Formation and Inhibition of Calcium Carbonate Crystals under Cathodic Polarization Conditions

Kun Sheng,Yanfang Song,Yi Zhang,Yuzeng Zhao,Xin Huang,Honghua Ge,Xinjing Meng,Fang Ge

doi:10.3390/cryst10040275

Kun Sheng, Yanfang Song + Show 6 more

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https://doi.org/10.3390/cryst10040275

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Journal: Crystals	Publication Date: Apr 6, 2020
Citations: 16	License type: CC BY 4.0

Affiliation: Shanghai University of Electric Power

Abstract

The formation of CaCO3 crystals on the cathode surface and the scale-inhibition performance of scale inhibitor 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) on the cathode surface were studied by methods of solution analysis, gravimetric analysis, SEM, FTIR, and XRD techniques. They were then compared with the results of the formation and suppression of CaCO3 crystals in aqueous solution. PBTCA had a good solution-scale-inhibition performance and good lattice-distortion effects on CaCO3 crystals in solution, which could change the CaCO3 from calcite to vaterite and aragonite crystals. The solution-scale-inhibition efficiency exceeded 97% when the PBTCA concentration reached 8 mg/L. Under cathodic polarization conditions, the surface-scale-inhibition efficiency of the cathode and solution-scale-inhibition efficiency near the cathode surface both exceed 97% at polarization potential of −1V. The addition of PBTCA significantly reduced the amount of CaCO3 crystals formed on the cathode surface and had good surface and solution-scale-inhibition effect. However, the lattice-distortion effect of PBTCA on CaCO3 crystals disappeared on the cathode surface, and the resulting CaCO3 contained only calcite crystals. The high-scale-inhibition effect of PBTCA under cathodic polarization was mainly due to the inhibition of the formation of calcium carbonate crystals by PBTCA, and not because of the lattice distortion of CaCO3 crystals.

Highlights

The scaling phenomenon is common in industrial production processes, such as circulating cooling water systems, oil field facilities, and pipe flow systems [1,2,3]
PBTCA had strong solution-scale-inhibition and lattice-distortion effects on the CaCO3 crystals generated in the scaling solution
When the PBTCA concentration reached 8 mg/L, the solution-scale-inhibition efficiency exceeded 97%, and the solution-scale-inhibition efficiency increases with the increase of PBTCA concentration

Summary

Introduction

The scaling phenomenon is common in industrial production processes, such as circulating cooling water systems, oil field facilities, and pipe flow systems [1,2,3]. The scale-forming substances are apt to appear on heat-exchange surfaces. As the solubility of most scale-forming substances such as. CaCO3 decreases with increasing temperature, it is easy for scale-forming substances to form on heat exchange surfaces which have higher temperatures [4]. When a piece of electrocatalytic oxidation equipment is used to degrade organic pollutants, such as printing and dyeing wastewater, petroleum, and chemical wastewater [5,6], the pH value of solution near the cathode surface would increase due to the hydrogen evolution reaction at the cathode [7], causing the precipitation of insoluble substances, such as calcium salt, on the surface of the cathode. The nature of scaling is usually the precipitation, adhesion, and film formation of inorganic salt crystals on the solid surfaces. The scaling on the heat-exchange surfaces causes a decrease in heat-exchange efficiency and an increase in the energy consumption of the system [8,9].

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