ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Pertraction of Silver through Bulk Liquid Membranes

M. Vajda, Š. Schlosser, and K. Kováčová

Department of Chemical and Biochemical Engineering, Faculty of Chemical Technology, Slovak University of Technology, SK-812 37 Bratislava

E-mail: vajdam@cvt.stuba.sk

Received: 19 May 2000

Abstract: Extraction equilibrium of silver for the solvent containing Cyanex 471X in a mixture of alkanes and isodecanol as both diluent and modi er in the mass ratio of 40 : 60 was studied. The value of the distribution coefficient of Ag increased with increasing concentration of the extractant in the solvent and concentration of HNO₃ in the aqueous phase, but it decreased with increasing concentration of Ag in the aqueous phase. The value of the loading of the extractant is independent of its concentration and at higher aqueous concentrations of Ag it approaches the value 0.5. This suggests the mole ratio of silver to carrier in the complex to be 1:2. The model based on this complex and the extraction constant defined on concentrations of species did not describe equilibrium data well and therefore activities of species should be used. In the present paper the transport of Ag through layered bulk liquid membranes (BLM) was studied. A simple model of the transport through the BLM to the stripping phase with diffusional resistances in series described experimental data relatively well. With increasing concentration of the carrier in the solvent, the mass flux through the extraction interface increased only 1.2 times, while the distribution coefficient of Ag increased 3.3 times. The maximum mass flux through the stripping interface was much lower (6 to 8 times) than the initial mass flux through the extraction interface. The concentration of the carrier in the solvent, concentration of HNO₃ in the aqueous phase, and composition of the stripping solution did not influence these fluxes. This suggests that the kinetics of the stripping determine the overall transport rate.

Full paper in Portable Document Format: 546ba423.pdf

Chemical Papers 54 (6b) 423–429 (2000)