Tailored Multiarm Block Polymer via RAFT Polymerization: Dual Role of Cationic Micelles in Flocculation and Selective Flotation of Quartz

Abstract

The efficient processing of fine mineral particles remains a major challenge in the minerals beneficiation industry, primarily due to poor particle settling and low flotation recovery, which result from their limited attachment to air bubbles during froth flotation. In this study, a 4-arm star block polymer p(MeO2MA-co-OEGMA)-b-qDMAEMA (4A-MOQ) was designed and subsequently synthesized via RAFT polymerization and investigated for its dual role in quartz flocculation and selective flotation. The polymer consists of a poly(ethylene glycol)-based segment and a cationic quaternized DMAEMA block, enabling strong interactions with negatively charged quartz surfaces. Owing to its amphiphilic structure, the multiarm polymer self-assembled into cationic micelles in aqueous solutions, with the critical micelle concentration (CMC) of around 6.8 mg/L and a hydrodynamic diameter of approximately 60 nm. Adsorption studies using total organic carbon (TOC) analysis confirmed the adsorption of polymer onto the quartz surface, while ζ-potential measurements revealed effective charge neutralization. Turbidity analysis and settling tests were carried out to demonstrate the effective flocculation performance of the polymer within the dosage range of 0.4–0.8 mg/g, while the in situ particle and aggregate size analysis using a BlazeMetrics probe further confirmed the increase in chord lengths following the addition of the polymer. In reverse flotation experiments, the multiarm polymer acted as an effective collector for quartz over a broad range of pH while maintaining low recovery for hematite, demonstrating pronounced selectivity toward quartz and achieving approximately 80% recovery and 84% quartz grade, with hematite recovery below 20%. The enhanced flotation recovery of quartz was attributed to the adsorption of cationic polymer on the mineral surface, improving the hydrophobicity of the mineral to promote particle-bubble attachment. Overall, this work highlights the scope of controlled polymer architectures as dual-functional reagents, providing opportunities for the design of advanced materials in mineral processing.