Synthesis of Nano-Calcium Carbonate from Cockle Shells using Supercritical Carbon Dioxide via Rapid Expansion of Supercritical Solution Technique

Abstract

Preparation of nano-calcium carbonate from cockle shells was carried out through chemical reaction by dissolved cockle shell with hydrochloric acid at the ratio of acid per cockle shell as 2:1 to prepare a solution of calcium chloride. This solution was changed into calcium chloride by adding calcium hydroxide at the ratio of base per solution is 2:1 and then operated together with rapid expansion of supercritical solution process at 150 bar, 110^oC for 30 minutes. Nano-calcium carbonate is identified as calcite structure by X-ray diffraction analysis that obtained in the 2θ position at 29.4^o angle. This result was consistent with the spectra from Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy that shown in the transmittance range at 1389, 880 and 713 cm^-1 which indicated the characteristic of calcite. In addition, the morphology from SEM was observed in a square cubic which are considered to be a calcite crystal structure and the particle size distribution of nano-calcium carbonate was found in 75 nm.