Transport of Zn(II), Cd(II), and Pb(II) across CTA plasticized membranes containing organophosphorous acids as an ion carriers

Abstract

In this work a competitive transport of an equimolar mixtures of Zn(II), Cd(II), and Pb(II) across polymer inclusion membranes (PIMs) is presented. In PIMs di-2-ethylhexylphosphoric acid (D2EHPA) as well as commercial extractants, i.e. Cyanex ® 272, 301, and 302 were used as ion carriers. The influence of nature extractants on cation transport selectivity and efficiency has been explored. Cyanex ® 301 and 302 used as ionic carriers for competitive transport of Zn(II), Cd(II) and Pb(II) give preferential selectivity order: Pb(II) > Cd(II) > Zn(II). The selectivity coefficients for Pb(II)/Cd(II) and Pb(II)/Zn(II) for transport with Cyanex ® 302 have been found, they were equal to 2 and 4.4, respectively. To understand the influence of plasticizers nature on Zn(II), Cd(II), Pb(II) ions transport through PIM, membranes with different compounds, i.e. dioctyl phthalate (DOP), o-nitrophenyl octyl ether (ONPPE), bis(2-ethylhexyl) adipate (DOA), and tris(2-etylhexyl) phosphate (TOF) were prepared. The initial fluxes of metal ions increase in the following order of plasticizers: DOA < TOF < ONPOE, i.e. with their viscosity decrease, whereas DOP proved to be equally effective as ONPOE. The addition of 3,7-dinonyl-naphthalene-1-sulfonic acid into PIM with Cyanex ® 302 plays a role of a synergetic factor in the membrane process. A long-term experiment was carried out to demonstrate the durability of PIMs. The application of PIM transport process for 92% and 96% removal of lead(II) and cadmium(II), respectively, from technological sludge eluates is also shown.