Kinetic study of ytterbium(III) extraction from sulfate medium with Cyanex 923

The kinetics of ytterbium(III) extraction from sulfate medium with Cyanex 923 in heptane has been investigated with a constant interfacial cell with laminar flow, which aimed to identify the extraction regime, reaction zone and rate equations. It was found that the extraction rate of ytterbium(III) increased linearly with stirring speed and specific interfacial area. The activation energy E_a (9.56 kJ mol^?1), activation enthalpy ΔH^± (7.05 kJ mol^?1), activation entropy ΔS^±₂₉₈ (?0.31 kJ mol^?1) and Gibbs free energy of activation ΔG^±₂₉₈ (98.3 kJ mol^?1) were calculated from the dependence of extraction rate on temperature. The experiential rate equations were obtained by investigating the influence of the concentration of various species on the extraction rate. A diffusion regime has been deduced from evidence of the linear dependence of extraction rate on stirring speed and the low value of the activation energy. The liquid–liquid interface is most probably the reaction zone in view of the linear dependence of extraction rate on specific interfacial area, the high interfacial activity and low water‐solubility of extractant. Thus the mass transfer rate is controlled by interfacial film diffusion of species. Copyright © 2007 Society of Chemical Industry     

Supercritical CO2 Extraction of Essential Oil from Origanum Vulgare L.: Experiments and Mathematical Modeling

In this work, the supercritical CO₂ extraction of essential oil from Origanum Vulgare L. was investigated and modeled. An orthogonal test and ANOVA indicated that extraction pressure, extraction temperature, and extraction time had significant influence on extraction effects. Based on experiments, a mathematical model depended on mass conservation equation was established to describe and simulate supercritical CO₂ extraction of essential oil from Origanum Vulgare L. The mean diameter, accumulation properties, and the inside and outside transfer properties of extracted material particles were considered in the model. The model was solved numerically with the finite difference method and Runge-Kutta method synthetically. Model estimation was validated with small scale experimental data. Moreover, the effects of extraction pressure, extraction temperature, extraction time, concentration, and the flow rate of the entrainer on mass of essential oil were investigated using the model.     

Re-entrant dipole glass-like behavior and lattice dynamics of 0.65Bi(Mg1/2Ti1/2)O3-0.35PbTiO3

The 0.65Bi(Mg_1/2Ti_1/2)O₃-0.35PbTiO₃ (0.65BMT-0.35PT) ceramic, nearby morphotropic phase boundary (MPB), between tetragonal and rhombohedral was prepared. Dielectric permittivity dependence of temperature exhibits a re-entrance dipole glass-like behavior near room temperature. The behavior was described by the Vogel-Fulcher law and the new glass model. Furthermore, a phenomenological statistical model was employed to determine the distribution of clusters dependence of temperature. The lattice dynamics of the 0.65BMT-0.35PT ceramic was estimated by Raman spectroscopy from 298-723 K. A disruption of ferroelectric long-range order and an occurrence of local lattice distortion were revealed. The relaxor-ferroelectric (r-FE) nature of the 0.65BMT-0.35PT was characterized by polarization-electric field P(E). A close relation between the distribution of clusters and ferroelectric properties was established.     

Extraction of Oat Lipids and Phospholipids Using Subcritical Propane and Dimethyl Ether: Experimental Data and Modeling

Effects of subcritical solvents (propane, dimethyl ether (DME), and their 1:1 mixed solvents) and extraction temperatures (30 to 60 °C) on oat lipids and phospholipid extraction are investigated using the Patricelli kinetic model and thermodynamic analysis. The mass-transfer coefficient (k₁) of the washing stage is approximately ten times higher than the diffusion stage under different solvents and temperature conditions. Compared with the subcritical propane and mixed solvents, the maximum equilibrium yield of oat lipids and phospholipids are obtained using subcritical DME. With increased extraction temperature from 30 to 60 °C, the equilibrium yield of phospholipids increases, whereas the equilibrium yield of lipids increases to 5.30% at 40 °C and then decreases. The enthalpy and entropy changes for phospholipid extraction are higher than those for lipid extraction. The Gibbs free energy for phospholipid extraction rapidly decreases with increased extraction temperature. A loose endosperm of oat grain is observed, and the concentration of lipids in the bran layer is higher than in the endosperm. In conclusion, kinetic and thermodynamic analyses statistically prove that DME is more effective than propane and mixes solvents for extracting lipids and phospholipids from oat flakes, and that phospholipid extraction strongly depends on temperature. Practical Application: The removal of lipids and phospholipids benefits oat-product processing and storage. However, traditional industrial n-hexane extraction usually requires a high-temperature process for solute–solvent separation, which may result in low quality of the meal. Subcritical-fluid extraction is a rising technology for lipid and phospholipid extraction. The yields of lipids and phospholipids using subcritical dimethyl ether (DME) is higher than those propane and its mixed solvents. The temperature dependence of phospholipid extraction is more active than that of lipid extraction. Thus, use of subcritical DME is a promising lipid-extraction technique to obtain solvent­free oat oil and high-quality defatted oat flour with potential application in the oat-processing industry.     

TEMPERATURE EFFECTS IN THE EXTRACTION OF METAL IONS BY DIALKYL-SUBSTITUTED DIPHOSPHONIC ACIDS. I. THE Am(III) CASE

The extraction of Am(III) from HNO₃ by o-xylene solutions of P,P′-di(2-ethylhexyl) methylene- (H₂DEH[MDP]), ethylene- (H₂DEH[EDP]), and butylene- (H₂DEH[BuDP]) diphosphonic acids has been investigated. Thermodynamic parameters of the extraction process were determined by the temperature coefficient of the metal distribution ratio in the 25.0 to 60.0°C temperature range. The extractant aggregation and the extraction stoichiometries with the different diphosphonic acids did not exhibit any significant temperature dependence. Extraction of Am(III) by H₂DEH[MDP] is favored by both enthalpy and entropy variations. When Am(III) is extracted by either H₂DEH[EDP] or H₂DEH[BuDP] the process is entropy controlled. The enthalpy variation for Am(III) extraction exhibited a trend along the series H₂DEH[MDP], H₂DEH[EDP], H₂DEH [BuDP], with the reaction being exothermic for the first, thermoneutral for the second, and endothermic for the third extractant, respectively. This trend was explained as arising from the formation of progressively less stable chelate rings along the diphosphonic acids series. The zero or positive enthalpy variation with a concomitant favorable entropy variation confirm for H₂DEH[EDP] and possibly for H₂DEH[BuDP] a micellar-like type of extraction process.

     

Optimisation of SFE method on-line coupled to FT-IR spectroscopy for the real-time monitoring of the extraction of tagitinin C in T. diversifolia

The monitoring in real time of dynamic extractions of tagitinin C from Tithonia diversifolia leaves was carried out with a home made high-pressure fiber optic cell which coupled a supercritical fluid extractor with carbon dioxide as the extraction medium and a FT-IR spectrometer equipped with a mercury cadmium telluride detector (MCT). The shape of extraction curves obtained during the monitoring was used to decide when to stop the supercritical fluid extraction (SFE).No significant density dependence of the molar absorption coefficient or wavenumber of the CO stretching vibration (ν_CO) of tagitinin C at 1668 cm⁻¹ was noticed.The physical characteristics of SCCO₂ governing the extraction yield of the active component from leaves were optimized by means of a central composite design (CCD). The studied variables were temperature (40, 60 and 80 °C) and pressure (8.0, 14.0 and 20.0 MPa) of the supercritical fluid.The composition profile of T. diversifolia extracts obtained by SFE was investigated in the range from 3400 to 2600 cm⁻¹ according to the pressure and temperature conditions of SCCO₂. The qualitative approach of the extracts composition was accomplished through the CH stretching vibrations (ν_CH) of components.     

Swelling behavior of crosslinked hydroxypropyl cellulose films retaining cholesteric liquid crystalline order. I. Effect of temperature

Temperature dependence of the swelling behavior in both water and propanol was determined for the crosslinked hydroxypropyl cellulose (HPC) films retaining cholesteric liquid crystalline order (CLCO) and for the crosslinked amorphous HPC films. The dependence of swelling behavior in water for the films retaining CLCO was different from that of the amorphous films. With increasing temperature, the equilibrium swelling ratio (B_e) for the films retaining CLCO decreased, whereas B_e for the amorphous films increased. In propanol, both films exhibited the same temperature dependence. B_e increased with increasing temperature. The increasing rate of the swelling in transient state showed similar temperature dependence on B_e. The increasing rate for the films retaining CLCO decreased with temperature, but that for the amorphous films increased in water; in propanol, the increasing rate for two types of films increased. The difference in the swelling behavior between the two types of films may be due to the difference in the number-average molecular weight between crosslinks. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1015–1022, 1999     

Optimization of Supercritical Carbon Dioxide Extraction of Gardenia Fruit Oil and the Analysis of Functional Components

Supercritical carbon dioxide (SC-CO₂) extraction of whole fruit oil from Gardenia jasminoides Ellis was performed. The effect of extraction pressure, temperature and CO₂ flow rate on the oil yield was investigated by response surface methodology (RSM). The results showed that experimental data had a good fit to the proposed model (R ² = 0.938). Extraction pressure, CO₂ flow rate, the quadratics of pressure, and the interaction between pressure and flow rate showed significant effects on the oil yield (p < 0.05). The optimum parameters that maximized the yield of gardenia fruit oil (GFO) were: extraction pressure of 36.8 MPa, temperature of 65 °C, and CO₂ flow rate of 15 kg/h. The main fatty acid of GFO was linoleic acid (about 44%), followed by palmitic acid (about 26.4%) and oleic acid (about 24.6%). α-Tocopherol was dominant in the total tocopherols of GFO, and showed the main antioxidant activity. The fatty acid composition and tocopherols content of GFO were not remarkably affected by the extraction by SC-CO₂ and n-hexane.     

A logistic kinetic model for isothermal and nonisothermal cure reactions of thermosetting polymers

A model describing the low‐temperature crystallization kinetics observed for thermoplastic polymers from the melt by differential scanning calorimetry (DSC) was shown to accurately predict the cooling curves as a function of time and temperature. The model was successful for treating data for several cooling rates as well as for isothermal DSC data. In this article, we extended the model to cure reactions of thermosetting polymers. The parameters representing lower and upper exotherm reference temperatures in crystallization events have a different meaning for curing events. Thus, the model was modified to account for this change of context. The new model was tested for exothermic reactions of a Hysol® FP4527 epoxy adhesive system using data from DSC ramp heating experiments at several heating rates and also from isothermal experiments. Good fits were obtained for all the varied experimental conditions. The model made use of three fitting parameters with physical significance: a lower critical temperature (T_c) an activation energy (E_b), and a reaction order (τ + 1). Additionally, to complete the kinetic fitting, the dependence of the time to reach the reaction peak maximum for isothermal cure was considered. That dependence was found to follow a more simple model which is formally equivalent to that observed in isothermal crystallization, and which makes use of two parameters related to the limits of the temperature range in which the polymerization may occur. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40670.     

Antiradical Efficiency of Essential Oils from Plant Seeds Obtained by Supercritical CO2, Soxhlet Extraction,and Hydrodistillation

The effect of supercritical CO₂ (SCCO₂) extraction conditions (pressure and temperature) on the system performance as well as the antiradical efficiencies of the essential oils from Japanese pepper (Xanthoxylum piperitum DC.), cardamom (Elettaria cardamomum Maton), and fennel (Foeniculum vulgare) seeds were investigated. A control study with the conventional Soxhlet extraction and hydrodistillation was also conducted to compare the performance of those processes. Antiradical efficiencies were investigated by utilizing 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay with a UV-vis spectrophotometer. Higher pressure and temperature had positive effects on the supercritical process performance due to higher CO₂ density and substrate solubility in SCCO₂. Antiradical efficiencies of cardamom and pepper were almost the same, being significantly higher than that of fennel seeds. However, this effect decreased dramatically for all the spices when the extraction method was changed to Soxhlet extraction and hydrodistillation. SCCO₂ extraction was found to yield more quality and effective essential oils than Soxhlet extraction and hydrodistillation.     

Separation of Penicillin G from Fermentation Broth Using N,N-Dioctyloctan-1-amine Extractant in Different Diluents

The extraction of penicillin G was investigated using N,N-Dioctyloctan-1-amine (TOA) with different diluents having distinct functional groups. Nine diluents were used in the study, namely, octan-1-ol, nonan-1-ol, isoamyl alcohol, ethyl ethanoate, propyl ethanoate, methyl iso butyl ketone(MIBK), octan-2-one, octane, and decane. The measurements were performed at a temperature of 298.2 K. The experimental results of batch extractions were used to calculate distribution coefficients (K_D), loading factors (Z), and extraction efficiency (E). The highest distribution coefficient (K_D = 5.79) was obtained with isoamyl alcohol, and its extraction efficiency was 85.27%. Further, the highest loading factor was reached to a value of 0.130 at 0.374 mol.kg^?1 amine concentration. Overloading was not observed at any amine concentration. Solvatochromic model (Linear solvation Energy Relationship (LSER)) for data which obtained from alcohols experiments gives the good results as near as same to experimental results. Suitability of data between experiments and model predictions have been tested with root main square deviation (RMSD) with 0.99.     

Plasticating single-screw extrusion of amorphous polymers: Development of a mathematical model and comparison with experiment

A mathematical model was developed for plasticating single-screw extrusion of amorphous polymers. We considered a standard metering screw design. By introducing a ‘critical flow temperature’ (T_cf), below which an amorphous polymer may be regarded as a ‘rubber-like’ solid, we modified the Lee-Han melting model, which had been developed earlier for the extrusion of crystalline polymers, to model the flow of an amorphous polymer in the screw channel. T_cf is de facto a temperature equivalent to the melting point of a crystalline polymer. The introduction of T_cf was necessary for defining the interface between the solid bed and the melt pool, and between the solid bed and thin melt films surrounding the solid bed. We found from numerical simulations that (1) when the T_cf was assumed to be close to its glass transition temperature (T_g), the viscosity of the polymer became so high that no numerical solutions of the system of equations could be obtained, and (2) when the value of T_cf was assumed to be much higher than T_g, the extrusion pressure did not develop inside the screw channel. Thus, an optimum modeling value of T_cf appears to exist, enabling us to predict pressure profiles along the extruder axis. We found that for both polystyrene and polycarbonate, T_cf lies about 55°C above their respective T_gs. In carrying out the numerical simulation we employed (1) the WLF equation to describe the temperature dependence of the shear modulus of the bulk solid bed at temperatures between T_g and T_cf, (2) the WLF equation to describe the temperature dependence of the viscosity of molten polymer at temperatures between T_cf and T_g + 100°C, (3) the Arrhenius relationship to describe the temperature dependence of the viscosity of molten polymer at temperatures above T_g + 100°C, and (4) the truncated power-law model to describe the shear-rate dependence of the viscosity of molten polymer. We have shown that the T_g of an amorphous polymer cannot be regarded as being equal to the T_m of a crystalline polymer, because the viscosities of an amorphous polymer at or near its T_g are too large to flow like a crystalline polymer above its T_m. Also conducted was an experimental study for polystyrene and polycarbonate, using both a standard metering screw and a barrier screw design having a length-to-diameter ratio of 24. For the study, nine pressure transducers were mounted on the barrel along the extruder axis, and the pressure signal patterns and axial pressure profiles were measured at various screw speeds, throughputs, and head pressures. In addition to significantly higher rates, we found that the barrier screw design gives rise to much more stable pressure signals, thus minimizing surging, than the metering screw design. The experimentally measured axial pressure profiles were compared with prediction.     

Swelling and mechanical properties of cellulose hydrogels. III. Temperature effects on the swelling and compliance levels studied by dilatometry and 1H-NMR spectroscopy

The temperature dependence of the swelling and the creep compliance has been investigated for swollen isotropic cellulose hydrogels. The measurements were performed in a high precision type of dilatometer between 5 and 65°C. The thermal expansion of the gels in silicone oil (closed system) and the temperature dependence of the equilibrium swelling in water (open system) were studied. The influence of compressive stress in these experiments was also evaluated. The swelling level in equilibrium with water diminishes slightly with increasing temperature due to migration of water from the gel phase to the surrounding water phase. A secondary transition was found at 35°C where the temperature dependence of the swelling level is changed. When measured at constant gel composition the creep compliance of a highly swollen gel decreases with increasing temperature. The decrease is not, however, large enough for entropy elasticity to dominate over energetic elasticity. The energetic contribution f_U/f was determined to be 0.61 for a gel swollen to 3.9 g water/g dry gel (g/g) and 1.24 for a gel swollen to 1.05 g/g. The swelling and compliance data have also been analyzed in terms of a model where the gels are assumed to behave as a filler-reinforced rubbery network. The amorphous parts of the hydrogels are thus assumed to be described by the statistical theory for polymeric networks. In proton magnetic resonance studies of a gel swollen to 4.4 g/g the spin-lattice relaxation time T₁ was determined to be considerably longer than the spin-spin relaxation time T₂. T₂ has a maximum at 30°C. This maximum marks the onset (on the NMR time scale) of an exchange process between two types of proton species. These species are suggested to be specific hydration water and free gel water, respectively.     

Electric field tunable thermal stability of energy storage properties of PLZST antiferroelectric ceramics

The electrical hysteresis behaviors and energy storage performance of Pb_0.97La_0.02(Zr_0.58Sn_0.335Ti_0.085)O₃ antiferroelectric (AFE) ceramics were studied under the combined effects of electric field and temperature. It was observed that the temperature dependence of recoverable energy density (W_re) of AFE ceramics depends critically on the applied electric field. While W_re at lower electric fields (<8 kV/mm) shows increasing tendency with increasing temperature from 20°C to 100°C, W_re at higher electric fields (>8 kV/mm) demonstrates decreasing dependence. There exists an appropriate electric field (8 kV/mm) under which the AFE ceramics exhibit nearly temperature‐independent W_re (the variation is less than 0.5% per 10°C). The underlying physical principles were also discussed in this study. These results indicate that the temperature dependence of W_re of AFE materials can be tuned through selecting appropriate electric fields and provide an avenue to obtain thermal stable energy storage capacitors, which should be of great interest to modern energy storage community.     

Interphase of polyoctenamer-single-wall carbon nanotubes by thermogravimetric analysis in air

Non-isothermal thermogravimetric analysis in air, of polyoctenamer-single wall carbon nanotubes (PO-SWNTs), loaded by various amounts of SWNTs up to 10% wt., at different heating rates (ranging from 5 to 40°C/min) is reported. The thermal degradation in the air of PO_SWNTs is dominated by a main single sigmoidal dependence, assigned to the polymer and eventually polymer-nanofiller interphase, over which a weaker sigmoid assigned to the thermo-oxidative degradation of the nanofiller is superimposed at higher temperatures. The temperature at which the nanocomposite's residual mass fraction reaches x% wt. of the initial mass, T_x%, is reported (for x = 5, 50, and 85). The dependence of T_x% on the heating rate and the loading by nanotubes is analyzed. The temperature derivative of the thermograms defines new parameters (inflection residual mass fraction and inflection temperature) and (degradation) width. Their dependence on the loading by SWNTs was reported. Estimation of the interphase in polymer-based nanocomposites is based on the postulate that the dependence of the inflection temperature on the composition of the nanocomposite obeys a Fox-like dependence, where the bulk polymer and the polymer trapped within the interphase are considered as a blend of two miscible polymers. Complementary Raman, x-ray diffraction, and differential scanning calorimetry support these results.     

Mass transfer kinetics of neodymium(III) extraction by calix[4]arene carboxylic acid using a constant interfacial area cell with laminar flow

BACKGROUND: Thermodynamics and kinetics data are both important to explain the extraction property. In order to develop a novel separation technology superior to current extraction systems, many promising extractants have been developed including calixarene carboxylic acids. The extraction thermodynamics behavior of calix[4]arene carboxylic acids has been reported extensively. In this study, the mass transfer kinetics of neodymium(III) and the interfacial behavior of calix[4]arene carboxylic acid were investigated. RESULTS: The rate constant (K_ao) becomes constant when the stirring speed was controlled between 250 rpm and 400 rpm. The activation energy (E_a) was calculated to be 21·41 kJ mol^?1 or 88·17 kJ mol^?1 (dependent on temperature) from the slope of log K_ao against 1000/T. The linear relationship between the specific area and the extraction rate is the characteristic of an interfacial reaction control. The minimum bulk concentration of the extractant necessary to saturate the interface (C_min) is lower than 4·19 × 10^?4 mol L^?1. CONCLUSION: The effect of stirring speed, temperature, and species concentration on the extraction rate demonstrates that the extraction regime depends on the extraction conditions. The chemical reaction control governs the extraction regime at temperatures below 303 K and a mixed control regime occurs when the temperature is between 303 K and 318 K. The probable locale for the chemical reaction is at the liquid–liquid interface and the rate equation is deduced to be: ? d[Nd³⁺]_(a)/dt = k_f[Nd³⁺]_(a)[H₄A]_(o)^0·727[H⁺]_(a)^?0·978. The rate‐controlling step was suggested by the analysis of the experimental results. Copyright © 2008 Society of Chemical Industry     

Magnetization of Manganese Perovskites

Temperature dependence of spontaneous magnetization at a separate site in the compounds La_1-xCa_xMnO₃ (0 ⩽ x ⩽ 1) is investigated in the molecular field approximation using a homogeneous model for the magnetic sub-lattice with allowance for the Heisenberg superexchange and double exchange between nearest neighbors. Unlike with the usual magnets having one type of magnetic ions, in this case there appears a system of equations with two unknowns, mean spins of ions Mn³⁺ and Mn⁴⁺. In the vicinity of the ordering temperature, this system can be solved analytically and the expression for the ordering temperature can be obtained as well. To find the temperature dependence of magnetization in the whole temperature range, we used the exact expression for the double exchange operator containing spin operators under the square root. The numerical solutions were found in this case.     

Ideality of pressure‐sensitive paint. I. Platinum tetra(pentafluorophenyl)porphine in fluoroacrylic polymer

The pressure sensitive paint (PSP) properties of a fluoroacrylic polymer, FIB, with the luminophor platinum tetra(pentafluorophenyl)porphine (PtTFPP) are presented. This paint forms a hard coating that displays Stern–Volmer plots with a high dynamic range (∼ 0.9) [defined as (I_vac − I_atm)/I_vac], good photostability, a response time of less than 1 s and a relatively low temperature dependence (∼ 0.6% per degree). The temperature dependence is low because FIB has a unusually low activation energy for the diffusion of oxygen. Pressure and temperature affect intensity independently making this PSP “ideal.” The basecoat affects the functionality of the PSP it underlies, and the optimal basecoat used to date also includes the FIB polymer. The synthesis of the FIB polymer is a copolymerization that occurs in one step with a peroxide initiator. Annealing the painted model above T_g = 70°C procures adhesion and ideality. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2795–2804, 2000     

Modeling and optimization of process parameters for supercritical CO2 extraction of Argemone mexicana (L.) seed oil

This research article deals with the determination of optimal conditions of extraction parameters (e.g. temperature (60–100?°C), pressure (200–350?bar), particle size (0.5–1.0?mm), flow rate-CO₂ (5–15?g/min), and the % of co-solvent (0.0–10% of flow rate-CO₂) resulting to the optimal cumulative extraction yield during the supercritical fluid extraction of Argemone mexicana (L.) seed oil with and without a modifier (ethanol) using a supercritical carbon dioxide as solvent. A “five-factors-three-levels” Box-Behnken design under the response surface methodology was used to show independent and interactive effects of extraction parameters. A mathematical regression model was expressed properly by a quadratic second-order polynomial equation. The maximum oil yield (42.86%) from A. mexicana seeds was obtained with the optimal conditions (85?°C, 305?bar, 0.75?mm, 11?g/min, and 9% of flow rate-CO₂) of extraction parameters. The fatty acids analysis of the seed oil was done using gas chromatography and found its suitability as bio-fuel.