Preconcentration of Trace Uranium from Natural Water with Solid-Phase Extraction

In the present study, an effective method was used for the preconcentration and determination of uranium(VI) by solid-phase extraction (SPE). For this purpose, a microcolumn of alumina modified with sodium dodecyl sulfate (SDS) and 1-(2-pyridylazo)-2-naphthol (PAN) was prepared for the preconcentration of trace uranyl (VI) from water samples. The uranium(VI) was completely eluted with 6.0 mol dm^-3 HCl and determined by a spectrophotometric method with Arsenazo III. The SPE conditions were optimized by evaluating the effective factors such as pH, flow rate and masking agent. By the proposed method a preconcentration factor more than 150 was achieved. The average recovery of uranium(VI) was 99.8%. The relative standard deviation was 2.6% for ten replicate determinations of uranyl(VI) ion in a solution with a concentration of 50 ng cm^-3. Some concomitant ions such as Cd^2+, Ni^2+, MoO4^2-, Cu^2+, Th^4+ and Ce^3+, which interfere in the determination process of uranium(VI), were masked with EDTA in the aqueous phase during the extraction process. The proposed method was successfully used for the determination of uranium in natural water.