Effect of Sodium Sulfate on Nucleation Behavior and the Crystal Morphology of Taurine

Two theoretical methods, self-consistent Nyvlt-like approach and Sangwal's classical 3D nucleation theory-based method, are employed to analyze the effects of additives (sodium sulfate) on the nucleation behavior of taurine. By correlating the measured metastable zone width of taurine containing different sodium sulfate concentrations, with saturation temperature and cooling rate, nucleation kinetic parameters in both two methods are determined. Fitting results demonstrate that higher sodium sulfate concentration results in the increase of solid-liquid interfacial energy gamma, contrarily higher saturation temperature has the opposite effect thus changing of nucleation rate. The molecular modeling techniques are then applied to investigate the changes in the morphology of taurine which caused by the presence of sodium sulfate. Through molecular dynamic simulations, the interaction energy of sodium sulfate with taurine crystal faces are obviously larger than those of taurine and these differences on the (011) and (11-1) are more significant than those on (021) and (111) faces. As a result, the growth of (011) and (11-1) faces is inhibited and the morphology of taurine crystal is modified from needle to columnar. The influence of sodium sulfate on taurine studied in this work provides theoretical guidance for industrial production.