A novel and efficient CaCO 3 scale inhibitor in high‐temperature and high‐salinity geothermal systems: A deprotonated quadripolymer

Scale inhibitors are effective in preventing CaCO 3 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 CaCO 3 scale inhibition efficiency of D‐CAAS reached 90.8% at 100°C and 800 mg/L Ca 2+ . 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 CaCO 3 , 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 CaCO 3 . This study is expected to provide a low‐cost and high‐efficiency CaCO 3 scale inhibitor for geothermal applications.