Separation and Selective Transport of Zirconium (IV) and Niobium (V) from Hydrochloric Media Through a Bulk Liquid Membrane

The separation of zirconium and niobium from lanthanides in hydrochloric medium and the selective transport of them via bulk liquid membrane (BLM) was examined. Tri-n-butyl phosphate (TBP), tri-n-octylamine (TNOA) and dibenzo-18-crown-6 (DBC 6) diluted in kerosene and benzene were used as a carrier. The various effects on the transport and separation of zirconium (IV) and niobium (V) were studied: concentration of  hydrochloric acid in the feed and strip solutions, type and concentration of  the carrier (TBP, TNOA, DBC 6) in the membrane phase. The extraction of zirconium (IV) and niobium (V) in the membrane phase from 9.0 M hydrochloric acid by 30% (v/v) TBP was achieved by leaving lanthanides in the feed solution. The quantitative recovery of zirconium (IV) and niobium (V) were achieved by 0.5 M HCl. Furthermore, the transport  kinetics study showed that niobium transport process exhibits slightly faster kinetics than zirconium.The kinetics of Zr(IV)/Nb(V) transport were investigated assuming a consecutive, irreversible second-order reaction on the interfaces. It was found that the rate constant of  niobium (V) transport from the donor phase-to-the membrane and from the membrane to the acceptor  phase was, respectively, about 98 and 24% more than the zirconium (IV) transport rate constant.