RESUMO
Emulsion liquid membranes have been successfully used for the removal of different types of organic and inorganic pollutants by means of carrier-mediated transport mechanisms. However, the models that describe the kinetics and transport of such mechanisms are very complex due to the high number of model parameters. Starting from an analysis of the similarity between the elemental mechanisms of carrier-mediated transport in liquid membranes and of transport in adsorption processes, this paper presents an experimental analysis of the possibility of applying kinetic and mechanistic models developed for adsorption to carrier-mediated transport in emulsion liquid membranes. We study the removal of a target species, in this case, Cu(II), by emulsion liquid membranes containing membrane phase solutions of benzoylacetone (carrier agent), Span 80 (emulsifying agent) and kerosene (diluent), and hydrochloric acid as a stripping agent in the product phase. The experimental results fit the pseudo-second-order adsorption kinetic model, showing good relationships between the experimental and model parameters. Although both Cu(II) diffusion through the feed/membrane interface boundary layer and complex Cu-benzoylacetone diffusion through the membrane phase controls Cu(II) transport, it is the former step that mainly controls the transport process.
RESUMO
Pertraction of Co(II) through novel supported liquid membranes prepared by ultrasound, using bis-2-ethylhexyl phosphoric acid as carrier, sulfuric acid as stripping agent and a counter-transport mechanism, is studied in this paper. Supported liquid membrane characterization through scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy shows the impregnation of the microporous polymer support by the membrane phase by the action of ultrasound. The effect on the initial flux of Co(II) of different experimental conditions is analyzed to optimize the transport process. At these optimal experimental conditions (feed phase pH 6, 0.5M sulfuric acid in product phase, carrier concentration 0.65M in membrane phase and stirring speed of 300 rpm in both phases) supported liquid membrane shows great stability. From the relation between the inverse of Co(II) initial permeability and the inverse of the square of carrier concentration in the membrane phase, in the optimized experimental conditions, the transport resistance due to diffusion through both the aqueous feed boundary layer (3.7576×104 s·m-1) and the membrane phase (1.1434×1010 s·m-1), the thickness of the aqueous feed boundary layer (4.0206×10-6 m) and the diffusion coefficient of the Co(II)-carrier in the bulk membrane (4.0490×10-14 m2·s-1) , have been determined.
RESUMO
A novel ultrasound assisted method for preparing supported liquid membranes is described in this paper. The stability and efficiency of the supported liquid membrane obtained was tested by removing cobalt(II) from aqueous solutions through a facilitated countertransport mechanism using CYANEX 272 as carrier and protons as counterions. The results are compared with those obtained using supported liquid membranes prepared by soaking the polymeric material in the organic solution of the carrier at atmospheric pressure and under vacuum, both for 24h. Higher transport efficiency (>5%), flux (â¼18%), permeability (â¼20%) and stability (>6% in the second run and â¼10% in the third run) were obtained by the supported liquid membrane prepared using the ultrasound assisted method. These findings can be explained by the effects of cavitation and acoustical streaming - which result from the ultrasound passing through the organic solution of the extractant - on the porous structure of the polymer support and on the pore filling.