Growth behaviors of CACO3 polymorphs under various environmental conditions

Using the constant-composition technique, in which two autotitrators were applied for maintaining the composition and pH constant in a growth process, the growth rates of calcium carbonate polymorphs, i.e., calcite and aragonite, were measured at different operating conditions. The conditions were chosen as closely as possible to that in the magnetic water- treatment for preventing scale formation. The transient effects of magnetic field on the growth of CaCO3 polymorphs were presented first. Then, the steady growth rates of calcite and aragonite were measured in the absence/presence of magnetic field at various conditions as follows: temperature between 25¢XC and 40¢XC, pH between 8.0 and 10.0, activity ratio of Ca2+/CO3 2? (R) between 0.2 and 6.0, impurity concentration of Fe2+ and Sr2+ between 0 and 2.0 ppm. The growth rates of polymorphs responded differently to a change in operating variables. The results were most surprising with regard to the effects of impurities. In addition, a hypothesis of cluster- transformation mechanism was proposed to explain the experimental results obtained in our laboratory and some cases reported in the literature. ? 2017 Nova Science Publishers, Inc.