Solubility of the nadorite group minerals: implications for mobility of Sb and Bi in oxidised settings

Abstract

Environmental contextThe dispersion of antimony in the environment has been misunderstood over the last few decades. Investigating the solubility of naturally forming mineral phases such as nadorite resulted in determination of its limited role in Sb dispersion, providing evidence that nadorite can only limit antimony dispersion in mildly oxidising conditions. Nadorite can only play a significant role in Sb immobilisation in a particular redox window, which forms only a minor part of the framework of Sb dispersion. AbstractAs part of a study of the control that secondary minerals exert on the dispersion of antimony and bismuth in the supergene environment, syntheses and stability studies of nadorite (PbSbO2Cl) and perite (PbBiO2Cl) have been undertaken. Solubilities in aqueous HNO3 were determined at 298.2K and the data obtained used to calculate values of ΔGfθ(298.2K). The ΔGfθ(s, 298.2K) values for PbSbO2Cl (–622.0±2.8kJmol–1) and PbBiO2Cl (–590.0±1.3kJmol–1) have been used in subsequent calculations to determine relative stabilities and relationships with other common secondary Sb and Bi minerals. While the role of nadorite in immobilising Sb is dependent upon the prevailing redox potential such that SbIII is stable, perite may be a significant phase in limiting the dispersion of Bi in certain supergene settings.