Hydrometallurgical recovery of zinc from electric arc furnace dust was investigated on a laboratory scale, using aqueous sodium hydroxide solution as a leaching agent. Special attention was paid to the effect of NaOH concentration, temperature and liquid/solid phase ratio on the zinc leachability. It was found that all tested factors increased the leachability, with the maximum efficiency of 88% obtained in a 6 M NaOH solution at a temperature of 80 °C and the liquid/solid phase ratio of 40. The test results confirmed the high selectivity of the zinc leaching agent. In spite of this, complete recovery of zinc from steelmaking dust has proved to be very difficult due to the occurrence of this element in the form of stable and sparingly soluble ZnFe₂O₄ ferrite. Purification of the solution by cementation and electrolysis gave zinc of purity 99.88% in powder form.

During different aluminum smelting processes occur direct contact of liquid metal and carbon materials, which are the main constituent for the lining of the cells, furnaces, crucibles and ladles, etc. As a result, processes of aluminium carbide formation at the interfacial area and its subsequent dissolution occurs. Those are recognized as one of the most important mechanisms causing surface wear and decrease lifetime of the equipment, especially in aluminium electrolysis. Present work is aimed at deeper study of the initial steps of Al₄C₃ formation at the aluminium/ carbon interface. Three types of carbonaceous materials: amorphous, semigraphitic and graphitized, in the presence and absence of cryolite melts, were examined. As it is very difficult to study layer of Al₄C₃ in situ, two indirect experimental techniques were used to investigate aluminium carbide formation: measurements of the potential and the electrical resistance. It was concluded that the process of early formation of aluminium carbide depends on many processes associated with the presence of electrolyte (intercalation, penetration and dissolution) as well as the structure of carbon materials - especially the presence of the disordered phase.

Electrical conductivity is one of the most important physico-chemical parameters in chemical engineering as well as in the technology of many industrial process. Especially in the metals production by the electrolysis from molten salts or metals recovery from slags in the electric furnaces, where the great energy is needed.In this work the continuously varying cell constant (CVCC) technique for measuring conductivity of non-ferrous slags and molten salts was used. This is high-accuracy technique, which requires no calibration. The technique was verified by measuring conductivity of standard KCl solution and molten KCl. A good agreement was obtained between measured and commonly accepted literature values. The results of measured conductivity of KF-AlF₃ melts were compared with data obtained by other authors. It was proved that CVCC technique can measure accurately the electrical conductivity of high-temperature molten salts and metallurgical slags.

The main aim of the present work was to perform conductivity measurement of fluoride electrolytes in binary system Na₃AlF₆- CaF₂ and ternary system Na₃AlF₆- AlF₃ - CaF₂. The experiments were done in a wide range of temperature (580-1300 K), including the liquid and solid phase. Temperature dependencies of the conductivity of the liquid and solid cryolite mixtures with CaF2 (2, 4 and 6 wt %) and ternary solution (88 wt % Na₃AlF₆ - 8 wt % AlF₃ -4 wt % CaF₂) were determined by an A.C. two-electrodes technique. The simultaneous measurements of conductivity and temperature were made in 1min steps during heating and cooling of the sample with rate 0,5 K·min^-1. It was confirmed, that the addition of CaF₂ to liquid electrolyte decreases its electrical conductivity and liquidus temperature, whereas addition of aluminium fluoride up to 4 wt % in solid state has the inverse influence on conductivity. The studied ternary system showed the highest conductivity in the solid state at temperatures up to phase transition α-β in solid cryolite (ca. 780 K). This may be due to the formation of a solid solution of NaCaAlF₆ in -Na₃AlF₆ and the formation of cationic vacancies, which facilitate the transport of electrical charge.

Electric arc furnace (EAF) waste, a mixture of dust and slag, was investigated as a potential secondary source of zinc. The waste primarily consisted of zinc and iron oxides, with the presence of refractory zinc ferrite, which hinders the complete recovery of zinc. This is the first study that examined the effect of mechanical treatment through high-energy planetary ball milling on the phase transformation, metal speciation, and leachability of the EAF waste. The raw material was characterized by particle size distribution, morphology, phase composition, and sequential extraction, and then subjected to milling at different rotation rates (100–400 rpm). The resulting powders were analyzed using XRD, SEM–EDS, and sequential leaching, and tested for acid (H₂SO₄) and alkaline (NaOH) leachability. Milling progressively reduced particle size, increased surface roughness, and induced structural changes, including the mechanical activation effect at low milling rates (100 rpm) and the synthesis of secondary franklinite at higher milling energies (200 rpm and 400 rpm). Sequential extraction revealed changes in zinc and iron speciation from acid-soluble to residual fractions for increased milling intensities. Leaching experiments showed rapid zinc dissolution in both acidic and alkaline solutions, while iron dissolved only in acid. The highest zinc extractions (67% in H₂SO₄, 55% in NaOH) were obtained from mechanically activated material at 100 rpm, while zinc leachability decreased for higher milling rates due to the induced mechanical synthesis of refractory phase. The kinetic model of leaching of the main components of the EAF was also established.