Effect of frictional grinding on ore characteristics and selectivity of magnetic separation

Frictional grinding was evaluated to improve the selectivity of two magnetite samples A and B in the magnetic separation process. Sample A containing 64.42% Fe was a magnetite concentrate upgraded from a low grade magnetite Ore, Sample B, containing 46.63% Fe, through an upgrading process involving 1-stage ball milling and 3-stage wet magnetic separation in a beneficiation plant. Frictional grinding was found extremely efficient in dispersing the grains in the agglomerates and on the surface, consequently improving the selectivity of the sample. A magnetite concentrate containing 66.22% Fe was produced from Sample A at an iron recovery of 96.86% by introducing a simple dry frictional grinding step prior to the magnetic separation process. The results have demonstrated that Sample A can be further upgraded even though it was processed through 3-stage magnetic separation. Given its beneficial effects, frictional grinding was further adopted in a multiple-stage flowsheet to upgrade both Samples A and B. A magnetite concentrate containing 68.75% Fe was produced from Sample A at an iron recovery of 97.23% through the multiple-stage wet frictional grinding-magnetic separation flowsheet. When the same flowsheet was applied to process Sample B, a concentrate of 69.97% Fe, higher than Sample A obtained by ball milling, was produced at an iron recovery of 86.44%.