Changing of Particle Size and Pore Structures of Calcium Oxide during Calcinations of Industrial Eggshell Waste

Abstract

Surface area and particle size are significant properties of a catalyst that determine the reaction rate of the heterogeneous catalyst. In this research, calcium oxide derived from industrial eggshell waste was synthesized by thermal decomposition method under air-atmosphere. The obtained eggshell waste was washed, dried, and ground to 420 μm followed by calcination of the ground eggshell in different conditions including calcination temperature (800 to 900 °C) and holding time (1 to 4 hours). Changes of pore structure and the median particle size diameter of the obtained calcium oxides were systematically investigated by various scientific instruments. Results from powder X-ray diffractometer (PXRD) indicated that the calcium oxide can be obtained after calcination at both 800 and at 900°C. Laser diffractometer shows that median particle size diameter of calcium oxide significantly decreased by about 76-95 % with increasing of both calcination temperature and holding time. Additionally, specific surface area of calcium oxides determined by N2 adsorption experiment at-195 °C shows that surface area of calcium oxide dramatically decreased (37-84 %) with increasing both calcination temperature from 800 to 900 °C and calcination time from 1 to 4 hours. These results indicated that both calcination temperature and time play an important role in the shrinkage of pores of calcium oxide. Higher calcination temperature and longer holding time induce more shrinkage of pore leading to smaller particle size diameter and lower surface area of the calcium oxide catalyst.