Factors Affecting the Particle Size of Bio-Calcium Carbonate Synthesized from Industrial Eggshell Waste

Abstract

Calcium carbonate is broadly used as a catalyst support, filler, additive, and reinforcement in several types of industry e.g. chemical, food, and biomedical industry. Recently, eggshell waste has attracted much attention for the purpose of calcium carbonate production due to its compost about 96% calcium carbonate. However, direct use of egg shells as filler material can probably cause product defects. In this research, calcium chloride was extracted from chicken-eggshell waste followed by precipitation of micron size calcium carbonate. The effect of agitation time, the initial concentration of calcium chloride and synthesis temperature on particle size, and selected physicochemical properties of this precipitated calcium carbonate (PCC) were investigated. Scanning electron micrographs of the prepared materials illustrated that all of the PCCs obtained from these experiments exhibit uniform-round shape. The laser diffraction results show that the median size of the PCC particles increased significantly from about 6 µm to 19 µm with increasing agitation time and with decreasing initial concentration of calcium chloride. However, increasing the synthesis temperature from 30°C to 160°C only slightly increased the median size of the PCC particles. The results of X-ray diffraction indicated that both agitation time and initial concentration also have an effect on the crystalline morphology of the PCCs. In addition, calcite crystalline phase became dominant over the other crystalline phases when agitation time and initial concentration were increased. In comparison, PCCs synthesized from this eggshell waste have much smaller median particle size than commercial calcium carbonate. Furthermore, the purity of the PCC derived from shell waste was comparable to commercial calcium carbonate. This facile synthesis is environmentally friendly and cost effective.