Nucleation kinetics of nesquehonite (MgCO3·3H2O) in the MgCl2−Na2CO3 system

The nucleation of nesquehonite (MgCO3·3H2O) in MgCl2−Na2CO3 system with and without the addition of NaCl was studied within a supersaturation range of 1.06–1.48 at 288.15–308.15 K. The supersaturation (S) of MgCO3·3H2O was exactly calculated by aqueous (H+ ion) model through OLI platform. The conductivity method was applied in this experiment to determine the induction period of MgCO3·3H2O. The effects of temperature, supersaturation, and presence of additive (NaCl) on the induction period of MgCO3·3H2O were studied experimentally. As expected from theory, it was found that the induction period decreases when either temperature or supersaturation increases. The induction period was prolonged by adding NaCl in solutions at a constant supersaturation. From the dependence of the induction period on temperature and supersaturation, it was possible to distinguish between the homogeneous and heterogeneous nucleation mechanisms. At last, the activation energy (Eact) for MgCO3·3H2O crystallization and the interfacial tension between MgCO3·3H2O and aqueous solutions of homogeneous (γS,hom) and heterogeneous (γS,het) nucleation were calculated from measurements of the induction period for the MgCO3·3H2O nucleation with and without the addition of NaCl.