Synthesis of modified polyaspartic acid and evaluation of its scale inhibition and dispersion capacity

• A new scale inhibitor and dispersing agent, modified polyaspartic acid (Ser-PASP), was synthesized.
• Inhibition efficiency is close to 100% against CaCO3 when the dosage is 4 mg/L.
• It achieves complete inhibition effect on CaSO4 scale when the dosage is 5 mg/L.
• When Ser-PASP was added, the scale crystals became irregular.

Polyaspartic acid (PASP) is an environmentally friendly scaling inhibitor. In order to enhance the performance of its scale inhibition and dispersion capacity, PASP is commonly modified with side chain functional groups via polysuccinimide (PSI) ring-opened. In this work, environmentally friendly serine was selected as ring-opened agent to prepare modified polyaspartic acid—Ser-PASP. The synthesized polymer was characterized by infrared spectrometry (FTIR) and 1H NMR. The performance of Ser-PASP on the inhibition of CaCO3, CaSO4 and Ca3(PO4)2 and its dispersion ability on Fe2O3 were also studied. The results show that the inhibition efficiency of Ser-PASP is close to 100% for CaCO3 with 4 mg/L inhibitor, and reach up to 100% for Ca3(PO4)2 with 22 mg/L inhibitor. The best dispersion efficiency for ferric oxide is 70.4% when Ser-PASP is 25 mg/L. Ser-PASP and PASP have similar inhibition performance against CaSO4. The effects on the formation of CaCO3 and CaSO4 were investigated by scanning electronic microscopy (SEM) and X-ray powder diffraction (XRD), respectively.