The limitations of flotation technique in processing complex Um Nar BIF: exploring sustainable alternatives

Abstract Iron is essential for industry and the economy. It is used in construction, transport, and manufacturing. However, its extraction remains challenging due to geological complexity. Iron ore is tightly interlocked with silica, which limits the efficiency of conventional beneficiation methods. This study investigated the upgrading of the Um Nar Banded Iron Formation using froth flotation, including micro-scale tube and column flotation. Both anionic and cationic reverse flotation routes were explored. It was found that using anionic reverse flotation is more effective than cationic reverse flotation for upgrading the Um Nar Banded Iron Formation (BIF). Under optimal conditions (i.e. collector type: oleic acid, dosage: 1 kg t −1 ; calcium oxide dosage: 0.25 kg t −1 (as activator); pH 11; and starch dosage: 0.75 kg t −1 (as depressant)), a concentrate with 58 % total Fe grade, 71 % total Fe recovery, and 10.75 % SiO 2 was produced at superficial air flow rate of 2.00 cm s −1 , which was attributed to the intricate mineralogy of the ore. To overcome the limits of flotation, the study used reduction roasting with biomass sawdust as a green reductant. After roasting, a low-intensity wet magnetic separation was applied. This two-step process yielded improved results, achieving a Fe grade of 59.55 %, a Fe recovery of 78 % and a SiO 2 content of 5 % in the concentrate, rendering it suitable for processing complex iron ores.