Advances and gaps in the knowledge of thermodynamics and crystallography of acid mine drainage sulfate minerals.

Acidic and metal-rich waters produced by sulfide decomposition at mining sites are termed acid mine drainage (AMD). They precipitate a number of minerals, very often sulfates. The recent advances in thermodynamic properties and crystallography of these sulfates are reviewed here. There is a reasonable amount of data for the divalent (Mg, Ni, Co, Fe(2+), Cu, Zn) sulfates and these data may be combined with and optimized by temperature-relative humidity brackets available in the literature. For the sulfates with Fe(3+), most data exist for jarosite; for other minerals and phases in this system, a few calorimetric studies were reported. No data whatsoever are available for the Fe(2+)-Fe(3+) sulfates. A significant advance is the development of the Pitzer model for Fe(3+)sulfate solutions and its confrontation with the available thermodynamic and solubility data. In summary, our knowledge about the thermodynamic properties of the AMD sulfates is unsatisfactory and fragmented.