Abstract
Eggshell are rich sources of calcium carbonate and calcium oxide, but treated as bio-waste material. The natural origin and wide availability of eggshell are suitable to synthesize hydroxyapatite having chemical composition and crystalline structure similar to human teeth and bones. In present work, eggshell powders are sintered at different temperature 200°C, 400°C, 600°C, 800°C and 900°C for 1 h time duration in muffle furnace. The sintered powders are cold compacted at a fixed load of 15 tons for 10 min duration in a hydraulic pellet press. A suitable die set having 13 mm diameter is used to prepare compacted powder samples of 6 mm height. The sintered eggshell pellets are characterized using X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM) and Vickers hardness tester. Chemical composition of eggshell pellet changes from calcium carbonate to calcium oxide at 900°C for 1 h time duration and noticed through XRD. Increased hardness of the sintered eggshell pellet is noticed at more than 600°C temperature. The waste eggshells can be utilized to synthesize hydroxyapatite with the help of ball milling and subsequently heat treatment. A straight forward and cost effective method (i.e. hydrothermal method) is proposed for converting eggshell into hydroxyapatite. In this method, a solution of calcium oxide powder obtained from eggshell, tri calcium phosphate powder and demineralized water in stoichiometric proportions is employed as the precursor. Now, this solution is heat treated at 1050°C for 3 h time duration in muffle furnace to complete the reaction. X-ray diffraction result confirms the formation of hydroxyapatite, apart from little amount of other compounds in final product.
Published Version
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