity difference between zinc melt and Fe–Al–Zn dross phase, the deleterious zinc dross particles causing surface defects of galvanising steel sheets can be continuously separated from the zinc bath under alternating magnetic field, and the separation efficiency increases with the increase in processing time. When the magnetic frequency is 17·5 kHz, the effective magnetic flux intensity is 0·1 T, the cross-section of the ceramic square pipe is 10 × 10 mm, and the processing time is 0·6–2·5 s, the separation efficiency of zinc dross varies from 43·76 to 85·71%, and the experimental results are in reasonable agreement with the theoretical results.     

Oxidation of Np(V) and Np(IV) with Fe(CN) 6 3− ions in carbonate solutions

The formal potential of the Fe(CN) ₆ ^3? /Fe(CN) ₆ ^4? couple in 1 M NaHCO₃ and 1–2 M Na₂CO₃ solutions was determined. It is equal to 505 and 510 mV, respectively, exceeding the potentials of the Np(VI)/(V) and Np(V)/(IV) couples in carbonate solutions. The equilibrium of the reaction Np(V) + Fe(CN) ₆ ^3? = Np(VI) + Fe(CN) ₆ ^4? was studied. Fe(CN) ₆ ^3? ions oxidize Np(IV) to Np(V) and then to Np(VI). The arising Np(VI) oxidizes Np(IV). The Np(IV) oxidation accelerates in going from NaHCO₃ to Na₂CO₃. An increase in [Na₂CO₃] or in the ionic strength (by adding neutral salts) decelerates the oxidation. Np(IV) introduced in an HCl solution reacts with Fe(CN) ₆ ^3? or with Np(VI) faster than Np(IV) introduced in a Na₂CO₃ solution. The activation energy of the reaction of Np(IV) with Fe(CN) ₆ ^4? in the range 20–45°C is 107 kJ mol^?1. The reaction mechanism involves formation of the activated complex from ions of Np(IV) hydroxocarbonate and oxidant.     

Formation of a sol of mixed U(IV) · U(VI) hydroxide in aqueous solutions with pH 1.5–4

containing U(IV) polymer start to form. With an increase in pH from 1.5 to 4 or in temperature, the induction period becomes shorter. Under anaerobic conditions, the colloidal solution is stable for more than a month. Centrifugation at 8000 rpm (5500g) allows separation of the colloidal particles from the liquid phase. The colloid slowly dissolves in mineral acids saturated with argon or in a K₂CO₃ solution, whereas precipitates of individual freshly prepared U(IV) and U(VI) hydroxides dissolve rapidly. Short UV irradia-of a UO₂(ClO₄)₂ solution saturated with argon and containing ethanol (pH 2.5) results in the appearance of U(V) which then disproportionates, and U(IV) forms with U(VI) a black colloid similar to that arising on mixing U(IV) and U(VI) solutions.     

Supercritical extraction from solid: process design data (2001–2003)

Supercritical extraction from solid substrate using carbon dioxide as solvent, with or without the addition of cosolvent, has proved to be technically feasible. The relatively high investment costs associated with high pressure processes are responsible for the elimination of this technology at the very early stages of the process design, that is, during the selection of an extraction process. In order to avoid this, a preliminary analysis of the manufacturing costs must be done with a minimum of experimental information. In this review a compilation of the process parameters required for the economic analysis is presented.     

Fabrication, nanostructure evaluation, 3D electrical transport and electrochemical capacitance of PEDOT–Ti(IV)-doped iron(III) oxide nanocomposite

Poly[3,4-(ethylenedioxy)thiophene] (PEDOT) nanocomposites (NCs) reinforced by varying titanium(IV)-doped iron(III) nano oxide (NITO) particles have been fabricated in dodecylbenzene sulphonic acid by in situ polymerization process using ammonium perdisulfate as initiator. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, electron microscopy, BET surface analysis etc. followed by subsequent evaluation of thermal properties, temperature-dependent 3D electrical transport. Thermal stability of the NCs increased with increasing NITO amount in PEDOT matrix. Electrical conductivity of the NCs increased significantly with increasing NITO content (0.45–67.73 S cm^?1) and also with the temperature (50–300 K). 3D variable range hopping conduction mechanism explained the conduction pathways. Specific capacitance of NCs are enhanced with higher NITO content in polymer from 107 F g^?1 (pristine PEDOT) to 158 F g^?1 (NC) owing to the development of mesoporous (pore size: 4.1 nm and cylindrical pore volume: 0.103 cm³ g^?1) structure and high specific surface area (~104 m² g^?1).