Optimum conditions for preparation of bio-calcium from blood cockle and golden apple snail shells and characterization

Abstract

Research on the utilization of calcium compounds from seashells has attracted much interest in diverse applications. However, the optimum temperature and time for preparation of calcium compounds from shells remains unknown. These factors have a direct effect on the purity of the obtained calcium phases. In this study, the influence of calcination temperature and holding time on the phase transformations of CaCO3 from sea shells and freshwater shells, i.e., blood cockle and golden apple snail shells, was studied. High purity and crystalline CaCO3 and CaO was produced from both types of shells by calcination at 600 °C and 800 °C, respectively. Overall both blood cockle and golden apple snail shells could be used to produce calcium compounds with 95–98% pure calcium with trace amounts of As, Cd, Hg, and Pb. Phase transformation of CaCO3 depends on calcination temperature and holding time. The calcium content in CaCO3 and CaO from golden apple snail shells was higher than that from blood cockle shells. This result also indicated that the calcium compounds from blood cockle shell were easier to grind than those from golden apple snail shells primarily due to an early transformation of the calcium phase of golden apple snail shells.