Umweltmobilität des Elementes Zinn
Zusammenfassung der Projektergebnisse
In this project, we determined that the element tin is in general immobile, even after centuries of weathering in mining waste that contains Sn sulfides. Combination of experimental (thermodynamic) work and investigation of natural materials showed that tin could be mobilized in strongly acidic or strongly alkaline aqueous media. We suspect that in nature, acidic solutions could carry tin over greater distances. Such conditions existed perhaps at some localities in Cornwall (England) where tin hydroxides form. In the sites investigated in this work, this degree of mobility was not observed. We did find, however, that Sn was mobilized by acidic ground water at the localities studied, by geochemical modeling of water analyses published previously by Czech Geological Survey. The final product of weathering of Sn sulfides is the mineral cassiterite (SnO2), an insoluble and immobile material that persists for indefinite periods of time under the conditions of surface weathering. From that point of view, tin does not seem to be of environmental significance. The release of tin from paints of large ships into the oceans could lead to precipitation of cassiterite or some of the tin hydroxides investigated in this work. Degradation of solar cells whose main component are tin sulfides may lead to limited input of Sn into the environment but this Sn will be quickly immobilized. A surprising observation was the initial degradation of the stannite-kësterite phases into Sn-rich chalcopyrite. It means that the initial stages of the decomposition of the Sn sulfides are driven by diffusion. They do not result in oxidic phases which are commonly observed in weathering environments but in a structurally related sulfide. This observation can have some implications for the longer-term performance of solar cells that are based on chemically and structurally similar Sn sulfides. We will attempt to follow up with our techniques and capabilities to investigate the degradation of such solar cells. Parallels between the decomposition of the natural and synthetic materials may be drawn and used to explain the performance drop of such solar cells over time.
Projektbezogene Publikationen (Auswahl)
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Stability and solubility of members of the schoenfliesite subgroup, □2(BSn4+)(O,OH)6 (B = Ca, Fe3+, Mg, Mn2+, Zn)). Chemical Thermodynamics and Thermal Analysis, 1-2, 100005.
Haase, Patrick; Christensen, Helena Gorniak; Nielsen, Ulla Gro; Koch, Christian Bender; Galazka, Zbigniew & Majzlan, Juraj
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Weathering of stannite–kësterite [Cu2(Fe,Zn)SnS4] and the environmental mobility of the released elements. European Journal of Mineralogy, 34(5), 493-506.
Haase, Patrick; Kiefer, Stefan; Pollok, Kilian; Drahota, Petr & Majzlan, Juraj
