DECOMPOSITION STUDY OF CALCIUM CARBONATE IN COCKLE SHELL

Abstract

Calcium oxide (CaO) is recognized as an efficient carbon dioxide (CO2) adsorbent and separation of CO2 from gas stream using CaO based adsorbent is widely applied in gas purification process especially at high temperature reaction. CaO is normally been produced via thermal decomposition of calcium carbonate (CaCO3) sources such as limestone which is obtained through mining and quarrying limestone hill. Yet, this study able to exploit the vast availability of waste resources in Malaysia which is cockle shell, as the potential biomass resources for CaCO3 and CaO. In addition, effect of particle size towards decomposition process is put under study using four particle sizes which are 0.125-0.25 mm, 0.25-0.5 mm, 1-2 mm, and 2-4 mm. Decomposition reactivity is conducted using Thermal Gravimetric Analyzer (TGA) at heating rate of 20°C/minutes in inert (Nitrogen) atmosphere. Chemical property analysis using x-ray fluorescence (XRF), shows cockle shell is made up of 97% Calcium (Ca) element and CaO is produced after decomposition is conducted, as been analyzed by x-ray diffusivity (XRD) analyzer. Besides, smallest particle size exhibits the highest decomposition rate and the process was observed to follow first order kinetics. Activation energy, E, of the process was found to vary from 179.38 to 232.67 kJ/mol. From Arrhenius plot, E increased when the particle size is larger. To conclude, cockle shell is a promising source for CaO and based on four different particles sizes used, sample at 0.125-0.25 mm offers the highest decomposition rate.

Keywords

• Decomposition
• Kinetics
• Calcium carbonate
• Particle size
• Cockle shells
• TGA