Influence of alternating electromagnetic field and ultrasonic on calcium carbonate crystallization in the presence of magnesium ions

In the present study the efficiency to the CaCO3 crystallization caused by the different ordinal combination of alternating electromagnetic field (AEMF) treatment and ultrasonic (US) treatment was investigated by the measurement of the variations of the solution pH, conductivity, turbidity and particle size distribution when Mg2+ ions were present, and the crystal phases structure and micrographs of the precipitations obtained from experiments were analyzed by XRD and SEM. The experimental results show that the presence of Mg2+ ions can prolong the induction time of the formation of CaCO3 and make the CaCO3 particles gradually change into aragonite, the particle size also decreases with the increasing of Mg2+/Ca2+ ratio. The AEMF + US treatment decreases the size of CaCO3 particles, and the US + AEMF treatment accelerates the precipitation of CaCO3. It is interesting that with the presence of Mg2+ ions US + AEMF treatment makes the CaCO3 particles have larger size with looser structure, but at last form completely tiny aragonite needles. The results are advanced in that the proper addition of Mg2+ ions combined with the AEMF + US or US + AEMF can significantly improve the physical anti-scaling efficiency.