Papers by Keyword: Precipitated Calcium Carbonate (PCC)

Abstract: Calcium carbonate (CaCO3) is a natural occurring mineral or it can be produced by chemical means. This last product is often referred to as Precipitated Calcium Carbonate (PCC). PCC has various advantanges since it exhibits higher brightness and opacity. There can be considerable variation in the properties of the PCC depending upon the process conditions used to prepare it. In this work, the effect of different factors on the particle size of PCC has been investigated. The experiments were performed by bubbling CO2 in slaked lime suspensions. The pH of the lime slurry was 12 or higher at the beginning, but it decreased, down to an equilibrium pH of 8± 1, when the reaction was considered complete.

Abstract: The characteristics of nucleation and the crystal growth of aragonite-precipitated calcium carbonate in Ca(OH)2 – MgCl2 – CO2 system by a carbonation process is investigated. MgCl2, in this study, was added in order to increase the formation yield of aragonite precipitated calcium carbonate. Optimum conditions of the concentration of the reactants, the temperature and the amount of additives were studied. The formation yield of calcite gradually decreased, and the formation yield of aragonite increased with the addition of MgCl2. A higher formation yield of above 98% for aragonite is obtained by the adding of the Mg2+ ion in a 0.2M Ca(OH)2 – 0.6M MgCl2 – CO2 system at 80
. The nucleation rate increased as the temperature decreased and as the CO2 gas flow rate increased. The particle size and aspect ratio increased at a high temperature, a low flow rate of gas, and a high concentration of Ca(OH)2 slurry. Small-sized aragonite was obtained at a low temperature. The increase in crystal size with the decrease in the CO2 gas flow rate can be explained by the decrease in the nucleation rate, in addition to the increase in the crystal growth rate resulting from the decrease in the dissolution rate to CO3 2- ion.

Abstract: Homogeneous precipitated calcium carbonate(PCC) was synthesized by calcinations, hydration and carbonation of limestone which has been deposited in Danyang, Korea. In the reaction process, shapes(scalenohedral and cubic) and sizes(0.2~0.3μm and 2.0μm) of the powder were controlled by reaction temperature. Synthesized PCC was applied to hand-made paper as filler and coated paper. For the prepared papers, physical/optical properties(brightness, whiteness, opacity, roughness, gloss, tensile strength, internal tearing strength, stiffness, bursting strength) and printability(ink gloss, ink set-off, dry pick, wet pick) were characterized

Abstract: The objective of this study is to synthesize the single phase aragonite precipitated calcium carbonate by the carbonation process in the Ca(OH)2-MgCl2-CO2 system. Many researchers reported the influence of Mg2+ ion on the synthetic properties. The inhibition of calcite nucleation and crystal growth, distortion of calcite lattice, and change of surface electrification were investigated. Variety of particle size and aspect ratio were observed according to changes in the concentration of Ca(OH)2 slurry, temperature, and CO2 gas flow rate. The nucleation rate increased when decreasing the temperature and increasing the CO2 gas flow rate. Particle size and aspect ratio increased at high temperature, low CO2 gas flow rate, and high concentration of Ca(OH)2 slurry, however small-sized aragonite was obtained at low temperature.

Abstract: In this study, single phase aragonite PCC was synthesized by the solution process using Ca(OH)2 slurry and Na2CO3 solution as the main reactants. To begin with, the formation behavior of PCC polymorphs following changes in supersaturation was investigated, and the optimum synthetic condition of single-phase aragonite PCC was clarified after the role of NaOH in the reaction system was reviewed. In the results, it was considered that lower supersaturation was necessary to obtain a single phase aragonite; and, since the solubility of Ca(OH)2 was decreased with the addition of NaOH by a common ion effect, it is possible to perform a experiment at a lower Ca2+ concentration. In conclusion, in the case of the reaction of the 2.5M NaOH solution, single phase aragonite was obtained. Furthermore, NaOH solution was produced as a by-product in the solution process by reacting Ca(OH)2 slurry with Na2CO3. Thus, recycling of the NaOH solution was attempted in order to clear the environmental issue. It is difficult to recycle directly since the NaOH solution was diluted during the experiment. The optimum condition was investigated by control of experimental factors such as the concentration of Ca(OH)2, Na2CO3 and NaOH, and the reaction temperature, after which the NaOH solution was recycled without re-treatment. The formation characteristics of aragonite PCC, such as formation yield, particle morphology and aspect ratio, were investigated.