An antiscalant with chelating residues of amino acid glycine

Cyclopolymerization of diallylammonioethanoate [(H₂C[dbnd]CH[sbnd]CH₂)₂NH⁺CH₂CO₂⁻] afforded polyzwitterion (PZ) PZ-3800, PZ-4600 and PZ-6150 having respective M¯_n of 3800, 4600, and 6150 g mol⁻¹ in excellent yields. The PZs having residues of amino acid glycine were examined as antiscalant. PZ-4600 in the respective concentration and temperature ranges 1–20 ppm and 40–80 °C, effectively mitigated the scale formation from a supersaturated CaSO₄ solution. Antiscalant efficacies were found to increase in the order: PZ-6150 < PZ-4600 < PZ-3800. At a 2.5 ppm concentration, PZ-3800, −4600, and −6150 were shown to impart percent scale inhibition (PSI) of ≈ 100% up to 180, 60, and 30 min, respectively. At 1 ppm concentration, PZ-3800 and -4600 demonstrated respective induction times (after which the scale formation starts to occur) of 80 and 60 min with a PSI value of 99% up to 60 and 30 min, respectively. The inexpensive antiscalant has the potential in mitigating scale formation during the usual residence time (15 min) of the reject brine in an osmosis chamber. The smaller size PZ-3-3800 is found to be the most efficient in disrupting the crystal growth of CaSO₄.