Morphological control of precipitated calcite obtained by adjusting the electrical conductivity in the Ca(OH)2-H2O-CO2 system

This paper reports a new method to produce calcite (CaCO3) crystals with common and unconventional morphologies in the Ca(OH)(2)-H2O-CO2 system, without the use of any tailor-made additive. Operating at temperatures (T) of 20degreesC, 25degreesC and 30degreesC, the method used is based on the adjustment of the electrical conductivity (kappa(25)) of that system at fixed values of 1, 3, 5 and 7mS/cm. This variable was adjusted automatically by pumping a slaked lime suspension to a reactor containing deionized water, and provided with a constant flow rate of 20% CO2/ 80% N-2 (v/v). The results, represented in a T - kappa(25) space, show the production of calcite adopting different morphologies and sizes. Morphologies as diverse as rhombohedral, rhombo-scalenohedral and scalenohedral in the micrometric size range, as well as submicrometric chain-like particles and nanometric spherules are produced. The mechanism of formation of calcite with these morphologies is discussed. (C) 2002 Elsevier Science B.V. All rights reserved.