Amine-coated nanobubbles-assisted flotation of fine and coarse quartz

Abstract

This study investigates the role of alkyl ether monoamine-coated nanobubbles (NBs) in assisting the flotation process of quartz across various particle sizes, on a bench scale. Experiments were conducted in a mini lab column utilizing a consortium of bubble sizes: D32 = 1200 μm for macrobubbles and D32 = 180–220 nm for amine-coated NBs. The study revealed that an increase in amine-coated NBs correlates well with a decrease in the air/solution’s interfacial tension caused by the ether amine at less than 68 mN m⁻¹. True flotation recoveries with varying amine/g quartz, where the collector-frother amine may be amine-coated NBs alone or assisted by NBs generated in pure water, were compared with blank tests, in the absence of NBs. The flotation study evaluated size-to-size fractions from fine (−20 µm) to coarse (up to 150 µm) particles and their mixtures. In addition, the work extended to explore the behavior of the “super” coarse quartz from 150 µm up to 1000 µm. The results highlighted a clear dependence on the particle size, with NBs improving recoveries in all fractions, especially the difficult-to-treat ultrafine/fine and coarse quartz. Recovery results exceeded 90 % in all fractions (isolated or in mixtures) at a high rate with the amine-coated NBs. The mechanisms proposed improved flotation performance attributed to the high numerical concentrations of NBs (at least 2–3 × 10¹⁰ NBs per gram of quartz) rapidly attaching to quartz surfaces, serving as “seeds” for the adhesion of larger bubbles generated in conventional flotation cells. This interaction facilitates the formation of lightweight, cluster-like aggregates that swiftly rise to the column’s surface. Notably, larger quartz particles (+355 µm) form the bigger hydrophobic and buoyant clusters, leading to their rapid levitation and effective phase separation, with over 95 % separation efficiency. This innovative technique’s significance, outcomes, and potential scalability are thoroughly discussed, highlighting its promising applicability in diverse mineral and ore flotation systems, particularly those containing quartz and silicates.