Molecular dynamics simulation of the interaction between polyaspartic acid and calcium carbonate

Abstract

Polyaspartic acid (PASP) has important roles in scale decentralisation, scale inhibition and corrosion inhibition. Investigation on the microscopic interaction between PASP and calcium carbonate (CaCO₃) will be helpful for understanding its scale inhibition mechanism and can provide a theoretical guidance to developing new scale inhibitors. In this study, molecular dynamics simulations have been performed to simulate the interaction between the different configurations (α, β and hybrid α+β) of PASP and the (1 0 4) and () surfaces of CaCO₃ crystal in water. The results show that PASP can effectively prevent the growth of CaCO₃ scale. On the same surface of CaCO₃, the binding energy of various configurations of PASP has the order of α-PASP>α+β-PASP>β-PASP. On the different surfaces of CaCO₃, the binding energy of all configurations is greater on the () face than on the (1 0 4) face. The binding energies are mainly contributed from the coulomb interaction (including ionic bonds). All configurations deform in combination with CaCO₃ and the maximum deformation appears for α-PASP, whereas all deformation energies are much smaller than the non-bonding energies in magnitudes. van der Waals interactions are conducive to the stability of the system. The radial distribution function of O(α-PASP)–H(H₂O) implies that the solvent has effects on the anti-scale performance of PASP to CaCO₃. Water molecules cannot be ignored when the interaction models are constructed.

Keywords:

• polyaspartic acid
• calcium carbonate
• molecular dynamics
• binding energy
• radial distribution function

Acknowledgements

This work is financially supported by the National Natural Science Foundation of China (Grant no. 41101287) and the Priority Academic Program Development of Jiangsu Higher Education Institutions.