Flotation separation of limonite from calcite with sodium oleate: effects of calcite dissolution and addition of sodium pyrophosphate

摘要

Limonite is now considered as an important iron ore resource in China due to the rapidly depleting magnetite and haematite reserves. The separation of limonite from calcite by flotation is a problem to be solved, and it was investigated systematically in this paper. Flotation tests show that the recoveries of limonite and calcite are close to 95% within the pH range of 7.5-10.0 using 3 x 10~(-4) mol/L sodium oleate as collector. However, the flotation of limonite was depressed by calcium ions generated from the dissolution of calcite in the flotation of a mixture of limonite and calcite. The effects of depression on limonite can be enhanced by adding sodium pyrophosphate. Hence, the separation of calcite from limonite can be finished by reverse flotation. Under the test condition, the limonite-calcite mixture with Fe grade of 28.45% was upgraded to a concentrate with 50.5% Fe and 91.50% Fe recovery.