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 human kind pose a serious threat for the environment. The removal of chromate ani ons and zinc cations from dilute aqueous solutions by sorption was investig ated in the present paper as typical examples of toxic metals, existing in many wastewater streams. Seven inorganic materials have been examined as so rbents and compared, under similar conditions, using batch sorption experim ents. Four of the sorbents were applied in powdered form (magnesite mineral - consisting mainly from MgCO3 -, titanium dioxide, hydrotalcite and goeth ite), while the other three where applied in granulated form (activated car bon, ferric hydroxide and goethite, which was granulated by freezing/crysta llization). Main examined parameters were the pH value of metal solutions a nd their initial concentrations: Due to the obtained results, goethite gran ulated by freezing/crystallization was selected for further (batch) sorptio n experiments, which were found to fit sufficient by the Langmuir isotherm equation. (C) 1999 Elsevier Science Ltd. All rights reserved.