Ultrafiltration and alumina adsorption of micelles for the preconcentration of copper(II) in water.

Micellar-enhanced ultrafiltration was considered from the viewpoint of trace analysis, by taking copper(II) as an example. Copper(II) cations were collected electrostatically on micelles of sodium dodecyl sulfate, and separated from the mother liquor by ultrafiltration. However, the final solution contained a large amount of surfactant, which caused serious interference in the determination. This problem was overcome by using alumina adsorption, where negatively charged micelles were adsorbed on positively charged alumina particles and then recovered by conventional filtration. The copper was leached from the micelles with 4 mol l(-1) nitric acid, leaving the surfactant on the alumina. The proposed method was successfully applied to an analysis of certified reference water samples.