Kinetics of ultrasound assisted extraction of anthocyanins from Aronia melanocarpa (black chokeberry) wastes

Black chokeberry fruits are very rich in antioxidant phenolics. After juice extraction, the wastes of pressed berries (juice production by-products) still contain important amount of phenolic species and namely anthocyanins. Ultrasound assisted extraction (UAE) from such wastes was studied. The influence of extraction time (0–240 min), temperature (20–70 °C), solvent composition (0–50% ethanol in water) and ultrasound power (0–100 W) on anthocyanins and polyphenols yields and on antioxidant capacity of the extracts was studied. High temperature and ethanol content in the solvent improved greatly the extraction yields. Ultrasounds improved mainly the extraction kinetics. Ultrasound effect was higher in the beginning of extraction process and at low temperatures. Suitability of UAE for preparation of antioxidant-rich plant extracts at reduced time and energy was confirmed obtaining high extraction efficiencies and high antioxidant capacities of Aronia extracts. To optimize extraction conditions a kinetic mathematical model, based on Peleg's equation and considering also the rate of anthocyanins thermal degradation, was proposed. The influences of extraction time, temperature, solvent composition and ultrasound power on polyphenols and anthocyanins yields and on antioxidant capacity were considered. The optimal conditions for anthocyanins extraction predicted by this model were experimentally validated.     

Effect of drying catalysts on the properties of thermal copolymers from conjugated linseed oil–styrene–divinylbenzene

The effect of addition of a varying concentration of a drying catalyst (cobalt salt as primary drier) and a combination of catalysts such as cobalt, zirconium (secondary drier) and calcium (auxiliary drier) in a fixed concentration (1%) to a 50:20:30 compositions of 87% conjugated linseed oil, styrene (ST), and divinylbenzene (DVB) has been studied by characterizing the resulting polymers from thermal polymerization with various techniques such as soxhlet extraction, ¹H NMR (¹H nuclear magnetic resonance) spectroscopy, dynamic mechanical analysis (DMA), mechanical and thermogravimetric analysis. The thermal polymerization is performed in the temperature range of 85–160 °C. By soxhlet extraction, it is observed that the polymers contain approximately 64–77% crosslinked materials and the crosslinked insoluble fraction increases with an increase in cobalt catalyst concentration. For fixed concentration (1%) of catalysts, the insoluble fraction from the soxhlet extraction is maximum for the cobalt–zirconium mixture and minimum for the cobalt–calcium mixture. The micro-composition of these polymers obtained from the ¹H NMR spectroscopy indicates that the crosslinked materials are composed of both soft oily and hard aromatic phases. The polymers with varying cobalt concentrations up to 0.6 wt% exhibit two separate glass transition temperatures, indicating the presence of two separate phases, one soft rubbery phase with sharp glass transition temperature of −50 °C and a hard brittle plastic phase of broadened glass transition temperature of 70–120 °C. On the other hand, instead of sharp peaks, the polymers with 0.8 and 1.0% cobalt salts exhibit two humps and a distinct peak in between the humps in the tan δ plots, indicating the presence of an additional phase comprised of a copolymer of linseed oil–styrene and DVB. For fixed concentration (1%) of catalysts, the cobalt–calcium combination follows the similar trend in the tan δ as that for the polymers with 0.8–1.0% cobalt whereas other combinations exhibit two phases. These polymers possess crosslink densities of 0.63–0.91 × 10⁴ mol/m³ and compressive strengths of 2.0–26.6 MPa. The catalyzed polymers are thermally stable below 300 °C and exhibit a major thermal degradation with a maximum degradation of 82–88% at a temperature of 500 °C.     

Optimization of supercritical carbon dioxide extraction of Passiflora seed oil

This study investigates extraction of Passiflora seed oil by using supercritical carbon dioxide. Artificial neural network (ANN) and response surface methodology (RSM) were applied for modeling and the prediction of the oil extraction yield. Moreover, process optimization were carried out by using both methods to predict the best operating conditions, which resulted in the maximum extraction yield of the Passiflora seed oil. The maximum extraction yield of Passiflora seed oil was estimated by ANN to be 26.55% under the operational conditions of temperature 56.5 °C, pressure 23.3 MPa, and the extraction time 3.72 h; whereas the optimum oil extraction yield was 25.76% applying the operational circumstances of temperature 55.9 °C, pressure 25.8 MPa, and the extraction time 3.95 h by RSM method. In addition, mean-squared-error (MSE) and relative error methods were utilized to compare the predicted values of the oil extraction yield obtained from both models with the experimental data. The results of the comparison reveal the superiority of ANN model compared to RSM model.     

Sintering,microstructure and conductivity of La2NiO4+δ ceramic

Microstructure and electrical conducting properties of La₂NiO_4+δ ceramic were investigated in the sintering temperature range 1200–1400 °C. The results demonstrate that the microstructure and electrical conducting properties of La₂NiO_4+δ ceramic are sensitive to sintering temperature. Compared with a progressive densification development with sintering temperature from 1200 to 1300 °C along with an insignificant change in grain size, there is an exaggerated grain growth in the specimens sintered at higher temperatures. Increasing sintering temperature from 1200 to 1300 °C resulted in an enhancement of electrical conducting properties. Further increase of sintering temperature exceeding 1300 °C reduced the electrical conducting properties. A close relation between the microstructure and electrical conducting properties was suggested for La₂NiO_4+δ ceramic. With respect to the electrical conducting properties, the preferred sintering temperature of La₂NiO_4+δ ceramic was ascertained to be 1300 °C. The specimen sintered at 1300 °C exhibits a generally uniform microstructure together with electrical conductivities of 76–95 S cm⁻¹ at 600–800 °C.     

Cocoa (Theobroma cacao) shell-based activated carbon by CO2 activation in removing of Cationic dye from aqueous solution: Kinetics and equilibrium studies

Cocoa shell (CS) was used as a low-cost precursor for production of activated carbon (AC) and evaluated for its ability to adsorb Methylene Blue (MB) dye. Cocoa shell-based pellets were carbonized at 800 °C and subjected to 850 °C under a flow of CO₂ in different activation times. The cocoa (Theobroma cacao) shell-based activated carbon (CSAC) showed moderate surface area with the average pore size 2.7 nm. CSAC also displays the presence of aliphatic, aromatic hydrocarbons and near absence of C–O, carboxylic acid, and the –COOH functional group. Only the presence of O–H groups was detected. The influences of adsorption time and initial dye concentration on adsorption performance have been measured in a batch system. The results are well described by the Freundlich and Langmuir isotherms. The results from the kinetic study show that MB adsorption follows pseudo-second-order and Boyd models, which indicated the MB adsorption on the CSAC was controlled by film diffusion.     

Brazilian Ginseng extraction via LPSE and SFE: Global yields, extraction kinetics, chemical composition and antioxidant activity

Brazilian Ginseng extracts of two species, Pfaffia paniculata and Pfaffia glomerata, were obtained by supercritical fluid extraction (SFE) with CO₂ and by low-pressure solvent extraction (LPSE) with methanol, hexane and ethanol. The SFE assays were conducted at pressures of 100, 200 and 300 bar, and temperatures of 30 and 50 °C. The qualitative chemical compositions of the extracts were determined by thin layer chromatography (TLC). One of the active principles of interest from P. glomerata extract, β-ecdysone, was identified and quantified by HPLC. The antioxidant activities of Brazilian Ginseng extracts were determined by the coupled reaction of linolenic acid and β-carotene. For P. paniculata, the highest SFE yield was obtained at 200 bar/50 °C (0.22%, dry basis—d.b.), while the best extraction condition for P. glomerata was obtained at 200 bar/30 °C (0.18%, d.b.). The higher extract yields obtained by LPSE were 2.0% and 5.8% (w/w, d.b.) for P. paniculata and P. glomerata, respectively, both obtained with methanol as extraction solvent. From the overall extraction curve of P. glomerata, it was possible to obtain the kinetic parameters of extraction; the duration of the CER (constant extraction rate) period was determined as 134 min. The TLC plates showed the possible presence of flavonoids in the ethanolic extract for both Pfaffia species. The antioxidant activity analysis detected that LPSE extracts had higher activity than SFE extracts.     

The effect of synthesis procedure on the structure and properties of palladium/polycarbonate nanocomposites

In this paper, we compare two procedures for the synthesis of palladium (Pd)/polycarbonate (PC) nanocomposites as well as their morphological, optical, thermal and electrical properties. Pd nanoclusters were produced by the reduction of palladium chloride using a variation of Brust's method. Discrete Pd nanoclusters of ∼15 nm size were formed in the absence of PC in the reaction mixture (ex situ method) while agglomeration of Pd nanoclusters was noticed in the presence of PC in the reaction mixture (in situ method). Fourier transform infrared spectroscopy (FTIR) suggests nanoparticle-polymer interactions and polymer conformational changes in the in situ nanocomposite films. Even after having the same Pd content, the ex situ nanocomposites films were found to transmit more light than the in situ nanocomposites. The glass transition temperature (T_g), decreased by ∼16 °C for both the ex situ and in situ samples. Thermogravimetric analysis (TGA) indicated that the presence of Pd nanoclusters significantly improved the thermal stability of the nanocomposites, as evidenced by the enhanced onset of degradation by ∼20 °C and ∼40 °C for the in situ and ex situ nanocomposites, respectively. The electrical conductivity measurement shows a dramatic difference between these nanocomposites with a significantly higher value for the in situ nanocomposite (resistivity = 2.1 × 10⁵ Ωm) compared to the ex situ nanocomposite (resistivity = 7.2 × 10¹³ Ωm).     

Kinetic model of solute aqueous extraction from Fennel (Foeniculum vulgare) treated by pulsed electric field, electrical discharges and ultrasonic irradiations

This work investigates the aqueous extraction from Fennel (Foeniculum vulgare) assisted by pulsed electric field (PEF), electrical discharges (ED) and ultrasound irradiations (UI). It aims the improvement of the solutes yield and the extraction kinetics at room temperature.Fennel gratings of size (1.5 × 0.75 × 30-50 mm³; width × height × length), were treated by PEF (intensity: 50-1200 V/cm and number of pulses: 50-1000), ED (voltage: 40 kV and number of discharges: 10-60) and ultrasound (intensity: 400 W/cm² and treatment duration: 10-350 min). The liquid-to-solid (weight/weight) ratio equal to 2. All tests were carried out at room temperature (20 °C), under stirring at 250 rpm. The extraction kinetics was modelled using a simplified two-exponential kinetic model, which corresponds to mass transfer in two stages (rapid washing and slow diffusion).The optimal parameters of PEF, ED and UI, giving the maximal juice yield, were determined and the effect of these three treatments on the mass transfer rate was studied.     

Design of process parameters for the production of xylose from wood sawdust

Meranti wood sawdust (MWS) is a cheap and widely available lignocellulosic biomass, which can be a potential source of xylose. This xylose can be an economic raw material for the production of a wide variety of specialty chemicals, mainly xylitol. It is particularly important to establish rapid hydrolysis conditions, which can yield xylose-rich hydrolysate that do not require further treatment. The aim of this research was to study the effect of residence time, temperature, acid concentration, and liquid to solid ratio (LSR) on the formation of xylose and byproducts. Batch hydrolysis was performed using different levels of residence time (10–120 min), temperature (105–130 °C), H₂SO₄ concentration (2–12%), and LSR (8–20 g/g). One-factor-at-a-time (OFAT) method was followed to select the optimum level of parameters. The residence time, temperature, and acid concentration were found to be the major factors affecting xylose production with the effective level of 60 min, 125 °C, and 4%, respectively. In these conditions, the xylose concentration was 17.9 g/l, corresponding to a yield of above 86% of the potential concentration.     

Kinetics of methane combustion over Pt and Pt–Pd catalysts

A kinetic study was performed over thermally aged and steam-aged Pt and Pt–Pd catalysts to investigate the effect of temperature, and methane and water concentrations on the performance of catalysts in the range of interest for environmental applications. It was found that both catalysts permanently lose a large portion of their initial activity as result of exposure to 5 vol.% water in the reactor feed. Empirical power-law and LHHW type of rate equations were proposed for methane combustion over Pt and Pt–Pd catalysts respectively. Optimization was used to determine the parameters of the proposed rate equations using the experimental results. The overall reaction orders of one and zero in methane and water concentration was found for stabilized steam-aged Pt catalyst in the presence and absence of water. The apparent self-inhibition effect caused by methane over Pt–Pd catalyst in the absence of water was associated with the inhibiting effect of water produced during the combustion of methane. A significant reversible inhibition effect was also observed over steam-aged Pt–Pd catalyst when 5 vol.% water vapor was added to the reactor feed stream. A significant reduction in both activity and activation energy was observed above temperatures of approximately 550 °C for steam-aged Pt–Pd catalyst in the presence of water (the activation energy dropped from a value of 72.6 kJ/mol to 35.7 kJ/mol when temperature exceeded 550 °C).     

Effects of CuO addition on the structure and electrical properties of low temperature sintered Ba(Zr,Ti)O3 lead-free piezoelectric ceramics

CuO-doped Ba(Zr_0.05Ti_0.95)O₃ (BZT) ceramics were prepared using conventional solid state reaction method, and their structure and electrical properties were investigated. It was found that a small amount of CuO could lower the sintering temperature significantly and make their microstructure more densified than pure BZT. The ceramics with 1.2 mol% CuO, sintered at 1250 °C, showed excellent piezoelectric properties with d₃₃~320 pC/N and k_p=44%. The sintering temperature was decreased by 150 °C than that for pure BZT ceramics while showing comparable piezoelectric properties. Moreover, the influence of sintering temperature on the optimally 1.2 mol% CuO-doped BZT ceramics was studied. With the temperature change, different patterns of crystal growth were observed in the doped BZT ceramics. When the sintering temperature increased from 1200 °C to 1350 °C, the patterns of normal–abnormal–normal grain growth were changed accordingly.     

Structure and thermo-mechanical properties study of polyurethane-urea/glycidoxypropyltrimethoxysilane hybrid coatings

A series of organic–inorganic hybrid coatings were prepared using polyurethane (PU)-urea and glycidoxypropyltrimethoxysilane (GPTMS) To prepare this first acid terminated saturated polyester, having 230 hydroxyl value and acid value 25 mg/KOH, were reacted with coupling agent GPTMS at different concentrations in the presence of base catalyst and each of them were further reacted with isophorone diisocyanate (IPDI) at NCO/OH ratio of 1.6:1 for 4–5 h at 70–80 °C These prepolymers were casted on tin foil and cured at ambient conditions for 6 h and prepared the hybrid coating free films by amalgamation. These free films were stored in the room temperature for 40 days and used for further characterization. The coating without and with different concentrations of GPTMS were named as base polymer and hybrid coatings, respectively. FTIR spectroscopy was used for the structural analysis of the coatings. Thermogravimetric analysis (TGA) showed that thermal stability of the hybrids was significantly higher than the base polymer. The onset degradation temperature of the base polymer starts at 268.9 °C, while it ranges from 279.1 °C to 290.8 °C for the hybrids based on the concentration of GPTMS used. The glass transition temperature (T_g) and storage modulus as determined from DMTA were higher for hybrid coatings as compared to base polymer. T_g of base polymer was 42.3 °C while it varies between 65.8 °C to 83.5 °C for hybrids.     

Hydrolytic degradation of poly[(R)-3-hydroxybutyric acid] in the melt

Poly[(R)-3-hydroxybutyric acid] [R-P(3HB)] was hydrolyzed in high-temperature and high-pressure water at the temperature range of 180-300 °C and for a period of 360 min. The formation, racemization, and decomposition of 3-hydroxybutyric acids (3HBs) and molecular weight change of R-P(3HB) were investigated. The highest yield of (R)-3-hydroxybutyric acid (R-3HB), ca. 80%, was obtained at 200 °C in the hydrolytic degradation periods of 240-360 min. Too-high hydrolytic degradation temperature such as 300 °C induced the decomposition and racemization of formed 3HBs, resulting in decreased yield of R-3HB. The hydrolytic degradation of R-P(3HB) proceeds homogeneously and randomly via a bulk erosion mechanism. The molecular weight of R-P(3HB) decreased exponentially without formation of low-molecular-weight specific peaks originating from crystalline residues. The hydrolytic degradation rates in the melt estimated from M_n changes were lower for R-P(3HB) than for poly(l-lactide) (PLLA) in the temperature range of 180-220 °C. The activation energy for the hydrolytic degradation (ΔE_h) of R-P(3HB) in the melt (180-250 °C) was 30.0 kcal mol⁻¹, which is higher than 12.2 kcal mol⁻¹ for PLLA in the melt in the temperature range (180-250 °C). This study reveals that hydrolytic degradation of PHB in the melt is an effective and simple method to obtain (R)-3HB and to prepare R-P(3HB) having different molecular weights without containing the specific low-molecular-weight chains, because of the removal of the effect caused by crystalline residues.     

Mixed matrix membranes of Matrimid 5218 loaded with zeolite 4A for pervaporation separation of water–isopropanol mixtures

Mixed matrix membranes were prepared by incorporating zeolite 4A into polyimide of Matrimid 5218 using solution-casting technique. The fabricated membranes were characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and thermo gravimetric analysis (TGA). It was found that the higher annealing temperature of 250 °C is more favorable to improve adhesion between zeolite and polymer phases. Effects of different parameters such as temperature (30–60 °C), water content in feed (10–40 wt.%), zeolite loading (0–15 wt.%) and polymer content (10 and 15 wt.%) on pervaporation dehydration of isopropanol were studied. Sorption studies were carried out to evaluate degree of swelling of the membranes in feed mixtures of water and isopropanol. The experimental results showed that both pervaporation flux and selectivity increase simultaneously with increasing the zeolite content in the membranes. The membrane containing Matrimid 5218 (10 wt.%)–zeolite 4A (15 wt.%) exhibits the highest separation factor (α) of 29,991 with a substantial permeation flux (J) of 0.021 kg/m² h at 30 °C for 10 wt.% of water in the feed. The PV performance was also studied in term of pervaporation separation index (PSI). Permeation flux was found to follow the Arrhenius trend over the investigated temperature range.     

Extraction of pomegranate (Punica granatum L.) seed oil using superheated hexane

Superheated hexane extraction (SHHE), Soxhlet extraction and cold pressing method were compared for the extraction of pomegranate seed oil. The extraction efficiencies of different temperatures (80, 100, 120 °C), mean particle sizes (0.25, 0.50 and 1.00 mm), and n-hexane flow rates (0.5, 1.0 and 2.0 mL/min) were investigated. The fatty acids profile of the seed oils were quantitatively determined by GC-FID. The optimum extraction temperature, mean particle size, and flow rate were selected as 80 °C, 0.25 mm, and 1 mL/min, respectively. The SHHE showed a higher extraction efficiency (22.18 wt%) within 2 h than Soxhlet extraction (17.94 wt%) for 24 h and cold pressing (4.29 wt%) for 72 h. The fatty acids profile for SHHE was more similar to that obtained by cold pressing method than Soxhlet extraction.     

Microstructure and dielectric properties of Dy/Mn doped BaTiO3 ceramics

Dy/Mn doped BaTiO₃ with different Dy₂O₃ contents, ranging from 0.1 to 5.0 at% Dy, were investigated regarding their microstructural and dielectric characteristics. The content of 0.05 at% Mn was constant in all the investigated samples. The samples were prepared by the conventional solid state reaction and sintered at 1290°, and 1350 °C in air atmosphere for 2 h. The low doped samples (0.1 and 0.5 at% Dy) exhibit mainly fairly uniform and homogeneous microstructure with average grain sizes ranged from 0.3 μm to 3.0 μm. At 1350 °C, the appearance of secondary, abnormal, grains in the fine grain matrix and core–shell structure were observed in highly doped Dy/BaTiO₃. Dielectric measurements were carried out as a function of temperature up to 180 °C. The low doped samples sintered at 1350 °C, display the high value of dielectric permittivity at room temperature, 5600 for 0.1Dy/BaTiO₃. A nearly flat permittivity–temperature response was obtained in specimens with 2.0 and 5.0 at% additive content. Using a Curie–Weiss and modified Curie–Weiss low, the Curie constant (C), Curie like constant (C′), Curie temperature (T_C) and a critical exponent (γ) were calculated. The obtained values of γ pointed out the diffuse phase transformation in highly doped BaTiO₃ samples.     

Carbothermic reduction synthesis of Ti(C,N) powder in the presence of molten salt

In the presence of sodium chloride (NaCl), Ti(C, N) powder was successfully obtained by the carbothermal reduction of TiO₂ in lab-scale experiments. The effects of NaCl addition and reaction temperature on the formation of the powder were studied in the temperature range of 1100–1600 °C, the reaction time used in all cases was 3 h. The final powder was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The results indicated that addition of NaCl played a facilitating role in the formation process of Ti(C, N). Ti(C, N) was detected at 1100–1200 °C, and the yield of powder was purer at about 1300 °C when 10 wt.% NaCl was added. The as-prepared Ti(C, N) was uniform in shape and the particle size was about 5–8 μm. With increasing temperature, the residual carbon content in the products decreased but the degree of oxidation increased at temperatures above 1300 °C. The possible mechanism involved in the reactions was discussed.     

Phenolics extraction from Agave americana (L.) leaves using high-temperature, high-pressure reactor

The Agave americana plant has been largely used in traditional medicine. The setting up of efficient methods for phenolics extraction from A. americana leaves is one of great interest. With the aim of optimizing phenolics extraction from this material, the effects of temperature (from 25 to 150 °C) and extraction time (from 15 to 240 min) were investigated using a high-temperature, high-pressure (PARR) reactor, under either air or nitrogen atmosphere. Total polyphenols and flavonoids were determined, and their antioxidant activity was measured by the DPPH radical method. The use of PARR reactor for phenolics extraction proved to be more efficient compared to the conventional solid-liquid extraction at room temperature. The results of this work demonstrated that an increase in both temperature and extraction time led to a corresponding increase in the amount of phenolic compounds extracted and suggested that, after process optimization, this material could be used as an interesting alternative source of polyphenols.     

Synthesis and thermally responsive characteristics of dendritic poly(ether-amide) grafting with PNIPAAm and PEG

A series of thermally responsive dendritic core-shell polymers were prepared based upon dendritic poly(ether-amide) (DPEA), modified with carboxyl end-capped linear poly(N-isopropylacrylamide) (PNIPAAm-COOH) or both PNIPAAm-COOH and carboxyl end-capped methoxy polyethylene glycol (PEG-COOH) in different ratios via an esterification process to obtain DPEA-PNIPAAm or DPEA-PNIPAAm-PEG. Their molecular structures were verified by gel permeation chromatography, and ¹H NMR and FTIR spectroscopy. The temperature-dependent characteristics study has revealed that DPEA-PNIPAAm exhibits a lower critical solution temperature (LCST) of about 34 °C, whereas DPEA-PNIPAAm-PEG polymers with the PNIPAAm/PEG ratio of about 1.0 and 0.4 possess about 36 °C and 39 °C, respectively, compared with 32 °C for homopolymer PNIPAAm. The critical aggregation temperature was investigated using fluorescence excitation spectrum of pyrene as a sequestered guest molecule based upon the sharp increase of the I₃₃₈/I₃₃₃ value.     

Supercritical fluid extraction of flavonoids from Maydis stigma and its nitrite-scavenging ability

Supercritical fluid carbon dioxide (SF-CO₂) extraction (SFE) of flavonoids from Maydis stigma and its nitrite-scavenging ability were investigated. The effects of extraction time, particle size and co-solvent composition in terms of water content in ethanol were first optimized. Then, a Box-Behnken design combined with response surface methodology (RSM) was employed to study the effects of three independent variables (temperature, pressure and co-solvent amount) on the extraction yield of flavonoids. A maximal extraction yield of flavonoids of approximately 4.24 mg/g of M. stigma by SFE was obtained under optimal conditions (a temperature of 50.88 °C, a pressure of 41.80 MPa, a co-solvent amount of 2.488 mL/g and an extraction time of 120 min with 0.4-mm particle sizes and 20% aqueous ethanol as the co-solvent). Furthermore, the nitrite-scavenging ability of the flavonoid-enriched SFE extracts was assessed using the Griess reagent. The flavonoid-enriched SFE extracts exhibited the highest scavenging ability on nitrite (88.1 ± 3.04%) at the concentration of 500 μg/mL and at pH 3.0. The nitrite-scavenging ability of the extracts appeared to be concentration dependent but negatively correlated with the pH.