Kinetic mechanisms of organophosphine compounds on calcium carbonate crystal growth: Cruising effect and Spatial matching

Calcium carbonate (CaCO₃) is a common mineral in industrial water systems. Organophosphate is a widely used scale inhibitor with 100% inhibition of thousands of mg/L of calcium (Ca²⁺) ions at concentrations below 10 mg/L. However, chelating agent EDTA is hundreds of times more effective in achieving the same inhibitory effect. Our study explored the significant difference in CaCO₃ growth inhibition by these compounds. Through experiments combining molecular dynamics simulations and quantum chemical calculations, we have found that organophosphines dynamically capture and release Ca²⁺ ions, enhancing the solubility of Ca²⁺ ions and impeding CaCO₃ growth through a mechanism known as the “cruising effect”. Simultaneously, the lattice distortion induced by “spatial matching” was employed to inhibit the growth of CaCO₃. On the other hand, chelating agents exhibited robust coordination forces, particularly with ligand atoms (O and N), showcasing superior chemometric characteristics. These findings illuminated the distinct mechanisms of CaCO₃ growth inhibition.