Nanobubble-enhanced flotation of copper slag: Effects of grinding, frother type, and collector dosage on recovery and concentrate grade

Copper slag is a byproduct of pyrometallurgical copper extraction and contains usable copper (0.5–3%). Conventional flotation separation often involves a wide array of flotation reagents, often resulting in poor product grade and recovery. This work demonstrates how nanobubbles augment the flotation recovery of valuable copper at notably reduced collector dosages. The slag materials were adequately characterized to identify copper-bearing oxide and sulfide phases. Based on this, a series of microflotation tests was designed and performed in a Hallimond tube. A 30-minute grinding period was identified as ideal, balancing mineral liberation and ultrafine particle formation. It was observed that nanobubbles boosted copper recovery by up to 18% and improved the concentrate grade to ∼12% Cu, twice that of traditional flotation. Most importantly, using nanobubbles yielded a maximum measured recovery of approximately 74% and an estimated ∼38% overall collector reagent reduction at comparable recovery under the 25–75 g/t collector dosage range while simultaneously improving recovery and grade, demonstrating a real reduction in reagent consumption. The cationic frother CTAB achieved greater recovery, whereas the nonionic frother terpineol resulted in better concentrate grades. The results show that nanobubbles- assisted flotation is a viable and reagent-efficient approach for sustained copper recovery from low-grade slag systems.