Scale-inhibition and flocculation dual-functionality of poly(acrylic acid) grafted starch

Abstract

Natural-polymer based water treatment agents have recently received much more attention due to their environmental friendliness, widespread availability, and prominent structural features. Starch-graft-poly(acrylic acid) (St-g-PAA) is a simple natural-polymer based material that can be obtained easily by a one-step graft copolymerization. When used as a water treatment agent, St-g-PAA exhibits both effective scale-inhibition performance and high turbidity removal efficiency. The scale-inhibition efficiency of St-g-PAA against calcium carbonate (CaCO3) is approximately 94% at the optimal dose in a static test of approximately 40 mg/L. Dispersion, crystal lattice distortion, and chelating effects all play important roles in the scale inhibition. When St-g-PAA is used as a coagulant aid for polyaluminum chloride (PAC) in the flocculation of a real hairwork wastewater, the highest reduction of the optimal PAC dose is more than 30% while the turbidity reduction is about 97% at the same time, both floc size and compactness increase, and the final settling efficiency also improves evidently. The efficient bridging flocculation effects account for the effective turbidity removal. The prominent scale-inhibition and flocculation dual-functionality of St-g-PAA is intrinsically ascribed to its distinct anionic linear branched-chain structure.