A novel and efficient CaCO3 scale inhibitor in high‐temperature and high‐salinity geothermal systems: A deprotonated quadripolymer

Scale inhibitors are effective in preventing CaCO3 scaling in geothermal systems, but the scale inhibition performance and price of commercial scale inhibitors in high‐temperature and high‐salinity water are still not ideal. In this work, a novel modified carboxymethylated β‐cyclodextrin tetrameric (CAAS) scale inhibitor was synthesized using carboxymethylated β‐cyclodextrin, acrylic acid, 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS), and p‐styrenesulfonate (SSS) by free radical polymerization, and deprotonated CAAS (D‐CAAS) was prepared based on CAAS. The results of the static test showed that the CaCO3 scale inhibition efficiency of D‐CAAS reached 90.8% at 100°C and 800 mg/L Ca2+. Compared with that of previous commercial scale inhibitors, the scale inhibition efficiency of D‐CAAS was increased by 13.5%, and the price can be decreased by 26.1%. The results of SEM, XRD and molecular dynamics (MD) simulation showed that at 100°C–120°C, the deprotonation of D‐CAAS enhanced the weak interaction between D‐CAAS and CaCO3, inducing the transformation between calcite and vaterite and forming a loose scale. Deprotonation weakens the hydrogen bond between D‐CAAS and water to reduce the energy required for the binding of D‐CAAS to the surface of CaCO3. This study is expected to provide a low‐cost and high‐efficiency CaCO3 scale inhibitor for geothermal applications.