Morphological characteristics and aggregation of calcite crystals obtained by bubbling CO2 through a Ca(OH)2 suspension in the presence of additives

In this work, the authors studied the influence of citric acid, sucrose, calcium lignosulfonate, sodium dodecyl sulfate, polyethylene glycol and triethanolamine (1 wt.%) as well as of CaSO4·1/2H2O and aerosol OT (0.5 wt.%) on the morphology and aggregation of calcite precipitated by carbonation of slaked lime. It was found that the three first additives modify the precipitation mechanism yielding elongated agglomerates similar to those known as chain-like, precursors of colloidal nanometric calcite. The other additives used do not modify the mechanism and yield scalenohedral calcite of submicrometric/micrometric size, similar to that obtained in the absence of additives. These results are explained in terms of the effect of these additives on the dissolution rate of Ca(OH)2 and their inhibitory effect in the chain-like to colloidal calcite transformation. Concerning the aggregation phenomena, sucrose and citric acid act aggregating the primary chain-like particles. Lignosulfonate aggregates on the whole size range. The other additives showed a small dispersing effect.