Improving the grades of fine-grained magnetite concentrates by combining sulfide and silicate flotation

The practical experience of processing fine-grained magnetite ores shows that silicon dioxide and sulfur are the main impurities in iron ore concentrates negatively affecting the concentrate grade. Reverse flotation is the most effective method for improving concentrate grade, as it efficiently extracts gangue minerals into the froth product. Using magnetite concentrates obtained from ore at one of the Arctic Zone deposits in Northwestern Russia as an example, this study explores the potential to enhance their grades through flotation methods. The majority of the concentrate samples studied consisted of material sized at 92–93 % of the –0.05 mm class. Optimal conditions for sulfide and silicate flotation have been established. It has been demonstrated that sulfide flotation using xanthate as the collector is most effective at natural pH values, without the addition of pH regulators. Higher silicate recovery is observed when using cationic collectors at pH 9.4–10.0. Sulfide flotation followed by silicate flotation on two iron ore concentrate samples, initially containing 69.7 % and 68.5 % iron, produced high-grade concentrates with iron content ranging from 70.2 % to 70.6 %. The iron losses to tailings under the optimal conditions were 11.3 % (for sample K-1) and 8.5 % (for sample K-2). In order to reduce iron losses, it is advisableto include cleaner flotation of the silicate product at pH 9.2–9.4 using sodium oxalate as a depressant of iron-containing minerals. The resulting products can be returned for additional processing, thereby reducing iron losses to tailings.