Microwave-assisted extraction kinetics of terpenes from caraway seeds

The process conditions during the extraction of carvone and limonene from caraway seed (Carum carvi L.) with microwave-assisted extraction have been studied with respect to microwave power, radiation dose and extraction time in order to obtain the secondary metabolites selectively. Using classical solid–liquid extraction, limonene, carvone and fatty oils in both the raw material and the residual matrix material were extracted. Yields of limonene, carvone and total oil (C₁₆, C₁₈) were determined by GC and GC/MS analysis for both extracts. The effects of microwaves on cell walls and cells destruction could be seen on SEM micrographs.     

汽相萃取法制备无水乙醛肟

研究以二氯甲烷为萃取剂,利用汽相萃取由乙醛肟水溶液制备无水乙醛肟的工艺过程,所得乙醛肟贮存稳定性好,含量在９９％以上,收率达９３％。     

The dehydration kinetics of calcium sulphate dihydrate influence of the gaseous atmosphere and the temperature

The dehydration reaction rate of calcium sulphate dihydrate decreases monotonically with the water vapour pressure. The kinetics curves, of sigmoidal form, may be described, beyond the point of inflexion by a process of interface advance. The influence of foreign gases provide evidence that it is necessary for crystallizing water to pass through an adsorbed state.     

MOCVD生产废料中镓、铟提取工艺及其动力学研究

近年来，LED以其节能及环境友好等特性被广泛运用于各类照明领域。作为LED产品关键部件，采用金属有机气相沉积(MOCVD)生产外延片过程产生大量的生产废料。随着LED行业的快速发展，绿色、清洁回收MOCVD生产废料备受关注。本研究以硫酸为浸出剂，重点研究了MOCVD生产废料中Ga和In元素的浸出行为和浸出动力学。通过对浸出试剂种类、H2SO4浓度、固液比、浸出温度和浸出时间等参数的过程优化，在H2SO4浓度3 mol/L、固液比50 g/L、温度80℃、反应2 h的最佳工艺条件下，Ga和In的浸出率仅为67.50%和91.46%。动力学研究表明，在293.15~333.15 K温度范围内，Ga和In的浸出动力学符合收缩核模型，浸出过程受表面化学反应和外扩散混合控制。同时，XRD和SEM-EDS结果也印证了符合收缩核模型。在293.15~333.15 K温度范围内，Ga和In的浸出活化能分别为25.7和21.7 kJ/mol。基于对Ga和In浸出行为的动力学分析，提出并验证了MOCVD生产废料强化焙烧-浸出工艺的可行性。研究结果表明，强化焙烧-酸浸工艺可以使Ga和In的浸出率分别由67.50%和91.46%提升至88.27%和98.32%，并得到了氧化镓副产品。本研究结果有望为MOCVD生产废料的工业化资源循环提供基础数据支撑和新路径选择。     

Using membrane-supported liquid-liquid extraction for the measurement of extraction kinetics

Membrane-supported liquid-liquid extraction uses artificial membranes for the generation of a phase interface between the two liquid phases involved in extraction. Additional equipment for the generation of droplets as well as phase separation afterwards is no longer necessary. Since the membranes used for this special type of extraction are quite well described concerning thickness, porosity, tortuosity and material it is possible to generate information about the diffusion coefficient of the component to be extracted within the preferred solvent from extraction trails easily. This article describes an experimental set-up for both the proof of principle of membrane-supported liquid-liquid extraction and, using a dedicated computer-aided data treatment, how to calculate the overall mass transfer coefficient as well as the diffusion coefficient for a given system within moderate testing duration.     

Non-isothermal crystallization kinetics of poly(ethylene terephthalate)/mica composites

The non-isothermal crystallization kinetics of pure poly(ethylene terephthalate) (PET), PET/mica and PET/TiO₂-coated mica composites were investigated by differential scanning calorimetry with different theoretical models, including the modified Avrami method, Ozawa method and Mo method. The activation energies of non-isothermal crystallization were calculated by Kissinger method and Flynn–Wall–Ozawa method. The results show that the modified Avrami equation and Ozawa theory fail to describe the non-isothermal crystallization behavior of all composites, while the Mo model fits the experiment data fair well. It is also found that the mica and TiO₂-coated mica could act as heterogeneous nucleating agent and accelerate the crystallization rates of PET, and the effect of TiO₂-coated mica is stronger than that of mica. The result is further reinforced by calculating the effective activation energy of the non-isothermal crystallization process for all composites using the Kissinger method and the Flynn–Wall–Ozawa method.     

非平衡等离子体降解气态污染物反应动力学模

建立了非平衡等离子体降解气态污染物反应动力学模型,并将文献报道的对各种有机污染物降解实验数据代入模型,得到了各污染物的反应速率常数。结果发现,在不同的放电方式、电极结构和操作条件下,对同一物质的降解反应速率常数比较接近,表明所建立的动力学模型具有一定的通用性,而与放电方式、反应器结构无关。对不同污染物的反应速率常数和化学键结构数据进行了分类整理,分析讨论了反应速率常数的大小与分子结构中最弱化学键离解能之间的关系,发现分子结构中最弱化学键的离解能较小的物质反应速率常数较大;而结构稳定,最弱化学键的离解能较大的物质反应速率常数较小。     

粉煤灰中战略金属镓的提取与回收研究进展

镓被广泛应用于半导体、催化、医疗等多个领域。随着半导体行业的蓬勃发展,对镓需求量的日益增长促使人们寻找新的来源。从粉煤灰中回收镓不仅可以减少环境污染和资源浪费,还可以一定程度上缓解对镓资源日益增长的需求。综述了粉煤灰中镓的赋存形式、浸出工艺和镓提取分离方法的最新研究进展,重点介绍了溶剂萃取法和吸附法用于粉煤灰中镓资源回收的现状,总结了现有技术存在的问题,并对粉煤灰中镓资源的回收进行了展望,提出了粉煤灰中镓和其他伴生元素协同提取的资源化利用方向。     

Comparative study of the extraction methods for recovery of carotenoids from algae: extraction kinetics and effect of different extraction parameters

Carotenoid extraction from algae is currently under intensive research due to the increased demand for naturally occurring compounds, which are especially rich in biologically active isomers. Furthermore, natural carotenoids exhibit greater stability than synthetic ones. Conventional liquid extraction suffers from several drawbacks, such as use of high amounts of solvent, and several extraction steps. In this work carotenoid extraction from algae using different methods, such as microwave and ultrasound assisted extraction as well as pressurized liquid extraction and extraction with supercritical CO₂ and ethane, is summarized together with modelling of extraction kinetics. In addition carotenoid availability, algae pretreatment, stability of extracts, their antioxidative and antimicrobial activities as well as downstream processing and storage of algae extracts have been reviewed. As a conclusion it can be stated that carotenoid extraction is complex, demanding optimization of the carotenoid yield and antioxidative stability, which are often inversely proportional. © 2014 Society of Chemical Industry     

The electrodeposition of gallium from synthetic Bayer-process liquors

Gallium was electrodeposited from a synthetic Bayer solution comprising 4.5m NaOH/0.2m Na₂CO₃/0.3m NaCl/1.7m Al(OH)₃. Hydrogen evolution occurred in parallel with gallium deposition, the latter process being in part controlled by mass transfer and in part by the electron transfer step. Combined coulometric and voltammetric measurements allowed estimation of a diffusion coefficient for Ga (III) of 3.6×10^–6 cm² sec^–1 at 40° C. The coulombic efficiency for gallium deposition was a function of current density, deposition time, electrode rotation rate, temperature and gallium concentration. Values of up to 11% were obtained on a copper electrode from a solution containing 3.2×10^–3 m Ga (III). Heavy-metal impurities, such as iron and vanadium, usually found in these liquors, promote the hydrogen evolution reaction, completely inhibiting gallium production if present above certain critical concentrations.     

Isothermal crystallization kinetics of poly(lactic acid)/synthetic mica nanocomposites

The isothermal crystallization kinetics of PLA/fluoromica nanocomposites was studied. Three types of synthetic mica at three concentrations (2.5, 5.0, and 7.5 wt % mica) were used and the effect of these micas on the crystallization and thermal properties of PLA was investigated by differential scanning calorimetry (DSC). The Avrami and Hoffman‐Weeks equations were used to describe the isothermal crystallization kinetics and melting behavior. Addition of these micas to the PLA matrix increased the crystallization rate, and this effect depended on the mica type and concentration. While the nonmodified Somasif ME‐100 exerted the smallest effect, the effect observed for the organically modified Somasif MPE was the most pronounced. The lower half‐time of crystallization t_1/2 was around 3 min for the PLA/Somasif MPE nanocomposites containing 7.5 wt % of filler at 90°C, which is about 16 min below that found for neat PLA. The equilibrium melting temperature ( ) of PLA were estimated for these systems, showing an increase in the composites and an increase with increasing loading, except for PLA/Somasif MPE, in which the increase of the mica content decreased about 5°C. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40322.     

Study of kinetics of the d-pinitol extraction from carob pods using supercritical CO2

There is a growing interest in the use of d-pinitol (d-3-O-methyl-chiro-inositol) as a food supplement, thus the use of green and efficient process, such as the supercritical fluid extraction (SFE), to isolate d-pinitol from vegetable raw materials is also an interesting area of research and development. The objective of this work was to study the influence of operating conditions on the SFE of d-pinitol from carob pods. The crucial parameters in SFE, like temperature, pressure, CO₂ flow rate and duration of the process, have been studied. Finally, Naik and Barton models have successfully tested in order to fit the experimental extraction curves.     

Use of chemical kinetics to predict critical parameters of gaseous detonations

Computational modeling of chemical kinetics of fuel oxidation under conditions similar to those encountered in detonation waves is described. Sample applications to predicting critical detonation parameters are described, including lean and rich limits to detonation in linear tubes, direct initiation of unconfined spherical detonations by means of high explosive charges or by transition from a linear tube, and kinetic inhibition of detonation.     

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.     

Leaching kinetics of magnesium extraction from boron mud in ammonium bisulphate solutions

In this study, the leaching kinetics of magnesium of boron mud (BM) is evaluated using NH₄HSO₄ solution. The effects of leaching temperature, leaching time, ammonium bisulphate solution concentration and liquid–solid ratio on the extraction ratio of magnesium are investigated. Optimum leaching parameters are determined through an orthogonal test based on single factor experiments. Under the optimum leaching temperature (333 K), leaching time (40 min), NH₄HSO₄ concentration (2.8 mol · L⁻¹), and liquid–solid ratio (9:1 mL · g⁻¹), the extraction ratio of magnesium was 76.73%. In addition, the leaching kinetics data of magnesium from BM are analyzed through graphical and statistical approaches, which reveal that the leaching process conforms to the grain model. The leaching process is diffusion-controlled with an activation energy of 41.67 kJ · mol⁻¹.     

Preferential extraction of gallium from Bayer liquor using ion exchange chelating resin containing hydroxamic acid functional group

Gallium extraction studies were carried out using resin containing an hydroxamic acid functional group. Extraction was dependant on reaction time and alkali concentration. The resin did not extract aluminium. Vanadium extraction kinetics were slower than those of gallium. The gallium and vanadium separation efficiency increased with decreasing contact time with extractions of 64% and 32% respectively after 1 min. Gallium extraction was independent of alkali concentration up to 250 g dm^?3 and thereafter decreased with increasing alkali concentration. Vanadium extraction decreased with increasing alkali concentration. Cyclic batch and column studies were carried out with synthetic as well as actual Bayer liquor to test the stability and preferential extraction of gallium using the resin. It was observed that using resin partially loaded with gallium, the co‐extraction of vanadium could be minimised. Copyright © 2003 Society of Chemical Industry     

The direct adsorption of low concentration gallium from fly ash

This study is mainly focused on the direct adsorption of low concentration gallium from the feed solution in pre-desilication soda-lime sintering process from coal fly ash. The adsorption kinetics, mechanism, and the influence of impurities, cyclic times, and eluant content are systematically researched. Results showed that the adsorption capacity was 2.89 mg/g resin with gallium concentration of 50 mg/L. The adsorption mechanism could be explained by the interaction between the oxygen atoms and nitrogen atoms of amidoxime group. Gallium was eluted efficiently by NaOH and Na₂S mixed solution and the concentration could be reached to 2400 mg/L.     

Effect of high pressure pretreatment on drying kinetics and oleoresin extraction from ginger

The present study reports for the first time the effect of high pressure pretreatment (100–400?MPa, 10?min) on drying kinetics of ginger and its oleoresin extraction. High pressure pretreated samples were dried, powdered and solvent extracted. The increase in drying temperature (55–85°C) increased the moisture diffusivity (2.03–4.87?×?10^?9?m²/s) but resulted in decrease in 6-gingerol (53.98%) and oleoresin yield (57.31%). However, high pressure pretreatment followed by dehydration (55°C) resulted in higher moisture diffusivity (2.84–6.09?×?10^?9?m²/s) as well as enhanced extraction yield of 6-gingerol (34.05%) and oleoresin (28.29%).