Desorption of cadmium from goethite (α-FeOOH) Original Research Article

Factors influencing the desorption behavior of cadmium from goethite in aqueous solution are investigated using batch desorption experiments. Less cadmium was desorbed with increasing pH from 5 to 7. The presence of calcium increased the desorption at high Cd(II) loadings due to competition between cadmium and calcium for goethite surface sites. Limited effects of ionic strength are noted. EDTA at concentrations less than that of total Cd(II) present are found to inhibit cadmium desorption, especially at pH 5. Minimum Cd(II) desorption occurred near a 1:1 EDTA:Cd(II) total concentration ratio. Additions of chloride and NTA also suppress Cd(II) desorption. The inhibited desorption is attributed to re-adsorption of metal-ligand complexes onto the goethite.