Transfer of Cd(II) chloride species by a tri-n-octylamine-secondary octyl alcohol-kerosene multimembrane hybrid system

An experimental study of Cd(II) transport through a multimembrane hybrid system (MHS) containing tri-n-octylamine (TNOA, R3N)-secondary octyl alcohol (ROH)-kerosene is reported. An apparatus composed of three compartments, including a reservoir of organic solution, with double solid supports was used in this study. Factors affecting cadmium permeability, such as stirring speed in the feed and membrane solution, carrier concentration, membrane solvent, HCl and Cl- concentration in the feed phase, have been analyzed. The experiments reveal that Cd(II) could be effectively transported from hydrochloric acid solutions to ammonium acetate solution and the transport of Cd(II) ions is coupled by the co-transport flow of protons. A model describing the transport mechanism consisting of diffusion through a feed aqueous boundary layer, a fast interfacial chemical reaction, and diffusion through the membrane is depicted. The model successfully treats the two membranes as a single membrane with twice the geometrical thickness of the polymer support. The uptake of carriers out of membrane phase into the feed and stripping phase is quantitatively determined.