Simple Thermal Treatment of Waste Oyster (Crassostrea belcheri) Shells for the Production of Calcium Minerals in Biomaterials Application

Abstract

The effect of the thermal treatment of waste oyster (Crassostrea belcheri) shells on different properties was explored. In this preliminary work, the waste oyster shells were collected from Muar River, Malaysia. All samples were cleaned, dried, and subjected to a simple heat treatment in air at 500–1 200 °C. All heat-treated samples were characterized to determine their mass loss, chemical composition, crystalline phase, surface morphology, and powder density properties. Changing the temperature from 500 to 1 200 °C increases the calcium (Ca) food content in oyster shells. Furthermore, the decomposition of calcium carbonate (CaCO3) from 98.15 wt.% to 99.07 wt.% was completed at 682 °C with 45 wt.% mass loss in a controlled nitrogen environment. When heat treatment processes are conducted in air, only 14.74 wt.% mass loss is recorded. The X-ray diffraction results confirmed that CaCO3 successfully transformed α peak (CaO4) to γ peak and η peak (CaO) at an angle (θ) of 30° and at above 800 °C. The Fourier transform infrared (FTIR) Result revealed changes in functional groups as the temperature increased. The phase transformation and morphological analysis agree with measured powder density values from 2.63 to 2.30 g·cm−3. All these findings indicate that heated waste oyster shells are a potential source of calcium minerals and can be used for biomaterial products.