Senarmontite volatilization kinetics in nitrogen atmosphere at roasting/melting temperatures

The volatilization kinetics of senarmontite (Sb₂O₃) was analyzed in a neutral atmosphere in two temperature ranges: 550-615 °C (roasting temperature) and 660-1100 °C (melting temperature) by using a thermogravimetric analysis method under various gas flow rates and using a 1.3 mL ceramic crucible (11 mm in internal diameter and 14 mm in height). The effect of particle size was also analyzed. The experimental results of mass loss data, X-ray diffraction (XRD) analysis of partially reacted samples and thermodynamic studies indicate that the senarmontite becomes volatile in the form of Sb₄O₆(g) without the formation of any intermediary compound in the entire temperature range. At roasting temperatures, the volatilization kinetics of Sb₂O₃ was analyzed using the model X=k_appt. The volatilization reaction was controlled by the surface chemical reaction and an activation energy value of 193.0 kJ/mol was obtained in this temperature range. Based on the volatilization kinetics at the melting temperatures, for linear behaviour in nitrogen gas, kinetic constants were determined, and an activation energy of 73.9 kJ/mol was calculated for the volatilization reaction with a surface area of 8.171×10^-5 m².