Vanadium-bearing shale beneficiation pre-enrichment: Selective flotation separation of garnet and quartz in an acidic environment using a dodecylamine–sodium fluosilicate system

Abstract

Preconcentration of vanadium-bearing shale via the flotation separation of aluminosilicate minerals, such as garnet, from quartz is a promising approach to meet the growing demand for vanadium. However, several issues, including poor selectivity, must be addressed and the separation mechanism should be elucidated. In this study, a flotation system for selectively separating garnet from quartz under acidic conditions was developed. The use of dodecylamine as the collector and sodium fluorosilicate as the depressant yielded satisfactory technical performance. Additionally, the mechanism by which dodecylamine captures garnet and sodium fluorosilicate inhibits quartz was investigated through microflotation experiments, zeta potential measurements, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). At pH 3 with 5.6 × 10⁻⁴ mol/L dodecylamine and 8.4 × 10⁻⁴ mol/L sodium fluorosilicate, microflotation experiments achieved a garnet recovery rate of 90.62 %, whereas that of quartz was only 0.6 %, resulting in effective separation of these minerals. As the pH of the slurry decreased, the zeta potential of quartz tended to become more positive, which hindered the adsorption of the collector, cationic dodecylamine, on the quartz surface. The XPS results indicated that at pH = 3, the binding of dodecylamine to the potential at the Fe2p_1/2 site of garnet was promoted, resulting in enhanced floatability of the garnet. Furthermore, sodium fluorosilicate competed with dodecylamine for the Si–OH groups on the surface of quartz, resulting in reduced floatability.