Synthesis of polyaspartic acid–aminobenzenesulfonic acid grafted copolymer and its scale inhibition performance and dispersion capacity

Polysuccinimide (abridged as PSI) was synthesized by urea and maleic anhydride. Aminobenzenesulfonic acid (ABSA) was introduced at different mole ratio to PSI to generate polyaspartic acid (abridged as PASP)/ABSA graft copolymer. The scale inhibition behavior of resultant PASP/ABSA copolymer was evaluated by using static scale inhibition method. The transmittance of the supernatant of the copolymer solution was measured to evaluate its dispersion ability for ferric oxide. The corrosion inhibition performance of the copolymer for iron plates immersed in the refined testing water (including 0.555 g of CaCl2·2H2O, 0.493 g of MgSO4·7H2O, 50 mg PASP/ABSA graft copolymer and 0.168 g of NaCl) was tested. It was found that PASP/ABSA copolymer was able to efficiently inhibit CaCO3 and Ca3(PO4)2 scales and had good corrosion inhibition ability as well, and it also had good dispersion ability for Fe2O3. Besides, the inhibition efficiency of PASP/ABSA against CaCO3 and Ca3(PO4)2 scales and its dispersion capacity for Fe2O3 was highly dependent on dosage. The reason may lie in that PASP/ABSA copolymer simultaneously possesses carboxylic ion and sulfonic group which can chelate Ca2+ to form stabilized and dissoluble chelates, resulting in increase of solubility of calcium salts in water. Also it may lie in that the introduction of acidic hydrophilic sulfonic group with a strong electrolytic capacity into PASP molecule simultaneously enhances the dispersion of the inhibitor molecules and hinders the formation of Ca3(PO4)2 scale.