Helena Sovova

The Czech Academy of Sciences | AVCR · Department of Separation Processes

Research on enzyme-catalysed reactions of oils in supercritical CO2 (scCO2) aims at solvent-free natural products enriched in bioactive substances. Easy tailoring of scCO2 properties and low mass transfer limitations belong to advantages of the method, which perspective of large-scale application depends on enzyme stability in scCO2. Mathematical m...

Continuous flow hydrolysis of blackcurrant seed oil dissolved in supercritical carbon dioxide (scCO2) was catalyzed by immobilized lipase Lipozyme TL IM. HPLC-MS and acid-base titration were used to determine composition of oil and hydrolysis products comprised of tri-, di- and monoglycerides, free fatty acids and glycerol. The oil contained 10 % l...

Stereospecific composition of triacylglycerols (TAGs) wascalculated for a set of analytical data on genetically modified sunflower and soybean seed oils, using different mathematical models for TAG assembly. The models wererelated to biochemical pathways. The data (Reske et al., JAOCS 74 (1997) 989-998) consist of total fatty acid profiles, fatty a...

Turmeric (Curcuma longa L.) was extracted with supercritical carbon dioxide (sc-CO 2 ) and turmerones, compounds with strong biological activity, were concentrated using semi-preparative supercritical chromatography (p-SFC) with sc-CO 2 . The extraction was performed at temperature of 40 °C and pressures of 9–66 MPa. Influence of pressure, type of...

Literature data on the extraction of carotenoids from microalgae with supercritical carbon dioxide (scCO 2 ) were used to describe the process as an extraction of a solution of carotenoids in oil. A mathematical model for oil extraction from microalgae, including also the adsorption on microalgal surfaces, was extended for this purpose. The working...

Stilbenes were extracted from grape cane using supercritical fluid extraction and pressurized liquid extraction, and the extracts were analysed by HPLC. The results of the high-pressure experiments were compared with ethanolic Soxhlet extraction, which yielded 2.31 mg/g dw trans-resveratrol, 1.56 mg/g dw trans-epsilon-viniferin, and 0.69 mg/g dw r2...

Wine industry produces a significant amount of grape waste such as grape cane and grape pomace which are mostly used for basic applications (wooden pellets, compost or grappa), despite the fact they contain quite a high amount of polyphenols as trans-resveratrol and its oligomers viniferins, belonging to the group of stilbenes. Trans-resveratrol is...

Microcellular polystyrene (PS) foams blown with supercritical CO2 in batch processes have usually porosities lower than desired for good heat insulators. Porosities can be increased by co-blowing agents. We studied effects of n-pentane (nC5) and cyclopentane (cC5) on foaming in a batch. Neat PS films were impregnated first with nC5 or cC5, then wit...

Experiments with CO2-blown hanging polystyrene (PS) films were carried out. The porosity of foams decreased with decreasing film thickness, indicating thus effects of heat and/or mass transfer. Taking into account the Joule-Thomson effect, mathematical model based on a simplified heat balance for the system PS + CO2 at the conditions of PS saturati...

In this work, a multicomponent model for understanding the relationship between the chemical compositions of an extract and extracted plant is developed and presented for the first time. Its robustness and efficiency were validated on the example of furanocoumarins and waxes extracted from aerial parts of common rue with supercritical CO2 at pressu...

One group of mathematical models for supercritical fluid extraction from plants is based on the Broken-and-Intact Cell (BIC) concept. A simplified BIC model with analytical solution, derived for the extraction of vegetable oils from seeds, was published in 1994. It has been used by several researchers also for the extraction of other solutes from o...

Structure and phase composition of titania aerogels can be substantially influenced simply by the process of drying their parent water colloid suspensions prepared by the reaction of hydrogen peroxide with suspension of precipitates obtained by neutralization of solution of titanyl sulfate with ammonia. Two methods of drying are compared: (1) lyoph...

Microalgae contain valuable biologically active lipophilic substances such as omega-3 fatty acids and carotenoids. In contrast to the recovery of vegetable oils from seeds, where the extraction with supercritical CO2 is used as a mild and selective method, economically viable application of this method on similarly soluble oils from microalgae requ...

This paper presents a new approach to modelling the kinetics of a supercritical fluid extraction of a mixture of solids. Experimental data on pure long-chain n-alkanes solubility in supercritical CO2 (scCO2) was reviewed and selected data was correlated applying a semi-empirical density-based model and an equation of state. On the example of extrac...

The ethanolysis of fish oil in various reaction medium (tert-pentanol, n-hexane and solvent free system) catalyzed by the immobilized commercial lipase Lipozyme(®) 435 (Candida Antarctica) at atmospheric pressure has been studied in this work. The effect of some kinetic parameters, such as the amount of lipase, temperature and the initial reactant...

Volatile oil rich in thymoquinone (TQ) was extracted from dry aerial parts of scarlet bee balm (Monarda didyma) and wild bergamot (Monarda fistulosa) with supercritical CO2. The optimum extraction conditions were determined as 12 MPa and 40 °C for both yield (0.6 mg TQ/g M. didyma and 1.7 mg TQ/g M. fistulosa) and high TQ concentration in extract (...

Supercritical fluid extraction was used to isolate volatile compounds from savory (Satureja hortensis L.), thyme (Thymus vulgaris L.), lavender (Lavandula angustifolia L.) and peppermint (Mentha piperita L.). Three types of extracts were prepared using the benefit of variable solvent power of supercritical carbon dioxide under different extraction...

The solubility of (−)-α-bisabolol, ((−)-6-methyl-2-(4-methyl-3-cyclohexen-1-yl)-5-hepten-2-ol), a monocyclic sesquiterpene alcohol, in sub- and supercritical CO2 was measured at the temperatures (313.2, 323.2, and 333.2) K and pressures ranging from (7 to 12.5) MPa by a dynamic method. To the best of our knowledge, there are no previous measurement...

The kinetics of a batch solid-liquid extraction of total phenolic compounds (PC) from milled grape seed (Vitis vinifera L. cv. "Frankovka") using 50% ethanol at different extraction temperatures (25-80°C) was studied. The maximum yield of PC was 0.13kg(GAE)/kg(db) after 200min of extraction in agitated vessel at 80°C. A new model based on the assum...

In this work, the SFE was applied to extract selected medicinal substances from sea buckthorn (Hippophae rhamnoides L.) leaves at different conditions (pressure 20-28 MPa, temperature 40-60 °C and ethanol concentration in CO2 0-6.9 wt. %) influencing solvent power of CO2. Interest was focused on the leaf oleoresin (total extract) and its minor comp...

An overview of the studies carried out in our laboratories on supercritical fluid extraction (SFE) of volatile oils from seven aromatic plants: pennyroyal ( Mentha pulegium L.), fennel seeds ( Foeniculum vulgare Mill.), coriander ( Coriandrum sativum L.), savory ( Satureja fruticosa Béguinot ), winter savory ( Satureja montana L.), cotton lavender...

The microalga Nannochloropsis sp. was used in this study, in a biorefinery context, as biomass feedstock for the production of fatty acids for biodiesel, biohydrogen and high added-value compounds. The microalgal biomass, which has a high lipid and pigment content (mainly carotenoids), was submitted to supercritical CO(2) extraction. The temperatur...

Kinetics of supercritical fluid extraction (SFE) from plants is variable due to different micro-structure of plants and their parts, different properties of extracted substances and solvents, and different flow patterns in the extractor. Variety of published mathematical models for SFE of natural products corresponds to this diversification. This s...

Different types of mathematical models were applied in the last decade to simulate kinetics of supercritical fluid extraction (SFE) of essential oils from aromatic plants. Compared to the extraction of fatty oils, modeling of extraction of essential oils is more complicated due to their potential fractionation, co-extraction of less soluble compoun...

The apparent solubility controls the initial stage of supercritical fluid extraction of natural products, which is most important for the process economics. Based on the literature, data on CO2 apparent solubility of volatile substances from different matrices as leaves, flowers, rhizomes and seeds were collected and compared with their thermodynam...

In the 21st century, the mission of chemical engineering is to promote innovative technologies that reduce or eliminate the use or generation of hazardous materials in the design and manufacture of chemical products. The sustainable use of renewable resources, complying with consumer health and environmental requirements, motivates the design, opti...

The extracts of valuable vegetable oils containing a number of minor components (sterols, tocopherols, carotenoids, etc.) have added value as pharmaceuticals and food additives. Beta-sitosterol (BS) as minor component of vegetable oil was extracted from ground seeds of sea buckthorn with supercritical CO2 at pressures 15–60 MPa and temperatures 40–...

The modelling of the experimental data of the extraction of the volatile oil from six aromatic plants (coriander, fennel, savoury, winter savoury, cotton lavender and thyme) was performed using five mathematical models, based on differential mass balances. In all cases the extraction was internal diffusion controlled and the internal mass transfer...

CO2 extracts and essential oil obtained by hydrodistillation from feverfew aerial parts were applied to Spodoptera littoralis (Boisduval) larvae to examine their effects on mortality, antifeedancy and growth inhibition, and their composition of volatile substances was determined using GC. The mortality strongly correlates with the content of terpen...

Supercritical fluid extraction represents an efficient and environmentally friendly technique for isolation of phytosterols from different plant sources. Sea buckthorn (Hippophae rhamnoides L.) seeds were extracted with supercritical carbon dioxide at pressures ranging from 15-60 MPa and temperatures of 40-80 degrees C. Oil and beta-sitosterol yiel...

Two types of lipases (extracellular and cell-bound) were produced by Geotrichum candidum 4013 in liquid medium and were used as biocatalysts in blackcurrant oil hydrolysis. Reaction products were analysed for the degree of conversion from which enzyme activity was evaluated, and the composition of free fatty acids was compared to the composition of...

The selection of column packing during the development of high-performance liquid chromatography method is a crucial step to achieve sufficient chromatographic resolution of analyzed species in complex mixtures. Various stationary phases are tested in this paper for the analysis of complex mixture of triacylglycerols (TGs) in blackcurrant oil using...

Extracts from savory (Satureja hortensis L.) and thymus (Thymus vulgaris L.) were obtained by supercritical fluid extraction, hydrodistillation, and Soxhlet extraction with benzene and ethanol. The composition of volatile compounds in the extracts was determined by gas chromatography, and the toxicity and antifeedant effects of the extracts on larv...

Nigella sativa L. seed essential oils obtained by hydrodistillation (HD), dry steam distillation (SD), steam distillation of crude oils obtained by solvent extraction (SE-SD), and supercritical fluid extraction (SFE-SD) were tested for their antibacterial activities, using the broth microdilution method and subsequently analyzed by gas chromatograp...

The acute toxicity of savory (Satureja hortensis) extracts obtained with supercritical CO2 and by traditional extraction techniques was tested on larvae of Musca domestica, Spodoptera littoralis, Culex quinquefasciatus and Leptinotarsa decemlineata and on adults of M. domestica, and the composition of volatile compounds in the extracts was determin...

Blackcurrant seed oil is rich in linoleic and linolenic acids. Selective enzyme-catalysed oil hydrolysis was studied with aim to obtain different levels of α- and/or γ-linolenic acid in the mixture of liberated fatty acids and in the fraction of di- and monoacylglycerols, making them suitable for special dietary needs. The oil was dissolved in supe...

The activity of lipases from porcine pancreas, Candida antartica recombinant from Aspergillus oryzae, Candida cylindracea (immobilized), Penicilium roqueforti, Aspergillus niger, Rhizopus arrhizus, Mucor miehei (two types of immobilization), and Pseudomonas cepacia (two types of immobilization) was studied after using them as biocatalysts of blackc...

Leuzea carthamoides is an adaptogenic plant containing biologically active compounds as ecdysteroids and guaianolide-type sesquiterpene lactones, conventionally extracted from the plant with ethanol. It may be a potential source of the mentioned natural compounds. Ethanol-modified near-critical CO(2) was used as selective solvent with the aim to in...

Internal structure of soybeans was modified by the instantaneous controlled pressure drop process (DIC) when the material is heated by saturated steam for a short period of time and then rapidly evacuated. The bursting evaporation of moisture from all the mass of material caused by the pressure drop blows cavities in the material, breaks their wall...

The fatty acid distribution in triacylglycerols (TG), the major components of vegetable oils, affects the physical properties of oils and their physiological effects as components of the human diet. A computational scheme is proposed for estimating the stereospecific distribution of fatty acids in TG on the basis of the data from HPLC analysis, usi...

Biologically active lignans from caulomas (stems) and leaves of Schisandra chinensis were extracted with supercritical carbon dioxide at the pressures 20–27 MPa, temperatures 40, 50 and 60 °C, and solvent-to-feed ratio 36–43. Six major lignans were determined by means of HPLC: schizandrin, gomisin A, deoxyschizandrin, γ-schizandrin, gomisin N and w...

Data on menthol + CO2 phase behaviour and menthol solubility in dense CO2 are needed to optimise supercritical extraction of peppermint oil. The paper presents novel experimental data for the phase diagram of (−)-menthol + CO2 binary system in the temperature range 5–40 °C and pressures up to 8.2 MPa, including menthol melting point depression, as...

Essential oil was extracted from yarrow flowers (Achillea millefolium) with supercritical CO2 at pressure of 10 MPa and temperatures of 40–60 °C, and its composition and yield were compared with those of hydrodistillate. The yield of total extract, measured in dependence on extraction time, was affected by extraction temperature but not by particle...

Dry sage leaves were extracted with dense carbon dioxide under the following conditions: pressure, 9–12.8 MPa; temperature, 25–50 °C; sage feed, 3–4 g; carbon dioxide flow rate, 0.05–0.35 g/min; solvent-to-feed ratio, 16–21. The oil in finely ground particles was easily accessible to the solvent and its extraction was controlled by phase equilibriu...

While many naturally occurring mixtures of free fatty acids are conveniently analyzed by hyphenated technique of LC-NMR, a complete separation of alpha- and gamma-linolenic acids for their quantitative determination appears impossible at least by the methods of reversed phase HPLC. However, they can be differentiated and quantified from 1H NMR spec...

Hydrodistillation of essential oils was studied using a model with broken and intact cells, in which the solute located in the cells with broken walls is rapidly extracted and the solute from intact cells diffuses slowly to the surface of botanical material. The essential oil is regarded as a pseudo-component. Model equations describe two types of...

Nigella sativa L. is used in folk medicine all over the world for the treatment of a number of diseases. Its seed essential oil (EO) has previously demonstrated a wide range of biological activities, including antimicrobial effect [1]. In our study, we aimed to determine the influence of four different extraction methods on the chemical composition...

Blackcurrant (Ribes nigrum) seed oil is rich in alpha- and gamma-linolenic acids, the latter in particular being of potential use in medicine. The enzymatic hydrolysis of the oil was carried out in supercritical carbon dioxide using lipase Lipozyme as catalyst and changes in the composition of acylglycerols were recorded. Mono-, di-, and triacylgly...

Glycerolysis–hydrolysis reactions to produce monoacylglycerol (MAG) and diacylglycerol (DAG) used in the production of functional foods and nutraceuticals were conducted in supercritical carbon dioxide (SC-CO2) media to elucidate the reaction kinetics, provide the reaction mechanism and assess the potential catalytic agent involved. Reactions were...

The paper reports new experimental data and the results of the thermodynamic modeling of menthol solubility in pressurized CO2. The solubility was measured using the dynamic method and modeled with the Soave-Redlich-Kwong equation of state in the temperature range 30-60?C and pressure range 66-144 bar. The results obtained were compared with the so...

Peppermint, creeping thyme, and sage herbs, as well as yarrow flowers were extracted with supercritical and liquid carbon dioxide at 9-13 MPa and 25-60°C. Two extraction periods were distinguished except in the case of thyme extraction. Almost pure essential oil was extracted in the first, fast period. The extraction was retarded in the second peri...

A substance is in a supercritical state when both its pressure and temperature are higher than its critical pressure and temperature. Supercritical fluids, due to their liquid-like density and gas-like viscosity, are very well suited for extraction of valuable substances from plant materials. The most frequently used supercritical solvent is superc...

β-Sitosterol (22,23-dihydrostigmasterol) and scopoletin (7-hydroxy-6-methoxycoumarin) were extracted from roots of stinging nettle (Urtica dioica L.) with supercritical and liquid CO2. Extraction rates were measured for both oleoresin and the individual substances in dependence on extraction conditions. The solvent modified with ethanol (0–9.4 wt.%...

New model for supercritical fluid extraction (SFE) of natural products is presented. Like other models based on the concept of broken and intact cells, it is particularly suited to fit experimental data as it almost independently simulates two extraction periods, the first one governed by phase equilibrium and the second one governed by internal di...

The drug Wuweizi (dried fruits of Schisandra chinensis or S. sphenantherd) is one of important medicinal means used in the Oriental medicine. The lignans of dibenzo[a,c]cyklooctadiene type are major constituents, a volatile oil with mono- and ses-quiterpens, an oil, organic acids and small amounts of additional compounds are also present. The conte...

Chlorophylls and carotenoids were extracted from leaves of stinging nettle (Urtica dioica L.) with supercritical and liquid CO2. The solvent modified with ethanol (0–7wt.%) was applied at the pressures of 200, 250 and 280bar and the temperatures of 25, 40 and 60°C. Extracts were analysed by means of HPLC and RP-HPLC methods. The maximum yields of c...

The effect of reaction conditions on the extent of conversion in hydrolysis of blackcurrant oil was investigated. The enzyme used was Lipozyme, a lipase from Mucor miehei immobilised on macroporous anionic resin. The reaction was carried out in a continuous flow reactor at 10–28MPa and 30–50°C with carbon dioxide saturated with oil and water (55–10...

Six major lignans (schizandrin, gomisin A, deoxyschizandrin, y-schizandrin, gomisin N, wuweizisu C) in the caulomas and leaves of Schizandra chinensis (Turcz.) Baill., and cinnamic acid in the leaves of the plant, were quantitatively analysed by high-performance liquid chromatography in reversed-phase mode with UV detection. Resolution of the deter...

Solubilities of trans-β-carotene in supercritical CO2, both pure and modified, were measured at temperatures 313.2, 323.2 and 333.2 K and pressures up to 28 MPa using a one-pass flow apparatus. The solubility data measured in pure CO2 were correlated by the density-based equation proposed by Chrastil, and modelled using the Soave-Redlich-Kwong cubi...

The solubility of ferulic acid in supercritical carbon dioxide (SC-CO2), both pure and ethanol modified, was measured using a flow type apparatus. The mass of solute trapped after decompression was determined spectrophotometrically. The solubility was measured at (313.2, 323.2, and 333.2) K over the pressure range from (12 to 28) MPa. Solubility da...

Fatty oil influence on the solubility of limonene in CO2 was investigated under pressures 8–12 MPa at 313.2 K, a temperature typically applied in supercritical fluid extraction of essential oils. Solubility in CO2 was measured using the dynamic method both for limonene and for the mixture of limonene and blackcurrant seed oil. In the whole range of...

Dynamic method was applied to measure the solubility of oils from seed of Ribes nigrum (blackcurrant) and Vitis vinifera (grape-vine) in supercritical CO2 at pressures up to 29 MPa. The solubility of blackcurrant seed oil, which had been refined prior to the measurement and therefore it contained only triglycerides, was measured at 40–60°C. It was...

Supercritical fluid extraction (SFE) with carbon dioxide and hydrodistillation (HD) were compared as methods to isolate essential oil from thyme herb (Thymus serpyllum, L.). The SFE extraction was performed in a semibatch apparatus and the rate of extraction was found dependent on the extraction pressure and temperature and on the amount of carbon...

Extraction of peppermint oil was performed with supercritical and liquid carbon dioxide at 9-12 MPa and 25-50 °C. Rate of extraction was dependent on the extraction pressure and temperature and on the amount of carbon dioxide passed through the extractor. Under experimental conditions, the extraction rate did not depend on the CO2 flow rate nor on...

The solubilities of two low volatile liquids of different polarity — squalane and dinonyl phthalate — were measured in supercritical carbon dioxide entrained with a small amount of n-hexane, toluene or ethanol. A dynamic method of measurement was applied. Extraction pressure was 9–10MPa, extraction temperature 303.15K and 313.15K. The concentration...

The supercritical fluid extraction with carbon dioxide and Soxhlet extraction of grape seeds oil was examined. Supercritical fluid extraction was performed in a 150 cm 3 laboratory extractor, at 280 ± 2 bar, 40 ± 0.1 o C and a CO 2 flow rate, 0.5 standard dm 3 /min; and the extraction (processing) time, 3 h. With the investigated grade of milling o...

Supercritical fluid extraction with carbon dioxide (SFE) and Soxhlet extraction of grape seeds oil was examined. Supercritical fluid extraction was performed in a 13 cm3 laboratory extractor, at 28 MPa and 40 oC with a flow rate 0.9 g CO2/min. During 2 hours of extraction, 61 to 69 % of oil was extracted from 8 g of the ground grape seeds of mean p...

The solubilities of three low-volatile liquids were measured in supercritical and liquid carbon dioxide at 7–28 MPa and 296–333 K. Solutes of different polarities were selected, namely non-polar squalane, polar glycerol, and dinonyl phthalate of medium polarity. Dynamic method of measurement with gravimetrically determined amount of the extracted s...

Oil from the seed and pulp of sea buckthorn berries (Hippophaë rhamnoides L.) was extracted with carbon dioxide at pressures 9.6–27 MPa and temperatures 25–60°C. Influence of extraction conditions on solubility and mass transfer rate was studied. No marked changes in composition of extracted oil in the course of extraction were observed. Experiment...

Oleoresin was extracted from ground black pepper with carbon dioxide at 28 MPa and 24 to 60 °C. The yield and contents of piperine in the extract were determined as a function of extraction time and the solvent amount. The concentration profile of piperine inside the fixed bed of pepper was also measured. The total extract contained piperine and es...

The solubility of menthol [C10H20O] in supercritical carbon dioxide was measured by using a flow-type apparatus at 35-55-degrees-C and pressures ranging from 6.7 to 11.6 MPa. The results were correlated with the density of pure solvent according to the Adachi-Lu equation. This approach yielded deviations of 4.4%.

Caraway seeds were extracted with liquid and supercritical carbon dioxide at 23–40°C and 90–100 bar. The extracts were analyzed for carvone and limonene, and compared with essential oil obtained by steam distillation. Slight fractionation was observed during the extraction. The effect of process parameters, such as temperature, pressure, and solven...

Grape oil was extracted with carbon dioxide at 280 bar and 40°C. Effect of milling of grape seeds, solvent flow rate and flow direction on the course of extraction was investigated. Mass transfer coefficients in the supercritical and solid phases were evaluated from extraction curves using a plug-flow model. While the assumption of plug flow was co...

During the extraction from milled vegetable material, the easily accessible solute from the cells opened by milling is extracted first, and the slower extraction of the solute protected by the cell walls follows. Mathematical models based on the assumption of plug flow of supercritical solvent through a fixed bed of milled material were published f...

Compressed carbon dioxide is widely used as a solvent in supercritical and liquefied gas extraction. The knowledge of the fluid-phase viscosity as a function of temperature and pressure is indispensable for predicting the hydrodynamics and mass-transfer rates in these processes. Various equations, both generally valid and especially derived for car...

Richter, M. and Sovova, H., 1993. The solubility of two monoterpenes in supercritical carbon dioxide. Fluid Phase Equilibria, 85: 285-300.The solubilities in supercritical CO2 of two terpenes, α-pinene as a representative of the monoterpene hydrocarbons and cis-verbenol as one of the oxygenated terpenes, have been measured at temperatures from 40 t...

The motion of single-solvent drops in water in the countercurrent Karr column with vibrating plates was examined by means of multiple photography. Profiles of mean residence times along the height of the stage were evaluated from repeated experiments. Mean residence times in the stage were compared with the residence times of drops in the absence o...

Six published correlations for Sauter diameter d32 in pulsed and reciprocating plate columns are compared with drop size measurements from seven different data sources. The correlation of Kumar and Hartland gives the best fit of data in the whole range of agitation rates. Also the semiempiric equations of Míšek and of Boyadzhiev and Spassov are of...

In this work measurements of mean holdup of dispersed phase, of axial holdup profiles and of flooding points in a reciprocating plate contactor with both the VPE-type plates and the sieve plates were carried out. The experimental results were compared with a monodisperse model of steady-state column hydrodynamics and the model parameters were evalu...

For optimizing a production plant an objective function, "optimum criterion", was formulated and an optimum criterion of a part of the plant, an apparatus, consistent with that of the plant was proposed. This was specified for a counter-current extraction column with mechanical agitation and various sets of constraints were discussed. An optimizati...

Transfer functions relating the holdup to the intensity of plate reciprocation and to the velocity of the dispersed phase were determined from experiments in a 4m high VPE reciprocating plate solvent extraction column. The system under investigation was toluene dispersed in water without mass transfer between the phases. An ultrasonic technique of...

The article reviews the literature on the modeling of dynamic behavior of solute concentration and of the holdup of the dispersed phase in liquid-liquid extraction columns and their control.

A new method has been proposed of the continuous detection of the volume hold-up of the dispersed phase in a liquid-liquid system. The method utilizes different velocities of sound in the organic and the water phase and has been tested on four liquid systems typical for liquid extraction. These experiments have shown the dependence of the velocity...

A stagewise polydisperse model of the Karr vibrating plate extractor hydrodynamics is presented. It describes the drop size distribution and the dispersed phase hold-up as functions of drop transport, breakage and coalescence. 1 The predicted stationary hold-up profiles and drop size distributions are proved to be in good agreement with the experim...

The mean volumetric hold-up of the dispersed phase and the limiting flow rates of phases in five sizes of experimental vibrating plate extractors VPE were measured and the results compared with the relations of Richardson and Zaki, Míšek and Ishii and Zuber for the relative phase velocity. The experiments were performed with the system toluene-wate...

The frequencies of drop breakage and coalescence in a batch mixer are described by power functions of drop sizes. The shape of a steady state drop size distribution corresponding to the power functions is correlated with their exponents. The use of this correlation for direct determination of linear combination of power functions exponents from an...

Conditions of analogy between a continuous and a discrete models describing the processes of breakage and coalescence of drops in a batch stirred tank are defined. The discrete approach may simplify the numerical solution of the problem but an error is introduced into the resulting drop size distribution. Thus the question arises of minimizing this...

The model of dispersion proposed by Coulaloglou and Tavlarides is compared with published results from experiments in batch stirred tanks. An alternative to this model is developed by introducing a different formula for the efficiency of collisions—the mechanism of coalescence of drops by film drainage is replaced by a mechanism based on the effect...

A novel method of measurement of diffusivities of gases in liquids has been proposed consisting of measuring the rate of absorption of a gas into a laminar film of liquid flowing radially over the surface of a horizontal disc. The absorption cell works continuously with recirculation of liquid. The profile of velocities in the liquid film was inves...

Most applications of the photochromic technique of flow visualization have involved elaborate or expensive equipment. A simple, inexpensive application of the technique is described applied to a study of the fluiddynamics phenomena involved in mass transfer across a liquid gas interface. Essentially the set-up requires only a stirred beaker with ph...