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

TL;DR

This study investigates how hydrothermal carbonation conditions affect the textural properties of synthetic nano-calcite, revealing key influences on particle size, surface area, and morphology relevant for industrial uses.

Contribution

It provides detailed analysis of the effects of pressure, temperature, and CO2 concentration on calcite's textural properties during synthesis.

Findings

Pressure, temperature, and CO2 levels significantly influence particle size and surface area.

High purity calcite with nano-scale features can be produced under optimized conditions.

Synthesized nano-calcite has potential applications as adsorbents and fillers.

Abstract

The hydrothermal carbonation of calcium hydroxide (Ca(OH)2) at high pressure of CO2 (initial PCO2 1/4 55 bar) and moderate to high temperature (30 and 90 1C) was used to synthesize fine particles of calcite. This method allows a high carbonation efficiency (about 95% of Ca(OH)2-CaCO3 conversion), a significant production rate (48 kg/m3 h) and high purity of product (about 96%). However, the various initial physicochemical conditions have a strong influence on the crystal size and surface area of the synthesized calcite crystals. The present study is focused on the estimation of the textural properties of synthesized calcite (morphology, specific surface area, average particle size, particle size distribution and particle size evolution with reaction time), using Rietveld refinements of X-ray diffraction (XRD) spectra, Brunauer-Emmett-Teller (BET) measurements, and scanning electron microscope (SEM) and transmission electron microscope (TEM) observations. This study demonstrate that the pressure, the temperature and the dissolved quantity of CO2 have a significant effect on the average particle size, specific surface area, initial rate of precipitation, and on the morphology of calcium carbonate crystals. In contrast, these PTx conditions used herein have an insignificant effect on the carbonation efficiency of Ca(OH)2. Finally, the results presented here demonstrate that nano-calcite crystals with high specific surface area (SBET 1/4 6-10m2/g) can be produced, with a high potential for industrial applications such as adsorbents and/or filler in papermaking industry.