Enhanced high-gradient magnetic separation of copper-bearing limonite using elliptical magnetic matrix: Structural optimization and mechanism analysis

This study designed and fabricated elliptical magnetic matrix with various structural parameters to achieve enrichment and separation of copper-bearing limonite. Compared with the conventional cylindrical magnetic matrix, the use of an elliptical magnetic matrix in roughing increased iron recovery by 2 %∼3% and improved iron grade by 1 %∼2%. Under a magnetic field of 0.6 T, with a major axis length of 3.2 mm, a rod gap of 2.4 mm, and horizontal alignment of the major axis, a magnetic concentrate with 54.29 % Fe grade and 63.11 % recovery was obtained. Product characterization revealed that elliptical magnetic matrix exhibited superior efficiency in recovering fine-grained minerals. Under high-gradient magnetic fields, strongly magnetic iron minerals were preferentially captured into the magnetic concentrate, with approximately 50 % of the copper co-enriched due to its strong association with iron phases. Magnetic field characteristics analysis showed that increasing the major axis length enhanced the edge magnetic gradients but reduced the effective capture area. Compared with the short-axis horizontal alignment, the long-axis horizontal alignment produced stronger magnetic induction, while larger gaps weakened magnetic coupling and decreased field strength. An optimized “one-stage roughing, one-stage scavenging” process achieved 48.12 % Fe grade, 2.09 % Cu grade, 92.34 % Fe recovery, and 75.48 % Cu recovery at field strengths of 0.6 T (roughing) and 1.0 T (scavenging). Magnetic tailings can be directly leached for copper, while the concentrate can be further processed via hydrogen-based mineral phase transformation. This work provides theoretical and technical support for the magnetic separation of complex oxidized copper ores.