Concentration of uranium(VI) on long-chain 8-quinolinol liquid membrane

Extraction of U(VI) from weakly acidic media has been investigated by using alkyl derivatives of 8-quinolinol; 5-octyloxymethyl- (HO8Q), 5-decyloxymethyl(HO10Q) and 5-dioctylaminomethyl-8-quinolinol (HN8Q). The ability for the extraction of U increased in the order, HO10Q < HO8Q < HN8Q. Supported liquid membranes (SLM) containing these long-chain 8-quinolinols as a mobile carrier have been studied for their ability to transport and concentrate U from dilute solutions. Uranium was effectively transported by the HO8Q and HO10Q carriers from the feed solutions of pH around 5 into the stripping solution of dilute nitric acid against its concentration gradient. The concentration of U in the feed solution decreased as indicated by, ln([U]f,t/[U]f,0) = -kobst. Variation of carrier concentration and the feed pH gave a slight effect on kobs values. The recovery of U into the stripping solution attained 95 % with the HO8Q carrier and 70 % with the HN8Q carrier, leaving a small portion of U in the membrane layer. Approximately quantitative recovery of U was achieved by the HO10Q carrier; U was sufficiently concentrated from dilute solutions such as seawater spiked with 10-6 mol dm-3 U. (author)