THERMAL-DECOMPOSITION OF FERRIC AND AMMONIUM SULFATES OBTAINED BY BIOOXIDATION OF WATER PICKLING LIQUORS WITH THIOBACILLUS-FERROOXIDANS

Sulphuric water pickling liquor containing ferrous sulphates was oxidi zed by Thiobacillus ferrooxidans at different pHs. The oxidized soluti on was then evaporated and crystallized, and products characterized by X-ray powder diffraction, X-ray high temperature powder diffraction a nd Fourier transform infrared (FTIR) spectrometry. The thermal decompo sition of these materials, studied by calorimetric and thermogravimetr ic techniques, shows that iron(III) hydroxysalts and monoammonium and triammonium salts are formed during the oxidation-evaporation-crystall ization process. However, this formation depends upon pH.