Textural properties of synthetic nano - calcite produced by 1 hydrothermal carbonation of calcium hydroxide

1 2 The hydrothermal carbonation of calcium hydroxide (Ca(OH) 2) at high pressure of CO 2 3 (initial P CO2 = 55 bar) and moderate to high temperature (30 and 90°C) was used to synthesize 4 fine particles of calcite. This method allows a high carbonation efficiency (about 95% of 5 Ca(OH) 2-CaCO 3 conversion), a significant production rate (48 kg/m 3 h) and high purity of 6 product (about 96%). However, the various initial physicochemical conditions have a strong 7 influence on the crystal size and surface area of the synthesized calcite crystals. The present 8 study is focused on the estimation of the textural properties of synthesized calcite 9 (morphology, specific surface area, average particle size, particle size distribution and particle 10 size evolution with reaction time,) using Rietveld refinements of X-ray diffraction spectra, 11 BET measurements and, scanning and transmission electron microscope (SEM and TEM) 12 observations. This study demonstrate that the pressure, the temperature and the dissolved 13 quantity of CO 2 have significant effect on the average particle size, specific surface area, 14 initial rate of precipitation, and on the morphology of calcium carbonate crystals. In contrast, 15 these PTx conditions used herein have insignificant effect on the carbonation efficiency of 16 Ca(OH) 2. 17 Finally, the results presented here demonstrate that nano-calcite crystals with high specific 18 surface area (S BET =6-10 m 2 /g) can be produced, with a high potential for industrial 19 applications such as adsorbents and/or filler in papermaking industry.