Non-isothermal decomposition of potassium ferrioxalate trihydrate

Abstract

Non-isothermal decomposition of potassium ferrioxalate trihydrate, K 3Fe(C 2O 4) 3. 3H 2O, was studied between ambient temperature and 600°C. Thermogravimetry (TG), derivative thermogravimetry (DTG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) were used. Thermal decomposition experiments were carried out under different dynamic atmospheres of N 2, H 2 and air. Solid products at different decomposition stages were identified using IR spectroscopy and X-ray diffractometry. Major products are K 2CO 3 and Fe in N 2 and H 2, and Fe 2O 3 and K 2CO 3 in air. Gaseous decomposition products, identified using gas chromatography are CO and CO 2. Kinetic parameters (activation energy, E a, and frequency factor, ln A) together with thermodynamic parameters (enthalpy (Δ H) change, heat capacity ( C p) and the entropy change (Δ S)) were calculated for the different steps occurring during the course of dehydration and decomposition reactions. The rate of decomposition in air was higher than in N 2 and H 2. The effect of the atmosphere on the solid reaction products and on the kinetic and thermodynamic parameters is discussed.