Adsorption of Cd and Zn onto Micaceous Minerals - Effect of Siderophore Desferrioxamine B

Abstract The mobility, bioavailability and environmental fate of heavy metal ions in soil are controlled by adsorption onto soil minerals and solid organic matter. The adsorption is strongly affected by the presence of various low-molecular-weight organic acids. In this study, the effects of the hydroxamate siderophore ‘desferrioxamine B’ (DFOB) on cadmium (Cd) and zinc (Zn) adsorption by muscovite and phlogopite minerals were examined in batch experiments. Results showed that the presence of DFOB diminished the adsorption of Cd and Zn onto both minerals, particularly under neutral to alkaline pH conditions. For instance, at pH 8.2, the presence of DFOB caused a decrease in adsorption of Zn onto phlogopite by nearly 50%. The equilibrium adsorption of Cd and Zn was satisfactorily described by Freundlich isotherms. The adsorption isotherms showed that the affinity of Cd and Zn to the minerals decreased in the presence of DFOB. For example at pH 8.0, the presence of the siderophore caused a decrease in the Freundlich K F value for Zn adsorption on muscovite and phlogopite from 4.60 and 3.56 L g −1 to 0.07 and 0.36 L g −1 , respectively. These findings confirm a potential influence of siderophores on the fate of Cd and Zn in arid soils that contain substantial contributions of micaceous silicate minerals.