L. Boyadzhiev

Liquid Pertraction or Liquid Membranes—State of the Art

Abstract Liquid pertraction∗ or liquid membranes appeared as a prospective separation process relatively recently. Due to its obvious advantages over solid membranes and liquid-liquid extraction, liquid pertraction has attracted the attention of many scientists and engineers. At present there are more than 160 research teams around the world exploring this new, emerging separation operation.

Modeling of Carrier-Mediated Extraction

Abstract A two parametric mathematical model of carrier-mediated extraction is proposed for the case when emulsion technique is applied. Its simplified version, valid for diluted solutions, is solved analytically, and an implicit expression relating both parameters—rate of solute transfer and rate of emulsion destruction—is derived. Model parameters were evaluated from the experimental data obtained with two different three-phase systems: oil-in-water-in-oil and water-in-oil-in-water. In the first case, toluene and heptene were separated using water as an intermediate phase, and parameter evaluation was performed by means of an analog computer. In the second case, acetic, nitric, and hydrochloric acids were separated using a solution of tributylphosphate in carbon tetrachloride as a carrier phase. In this case the rate coefficients were found from the proposed implicit equation.

DEPHENOLATION OF PHENOL-CONTAINING WATERS BY ROTATING FILM PERTRACTION

Abstract The mass transfer of phenol in a rotating film (RF) pertractor was studied and the optimum performance regime for the system phenolic water-n-nonane-sodium hydroxide solution was obtained. The distribution coefficient of phenol between the hydrocarbon used and water is measured experimentally for various initial concentrations of the solute, and the corresponding relationship for 22°C is derived. A mathematical model is developed to describe the batch process of phenol removal in an RF pertractor. Based on the experimental results obtained and on the mathematical model proposed, the local mass transfer coefficients were evaluated and the effect of disc rotation speed was studied.

Kinetics and Mechanism of Copper Transfer by Hydroxy-Oximes in Three-Phase Liquid Systems

Abstract A model of copper-facilitated transport in a three-liquid-phase pertraction system is proposed. The model takes into account the diffusional transport of copper species (ions and complexes) in all three liquids as well as the kinetics of chemical reactions. The latter, according to the model suggested, occurs in narrow reaction zones: aqueous layers adjacent to the donor membrane and acceptor-membrane interfaces. Experiments were carried out in a two-compartment agitated diffusion cell with a bulk liquid membrane: a 5% (vol) solution of the commercial copper extractant LIX 860 in C11-C13 normal paraffins. The donor solution used contained 1 g/L copper and the acceptor liquid was a 4.5 N aqueous solution of sulfuric acid. On the basis of experimentally obtained pertraction curves and the model suggested, it was found that the overall rate of the process is controlled by the diffusion of copper ions in the donor phase as well as by copper-complex decomposition. By applying an optimization procedure...

Extraction and Liquid Membrane Preconcentration of Rosmarinic Acid from Lemon Balm (Melissa Officinalis L.)

Abstract Liquid membrane separation technique was applied for the recovery and preconcentration of rosmarinic acid from aqueous extract of dried leaves of Balm lemon (Melissa officinalis L.). Among several studied organic solvents, diisopropyl ether and ethylacetate appeared to be appropriate membrane liquids for recovery and selective preconcentration of the acid. The difference in pH values between the two aqueous solutions was the driving force in this case. An integrated process coupling the extraction of rosmarinic acid from ground Melissa leaves with a simultaneous stripping of membrane and accumulation of the extracted solute was demonstrated using a laboratory bulk liquid membrane contactor. The process provided an almost complete (96 percent) exhaustion of the herbal mass and highly enriched final extract, containing 87 percent RA after strip solution drying.

Properties of supercritical CO2 saturated poly(ethylene glycol) nonylphenyl ether

Density and viscosity of poly(ethylene glycol) nonylphenyl ether (PEG-NPE) saturated with supercritical carbon dioxide (SCCO 2 ), as well as the interfacial tension in the PEG-NPE-SCCO 2 system, were evaluated for the temperature range of 323 K to 343 K and pressures of 10.0 to 25.5 MPa. Remarkable polymer swelling as a result of solvent penetration was observed, and the coefficient of swelling for the above mentioned experimental conditions was evaluated. Data obtained show that the viscosity of polymer-rich phase is a decreasing function of both temperature and pressure. Moreover interfacial tension is a decreasing linear function of carbon dioxide density.

Recovery of zinc from chloride media by batch pertraction in a rotating film contactor

A liquid membrane (pertraction) process of zinc recovery from acidic chloride solutions was studied applying a pertraction in a rotating film contactor (RFC). Tri-n-octylamine (TOA or R3N) dissolved in n-octane was used as a carrier. The influence of the main process parameters, such as disc rotation velocity, hydrochloric acid concentration in the aqueous phases and carrier concentration in the membrane was investigated. Assuming the existence of two thin reaction layers in the feed and stripping solutions, adjacent to both water–oil interfaces, a mathematical model was developed to describe the zinc transport. On the basis of the experimental data obtained under various conditions and the model proposed, it was found that the extraction step is controlled mainly by the mass transfer resistance, whereas the stripping rate of zinc is controlled predominantly by the rate of zinc–carrier complex decomposition in the stripping side reaction layer.

Recovery of copper from solutions by rotating film pertraction

A liquid membrane (pertraction) process of copper recovery from dilute aqueous solutions is studied applying a rotating film pertraction technique. LIX 65®N dissolved in C10–C13 normal paraffins is used as the carrier. A mathematical model describing copper transfer is proposed, assuming that (1) the chemical reactions between copper ions and carrier molecules take place in the aqueous solution layers adjacent to the membrane phase, and (2) both the reaction kinetics and the mass transfer of the solutes control the overall rate of the process. In order to evaluate the reaction rate constants and the coefficients of mass transfer, the distribution coefficients for the active oxime carrier (mHR) and the copper-oxime complex (mCuR2) are obtained independently. The effects of temperature and disc rotation velocity on the pertraction rate are studied, as well as the possibility for the selective removal of copper from a solution containing ions of several bivalent metals.

Pertraction of Indole Alkaloids from Vinca minor L

Abstract The liquid‐membrane (pertraction) separation technique was applied for the recovery and preconcentration of the indole alkaloid vincamine from native acidic extracts of Vinca minor L. On the basis of the distribution coefficients of vincamine determined for eight couples of feed solution/membrane and membrane/strip solution, the most suitable pertraction three‐phase system was found to be: native extract (acetate buffer)–trichloroethylene–hydrochloric acid solution. This system, applied in a glass laboratory pertractor, proved the possibility of the direct recovery and preconcentration of the alkaloid from the plant extract without its alkalization. This permitted to integrate the processes of plant extraction and solute separation and preconcentration.

Selective recovery of silver from dilute polymetal solutions by rotating film pertraction

Recovery of silver from polymetal nitrate solution by means of rotating film pertraction technique was studied. Silver was successfully separated from the accompanying metals, viz. copper, zinc and nickel, using as a membrane phase a 0.06-M solution of tri-isobutylphosphine sulfide (TIBPS) in n-octane and an aqueous ammonia solution as a stripping phase. After 4 h of continuous contacting silver was practically completely extracted from the feed and transferred into the strip solution, while the other three metals remained unextracted.