Separation Of Scheelite Research Articles

Study of the Effect of Manganese Ion Addition Points on the Separation of Scheelite and Calcite by Sodium Silicate.

The flotation separation (FS) of both scheelite and calcite minerals with similar physicochemical properties remains challenging, since the Ca active sites exist on their surfaces. The present work investigated the effects of different addition points of MnCl2 on the FS of scheelite and calcite by micro-flotation tests, zeta potential measurements, UV-Vis spectrophotometer measurements, infrared spectrum analysis, and X-ray photoelectron spectroscopy (XPS) tests, and the mechanism of separation is elucidated. Interestingly, the recovery of scheelite was 91.33% and that of calcite was 8.49% when MnCl2 was added after sodium silicate. Compared with the addition of MnCl2 before Na2SiO3, the recovery of scheelite was 64.94% and that of calcite was 6.64%. The sequence of adding MnCl2 followed by Na2SiO3 leads to the non-selective adsorption of Mn2+ on the surface of scheelite and calcite firstly, and later, sodium silicate will interact with it to produce hydrophilic silicate. This substantially enhances the hydrophilicity on the surface of both minerals, making separation impossible. In contrast, the addition of MnCl2 after sodium silicate can promote the formation of a metal silicate and enhance the selectivity and inhibition effect on calcite. Meanwhile, under this dosing sequence, the adsorption of Mn2+ on the scheelite surface offered more active sites for sodium oleate, which improved the scheelite surface hydrophobicity. This leads to a great improvement of the FS effect of scheelite and calcite.

New insights into the depressive mechanism of citric acid in the selective flotation of scheelite from fluorite

The effects of citric acid (CA) as a depressant in the separation of scheelite and fluorite were evaluated by microflotation test. The underlying selective separation mechanism was revealed via wetting analysis, Fourier transform infrared (FTIR) spectroscopy, thermodynamic calculations, adsorption amount tests, inductively coupled plasma–optical emission spectroscopy (ICP–OES) and atomic force microscopy (AFM). Microflotation tests showed that CA strongly depressed the flotation of fluorite but not of scheelite. Artificial mixed mineral separation tests showed that scheelite and fluorite achieved a good flotation separation effect in the presence of CA as the depressant. Mineral surface wettability analyses and adsorption amount tests indicated that CA was more strongly adsorbed onto the surface of fluorite than onto the surface of scheelite. FTIR spectroscopy proved that CA had a strong chemical adsorption on fluorite surface. Thermodynamic calculations indicated that CA could spontaneously form the organic complex CaL− on the surface of fluorite but not on the surface of scheelite. ICP–OES revealed that a strong dissolution behaviour occurred on the surface of fluorite that caused more calcium ions to dissolve into the slurry, thereby decreasing the number of adsorption sites of calcium ions on the surface of fluorite. AFM intuitively confirmed the intense adsorption and the strong dissolution behaviour of CA on the surface of fluorite.

A novel metal–organic complex surfactant for high-efficiency mineral flotation

The separation of scheelite from other calcium-containing minerals via flotation is problematic because of their similar surface properties and response to conventional anionic collectors. Herein, we report, to the best of our knowledge, a new type of metal–organic complex collector prepared via self-assembly of benzohydroxamic acid (BHA) ligands and Pb(II). A new Pb(II) complex [Pb6L8(NO3)3]NO3 (HL = BHA) is synthesized using coordination reactions and structurally characterized using single-crystal X-ray diffraction. Further, its flotation behavior and adsorption mechanism at the solid–liquid–gas interface were investigated via flotation experiments, zeta potential, XPS, TOF–SIMS, AFM, SFG-VS, adsorption capacity, froth-stability testing, etc. The results show that the developed complex exhibited good collecting ability and absolute specificity for scheelite. The complex was chemically adsorbed on the scheelite surface by combining the lead functional group and oxygen atoms of scheelite to form multilayer adsorbents, rendering the scheelite particle surface strongly hydrophobic. The complex collector and frother assembly are co-adsorbed at the gas–liquid interface, which significantly reduced the solution surface tension, forming a stable foam layer. Therefore, selective flotation was achieved through the targeted adsorption at interfaces. A simplified flotation process for scheelite using complex collector has been successfully applied in industry, significantly improving the recovery of scheelite. This high selectivity makes metal–organic complex a novel and promising collector for high-efficiency mineral flotation and contributes to the efficient and clean development of mineral resources.

The Challenge of Tungsten Skarn Processing by Froth Flotation: A Review.

Recently, tungsten has drawn worldwide attention considering its high supply risk and economic importance in the modern society. Skarns represent one of the most important types of tungsten deposits in terms of reserves. They contain fine-grained scheelite (CaWO4) associated with complex gangue minerals, i.e., minerals that display similar properties, particularly surface properties, compared to scheelite. Consistently, the froth flotation of scheelite still remains, in the twenty first century, a strong scientific, industrial, and technical challenge. Various reagents suitable for scheelite flotation (collectors and depressants, mostly) are reviewed in the present work, with a strong focus on the separation of scheelite from calcium salts, namely, fluorite, apatite, and calcite, which generally represent significant amounts in tungsten skarns. Albeit some reagents allow increasing significantly the selectivity regarding a mineral, most reagents fail in providing a good global selectivity in favor of scheelite. Overall, the greenest, most efficient, and cheapest method for scheelite flotation is to use fatty acids as collectors with sodium silicate as depressant, although this solution suffers from a crucial lack of selectivity regarding the above-mentioned calcium salts. Therefore, the use of reagent combinations, commonly displaying synergistic effects, is highly recommended to achieve a selective flotation of scheelite from the calcium salts as well as from calcium silicates.

Interaction forces between scheelite and fluorite in calcium solution measured by atomic force microscopy

The effect of calcium ions on the separation of scheelite from fluorite was studied using atomic force microscopy (AFM) measurement, X-ray photoelectron spectroscopy (XPS) analysis and micro-flotation experiment. The XPS results confirmed the adsorption of calcium on scheelite and fluorite surface, and adsorption difference existed between calcium solution and gypsum solution. According to the AFM results, the adhesion forces between scheelite and fluorite would increase in the presence of calcium, so did the corresponding jump-in distance and separation distance. Besides, jump-in distance and separation distance in calcium solution were larger than those in gypsum solution. When using sodium silicate as depressant, the adhesion forces between scheelite and fluorite decreased observably, while regained in the presence of calcium ions. Micro-flotation results confirmed the depression of calcium on scheelite and fluorite. Besides, both scheelite and fluorite were depressed strongly by sodium silicate in the presence of calcium. These indicated that the adsorption of CaOH+ would increase their hydrophilicity and enhance the interaction forces. Meanwhile, the selectivity of sodium silicate was depressed in the presence of calcium ions. The combined results could help to understand how calcium-mineral surface properties would cause the difficult separation.

Impact of calcium and gypsum on separation of scheelite from fluorite using sodium silicate as depressant

The impact of calcium and gypsum on separation of scheelite from fluorite using sodium silicate as depressant was investigated by micro-flotation tests, X-ray photoelectron spectroscopy (XPS), zeta potential measurements and solution chemical analysis. The flotation results confirmed that sodium silicate exhibited certain selective inhibition on fluorite. According to the XPS results, silicate could adsorb on fluorite surface, but not on scheeltie in DI water. When treated in calcium solution and gypsum saturated solution, silicate could adsorb on both mineral surfaces. Zeta potential results showed that sodium silicate could shift the fluorite zeta potential obviously, while reduce the scheelite zeta potential a little in DI water. The similar change law of scheelite and fluorite zeta potential could be obtained in the presence of calcium ion, which was mainly contributed to the adsorption of calcium silicate formed in solution. The presence of calcium ion in solution would decrease the selectivity of sodium silicate, and obviously inhibit the floatability of scheelite and fluorite. The inhibition exists varying degrees of difference in gypsum saturated solution.

Study on comparison adsorption of calcium and sulfate on scheelite and fluorite surfaces

ABSTRACTThis study investigated the adsorption of calcium and gypsum on scheelite and fluorite using micro-flotation, X-ray photoelectron spectroscopy, scanning electron microscope with energy-dispersive spectrometer, and zeta potential measurements. Micro-flotation showed scheelite recovery is more sensitive to calcium, and gypsum shows stronger inhibition than calcium. Stick-shape precipitates as sulfate-bearing are only found on fluorite surface in gypsum solution. Change law of the zeta potentials of scheelite and fluorite in gypsum solution is obviously different from that in calcium solution. Therefore, we concluded that gypsum would make the separation of scheelite from fluorite more difficult than calcium.

Utilization of pyrogallol in flotation separation of scheelite from calcite

ABSTRACT Scheelite is a typical tungsten-containing mineral and usually co-exists with calcite in deposits. The flotation separation of scheelite from calcite is a hard work in mineral processing. In this paper, pyrogallol, a by-product of humic acid decomposition was utilized as a depressant in flotation separation of scheelite from calcite. Flotation tests on singe mineral and mixed binary mineral were conducted. The results show that using pyrogallol as depressant can realize the flotation separation of scheelite from calcite by controlling pulp pH in 7.0–8.5. Zeta potential measurements and FTIR studies were performed to define the depression mechanism of pyrogallol on calcite. The results show that the pyrogallol depresses calcite flotation through complex adsorption and H bond adsorption on calcite surface.