Goethite Mineral as a Sorbent for Heavy Metal Ions

A toxic metal cation (cadmium) and an oxyanion (arsenic in III or V valence state) removed from dilute aqueous solutions by mineral goethite. The simultaneous removal of cations and anions is a great advantage of goethite as a sorbent material. The pure mineral sample was initially characterised by adsorption (and desorption) of nitrogen at liquid nitrogen temperature. The metal ion removal was strongly dependent on the solution pH. The modification of the mineral by potassium hydroxide was examined. Its removal capacity was compared to that of a synthetic goethite. The modelling of the sorption isotherm was discussed. An efficient solid/liquid separation technique, such as flotation preceded by flocculation, may be necessary downstream, when the material used is in an ultrafme state, as in the present study.