Extraction separation of Fe(II), Fe(III) and Cu(II) in drinking water under pseudo three-phase equilibrium

Kunihiro Watanabe, Miki Katayama, Masayuki Itagaki

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A method of extraction-separation of Fe(II), Fe(III) and Cu(II) under pseudo three-phase equilibrium using a filter-paper phase separator with high speed stirring was examined. Under the optimum conditions, Cu(II) and Fe(III) were extracted into a dithizone-chloroform phase and an 8-quinolinol-chloroform phase, respectively, leaving Fe(II) in the water phase. Concentrated metal ions were analyzed quantitatively by means of an optical absorption spectrometer. At low concentrations, the metal ions were back-extracted with 5M nitric acid solution from the organic phases, and analyzed quantitatively with an inductively coupled plasma atomic emission spectrometer (ICP-AES). The results showed that it is possible to separate Fe(II) of not less than 1.5ppb, Fe(III) of not less than lppb and Cu(II) of not less than 1ppb from the mixture if this method is employed. When the rate of transport of the liquid from one flask to another was adjusted to be 2ml/min, 120 minutes were needed for this extraction-separation procedure, and according to this method, it was possible to determine the ratio of Fe(II) to Fe(III) in both tap water and well water. It is interesting to notice that Fe(II), which is easily oxidized by dissolved oxygen, co-exists in drinking water where the pH is 5-7. It was presumed that total organic carbon had some influence on this fact.

Original languageEnglish
Pages (from-to)85-100
Number of pages16
JournalSolvent Extraction Research and Development
Publication statusPublished - 1 Dec 2005

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