Sorption of toxic metals on goethite: study of cadmium, lead and chromium

In this study the trapping capacity of synthetically prepared goethite (a‐FeOOH) in the removal of Cr3+, Cd2+ and Pb2+ (10–4 M) in varying ionic strength conditions of the medium was determined. The adsorption study was carried out in the pH range of 4.0 to 10.0 and media ionic strengths of 0.1M, 0.01 M and 0.001 M KNO3. The metal ion adsorption on goethite is strongly pH‐dependent and the adsorption edges of Cr3+, Cd2+ and Pb2+ on goethite show an S‐shaped behavior. The highest adsorption medium observed was the 0.001 M KNO3. Furthermore, competitive adsorption of Cd2+, Cr3+ and Pb2+ on goethite showed the following adsorption capacity order Cr3+ > Pb2+ > Cd2+. The surface titration data showed that the iso electric point of goethite was 9.2.