Tin-bearing tailings generated during cassiterite processing often still contain valuable metal. Because cassiterite is brittle, grinding during ore beneficiation can produce very fine particles that are difficult to recover using conventional gravity or flotation methods, allowing tin to be lost to tailings streams.
Researchers from Kunming University of Science and Technology have proposed a new integrated process designed to recover both tin and iron from these materials. The study examined tailings containing around 0.20% tin and 21.08% iron, where cassiterite occurs alongside iron-bearing minerals such as hematite and limonite.
The first stage uses staged centrifugal–magnetic separation to pre-concentrate tin- and iron-bearing minerals while discarding low-value gangue. This step recovered around 89.6% of the tin while removing approximately 31% of the total tailings mass, significantly reducing the material requiring further processing.
The pre-concentrated material is then treated using simultaneous volatilisation and magnetic roasting, followed by magnetic separation. Under controlled reducing conditions, cassiterite is reduced to tin monoxide (SnO), which volatilises at high temperature, while iron oxides are converted into magnetite (Fe₃O₄), enabling magnetic separation of iron from the roasting products.
Using this integrated approach, the researchers achieved a tin volatilisation ratio of 91.3% and an overall tin recovery of 81.8%, while also producing iron concentrates with grades above 62% Fe.
By discarding gangue and separating iron before energy-intensive roasting, the process reduces processing energy demand and associated CO₂ emissions. Early separation of iron from tin is also beneficial for downstream tin metallurgy as during conventional cassiterite smelting, carbon reduces tin oxide to metallic tin, but iron may also be partially reduced due to the similar oxygen affinities of the two metals.
As demand for tin continues to grow across electronics, renewable energy technologies and emerging battery applications, technologies that enable improved recovery from tailings could help improve resource efficiency and support future supply. Visit Tin Valley to learn more.
