DETERMINATION OF TRACE COPPER IN NATURAL-WATERS AFTER SELECTIVE SEPARATION BY FLOTATION

Microgram amounts of copper(II) in one liter of water are quantitatively separated selectively as copper(II) acetate with oleic acid surfactant at pH range 6.5-7.5. The floated scum is separated, after shaking for few seconds, and measured colorimetrically at 700 nm. Beer's law is obeyed in the concentration range (0.5-5)x10(-4) mol dm-3, {3.18-31.8 ppm of copper(II)}. Alternatively, the copper in the scum is eluted by nitric acid 0.1 mol dm-3, completed to the suitable volume required for copper atomic absorption measurement at 324.7 nm with 1 ppm detection limit. The different factors affecting the selective flotation of copper(II) have been studied. It has been found that iron(III) seriously depresses the flotation efficiency. The flotation mechanism is discussed. The method of the separation and determination is rapid and applicable to 50 ppb copper(II) concentration level in natural waters.