Abstract
The influence of mono ethylene glycol (MEG) on the precipitation of calcium carbonate was investigated at constant supersaturation, 25°C, pH 8.5. Seeded and unseeded experiments were done in aqueous supersaturated calcium carbonate solutions containing MEG over the concentration range 0-80 % v/v. The induction times and the subsequent rates of precipitation in unseeded, spontaneous precipitation of calcium carbonate were affected by the presence of MEG. At low values of the supersaturation ratio (SRcalcite=19.95-60.26) and for MEG concentrations in the range 30-80% v/v, the solutions were stable for four days. Values lower than 30% v/v of MEG concentrations, gave induction periods for calcium carbonate precipitation between 160-500min. The precipitates were examined for their morphological characteristics and showed that, in the presence of low MEG concentrations (10-20 % v/v), the precursor phase, vaterite, was stabilized. The homogeneous nucleation and growth of calcium carbonate in the absence and in the presence of MEG was also investigated, by the inoculation of substrates, like quartz calcite seed crystals, in stable supersaturated solutions. Both cases had as a result the significantly reduction of nucleation and growth of calcium carbonate, by increasing MEG concentration in the solutions.
