Evaluation of a novel non-ionic graft starch-based antiscalant in reduction of CaSO4 scaling by static and reverse osmosis test

Abstract

A novel nonionic starch-based antiscalant (St-g-GMA) was designed and obtained by graft copolymerization of starch and glycidyl methacrylate (GMA). St-g-GMA not only achieved an obvious reduction of CaSO4 scaling in static test, but also effectively mitigated the flux decrease in dynamic reverse osmosis (RO) system. This improvement is ascribed to the grafted poly(GMA) chains on St-g-GMA. A suitable grafting ratio of this starch-based antiscalant achieve a high performance cost in control of CaSO4 scaling. Combination of the apparent antiscaling performance, observation under scanning electron microscopy, energy dispersive x-ray spectroscopy unit, x-ray diffraction pattern, conductivity measurement, and dispersion experiment, the scale-inhibition mechanism of St-g-GMA was investigated and mainly attributed to chelation, dispersion and lattice distortion effects. The oxygen-containing groups on poly(GMA) chains such as epoxy groups can chelate with Ca2+, causing the induction time of crystallization prolonged; St-g-GMA with the distinct branched chain configuration can well disperse the formed microcrystal of CaSO4. Moreover, molecular dynamics simulations confirmed that the grafted poly(GMA) chains well bind to the crystal surfaces and the oxygen-containing groups could even enter the crystal lattice to inhibit the crystal growth and change the morphologies. St-g-GMA still mitigated the flux decrease notably in treatment of a synthetic seawater during a 24-h RO measurement. This study provided an efficient, environmentally-friendly and low-cost antiscalant with high application potentials.