Rolf Marr

Use of supercritical fluids for different processes including new developments—a review

Supercritical fluids have a great potential for wide fields of processes. Extraction processes with supercritical fluids are established even in industrial scale and become again more interesting for industry. Beside this, developments like fractionation of products, dyeing of fibres, treatment of contaminated soils, production of powders in micron and submicron range and reactions in or with supercritical fluids are only a rough extract of possible investigations which will be covered in this paper.

Emulsion liquid membranes part I: Phenomenon and industrial application

Abstract Emulsion liquid membrane processes are discussed. The characteristics of the processes, research activities and commercial applications are surveyed and the advantages and disadvantages are outlined. The first large-scale plant for the separation of zinc is described as well as several pilot plants for the separation of various metals from aqueous solutions.

Separation of metal species by emulsion liquid membranes

Abstract Since the first invention of liquid membrane technology in 1968 many potential applications have been investigated. This paper reviews the applications of emulsion liquid membranes for the separation of metal ions out of waste water streams. Several specific properties of the emulsion liquid membranes are described as well as several pilot plants and a large-scale plant for the recovery of zinc from viscose wastes.

New approach in the modelling of the extraction equilibrium of zinc with bis-(2-ethylhexyl) phosphoric acid

Abstract The extraction equilibrium of the possible test system for reactive extraction zinc sulphate/bis (2-ethylhexyl)-phosphoric acid (D2EHPA)/n-heptane was studied at 25°C. The results from slope analysis, computer modelling and quantitative FT-IR spectroscopy have been compared. The computer program SXLSQA was used for modelling the equilibrium taking into account the non-ideality of both phases, based on the Pitzer approach for the aqueous phase and the regular solution theory of Hildebrand/Scott for calculating organic phase activity coefficients. The three methods employed provide the same result: that the dominating zinc complex in the organic phase is ZnR 2 (RH). Some analytical improvements have been carried out, such as purification of D2EHPA, a purity determination method for D2EHPA, an analytical method for the determination of D2EHPA concentration in aqueous solutions. Fr-IR has also been used to illustrate the role of water in the formation of the organic metal complexes. While in the extraction of nickel an appreciable amount of water is co-extracted, the extraction of zinc does not show the same behaviour.

A Low-Waste Process for the Production of Biodiesel

Abstract The acceptance of methylesters (biodiesel) as an alternative fuel has rapidly increased in recent years. This development has been followed by increasing research activities in the field of methylester processes. After listing reasons that supporte arguments for biodiesel and a survey of production methods, a low-waste process for biodiesel is introduced.

Extraction Processes for Bioproduct Separation

Abstract The three-phase extraction process, a modification of reactive extraction, has been investigated for its applicability in the separation of organic acids from fermentation broth. It has been compared with reactive extraction, liquid membrane permeation, and supercritical fluid extraction. These processes are based on the use of amine extractants, which have to be dissolved in nonpolar solvents, for the extraction of carboxylic acids, hydroxycarboxylic acids, and aminocarboxylic acids. This paper considers the comparison of the above-mentioned processes. Furthermore, the extractability of acids from synthetic aqueous solutions and fermented broths has been compared. Principal consideration has been paid to the extraction of lactic acid, gluconic acid, citric acid, and L-leucine.

Comparison of the separation of lactic acid and L-leucine by liquid emulsion membranes

Abstract A mass transfer model originally proposed for the permeation of zinc and l -phenylalanine was slightly modified and used for calculating the mass transfer resistances in lactic acid permeation (using the secondary amine Amberlite LA-2 as a carrier) and l -leucine permeation (using the quaternary ammoniumchloride Aliquat 336 as a carrier). The results show that under optimized conditions lactic acid permeation is controlled by the rate of reaction and that l -leucine permeation is controlled by the rate of reaction and the diffusion through the emulsion globule. The model results were compared with batch experiments separating lactic acid and l -leucine from real fermentation broths. The comparison shows that the separation rate is affected by co-transport of pH regulating agents and to a smaller extent by the co-transport of water.

Enzymatic catalysis in supercritical carbon dioxide: Comparison of different lipases and a novel esterase

SummaryThe resolution of racemic citronellol and menthol by enzymatically catalyzed transesterification in supercritical carbon dioxide (SC-CO2) was investigated. Different lipases and an esterase in connection with various acylating reagents were employed. While the transesterification of (±)-menthol was reasonably fast and gave high enantiomeric excess, resolution of (±)-citronellol was not feasible.

Liquid-membrane-permeation and its Experiences in Pilot-plant and Industrial Scale

Emulsion-Liquid-Membrane-Permeation (LMP) is an operation for the recovery of several harmful substances from industrial waste water streams. Within this process the substance is separated from the waste water and enriched by a factor up to 1000 in the receiving phase depending on the process conditions. The largest experimental experiences are in the separation of Zn, Cd, Pb, Cu, Ni, NH{3} and phenol from aqueous solutions.

Investigating the process of liquid-liquid extraction by means of computational fluid dynamics

Abstract Liquid-liquid two-phase flow in extraction columns of the rotating disc contactor type is analysed using the multi-dimensional computational fluid dynamics (CFD) technique. Euler-Euler and Euler-Lagrange models are employed to give insight into the global flow structure and to analyse the turbulence related dispersion processes. Laser-Doppler velocity measurements are used to check the Euler-Euler results while a measured residence time distribution allows the assessment of the Euler-Lagrange approach. The results give rise to the expectation that CFD will become an accepted design tool in chemical engineering.