Use of the Ion-Exchange Properties of Layered Double Hydroxides for Water Purification

Abstract

The sorption of chromate and dichromate ions by a [Zn-Al-Cl] layered double hydroxide was investigated. The anionic clay, prepared by coprecipitation at pH 8, was found to be pure upon characterization by X-ray diffraction, Fourier-transform infrared spectroscopy, and thermogravimetry and to have low BET surface area and small pore volume. The interaction of the clay with both chromate and dichromate ions has been studied by UV-VIS spectroscopy. The treatment of water containing 15-300 ppm of CrO42- or Cr2O72- was successful. The sorption capacities of the clay for CrO42- and Cr2O72- are close to 1 and 0.6 mmol/g, respectively.