Ultrasonically assisted extraction of total carbohydrates from Stevia rebaudiana Bertoni and identification of extracts

In the present study, in order to maximize the yield of total carbohydrates from Stevia rebaudiana Bertoni, Stevia LUYU-131 was used as test material, and response surface methodology (RSM) was employed to optimize the ultrasound-assisted extraction condition. The results indicated the optimal extraction conditions were an extraction temperature of 68 °C, a sonic power of 60 W and an extraction time of 32 min. Using the ultrasound-assisted extraction, the yield of extracts increased by a factor of 1.5 at the lower extraction temperature (68 °C) and the extraction time (32 min) substantially shortened compared with that of classical extraction. The components analysis of crude extracts revealed that the relative amount of rebaudioside A increased in the ultrasound-assisted extracts as compared with extracts obtained by classical process, and the ultrasound-assisted extracts had better quality.     

Supercritical CO2 and low-pressure solvent extraction of mango (Mangifera indica) leaves: Global yield,extraction kinetics,chemical composition and cost of manufacturing

Low-pressure solvent extraction (LPSE) and supercritical fluid extraction (SFE) were used to obtain extracts from mango (Mangifera indica) leaves. Kinetics curves were determined for both methodologies. The extracts chemical compositions and manufacturing costs were determined for both processes. Global yield isotherms for SFE process were determined at 10–40 MPa and 313–323 K. The highest yield was 2.24% at 30 MPa and 323 K; the LPSE yield (9.3%) was almost three times higher than that of SFE (3.6%). Thin layer chromatography showed that mango leaves extracts have several classes of compounds as alkaloids, flavonoids and terpenoids, recovered by both methods. The cost of manufacturing (COM) mango leaves extracts were US$ 32/kg and US$ 92/kg for LPSE and SFE, respectively.     

Optimization of ultrasound-assisted extraction for the maximum quantity and quality of phenolics from Stachys lavandulifolia

The response surface methodology was used to evaluate the effects of extraction time, power of ultrasound, liquid to solid ratio, and solvent composition on the quantity and quality (from aspect of antioxidant activity) phenolics of Stachys lavandulifolia. The best extraction time, power of ultrasound, liquid to solid ratio, and solvent composition for both the quality and quantity of phenolics were 14 min, 300 W, 40 (v/w), and 57% methanol, respectively. Only the liquid to solid ratio was effective on the quality of phenolics. Also, the comparison between the ultrasound-assisted extraction and maceration methods showed the suitability of ultrasound-assisted extraction for extracting phenolics from this plant.     

以高产量、高产率、高生产强度为目标的发酵过程优化技术

以高产量、高底物转化率和高生产强度为目标,综合运用微生物反应计量学、生化反应和传递动力学、生物反应器工程及代谢工程理论,开发了:(1)基于微生物反应计量学的培养环境优化技术;(2)基于微生物代谢特性的分阶段培养技术;(3)基于反应动力学模型的优化技术;(4)基于代谢通量分析的优化技术;(5)基于系统观点的生物反应系统优化技术。将这些技术广泛应用于多种产品的发酵过程优化研究中并取得了成功。在此基础上总结出“简化、定量化、模型化和阶段化”的发酵过程优化基本原理,这一基本原理对提高我国发酵工业技术水平、促进生物食品产业的健康发展将起重要作用。     

Supercritical fluid extraction from dried banana peel (Musa spp., genomic group AAB): Extraction yield, mathematical modeling, economical analysis and phase equilibria

Supercritical fluid extraction from dried banana peel (Musa spp., subgroup Prata, genomic group AAB, popularly known in Brazil as Enxerto) was studied. The aspects investigated were: overall extraction curve (OEC), mass transfer modeling of the yield curves, economical analysis of the process and phase equilibrium data for the pseudo-ternary system of banana peel extract, carbon dioxide and ethanol. The extraction operating conditions evaluated were: pressure ranging from 100 bar to 300 bar, temperature from 40 to 50 °C and constant solvent flow rate of 5.0 gCO₂/min. Experimental extraction data were correlated using three kinetic models based on mass transfer equations (logistic, diffusion and Esquível models). Phase equilibrium measurements were performed using pressure from 64.9 bar to 239.9 bar and mass fraction of supercritical extract from 0.52 to 3.55 wt%. Yield results ranged from 0.6 to 6.9% d.b. (dry basis). The lowest deviation between experimental and correlated data was obtained by the Logistic model, except for the curve at 300 bar and 40 °C which was best represented by the Esquível model. The economical analysis identified the possibility to apply the supercritical fluids to obtain extracts from banana peel in an industrial scale. Phase equilibrium for the supercritical extract from banana peel with carbon dioxide modified by ethanol exhibited liquid-liquid, vapor-liquid (bubble point) and vapor-liquid-liquid phase transitions. A crossover phenomenon for the systems evaluated was observed for pressures between 200 bar and 240 bar, for both groups of assays, i.e., supercritical extraction and phase equilibrium.     

Combination of ACO-artificial neural network method for modeling of manganese and cobalt extraction onto nanometer SiO2 from water samples

In this study, modeling based on ant-colony optimization – artificial neural network have been employed to develop the model for simulation and optimization of nanometer SiO₂ for the extraction of manganese and cobalt from water samples. The pH, time, amount of SiO₂ nanoparticles and concentration of 1-(2-pyridylazo)-2-naphthol (PAN) were the input variables, while the extraction% of analytes was the output. Under the optimum conditions, the detection limits were 0.52 and 0.7 μg L^?1, for manganese and cobalt, respectively. The method was applied to the extraction of manganese and cobalt from water samples and one certified reference material.     

Extracts from pitanga (Eugenia uniflora L.) leaves: Influence of extraction process on antioxidant properties and yield of phenolic compounds

Different extraction processes were employed to extract the polyphenolic compounds from pitanga (Eugenia uniflora L.) leaves: a one-step process using water, ethanol or supercritical CO₂ as solvents, and a two-step process using supercritical CO₂ followed by either water or ethanol. The total polyphenolic compounds, total flavonoids and antioxidant activity were determined in all the extracts obtained. The process performance was evaluated with respect to three variables: global extraction yield, concentration and yield of both polyphenols and flavonoids in the extracts. For the one-step extraction, the results showed that the extraction yield increased with solvent polarity. For the two-step process, the results suggested that water was more efficient in extracting the phenolic compounds from E. uniflora when the matrix was previously extracted with scCO₂. With respect to the antioxidant activity, the ethanolic extracts obtained from both processes, using either the DPPH radical scavenging method or the β-carotene bleaching method, presented high antioxidant activities.     

Equilibrium modeling,kinetic and thermodynamic studies on the adsorption of Cr(VI) using activated carbon derived from matured tea leaves

A new porous carbon with high surface area of 1,313.41 m² g^?1 with pore volume 1.359 cm³ g^?1 has been synthesized from matured tea leaves by chemical activation method using phosphoric acid. The carbon was found to be highly efficient for removal of Cr(VI) from aqueous solution. The effects of various parameters such as contact time, initial metal ion concentration, pH, temperature and amount of adsorbent on the extent of adsorption were studied. Langmuir, Freundlich and Temkin adsorption models were used to interpret the experimental data. The adsorption data were best fitted with Langmuir isotherm model. The adsorption capacity of Cr(VI) onto the activated carbon calculated from Langmuir isotherm was found to be 30.8 mg g^?1 at pH 4.8 and temperature 303 K. The adsorption capacity increases from 25.36 to 32.04 mg g^?1 with an increase in temperature from 303 to 323 K at initial Cr(VI) concentration of 60 mg L^?1. The adsorption process followed a pseudo second order kinetic model. Thermodynamic parameters ΔH⁰ (28.6 KJ mol^?1), ΔG⁰ at three different temperatures [(?0.145, ?1.09, ?2.04) KJ mol^?1] and ΔS⁰ (94.87 J mol^?1 K^?1) were calculated. These values confirm the adsorption process to be endothermic and spontaneous in nature.     

Optimization of simultaneous carotenes and vitamin E (tocols) extraction from crude palm olein using response surface methodology

In this study, response surface methodology was utilized to determine the optimal conditions for the extraction of carotenes (α- and β-carotene) and tocols (α-tocopherol, α-, γ-, and δ-tocotrienol) from crude palm olein using ethyl lactate (EL) and ethanol (EtoL) in a temperature-controlled mixer-settler system. Central composite design with four factors including temperature (X₁), mixing time (X₂), volume fraction (VF) of olein (X₃), and VF of EtOL (X₄) was used to investigate the multivariate relationship with the five responses including enrichment factor and recovery of both carotenes and tocols. The optimum extraction conditions were determined at 20°C, 10?min of mixing, 48% of crude palm olein, 31.2% of EL and 20.8% of EtoL (corresponding to 0.5 VF of olein and 0.4 VF of EtoL). The enrichment factors of carotenes and tocols were 0.88 and 2.56, respectively while 11.3% of carotenes and 31.2% of tocols were recovered.     

滇杨叶片提取物对马铃薯块茎蛾产卵选择性的影响

[目的]探讨滇杨叶片提取物对马铃薯块茎蛾产卵行为的影响。[方法]在室内利用选择性产卵试验方法分别测定了新鲜及萎蔫滇杨叶片的5种质量浓度(375～6000 g/L)的二氯甲烷提取物对马铃薯块茎蛾产卵选择性的影响。[结果]试验结果表明:不同质量浓度的新鲜滇杨叶片和萎蔫的滇杨叶片的二氯甲烷提取物均对马铃薯块茎蛾的产卵具有显著的抑制作用。对马铃薯块茎蛾产卵的抑制效果随浓度的升高而增强。     

Optimization of fermentation condition for co-production of ethanol and 2,3-butanediol (2,3-BD) from hemicellolosic hydrolysates by Klebsiella oxytoca XF7

Microbial production of ethanol and 2,3-butanediol (2,3-BD) from agro-residues has been attracting interest because of their applications in various industries, including generation of biofuel molecules. In the present investigation, the hemicellulosic fraction of corncob was hydrolyzed by indigenous holocellulase from novel psychrotolerant Aspergillus niger SH3 resulting in high xylose release (34.61?g?L^?1), followed by the bioconversion of xylose to ethanol and 2,3-BD. Taguchi design was adopted to optimize the process which resulted in 5.25- and 3.31-fold increase in 2,3-BD (12.18?±?0.53?g?L^?1) and ethanol (4.08?±?0.03?g?L^?1), as compared with un-optimized condition. For the first time, co-production of ethanol and 2,3-BD from the corncob hemicellulosic hydrolysate was performed using a newly isolated Klebsiella oxytoca XF7 strain, under the optimized fermentation conditions. These results suggest that K. oxytoca XF7 is a promising candidate for co-production of ethanol and 2,3-BD, with high xylose conversion efficiency (96.65%), facilitating the economical production of biofuel molecules.     

Mass transfer modeling of membrane carrier system for extraction of Ce(IV) from sulfate media using hollow fiber supported liquid membrane

A theoretical and experimental study on the extraction and stripping of Ce(IV) ions from sulfate media using microporous hydrophobic hollow fiber supported liquid membrane has been performed. The experiments were made in the recycling mode. Tri-n-octylamine (TOA) was used as extractant diluted in kerosene and sodium hydroxide was use as strip solution. The mathematical model focused on the extraction side of a liquid membrane system. The aqueous feed mass transfer coefficient (k_i) and the organic mass transfer coefficient (k_m) which were calculated from the model were 9.47 X 10^-2 and 6.303 cm/s, respectively. Therefore, the rate controlling step is the diffusion of the cerium complex across a liquid membrane. In addition, the mass transfer modeling was performed and the validity of the developed model was evaluated with experimental data and found to tie in well with the theoretical value when the concentration of TOA was higher than 5% (v/v).     

Supercritical fluid extraction of peach (Prunus persica) almond oil: Kinetics, mathematical modeling and scale-up

Peach almonds contain oil with important therapeutic and nutritional properties due to the presence of unsaturated fatty acids, high content of oleic acid and other substances. In this study, peach almond oil was obtained by means of supercritical fluid extraction (SFE), with yield up to 24% w/w. The objective of this work was to evaluate the effect of the operation variables in the process kinetics in order to define scale-up parameters, like extractor volume and solvent flow rate. In spite of the importance for industrial application, the definition of a scale-up methodology is difficult. Therefore, the main goal of this work was to study the kinetic aspects of the SFE by modeling the extraction curves and, with these results, suggests a scale-up methodology. The parameters evaluated were extraction pressure, CO₂ flow rate and particle size. The mass transfer models used to describe the extraction curves were logistic model, diffusion model and Sovová model. Four scale-up methodologies, based on mass transfer mechanisms, were applied. The results indicate the best curve fitting by means of Sovová’s model, while the best scale-up criterion was maintaining the ratio Q_CO2/M (solvent flow rate/raw material mass) constant. This study also indicated the convection as the dominant mass transfer mechanism, while the diffusion was the limiting factor. Moreover, the SFE of peach almond oil could be predicted by the scale-up method used.     

Modeling,Simulation, and Optimization of Hybrid Fe(II)/Fe(III) Redox Flow Fuel Cell System

The kinetic parameters of ferrous iron oxidation, covering both lag and growth phases at low pH, were determined using a free suspended culture of the bacterium Leptospirillum ferriphilum. A mathematical model was developed to simulate the dynamics of a continuous bioreactor used for operation of a novel hybrid Fe(II)/Fe(III) redox flow fuel cell system. By changing the current load within a predefined range, three runs were performed to predict time‐varying ferrous iron concentration, bacterial cell concentration, and pH as the major output variables of simulation program. The model was experimentally validated through three runs. It was found out that the key variable in dynamic analysis of the bioreactor was the current load applied. To optimize the bioreactor and the fuel cell conditions for a normal‐steady‐state operation, the optimal current profile for a transient phase was determined. A selected optimal policy was also implemented and validated during the mini‐pilot‐scale system experiments. © 2013 American Institute of Chemical Engineers AIChE J, 59: 1844–1854, 2013     

New liquid membrane technology for simultaneous extraction and stripping of copper(II) from wastewater

In this paper, a new liquid membrane technique, hollow fiber renewal liquid membrane (HFRLM), is presented, which is based on the surface renewal theory, and integrates the advantages of fiber membrane extraction, liquid film permeation and other liquid membrane processes. The results from the system of CuSO₄+D2EHPA in kerosene+HCl show that the HFRLM process is very stable. The liquid membrane is renewed constantly during the process, the direct contact of organic droplets and aqueous phase provides large mass transfer area. These effects can significantly reduce the mass transfer resistance in the lumen side. Then the mixture of feed phase and organic phase flowing through the lumen side gives a higher mass transfer rate than that of stripping phase and organic phase, because the aqueous layer diffusion of feed phase is the rate-controlling step. The overall mass transfer coefficient increases with increasing flow rates and D2EHPA concentration in the organic phase, and with decreasing initial copper concentration in the feed phase. The overall mass transfer coefficient also increases with increasing pH in the feed phase, and reaches a maximum value at pH of 4.44, then decreases. Also, there is a favorable w/o volume ratio of 20:1 to 30:1 for this process. Compared with hollow fiber supported liquid membrane and hollow fiber membrane extraction processes, HFRLM process has a high mass transfer rate. Mathematical model for the HFRLM process based on the surface renewal theory is developed. The calculated results are in good agreement with experimental results under the conditions studied.     

Measurements and modeling of heat generation in a trickling biofilter for biodegradation of a low concentration volatile organic compound (VOC)

The experimental and theoretical heat generation behavior of a trickling biofilter treating toluene is discussed. The experimental results show that the temperature of the packed bed has a significant effect on the purification performance of the trickling biofilter and that an optimal operation temperature exists between 30 and 40 °C. During the gas–liquid co-current flow, the temperature in the packed bed gradually rises along the direction of the gas and liquid flow due to the exothermic biodegradation of toluene. The temperature rise between the inlet and outlet of the trickling biofilter increases with an increase in the gas flow rate and inlet toluene concentration. In addition, a larger liquid flow rate leads to a smaller temperature rise. The heat generation process occurring in the trickling biofilter is modeled by representing the packed bed as an equivalent set of parallel capillary tubes covered by the biofilm. The temperature profile in the packed bed during the liquid–gas co-current flow is analyzed by simultaneously solving the problem of gas–liquid two-phase flow and heat and mass transfer through the liquid film and biofilm. It is shown that the model agrees well with the experimental data, predicting the variations of the temperature rise between the inlet and outlet of trickling biofilter with the increasing gas and liquid flow rates.     

逆向浸取法制取硫酸镁、氢氧化镁及氧化镁

介绍了以硫酸铵、白云石为原料制备硫酸镁、氢氧化镁、轻质氧化镁的实验条件及工艺过程。讨论了实验条件对产品质量、性能的影响。与白云石的开发利用其它工艺比较，该方法具有原料来源方便、生产成本较低等优点，无三废污染，废渣可加工成CaSO4产品，所排氨气也可回收利用。     

Comparative study of solvent extraction and supported liquid membrane for the extraction of gallium (III) from chloride solution using organophosphorus acids as extractants

ABSTRACT

The transport of Ga(III) from chloride solution by supported liquid membrane (SLM) using organophosphorus acids as carriers was studied and compared with solvent extraction results. The diffusion coefficient, permeability coefficient and mass transfer resistance for both processes were analyzed by investigating various parameters, such as flow pattern, flow rate, pH, Ga(III)/extractant concentration and temperature. Under optimized conditions, the extraction percentage of 97.0% and permeability coefficient of 9.22 × 10^?6 m/s was achieved for SLM process. Kinetic modeling was proposed to determine the mass diffusion coefficient of Ga(III) complex across the membrane and stability of this SLM system was also examined.     

Pseudo-Emulsion Based Hollow Fiber Strip Dispersion Technique (PEHFSD): Optimization,Modelling and Application of PEHFSD for Recovery of U(VI) from Process Effluent

Abstract

Pseudo emulsion based hollow fiber strip dispersion technique (PEHFSD) is the first of its kind ever explored in radioactive environment for the extraction of uranium from acidic process streams. Permeation of U(VI) was investigated as a function of various experimental variables such as hydrodynamic conditions (flow rates of pseudo-emulsion and feed phase), concentration of U(VI) in the feed phase, concentration of tri-n-butylphosphate (TBP), HNO₃ concentration in feed phase, O/A ratio and 0.01 M HNO₃ as stripping agent in pseudo-emulsion phase. The mass transfer coefficient was calculated from the experimental results and a model has been presented for determining mass transfer characteristics. PEHFSD has been demonstrated for separation/recovery of uranium from oxalate supernatant waste generated during plutonium precipitation by oxalic acid. PEHFSD and HFSLM (hollow fiber supported liquid membrane) performance has been compared in order to analyze the efficiency of the technique.