Molecular Dynamics Simulation on Scale Inhibition Mechanism of Polyepoxysuccinic Acid to Calcium Sulphate

Molecular dynamics simulation has been performed to simulate the interaction between PESA and the (001) face of anhydrite crystal CaSO₄ at different temperatures with the presence of various number of H₂O molecules. The results show that PESA can effectively prevent the growth of CaSO₄ scale at 323-343 K. At the same temperature, the binding energy between PESA and the (001) face of CaSO₄ for systems with various number of H₂O has the order of E_bind(0H₂O)>E_bind(200-400H₂O)>E_bind(100H₂O). For the same system at different temperatures the binding energies are close and are mainly contributed from the Coulomb interaction, including ionic bonds. The bonds are formed between the calcium atoms of anhydrite scale crystal and the oxygen atoms of the carboxyl group of PESA. Hydrogen bonds are formed between the O atoms of the carboxyl group of PESA and the H atoms of H2O. van der Waals interaction is conducive to the stability of the system of PESA, H₂O, and CaSO₄. The radial distribution functions of O(carbonyl of PESA)-H(H₂O),O(CaSO₄)-H(H₂O), and O(CaSO₄)-H(PESA) imply that solvents have effects on the anti-scale performance of PESA to CaSO₄.