Effect of alternating electromagnetic field and ultrasonic on CaCO3 scale inhibitive performance of EDTMPS

In this study, the influence of Ethylene Diamine Tetra Methylene Phosphonic Acid Sodium (EDTMPS) on the precipitation of CaCO3 under alternating electromagnetic field (AEMF) and ultrasonic (US) treatment were investigated. The variations of pH value and the Ca2+ concentration of hard water solution were monitored, and the crystalline phase and morphology of precipitated CaCO3 crystals were characterized by XRD and SEM. The experimental results show that the presence of EDTMPS can inhibit the precipitation of CaCO3. In the 30 mmol/L Ca(HCO3)(2) solution, when the EDTMPS concentration were 2.5 mg/L, 5 mg/L, 7.5 mg/L and 10 mg/L, the antiscale efficiencies were 34.08%, 63.67%, 70.79% and 71.16%, respectively. Thus, the antiscale efficiency correlates positively with EDTMPS concentration. The presence of EDTMPS can also inhibit the CaCO3 conversion from vaterite to calcite. The AEMF has the effect of hindering the precipitation of CaCO3 and inducing CaCO3 precipitates as vaterite crystals. Furthermore, it is significant that the AEMF can effectively improve the scale inhibition effect of EDTMPS, which means the EDTMPS used in combination with AEMF could be a good method to improve the scale inhibition. On the other hand, the US promotes the CaCO3 precipitation as calcite crystals with smaller size. Under the action of US, the EDTMPS loses its inhibition effect after a certain period of time, possibly due to the US destroys the connection between Ca and EDTMP and free the Ca2+ in the solution. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.