Xanthate-functional temperature-responsive polymers as selective flocculants and collectors for fines recovery

Abstract

A novel method to improve the recovery of fines in the flotation process involving the use of a temperature-responsive copolymer poly(N-isopropyl acrylamide-co-ethyl xanthate methacrylate) (PNEXMA) incorporating poly(N-isopropyl acrylamide) (PNIPAM) and xanthate functionality has been investigated. Above a lower critical solution temperature (LCST), the polymer functions as both a collector and flocculant, forming hydrophobic aggregates of the valuable fines that are amenable to beneficiation by flotation. The viability of using PNEXMA for the flotation of sulfide fines has been evaluated based on initial screening with adsorption, contact angle and aggregation studies followed by flotation tests. The studies were conducted at both temperatures below and above the LCST, and the results were compared with an industrial collector, potassium amyl xanthate (PAX). Adsorption isotherms indicate a strong polymer affinity for chalcopyrite surfaces. The quartz contact angles were found to remain relatively hydrophilic and unchanged in the presence of the PNEXMA and PAX, while the chalcopyrite surface turned hydrophobic with contact angles above 60°, comparable to PAX. Temperature-responsive reversible flocculation was also observed with the polymer on chalcopyrite, while no response was found with PAX or with quartz. Flotation studies with chalcopyrite confirmed that PNEXMA is able to act as a selective collector, with performances on par with PAX. However, no recovery improvement over PAX was observed in the −20μm fines fraction, which was attributed to the use of fully-liberated synthetic feed in the current work resulting in high fines recoveries with PAX not usually found in actual ground mineral ores.