Preparation and scale inhibition performance of modified polyaspartic acid (M-PASP)

Modified polyaspartic acid (M-PASP) was synthesized by modifying ammonia- polysuccinimide (ammonia-PSI) through a ring-opening reaction using a modifier derived from ethylenediamine, maleic anhydride, and NaOH. In addition to M-PASP, conventional polyaspartic acid (PASP) was also synthesized for comparison. The structure of conventional PASP and M-PASP were characterized by FT-IR and 1H NMR. The influence of raw materials ratio, reaction temperature and reaction time on the intrinsic viscosity of M-PASP were investigated in detail. The static scale inhibition method was used to evaluate the scale inhibition performance. The results showed that M-PASP exhibited significantly superior scale inhibition performance against CaCO3 compared to conventional PASP. Additionally, it was observed that the scale inhibition rate of M-PASP on CaCO3 increased with increasing intrinsic viscosity. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to examine the surface morphology and structure of CaCO3 crystals, respectively. The results revealed that the addition of M-PASP led to a reduction in the grain size of CaCO3 crystals and disruption of their surface morphology. In addition, molecular dynamics (MD) simulation was utilized to analyze the interaction mechanism between the polymers and calcium carbonate crystals. Based on the findings, it was postulated that the scale inhibition mechanism of M-PASP against CaCO3 involves a comprehensive interplay of several factors, including chelation solubilization, dispersion aggregation and lattice distortion.