SELECTIVE REMOVAL OF TRANSITION METAL IONS IN TRANSPORT THROUGH POLYMER INCLUSION MEMBRANES WITH ORGANOPHOSPHORUS ACIDS

摘要

Separation of transition metal ions from aqueous chloride solutions by transport through polymer inclusion membrane (PIM) process is presented. The competitive transport of equimolar mixtures of Zn(Ⅱ) and Cd(Ⅱ) as well as Zn(Ⅱ), Cu(Ⅱ), Co(Ⅱ), Cd(Ⅱ), and Ni(Ⅱ) was investigated. The selective transport of metal ions from aqueous chloride source phase through PIM-containing cellulose triacetate (support), o-nitrophenyl pentyl ether (plasticizer) and organophosphorus acidic compounds, i.e. di(2-ethylhexyl)phosphoric acid (D2EHPA), di(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272), di(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301) and bis(2,4,4-trimethylpentyl)monothiophosphinic acid (Cyanex 302) as ion carriers, is shown. The influence of extractant nature on the selectvity and efficiency of cation transport has been examined. Zn(Ⅱ) can be effectively removed from dilute aqueous chloride solutions containing equilmolar mixture of Zn(Ⅱ) and Cd(Ⅱ) ions in transport through PIMs with di(2,4,4-trimethylpentyl)phosphinic acids, bis(2,4,4-trimethylpentyl)rnonothiophosphinic acid or di(2-ethylhexyl)phosphoric acid as the ionic carriers into 1.0 M HCl as the receiving phase. The per cent removal of Zn(Ⅱ) and Cd(Ⅱ) ions increases with an increase in pH. but more efficient separation of Zn(Ⅱ) than Cd(Ⅱ) ions decreases with pH increase in the source phase. Zn(Ⅱ) can be also effectively removed from dilute aqueous chloride solutions containing equimolar mixture of Zn(Ⅱ), Cd(Il), Cu(Ⅱ), Co(Ⅱ) and Ni(Ⅱ) ions by its transport through PIMs with D2EHPA, Cyanex 272 and Cyanex 302. All ions investigated are effectively removed with di(2,4,4-trimethylpentyl)dithio-phosphinic acids (Cyanex 301) as the ionic carrier into 1.0 M HCl as the receiving phase. The per cent removal of all metal ions investigated increases with an increase in pH of solution in the source phase. The initial transport fluxes of all metal ions through PIM with Cyanex 272 increase with an increase in an initial chloride acid concentration in the receiving phase.