Synthesis of aragonite-precipitated calcium carbonate from oyster shell waste via a carbonation process and its applications

Oyster shells are abundantly available in nature without eminent use and are dumped into landfills in vast quantities. Their improper disposal causes environmental problems, resulting in a waste of natural resources. Recycling shell waste could potentially eliminate the environmental problems and, moreover, convert the waste into high-valueadded products, such as synthetic precipitated calcium carbonate (PCC), which can be obtained from oyster waste and which is used to enhance the mechanical properties of various materials. It can also be used as a filler material in the plastic and paper industries. This study presents a simple method for the extraction of aragonite needles from oyster shell waste via a carbonation process. The obtained aragonite-precipitated calcium carbonate (PCC) is characterized by XRD and SEM, which is used to assess the morphology and particle size. Using the proposed process, oyster shell waste powder was calcined at 1,000 °C for 2 h, after which the calcined shell powder was dissolved in water for hydration. The hydrated solution was mixed with an aqueous solution of magnesium chloride at 80 °C and CO2 was then bubbled into the suspension for 3 h to produce needle-shaped aragonite PCC. Finally, aragonite-type precipitated calcium carbonate was synthesized from the oyster shell powder via a simple carbonation process, yielding a product with an average particle size of 30-40 μm.