Removal of metal ions from dilute aqueous solutions: a comparative study of inorganic sorbent materials

Toxic metals produced and released by the technological activities of humankind pose a serious threat for the environment. The removal of chromate anions and zinc cations from dilute aqueous solutions by sorption was investigated in the present paper as typical examples of toxic metals, existing in many wastewater streams. Seven inorganic materials have been examined as sorbents and compared, under similar conditions, using batch sorption experiments. Four of the sorbents were applied in powdered form (magnesite mineral - consisting mainly from MgCO(3) -, titanium dioxide, hydrotalcite and goethite), while the other three where applied in granulated form (activated carbon, ferric hydroxide and goethite, which was granulated by freezing/crystallization). Main examined parameters were the pH value of metal solutions and their initial concentrations: Due to the obtained results, goethite granulated by freezing/crystallization was selected for further (batch) sorption experiments, which were found to fit sufficient by the Langmuir isotherm equation. (C) 1999 Elsevier Science Ltd. All rights reserved.