Studies on heteromacrocyclic polyether .12. Liquid membrane transport properties of metal cations by oxa-, thia-, selena- or tellura-crown ether

The liquid membrane transport rates of the nitrate salts of Na+, K+, Ag+ and Pb2+ by 10-tellurabenzo-15-crown-5 (TeB15C5) were firstly determined, and compared with those by the corresponding benzo-15-crown-5 (B15C5), 10-thiabenzo-15-crown-5 (SB15C5) and 10-selenabenzo-15-crown-5 (SeB15C5), At the same time, the effects of the concentrations of SeB15C5 in the membrane phase and K+ in the source phase on the transport rates of K+ were also investigated, The experimental data indicate that the relationship is linear between the transport rates of K+ and the concentrations of SeB15C5 and K+ respectively, The transport rates of Na+, K+ and Pb2+ by TeB15C5 are larger than those by SB15C5 and SeB15C5, but the transport rates of Ag+ by SB15C5 and SeB15C5, especially by SeB15C5, are much larger than those by TeB15C5. SB15C5 and SeB15C5 show a very high transport selectivity for Ag+ over Na+, K+ and Pb2+, and can be used to separate and recover noble metals such as silver.