A novel mixed depressant for the flotation separation of scheelite and cassiterite: Adsorption mechanism and performance

Citric acid (CA) exhibits weak inhibitory on some oxidized gangue minerals owing to its relatively few hydrophilic polar groups ( OH and COOH). This study investigate the synergistic mechanism of ferrous ions (Fe 2+ ) to enhance both the selective adsorption capacity and stability of CA. The separation of scheelite and cassiterite through a flotation process was successfully achieved using a Fe 2+ /CA mixed depressant. Micro-flotation test results revealed that with the addition of Fe 2+ /CA, 84.60 % of scheelite and 23.64 % of cassiterite were recovered in the foam concentrate, with grades of 66.26 % and 17.73 %, respectively. Fe 2+ /CA had a strong depressing effect on cassiterite, resulting in a 69.30 % decrease in its recovery and a 20.33 % decrease in its grade. This indicates the effective separation of scheelite from cassiterite. Fe 2+ /CA exhibited a high adsorption affinity for the cassiterite surface, which mainly comprised L 3– , Fe 2+ , and FeOH + components. Additionally, the FeOH + complex, formed from the pre-reaction between Fe 2+ and CA, exhibited significant chemical adsorption at the Sn active sites, thereby depressing cassiterite. The high-intensity adsorption peaks at cracks and the significant increase in the normalized intensity of FeOH + on the cassiterite surface indicated that the FeOH + complex had stronger adsorption on cassiterite and selectively depressed cassiterite. This enhanced both the selective adsorption capacity and stability of CA on the cassiterite surface. The Fe 2+ /CA mixed depressant achieved efficient flotation separation of scheelite and cassiterite.