Results
The iron product contained 92.30 wt% iron. Recovery was 93.96% from the pre-concentrate, equivalent to 78.79% from the original tailings. Mortar containing the 20% residue/80% slag admixture reached 33.11 MPa at seven days and 50 MPa at 28 days.
How it was tested
Qidashan tailings were pre-concentrated magnetically. The selected roast used 1,250°C for 50 minutes and a pre-concentrate:coal:lime:sodium-carbonate ratio of 100:17.5:12.5:7.5. Silica-rich residue from pre-concentration was ground with slag for 30 minutes and tested in mortar. The mortar used 225 g cement, 225 g composite admixture, 1,350 g sand and 225 g water: the admixture replaced half of the cement by mass.
Study limits
The authors state that the combined effects of sodium carbonate, lime and other factors on iron recovery were not investigated. The reported settings came from single-factor tests.
Authors’ recommendations
The authors favour 20% residue for admixture performance, while suggesting 30% may suit greater residue use. They say strength and flow should be considered together when choosing the proportion.
Original sources
Chang Tang; Keqing Li; Wen Ni; Duncheng Fan (2019). Recovering Iron from Iron Ore Tailings and Preparing Concrete Composite Admixtures.