Steel quality depends on various factors, i.a. on the slag basicity and oxidation potential. These values can be determined by means of emf measurement using solid electrolyte based sensors. Liquid iron can serve as a cation electrode. Activity of ferrous oxide and manganese oxide can be found out. Ferrous oxide activity determines the oxidation potential and manganese oxide activity can be used for the basicity estimation. Sulphide and phosphate capacity can be calculated and distribution coefficients of oxygen, sulphur, manganese, and other elements can be predicted. Metallurgical wastes are classified as hazardous because of high content of heavy metals and their waste disposal is problematic. Their hydrometallurgical recycling is difficult due to poorly soluble zinc ferrite. Thermal treatment is expensive because of high energy consumption. A new method of acid leaching applying diluted acids was developed. Entire zinc from the ferritic wastes can be extracted. A solid residue is hematite. The present study should be useful for research workers dealing with thermodynamics of melts and waste treatment.

Sárka Langová, Doc. Ing. CSc.: Studied chemical engineering at Institute of Chemical Technology in Prague. Senior lecturer at VSB-Technical University of Ostrava. Participation in projects - Thermodynamic equilibrium between liquid iron and slag; Zinc recovery from steel-making wastes.