Tunable amylopectin graft copolymers for flocculating and dewatering iron ore tailings

Abstract

Polyacrylamide (PAM), the standard flocculant for mining tailings, often produces turbid supernatants and poorly dewatered sediments, limiting water reuse and tailings densification. We synthesized amylopectin-graft-poly[(2-methacryloyloxy)ethyl]trimethylammonium chloride (AP-g-PMETAC) copolymers with systematically varied graft frequency (N = 0.83–6.67 per 1000 anhydroglucose units) and graft length (L = 20–80). Their flocculation performance was tested on iron-ore tailings suspensions at pH 10. Higher graft frequencies and longer grafts improved clarification and settling at lower dosages, reducing supernatant turbidity to 12.7 NTU and accelerating settling. However, excessively long, hydrophilic METAC grafts hindered sediment dewatering. Compared to commercial PAM, AP-g-PMETAC required lower dosages, produced denser flocs, and shortened capillary suction times (down to 10.1 s). These results establish AP-g-PMETAC as a tunable and more sustainable alternative to PAM for tailings treatment, where graft frequency and length can be tailored to balance clarity, settling, and dewatering.