Thermoanalytical investigations of decomposition course of copper oxysalts

The thermal decomposition of basic copper carbonate (malachite; CuCO₃·Cu(OH)₂) in a dynamic atmosphere of air or nitrogen was studied via TG, DTA and DSC at different heating rates. The non-isothermal kinetic and thermodynamic parameters were estimated. The decomposition course was thoroughly followed by examining the structural and morphological consequences of calcining the material at elevated temperatures by IR, XRD and SEM. The results obtained showed that in air CuCO₃·Cu(OH)₂ released 0.5 H₂O at 195°C, transforming into the azurite structure 2CuCO₃·Cu(OH)₂. Decomposition then commenced, through two endothermic steps maximized at 325 and 430°C. The resultant product maintained the water released from the decomposition process up to 650–750°C. A schematic decomposition pathway has been proposed in terms of the thermal and physicoanalytical results.