Influence of Different Ions on Pulse Electrodeposition of CaCO3 Scales in the Simulated Seawater.

Abstract

In the circulating water system of coastal power plants, various kinds of ions have a great influence on the formation and growth of CaCO₃ scales. This paper focuses on investigating the influence of existing ions on the pulse electrodeposition behaviors of CaCO₃ scales. Different concentrations of ions, such as Fe³⁺, Mg²⁺, PO₄^3- and SiO₃^2-, are introduced to simulate the actual seawater environment, and their influence on the CaCO₃ scale deposition behaviors is assessed by linear sweep voltammetry, chronoamperometry, and electrochemical impedance spectroscopy tests. The surface coverage of the CaCO₃ scale layer is evaluated through the residual current density and polarization resistance values, while the crystal structure and surface compactness of the layer are confirmed by the scanning electron microscope and X-ray diffractometer tests. Results indicate that high concentrations of Mg²⁺, Fe³⁺, and PO₄^3- ions have the most significant inhibitory effect on the pulse electrodeposition of CaCO₃ scales, among which the inhibition effect of Mg²⁺ ions is mainly reflected in the change of crystal morphology of CaCO₃, that is, the crystallization growth process is inhibited. The inhibition effect of PO₄^3- ions is mainly reflected in the gradually reduced coverage and density of CaCO₃ crystals on the electrode surface, suggesting that the crystallization nucleation process is inhibited, while Fe³⁺ ions have a certain inhibition effect on both the crystallization nucleation and growth processes. Furthermore, lower concentrations of SiO₃^2- ions also display a significant inhibition effect on the crystallization nucleation and growth process, and the inhibition effect weakens with increased concentration. This study provides a theoretical basis for exploring the removal of ions in the industrial water softening field.