Investigation of effect of mechanical activation on chromate production from chromite

Chromite is the only ore mineral of metallic chromium and chromium compounds and chemicals. Chromite comprises a range of the spinel group of mineral, described as (Mg,Fe+2)O.(Cr,Al,Fe+3)2O3. The most important uses of chromium are in metallurgical applications, like as stainless steel production, and in chemical applications, like as leather tanning, pigments, dyes, the printing and photography, metal plating.In conventionally, chromite concentrates are roasted with sodium carbonate at temperatures of 1100-1150°C. The chromium ion (Cr+3) from the spinel of the chromite mineral reacts with sodium carbonate to form a water-soluble sodium chromate compound. It is a main material for chromium chemicals.Mechanical activation of minerals by intensive grinding is a non-traditional way of influencing the processes in extractive metallurgy. The resulting creation of fine particles, the increase in specific surface area and the formation of defective structures accelerate metallurgical processes. The reaction temperatures decrease and yields increase with mechanical activation.In this thesis, chromite was activated mechanically for different grinding times and structural disorderings were examined by different analysis techniques. The effects of mechanical activation on soda roasting of chromite were also investigated. As a result, the efficiency of conversion of chromite to chromate by soda roasting at 800°C was ~74% for chromite that had been activated for 120 minutes, compared to ~18% for non-activated chromite. Mechanical activation caused amorphization and structural disordering in the chromite structure allowing for the use of lower reaction temperatures.