Characterization of Stainless Steel Spent Pickling Sludge and Prospects for Its Valorization

Fluorspar is considered a critical raw material for the European Union, due to its industrial uses and lack of sufficient extraction in countries. It source hydrofluoric acid manufacture, this latter chemical being employed, among other uses, pickling stainless steels. From activity, sludge generated need used water treatment. In article, we report full characterization residue, obtained an plant Vieira de Leiria, Portugal. Its mineralogical characteristics were determined, showing that it mostly mixture calcium fluoride sulfate with some heavy metals content. Thermal behavior allowed us determine melts at around 950 °C. The influence calcining operation on residue was especially concerned leachability elements. Taking into account results considerations are presented about potential valorization residue.