Separating Cassiterite from Quartz with New Collector 3-(Dodecylthio) Propionic Acid

Tin, which is primarily extracted from cassiterite, finds extensive applications across various domains. Although compared with gravity separation, flotation offers a broader operational flexibility, commonly used collectors struggle to achieve an optimal balance between selectivity and collectability. In this study, a new collector 3-(dodecylthio) propionic acid (3-DTP) with high selectivity enhanced the separation of cassiterite and quartz. Flotation experiments confirmed that 3-DTP could achieve separation efficaciously across a broad pH range and could withstand the impact of unavoidable ions. With a collector concentration of 40 mg/L at pH 6, artificial mixed-minerals experiments of cassiterite yielded a concentrate with SnO₂ grade and recovery of 97.38% and 87.61%, respectively. To further elucidate the adsorption mechanism, contact-angle measurement, zeta potential analysis, FT-IR spectroscopy, XPS analysis, and ToF-SIMS analysis were employed. These analyses revealed that 3-DTP could interact with both quartz and cassiterite. The 3-DTP adsorbed on the surface of quartz through weak hydrogen bonds. However, the amount of 3-DTP adsorbed onto quartz was too low to make the surface hydrophobic. Therefore, their recovery remained poor. Conversely, the S site and the O site of 3-DTP interacted with the Sn site of cassiterite by forming chemical bonds and formed stable adsorption by generating a six-membered ring structure. The chemical reaction was vigorous, which made the surface of cassiterite hydrophobic. Thus, cassiterite achieved a high recovery. Different adsorption behaviors of 3-DTP on the two minerals enable selective separation of cassiterite from quartz.