Selective Flotation Of Scheelite Research Articles

Application of a Superplasticizer in Scheelite Selective Flotation from Calcite

The superplasticizer sulfonated acetone formaldehyde condensate (SAF) was first used as a depressant in the selective flotation of scheelite and calcite in this paper. First, single mineral flotation tests were performed to compare the depressing performance of SAF and the traditional depressant water glass. Results showed that both −0.074 + 0.037 mm and −0.037 mm particles could be well treated by SAF with more satisfactory results than that of water glass. Contact angle test results showed that SAF could amplify the wettability difference between scheelite and calcite surfaces. Then, the effect of SAF on the surface electrical properties of scheelite and calcite was studied by zeta-potential tests. SAF could negatively charge the calcite surface before adding the collector and hinder the subsequent adsorption of the collector while having little effect on the scheelite. Moreover, microscopic analysis of slurry suspensions showed that SAF could prevent calcite particles from forming hydrophobic agglomerates to achieve the dispersion of gangue minerals. Finally, the selective adsorption effect of the SAF on the calcite and scheelite surfaces was studied by surface analysis using FTIR (Fourier transform infrared) and XPS (X-ray photoelectron spectroscopy). Results showed that Ca2+ on the calcite surface was the main adsorption site for the chemisorption of sulfonic acid groups in SAF.

Unraveling roles of lead ions in selective flotation of scheelite and fluorite from atomic force microscopy and first-principles calculations

Metal ions are widely used to achieve selective hydrophobization of different mineral particles. However, the atomic understanding of the roles of metal ions is insufficient due to the limitation of experimental techniques. Herein, the in-situ atomic force microscopy (AFM) force curves and first-principles calculations were combined with the conventional experiments [i.e., batch flotation, zeta potential tests, and X-ray photoelectron spectroscopy (XPS)] to investigate the roles of lead ions (Pb2+) in flotation separation of scheelite and fluorite. The conventional experiments showed that Pb2+ could enhance the flotation recovery of scheelite but suppress fluorite. AFM force curves showed that, due to the presence of Pb2+, the interaction force between benzohydroxamic acid (BHA) and the scheelite surface was a stronger adhesion than the adhesion between BHA and fluorite without lead ions. First-principles calculations revealed that the strong electrostatic attraction resulted in the adsorption of BHA on fluorite surfaces. However, BHA could hardly bond with the scheelite surface with negative charges and hydroxylated Ca sites. The reaction between BHA and Pb2+ was the most favorable. The formed BHA-Pb complexes demonstrated repulsive interactions on fluorite surfaces but attractions on scheelite surfaces. Lead ions played as an inhibitor for fluorite flotation and an on-off switch for scheelite flotation. AFM and first-principles calculations have shown great potential in the analysis of the complicated interface interactions.

Selective flotation of scheelite from calcite using a novel self-assembled collector

Both being Ca-bearing minerals, scheelite and calcite cannot be well separated by froth flotation due to their similar surface properties. To date, there is no report that scheelite and calcite can be well separated using collectors alone (including traditional NaOL and selective Pb-BHA complexes). Therefore, in this study, Pb(NO3)2, benzohydroxamic acid, and sodium oleate with specific combination (Pb-BHA-NaOL) were firstly used to form a novel collector to selectively separate scheelite and calcite. The flotation results of single and binary mixed minerals showed that the mixture of Pb, BHA and NaOL (molar ratio 6:6:1) exhibited excellent separation selectivity for scheelite and calcite at pH 9.0. Zeta potential measurements indicated that the dominant species of Pb-BHA-NaOL were positively charged and had stronger adsorption on negatively charged scheelite surfaces. Infrared spectroscopy and X-ray photoelectron spectroscopy further showed that Pb-BHA-NaOL had strong chemical interaction with Ca sites in the form of Pb(OH)-BHA-OL−, especially with O sites in the form of Pb-BHA+ on scheelite, but had no interaction with O sites on calcite. Therefore, the novel collector proposed in this work can provide a meaningful guide for the design of other novel collectors and have potential application prospects in scheelite flotation.

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.

Effects of Ferrous Sulfate Addition on the Selective Flotation of Scheelite over Calcite and Fluorite

The addition of ferrous sulfate as a depressant for Ca-bearing minerals such as calcite and fluorite during scheelite flotation was investigated to recover scheelite from tungsten mine tailings, using Hallimond-tube flotation tests, zeta-potential measurement and Fourier-transform infrared (FT-IR) analyses. The flotation tests indicate that the selectivity of scheelite recovery was the largest over calcite and fluorite under the following conditions: 0.5 g sample, 50 g/ton AF65, 1 × 10−3 M sodium oleate, 1200 g/ton SF2 (sodium silicate and ferrous sulfate) depressant with the 8:2 ratio of sodium silicate and ferrous sulfate, 50 mL/min air injection rate, 5 min flotation time, and pH 8. The selectivity of scheelite flotation increased when the amount of SF2 depressant addition increased to 1200 g/ton, but it decreased by adding 1400 g/ton SF2, which would result from the precipitation of iron components. In the zeta potential results, the zeta potentials of scheelite with the collector show similar results regardless of the addition of SF2, while the change of zeta potentials of calcite and fluorite by adding NaO collector diminished when SF2 was added. In FT-IR analyses, the spectrum of NaO in scheelite results was observed regardless of the addition of SF2, while the spectra of NaO in calcite and fluorite results disappeared when SF2 was added. These results suggest that the addition of SF2 prevents the adsorption of NaO on the surface of calcite and fluorite. Therefore, the addition of SF2 could enhance the selectivity of scheelite flotation over calcite and fluorite.

Selective Flotation of Scheelite from Calcite Using a Novel Reagent Scheme

ABSTRACT Scheelite and calcite are usually intergrown calcium minerals that are separated via froth flotation. However, their selective separation remains difficult because of their similar surface properties. 2-phosphonobutane −1, 2, 4-tricarboxylic acid (PBTCA or H5L) is widely used in water treatment due to its low phosphorus content and efficient anti-scaling performance. With its excellent calcium-chelating ability, PBTCA was used as a novel depressant to selectively separate scheelite from calcite in this study. The flotation results of single mineral, binary mixed minerals, and real ore showed that PBTCA could selectively depress calcite at pH 9.0 using sodium oleate as collector. The results of zeta potential measurements, solution chemistry calculation, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculation indicated that the dominant form of PBTCA was L5-. This anion had a stronger adsorption on negatively charged calcite surfaces through electrostatic interaction. Higher Ca density and stronger Ca activity on calcite promote the adsorption of L5-. Moreover, the active O atoms in L5- could better match with two Ca sites on calcite in the interatom distance. Thus, PBTCA provides a new option for calcite depressants and has great industrial application potential.

Acidified water glass in the selective flotation of scheelite from calcite, part II: species in solution and related mechanism of the depressant

Acidified water glass in the selective flotation of scheelite from calcite, part II: species in solution and related mechanism of the depressant

Acidified water glass in the selective flotation of scheelite from calcite, Part I: performance and impact of the acid type

Acidified water glass in the selective flotation of scheelite from calcite, Part I: performance and impact of the acid type

Investigation of the depressants involved in the selective flotation of scheelite from apatite, fluorite, and calcium silicates: Focus on the sodium silicate/sodium carbonate system

Flotation tests were performed on a skarn ore to attain the selective separation of scheelite (CaWO4) from fluorite, apatite, and silicates. Fluorite and apatite constitute common gangue minerals in scheelite ores. Due to their similar surface properties and good floatability, the separation of scheelite from fluorite is particularly difficult. These ores are usually processed at basic pH using sodium silicate as a gangue mineral depressant and a fatty acid as the collector. Sodium silicate was not efficient enough to depress the fluorite in the studied ore. Thus, different depressants were tested in the flotation of scheelite using a commercial mixture of fatty acids. The effect of adding metallic salts [FeSO4, Al(NO3)3, and Zn(SO4)] prior to sodium silicate was therefore investigated. The sole use of organic molecules (starch, lignin sulfonate, tannin, carboxymethyl cellulose, and citric acid), instead of sodium silicate, was also studied. This led to a global depression of the minerals, including scheelite, and did not improve the selectivity of the separation. The addition of metallic cations did not significantly enhance the selectivity of the flotation; however, iron sulphate slightly increased the sodium silicate performance. Overall, among all the studied depressants, the combination of sodium carbonate and sodium silicate presented the best efficiency. This system was then studied through the design of experiments methodology. Strong synergistic effects existed between the two reagents, mainly impacting the scheelite and fluorite recovery as well as the scheelite grade. This was attributed to surface carbonation of the minerals, subsequently leading to a better depression by sodium silicate. The effect of sodium carbonate on the apatite and silicates was small. This was attributed to spontaneous carbonation and the presence of complex crystallographic structures, respectively. The efficiency of the sodium carbonate/sodium silicate combination was limited (maximum WO3 enrichment ratio = 16.48) due to the lack of selectivity of the depressants. The proposed optimization of the flotation separation of scheelite from gangue minerals maximizes both the WO3 grade and recovery.

Selective flotation of scheelite from calcite using xanthan gum as depressant

Xanthan gum (XG), a clean, non-toxic macromolecular polysaccharide, was studied as a depressant in the flotation separation of scheelite from calcite. Its selective inhibition mechanism was investigated by adsorption experiments, fourier transform infrared spectroscopy (FTIR) analysis and X-ray photoelectron spectroscopy (XPS) analysis. It was found that the XG exhibited a strong selective depressive effect on calcite. However, XG had minimal effect on the flotation recovery of scheelite. Adsorption experiments indicated that the adsorption density of XG on the surface of calcite was much higher than that of scheelite. FTIR results indicated that XG was selectively chemisorbed on calcite surface, while sodium oleate (NaOL) can still be chemisorbed on scheelite surface in the presence of depressant XG. XPS results indicated that the carboxyl groups (COO−) of the XG can be chemically chelated with the calcium ions species on calcite surface. It was intuitively observed by atomic force microscopy (AFM) that the coverage and adsorption density of XG on calcite surface were higher than that of the scheelite surface. As such, the calcite surface adsorbed more depressant XG than that of scheelite, which hindered the further adsorption of the collector NaOL. This greatly deteriorated the flotation of calcite and achieved flotation separation between the two minerals.

Selective flotation of scheelite from calcite using Al-Na2SiO3 polymer as depressant and Pb-BHA complexes as collector

In previous studies, by regulating the Pb/BHA ratio and pH, lead complexes of benzohydroxamic acid (Pb-BHA) have been proven to be selective for the separation of scheelite from calcium minerals. In this study, sodium silicate (Na2SiO3) and Al-Na2SiO3 polymer were used as depressants for the further separation of scheelite from calcite. Flotation results indicated that both scheelite and calcite were depressed by Na2SiO3, while Al-Na2SiO3 polymer gave good selectivity. The depressing ability of Na2SiO3 for calcite was significantly improved due to the formation of some Al-Na2SiO3 species with aluminum ions, while the reverse was true for scheelite. Zeta potential results indicated that both colloidal Na2SiO3 and Al-Na2SiO3 particles were negatively charged and difficult to adsorb on the negative scheelite surface through electrostatic attraction, especially for Al-Na2SiO3. X-ray photoelectron spectroscopy analysis results showed that the Al-Na2SiO3 adsorbed amount on the scheelite surface was less than the Na2SiO3 adsorbed amount, while the reverse was true on the calcite surface. Binding energy analysis results indicated that calcium cations of scheelite and calcite surfaces could bond to oxygen atoms of Na2SiO3/Al-Na2SiO3 through chemisorption. However, compared with Na2SiO3, Al-Na2SiO3 showed weaker chemisorption on the scheelite surface, but adsorbed more powerfully onto the calcite surface. Therefore, Al-Na2SiO3 showed excellent selectivity for scheelite and calcite, which has been successfully applied at the Shizhuyuan mine.

Selective flotation of scheelite from calcite using calcium lignosulphonate as depressant

In this work, calcium lignosulphonate (CLS) was introduced as a novel flotation depressant for separation of scheelite from calcite. Sodium oleate (NaOl) acted as collector for scheelite. The flotation results showed that CLS had strong depressant effect on calcite flotation while exhibited little influence on scheelite flotation. Scheelite can be separated efficiently from scheelite-calcite mixed binary minerals in pH range of 7–11, when CLS was added prior to NaOl. The selective depressant effect of CLS on calcite was analyzed through interactions between the CLS micelles and mineral particles at water/particle interface.

Effect of depressants in the selective flotation of scheelite and calcite using oxidized paraffin soap as collector

Calcite, in most cases, is the major gangue mineral found in scheelite ores. It is difficult to separate scheelite and calcite due to the similarities in their formation properties. In this study, it was found that scheelite and calcite can be floated using fatty-acid collector oxidized paraffin soap in the pH regions of 8–11 and 6–12, respectively. The effects of sodium hexametaphosphate (SHMP), tanning extract, starch and acidified water glass (AWG) as depressants of calcite have been studied. The AWG was the appropriate depressant without imposing obvious adverse effects on scheelite flotation. In order to prove the validity of the findings, flotation of both mixed mineral (1:1 scheelite:calcite) and real ore were conducted as well as zeta potential measurements.

Selective flotation of scheelite from calcite: A novel reagent scheme

Sodium oleate (NaOl) has been widely used as a collector for the scheelite flotation. However, low selectivity of NaOl and large amount of sodium silicate (SS) needed remain tough problems. In this study, octyl hydroxamic acid (HXMA-8) was used as an associate collector with NaOl in scheelite flotation. The flotation tests showed that a novel reagent scheme, i.e., a lower dosage of SS (300mg/L) and mixed collectors of HXMA-8+NaOl (total concentration 4.5×10−4mol/L, preferred mass ratio of 1:2) achieved the selective separation of scheelite from calcite. Zeta potential measurements indicated that the depressant, SS, adsorbed more strongly on calcite surface than on scheelite surface. HXMA-8 adsorbed significantly on scheelite surface either in the absence or presence of SS by chemical bonding between oxygens of HXMA-8 and surface metal ions. NaOl also adsorbed on both mineral surfaces by chemisorption, but the adsorption on calcite surface was influenced adversely by the presence of SS.

Selective flotation of scheelite from calcite and fluorite using a collector mixture

Collector 733, a sodium soap (C12–16COONa) is widely used industrially for scheelite flotation. Low selectivity of 733 collector is always observed. In this study, a collector mixture of 733 and MES (sodium fatty acid methyl ester sulfonate) demonstrated a high selectivity for the flotation of scheelite from calcite and fluorite. An optimal mass ratio 4:1 of 733:MES was found, producing a 65.76% WO3 concentrate grade with a recovery of 66.04% from a feed material containing only 0.57% WO3. In addition, the effect of water hardness and water glass addition were studied. The results indicated that the presence of Ca2+ or Mg2+ had little effect on the adsorption of the collector mixture at the scheelite surface. Addition of water glass for depressing calcite and fluorite had no significant effect on the adsorption of the collector mixture on the scheelite surface. The advantages of this new collector mixture (733+MES) include lower cost, low dosage, high tolerance against water hardness and high selectivity, and this collector mixture has great potential for industrial application.

Selective flotation of scheelite from calcium minerals with sodium oleate as a collector and phosphates as modifiers. II. The mechanism of the interaction between phosphate modifiers and minerals

The respective effects of phosphate modifiers on the solubility of calcium minerals in water, on the surface charge of the minerals and on the adsorption of the phosphates and of sodium oleate on the mineral surface were examined. The Auger spectra and the infrared spectra of the minerals treated with these reagents were also investigated. The ability of the phosphates to complex metal ions was determined by nephelometric titration. The structures of the minerals and their effects on their floatability, as well as structures of the phosphates and their effects on the complexation power were discussed. A mechanism of depression of the calcium minerals through the selective complexing dissolution of calcium ions from the mineral surface was derived and explains the higher selectivity obtained in scheelite flotation when (NaPO 3) 6 or Na 4P 2O 7 are used as modifiers.