article · Minerals Engineering
Recovering rare earth element minerals such as monazite from complex, low-grade ores is often hampered by fine clay gangue minerals like kaolinite, which dilute concentrate grades during flotation. Laboratory microflotation experiments and surface characterisation techniques examined the separation of monazite from kaolinite using sodium oleate as a collector. Monazite demonstrated high floatability across pH values from 5 to 9, while kaolinite exhibited a consistently lower flotation response. At pH 9, sodium oleate chemically bonds to monazite surfaces via hydroxylated rare earth ions and surface metaphosphate components. In contrast, interactions between sodium oleate and kaolinite remain marginal or negligible. These distinct surface behaviours indicate that kaolinite is unlikely to report to the concentrate via true flotation under these alkaline conditions, confirming that sodium oleate can selectively separate monazite from kaolinite.
Rare earth elements are vital for modern technologies, but extracting them from low-grade deposits is difficult because fine clay minerals dilute the final product. Understanding the exact surface chemistry that allows collectors to bind to monazite while leaving clay gangue behind helps mineral processors design more efficient, targeted separation methods for challenging ores.
The findings are relevant to mineral processing engineers and mining operations treating complex rare earth ores containing problematic clay gangue. The work clarifies specific pulp pH settings and collector chemistry to improve concentrate grades. Based on the abstract, the research is at an early, laboratory stage, relying on microflotation and surface spectroscopy rather than pilot or full-scale industrial trials.
AI-generated from the published abstract. Always read the original work before citing.
Recently, the flotation of major rare earth elements (REE) minerals including bastnasite, monazite, and xenotime has been attracting high level of attention. However, there are numerous challenges associated with achieving selective recovery of REE minerals from different gangue minerals. Paramount among the challenges is the abundance of fine clay and silicate gangue minerals in complex low grade REE bearing ores. These gangue minerals are usually recovered along with REE minerals, which can result in concentrate grade dilution. In this study, laboratory microflotation tests, coupled with physicochemical characterization techniques including zeta potential and X-ray photoelectron spectroscopy (XPS) analyses were conducted on monazite and kaolinite using sodium oleate as a collector. Microflotation experiments established that the floatability of monazite is high at pH 5–9, where kaolinite had lower flotation response. Complementary zeta potential and XPS measurements revealed that at pH 9, sodium oleate adsorbs onto monazite surfaces via hydroxylated REE ions and the adsorbed oleate contributes oxygen atoms to the metaphosphate components on monazite surfaces, leading to the chemical bonding between oleate and monazite surfaces, whiles there was marginal/negligible interaction between oleate and kaolinite. The findings from this study demonstrate distinct differences in the flotation characteristics of monazite and kaolinite. The selective adsorption of oleate ions onto monazite surface was responsible for the distinct flotation response identified at alkaline pulp pH conditions. The learnings from this work indicate that kaolinite is not likely to be recovered via true flotation, at the conditions applied in this study, thus monazite can be separated from kaolinite when using sodium oleate as a collector.
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DOI: 10.1016/j.mineng.2024.108605
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