Flotation Of Rare Earth Minerals Research Articles

Understanding the role of water quality in separation of rare earth minerals from iron oxide minerals in a flotation circuit

In many mineral processing plants, using saline water has become necessary to improve water efficiency. However, the dissolved ions in the water such as Ca2+ and Mg2+ may have a significant negative impact on the flotation of RE (rare earth) minerals due to the chemical reaction with flotation reagents used in RE flotation. Although some researchers investigated flotation performance of pure rare earth minerals, there is no study investigating the role of water quality in the separation of rare earth minerals from iron oxide minerals in a flotation circuit. This study focused on investigating the effect of divalent cations like Ca2+ and Mg2+ on the flotation of RE minerals using a fatty acid collector and Na2SiO3 depressant. The results showed that the presence of Ca2+ and Mg2+ decreased the selectivity and recovery of RE minerals due to the formation of insoluble calcium and magnesium carboxylate, leading to the reduced residual collector concentration. Furthermore, the divalent cations acted as a bridge between the oxygen atoms of the adsorbed SiO32− and carboxylate ions, resulting in increased adsorption of fatty acid collector ions and higher recovery of FeO. Rheological measurements also revealed that the presence of Ca2+ and Mg2+ significantly increased the flotation pulp viscosity, which could be attributed to the reduced repulsive forces between particles due to the compression of electrical double layer. This study provides valuable insights into the mechanisms underlying the effects of Ca2+ and Mg2+ on RE mineral flotation.

Rheological properties of rare earth minerals flotation pulp in the presence of anions

Water quality has been found to significantly influence the flotation operations due to the alteration of surface properties of minerals. The effect of cations on the flotation of RE minerals has been studied, however, there are still very limited information regarding the effect of anions. The present study examined the impact of specific anions such as Cl−, SO42−, and HCO3− on the flotation performance of rare earth (RE) ore. This study integrates flotation experiments, rheology measurements, entrainment experiments, zeta potential measurements and settling experiments. It is observed that an increase in the concentration of these anions lead to a decrease in the recovery of RE minerals and an increase in the recovery of FeO minerals and thus negatively affecting flotation efficiency. This adverse effect is most pronounced with Cl− and least noticeable with HCO3−. An increase in the non-selective entrainment of gangue minerals is observed when the flotation pulp has higher viscosity. The reduction in the zeta potential of fine particles in the presence of these results in a higher pulp viscosity due to increased attractive forces between particles. These findings were verified by settling experiments and calculations based on the DLVO theory.

Activation mechanisms of apatite by purifying reagent polyacrylamide for backwater from mineral processing in flotation of rare earths

This study revealed activation mechanisms of apatite by polyacrylamide (PAM) during flotation of rare earth minerals in Bayan Obo Ore. This activation leads to high phosphorus content in rare earth concentrate. Ultraviolet (UV) absorption measurements show that adsorption of PAM on the surfaces of apatite and rare earths follows a pseudo-second-order reaction kinetic model. The isothermal adsorption process follows the Freundlich adsorption model, indicating that the adsorption of PAM on apatite is a multi-layer, non-uniform process, that is, physical and chemical adsorption occurs simultaneously. The measured zeta potential shows that under weakly alkaline conditions, amide groups with a negative charge are adsorbed on the surface of apatite, increasing the electronegativity, so that the potential is shifted negatively; however, the negative shift of the potential on the surface of rare earths is insignificant. Fourier transform infrared (FT-IR) test and X-ray photoelectron spectroscopy (XPS) results imply that PAM is chemically adsorbed on the surface of apatite, while 506E undergoes stronger chemical adsorption than PAM on the surface of rare earth minerals. It is found that multi-layer, non-uniform adsorption of PAM combining physical and chemical adsorption occurs on the surface of apatite and the process is dominated by physical adsorption: the adsorption of PAM on surfaces of apatite is stronger than that on the surface of rare earth minerals. Such adsorption activates the apatite, causing it to float during the flotation of rare earths, which is the reason for the high phosphorus content in the rare earth concentrate.

Effect of dissolved fluorite and barite species on the flotation and adsorption behavior of bastnaesite

The flotation of rare earth minerals, which is of current interest in the mineral processing field, is challenging owing to the dissolution of gangue minerals. In this study, dissolved fluorite and barite species were found to significantly affect the flotation behavior of bastnaesite. The mechanism was investigated using microflotation tests, zeta potential measurements, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and solution chemistry analysis. The microflotation results confirmed that the presence of gangue supernatants significantly reduces the recovery of bastnaesite during flotation with sodium oleate as a collector. The zeta potential and solution chemistry analyses showed that the supernatant species can adsorb onto the bastnaesite surface by forming hydroxy and carbonate compounds, thus affecting the zeta potential value and reducing the adsorption of oleate species. The FTIR analysis suggested that treatment with supernatants weakens the adsorption of oleate species, and that Ca/Ba-oleate complexes are adsorbed on the bastnaesite surface. The XPS analysis confirmed that lattice ions from the gangue minerals adsorb/precipitate on the bastnaesite surface, hindering the chemisorption of oleate species and thus decreasing the floatability of bastnaesite.

The effect of dissolved mineral species on bastnäsite, monazite and dolomite flotation using benzohydroxamate collector

Flotation is the most commonly used beneficiation method for rare earth (RE) ores. Due to the dissolution characteristics of the RE minerals and the gangue minerals, they may behave similarly in a flotation system. Previous work has shown that dissolved mineral species from gangue could precipitate/adsorb at the mineral surface affecting the minerals’ flotation behavior. In this work, the effect of dolomite supernatant on the surface of bastnäsite, monazite and dolomite are presented. Zeta potential measurements, complemented with flotation tests, were conducted with and without the presence of the supernatant using benzohydroxamate as the collector. XPS results confirmed the surface speciation, and DFT simulations detail the possible mineral - collector, mineral - precipitated species and precipitated species - collector interactions. The results show that carbonate precipitates and Ca2+ from the supernatant could adsorb onto the mineral surface through covalent bonding, both affecting the zeta potential and reducing collector adsorption. Another important finding of this study is the potential loss of the collector in the solution due to complexation with ions from the supernatant. These findings confirm that an effective rare earth mineral separation through flotation does not rely solely on the strength of collector-mineral interaction, but rather is highly dependent on the chemistry of the flotation solution. Taking advantage of, or controlling, the surface reactions should be the main target to developing a more efficient and cost-effective flotation process. Different measures have been proposed to reverse/reduce the detrimental effects of the dolomite supernatant to RE mineral flotation.

Explaining surface interactions for common associated gangues of rare earth minerals in response to the oxalic acid

In the flotation of rare earth minerals (REMs), oxalic acid is reportedly acting both as a depressant and pH modifier. Although results of testing have established the significance of oxalic acid in the flotation process, its specific role in either the recovery or selectivity of REMs over their common gangue minerals is not well understood. Pulp pH reduction trials with alternative acids have not shown the same effect on the REMs recovery or the depression of gangue phases. This work studies the effect of oxalic acid on the surface of common REMs gangue minerals (quartz and carbonates (dolomite and calcite)) in a series of conditioning tests. Gangue surface analyses by time of flight secondary ion mass spectroscopy (TOF-SIMS) indicate that oxalic acid inhibits the transfer of secondary ions generated during the conditioning process from one mineral to another. In this regard, the oxalate anion acts to fix ions in solution through chelation, limiting their participation in surface adsorption.

Ionic-liquid collectors for rare-earth minerals flotation⿿Case of tetrabutylammonium bis(2-ethylhexyl)-phosphate for monazite and bastnäsite recovery

Application of tetrabutylammonium bis(2-ethylhexyl)-phosphate ([N4444][DEHP]), a room temperature ionic liquid (IL), as an aqueous collector for flotation of model monazite and bastnäsite minerals was investigated through micro-flotation tests, zeta potential measurements, Fourier Transform Infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The ionic liquid was shown to have superior performance to float both model rare-earth (RE) minerals as compared with calcite, dolomite and quartz minerals as typical gangue minerals. Parallel to this, micro-flotation tests of a rare-earth ore containing bastnäsite and monazite minerals were found in line with [N4444][DEHP] stronger collecting power towards RE model minerals even outperforming hydroxamic acid-containing collectors. With regard to the mineral surface chemistry, zeta potential measurements, FTIR characterization and XPS analysis, it was established that [N4444][DEHP] uptake on bastnäsite and monazite surfaces was via chemisorption involving specifically the PO and PO groups of the IL anionic moiety. IL anionic and cationic interactions during RE mineral flotation were rationalized in terms of an inner synergistic pathway: IL anionic moiety chemisorbing on bastnäsite and monazite surfaces prompting uptake of cationic moiety via electrostatic attraction and/or via hydrophobic chain interactions of the cation alkyl chains with the chemisorbed IL anionic layer. Finally, for calcite as the most responsive among gangue minerals, the characterization techniques divulged the weaker IL-surface interactions. Hence, this investigation opens up new prospects for more selective ionic-liquid collectors to be used in the flotation of RE minerals.

A review of rare earth minerals flotation: Monazite and xenotime

This paper reviews rare earth minerals (monazite and xenotime) separation by flotation. A wide range of monazite and xenotime flotation test results are summarized including: reasons of variation in the point of zero charges on these minerals, the effects of various flotation conditions on zeta potential of monazite and xenotime, interactions of collectors and depressants on the surface of these minerals during flotation separation, relationship between surface chemistry of the minerals and different types of collector adsorptions and effects of the conditioning temperature on flotation of rare earth minerals. This review collects various approaches for the selective separation of monazite and xenotime by flotation and gives perspectives for further research in the future.

最近の中国における希土類鉱物の優先浮選に関する研究

最近の中国における希土類鉱物の優先浮選に関する研究