Understanding the Precipitated Calcium Carbonate (PCC) production mechanism and its characteristics in the liquid–gas system using Milk of Lime (MOL) suspension

Abstract

This study investigates the effect of operating variables and influence of milk of lime (MOL) conditions in PCC using a modified reactor. The variables includes: Ca(OH)₂ feed concentration at 0.5 M–2.0 M and CO₂ flow rates at 224.0 mL min^–1 and 379.5mLmin^–1, on the particle morphology and size in the gas–liquid route precipitation. The particle morphology and texture as well as the chemical content were sufficiently authenticated using X-ray diffraction (XRD), Fourier transforminfrared spectroscopy (FTIR), scanning electron microscope (SEM) and X-ray fluorescence (XRF). Experimental data show that lower concentration (<1.0 M) favoured the formation of rhombohedra calcite crystals with the particle size below 100 nm. However, increase in concentration and gas flow rate yielded a coarser crystal particles.Two polymorphs were produced at1Mreactant, i.e. rhombohedra calcite with CO₂ flow rate of 224 mL min^–1 and prismatic calcite at 380 mL min^–1. Molarities higher than 1 M yielded a coarser prismatic crystals, and also has a tendency to crystallize into scalenohedron species especially with higher reactant concentration.

Keywords: Milk of lime, precipitated calcium carbonate, morphology, particle size, carbonation