In this paper, we develop an xpression of Fick's law to be used in the diffusion-solution model when coupling exists. To derive this relationship we have manipulated the generalised Stefan-Mawell equation to get a more convenient generalised multicomponent Fick's law in which clearly defined diffusivities and coupling coefficients appear: the two equations are wholly equivalent. In the general accepted frame of hypotheses when using the solution-diffusion model we have written Fick's equation when coupling betwwen the fluxes exists. The order of magnitude of coupling is calculated, using previously published xperimental data, leading to the conclusion that coupling, in selective pervaporation process, can be neglected.

Based on the swelling action of organic solvents on hollow-fiber membranes, a new technique of solvent-swelling and dry-shaping for preparing coiled hollow fibers from straight hollow fibers was introduced. The mass transfer performance of these coiled fibers was tested with 30% TBP (in kerosene)-phenol-water as a working system in a membrane extraction process, and compared with the results obtained from the straight fibers. After long time test, it was proved that the coiled fibers were stable when they contacted with the organic solvent in the membrane extraction process. As to the mass transfer performance, it was found that the presence of vortices in the coiled fibers provided better mass transfer performance than the straight fibers. The improvement factor was in the range of 2–4.With an increase of the phase velocity inside the tube, the mass transfer coefficient and energy input in the coiled fibers grew up much more quickly than that in the straight fibers. An empirical correlation for predicting the mass transfer coefficients and an equation for pressure drop in the coiled fibers were suggested.

Two-phase electrophoresis, coupling traditional solvent extraction with electrophoresis, is a novel separation technique. Being bio-compatible, aqueous two-phase electrophoresis provides a successful method for separating mixtures of biomolecules. In this work, the separation of amino acids by aqueous two-phase electrophoresis was examined with dextran-polyethylene glycol-water as a working system. The influences of separation time, field strength, initial solute concentration and two-phase contact area were studied in intermittent separation equipment. The experiment results show that aqueous two-phase electrophoresis is an effective separation technique for amino acids. With time, field strength, and contact area increasing, mass fluxes across the interface are increased quickly.

Aqueous two-phase systems (ATPSs) formed by spontaneous phase separation of different water-soluble polymers are bio-compatible. Aqueous two-phase electrophoresis, coupling traditional solvent extraction with lectrophoresis, is a novel separation technique and provides a successful method for separating mixtures of biomolecules. In this work, the selective recovery of amino acids by aqueous two-phase electrophoresis was examined with dextran-polyethylene glycol-water as a working system. The experiment results show that glutamic acid can be separated from phenylalanine and tryptophan successfully. The influences of the electrophoresis time, field strength, and phase volume ratio were studied in an intermittent separation equipment.

The residence time distribution (RTD) curves were measured to observe the shell-side flow status in hollow fiber modules (HFMs) with different packing densities, and with 30%TBP in kerosene/phenol/water as experimental system, the membrane extraction was carried out in three polypropylene HFMs in counter-current flow. A random distribution model described by the Voronoi tessellation method based on normal distribution function was proposed to determine the effect of random packing on the flowstatus and mass transfer characteristics. The standard deviation in normal distribution function represented the packing irregularity in commercial HFMs. So the random distribution model related the packing irregularity with the flow status and mass transfer performance in random packing modules. The theoretical calculation and experimental results indicated that the random packing of fibers caused the non-ideal flow and significant decrease in mass transfer performance; furthermore, the non-ideal flow in shell side had an influence not only on the mass transfer performance in shell side but also on that in lumen side.