Fluorite Flotation Research Articles

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.

Utilization of Citric Acid to Improve the Depressive Efficiency of Sodium Silicate on the Flotation of Calcite and Fluorite

Utilization of Citric Acid to Improve the Depressive Efficiency of Sodium Silicate on the Flotation of Calcite and Fluorite

The Effect of Oleic Acid Emulsification using SPE on Fluorite and Dolomite Flotation.

Collector OA, oleic acid, is widely used industrially for fluorite flotation. Low selectivity, dispersibility and collecting capability of the OA collector are always observed. In this study, compared with flotation of dolomite, a collector mixture of OA and SPE (styrylphenol polyoxyethylene ether) demonstrated significantly better performances for the fluorite. An optimal mass ratio 4 : 1 OA : SPE was found, and the recovery of fluorite was increased from over 85 % to more than 94 % compared with pure OA. Furthermore, the dosage of the collector agent was reduced from 50 mg mL−1 to 20 mg mL−1, which did not negatively impact the recovery of dolomite. The results from the contact angle tests indicated that SPE selectively increased the surface hydrophobicity of fluorite but had little effect on dolomite. Besides, zeta potential measurements and IR analyses revealed that the addition of SPE led to strong chemical adsorption on the surface of fluorite, resulting in a significant difference in the flotation performances of the two minerals. Therefore, SPE‐emulsified OA is corroborated to prompt more selectivity and collecting capability on flotation of fluorite over dolomite.

A selective flotation of fluorite from dolomite using caustic cassava starch and its adsorption mechanism: An experimental and DFT Study

Due to the small difference in floatability between dolomite and fluorite, the problems of low grade of fluorite concentrate occur. It is very important to find a depressant that can selectively inhibit the floating of dolomite. As a natural polymer, starch is often used as a gangue depressant because of its low price and easy availability. In this paper, the effects of caustic cassava starch (CS) on the single mineral flotation performance of fluorite and dolomite and the flotation separation of mixed ore were studied. Its selective inhibition mechanism was investigated. The results of flotation tests with single minerals stated that the flotation of dolomite was vastly inhibited, while the fluorite was hardly affected when CS was added in flotation using sodium oleate as the collector. The concentrate grade of artificially mixed ore flotation fluorite reached 90.15%, and the recovery rate was 89.54%. The physical adsorption of CS on the surface of dolomite blocked the adsorption of hydrophobic sodium oleate on the surface of dolomite, thus depressing dolomite. The adsorption energy of dolomite and CS was much larger than that of fluorite and CS. This greatly deteriorated the flotation of dolomite and achieved flotation separation between fluorite and dolomite. The results demonstrate that CS is a promising depressant for dolomite in fluorite flotation.

Novel insights into the role of colloidal calcium dioleate in the flotation of calcium minerals

Previous studies on oleic acid systems have shown that calcium dioleate formed during the flotation process plays an important role. Calcium dioleate has been extensively studied as an important intermediate product in sodium oleate flotation of calcium-containing minerals sodium oleate, but its use as a collector to separate calcium-containing minerals remains unverified. The effect of calcium dioleate on fluorite, calcite and scheelite flotation and the adsorption mechanism on the mineral surface were examined using solution chemical analysis, flotation test, adsorption measurement, atomic force microscopy (AFM) and transmission electron microscopy (TEM) in this study. Solution chemical calculations prove that stable calcium dioleate colloid will be the dominant species at certain pH, calcium ion and oleate concentrations. Flotation experiments showed that the calcium dioleate plays an important role in the flotation process using sodium oleate. Calcium dioleate has better flotation effect for fluorite and scheelite but weaker effect for calcite than sodium oleate. Adsorption measurement showed that calcium dioleate is more easily adsorbed on the surface of scheelite and fluorite. AFM and TEM measurements exhibited that the formation of micelle adsorption on the surface of scheelite and fluorite caused by calcium dioleate clearly affects the surface roughness. Calcium dioleate colloids can likely enhance the surface roughness of scheelite and fluorite via selectively adsorption to improve the flotation of scheelite and fluorite.

Effects of Pb2+ ions on the flotation behavior of scheelite, calcite, and fluorite in the presence of water glass

Pb2+ ions and water glass are commonly used as the activator and depressant, respectively, in the flotation separation of scheelite from calcite and fluorite in industry. The interactive effects of Pb2+ ions and water glass are rarely reported. In this paper, the effects of Pb2+ ions on the flotation behavior of scheelite, calcite, and fluorite in the presence of water glass were investigated through single mineral flotation experiments, zeta potential measurements, solution chemistry calculations, and X-ray photoelectron spectroscopy (XPS) tests. The flotation results showed that at optimal conditions, Pb2+ ions could activate scheelite flotation and enhance the depression effects of water glass on the calcite and fluorite flotation compared with water glass alone. Solution chemistry calculations and zeta potential analysis indicated that after Pb2+ ions adsorption, water glass could strongly adsorb onto the calcite and fluorite surfaces and inhibit the NaOL adsorption, while on the scheelite surface, water glass could hardly adsorb and thus NaOL adsorption continued. XPS results further revealed that Pb2+ ions combined with WO bond to form the W-O-Pb2+ structure on the scheelite surface which could be the active sites for NaOL adsorption, while on the calcite and fluorite surfaces, the Pb-water glass polymers (polycondensation product of water glass and Pb2+ ions) and water glass combined with CaO bond to depress their flotation.

Selective adsorption of a novel X-shaped surfactant dioctyl di-hydroxamic acid on fluorite surface leading the effective flotation separation of fluorite from calcite and barite

During fluorite flotation, the separation efficiency of fluorite from barite and calcite was low owing to their similar surface properties, therefore, developing highly selective flotation collector for fluorite is urgently needed. In this study, a novel surfactant, dioctyl di-hydroxamic acid (DODHA), was found as an effective collector for flotation separation of fluorite, calcite, and barite. Results from flotation tests suggested that the effective enrichment of fluorite from calcite and barite could be realized without the addition of depressants. FTIR, ζ potential, and XPS results indicated that the interaction between DODHA and fluorite was strong, whereas the adsorption of DODHA on calcite and barite was negligible. The DFT calculation, surface property, and molecular structure analysis results indicated that the steric hindrance and lattice matching between DODHA and mineral surface determined the superior selectivity of DODHA.

Effect of active substance content and molecular weight of petroleum sulfonate on fluorite flotation: Molecular dynamics simulation

Fluorite is an important non-metallic mineral, and the most efficient way to separate it from gangue is flotation. The commonly used collectors are oleic acid and oxidized paraffin soap, but those two collectors both have a problem of bad solubility, this phenomenon worsens at low temperature. Sodium petroleum sulfonate exhibits a good collecting performance on fluorite, but it has not been systematically studied. In this paper, different types of sodium petroleum sulfonate were used to evaluate the effect of active substance content and average molecular weight. Molecular dynamics simulation was used to understand the mechanism that causes the flotation difference between mono-sulfonate and di-sulfonate. This study identifies that active content has a positive effect on the flotation recovery of fluorite while the molecular weight plays a negative role. The reason why di-sulfonate’s performance is relatively weak at high concentration lies on the steric-hindrance effect, larger cross-sectional area limits the tail–tail interaction between sulfonates.

Effect of Artemisia sphaerocephala Krasch. Gum on the flotation separation of fluorite from calcite

The effect of Artemisia sphaerocephala Krasch. gum (ASKG) on the flotation separation of fluorite and calcite with sodium oleate (NaOl) as collector was studied for the first time. Results of micro-flotation and artificial mixed mineral experiments proved that ASKG had a strong depression effect on calcite, but the flotation of fluorite was barely effected by ASKG within the pH range studied. Zeta potential analysis results confirmed an evident adsorption difference of ASKG, and the adsorption strength of ASKG on calcite was much stronger than that of fluorite. The results of Fourier-transform infrared spectroscopy analysis suggested that ASKG hardly affected the chemical interaction between NaOl and fluorite, but the pre-adsorption of ASKG on calcite surface could further prevent the adsorption of NaOl. Meanwhile, X-ray photoelectron spectroscopy analysis results indicated that ASKG could be adsorbed on calcite surface to improve the hydrophilicity by the strong complexation of hydroxyl (–OH) with Ca2+. Therefore, the flotation separation of fluorite and calcite could be realized due to the remarkable difference of NaOl adsorption by using ASKG as selective depressant.

Effects of barite size on the fluorite flotation using the reagent scheme of GS/NaOl

Barite is easily ground to slime fraction, which may affect the fluorite flotation. The role of barite particle size in the fluorite flotation was studied in this work. Single mineral flotation showed that gelatinized starch (GS) selectively depressed the barite flotation with different size fractions while it had little effect on fluorite flotation using sodium oleate (NaOl) as the collector, suggesting the sufficient separation of fluorite from barite using the reagent scheme of GS/NaOl. However, the flotation of mixed minerals presented that the existing of fine barite particle significantly interfere with the fluorite flotation. Zeta potential measurements, turbidity tests, and light microscope observations revealed that the hetero-coagulation occurred between fluorite and barite slimes, causing the slime coating of barite onto the fluorite surface. GS not only acted as the depressant but also act as the flocculant to improve the apparent size of barite, while it still could not completely eliminate the detrimental effects of slime coating due to the entrainment of fluorite-barite aggregates. The additional methods to obtain the effective flotation separation of fluorite from barite slime were tested and discussed. • Roles of barite size on the fluorite flotation using the reagent scheme of GS/NaOl were studied. • The barite particle size significantly affected the fluorite flotation in mixed mineral flotation. • The hetero-coagulation between fluorite and barite slimes caused the adverse “slime coating”. • GS could act as depressant and flocculant to enhance the flotation separation efficiency. • Additional approaches were tested and discussed to further eliminate the slime coating effects.

Comparison of Sodium Oleate and Sodium Petroleum Sulfonate for Low-Temperature Flotation of Fluorite and the Collecting Mechanisms

Comparison of Sodium Oleate and Sodium Petroleum Sulfonate for Low-Temperature Flotation of Fluorite and the Collecting Mechanisms

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.

Adsorption and depression mechanism of an eco-friendly depressant PBTCA on fluorite surface for the efficient separation of cassiterite from fluorite

Cassiterite is the most purist tin-containing mineral and plays a dominative role in the tin resources. Owing to the limited selectivity of conventional collectors, the efficient separation of cassiterite from fluorite is normally difficult. Herein, 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) was employed as an eco-friendly depressant to selectively depress the flotation of fluorite. The flotation experiments were conducted to evaluate the separation efficiency of the two minerals, and the results showed that cassiterite and fluorite could be efficiently separated at the flotation reagent scheme of 15 mg/L PBTCA and 20 mg/L NaOL when pH was 8.04. Furthermore, a series of detection and simulation technologies including wettability analysis, zeta potential measurement, FTIR analysis, XPS analysis and DFT calculation were performed to uncover the underlying adsorption and depression mechanism of PBTCA on cassiterite and fluorite. These further analyses indicated that PBTCA could be chemisorbed on the fluorite surface through the interaction between the phosphate group in PBTCA and the calcium sites in fluorite. Moreover, the adsorption of PBTCA on fluorite surface would intensively inhibit the adsorption of NaOL. However, PBTCA was only weakly adsorbed on the cassiterite surface and could not affect the interaction between NaOL and cassiterite. Finally, a most likely adsorption model of PBTCA onto fluorite surface with the “mono-polar group” interaction was proposed by DFT calculations.

The application and mechanism of high-efficiency depressant Na2ATP on the selective separation of cassiterite from fluorite by direct flotation

To achieve the efficient flotation separation of cassiterite from fluorite, an eco-friendly depressant, the disodium salt of adenosine 5′-triphosphate (Na2ATP), was employed for the selective depression of fluorite. The performance of Na2ATP as a depressant in the flotation of cassiterite and fluorite was evaluated by micro-flotation experiments in a sodium oleate (NaOL) system. The flotation tests revealed that Na2ATP significantly depressed the flotation of fluorite compared to that of cassiterite, and excellent separation was achieved using 1.0 mM Na2ATP and 0.14 mM NaOL at pH 8.02. Moreover, the mechanism of the selective depression Na2ATP on the two minerals was revealed by surface analyses, revealing that chemisorption between the phosphate group of Na2ATP and the calcium ions on the fluorite surface was responsible for the selective adsorption of Na2ATP on fluorite, and the significant pre-adsorption of Na2ATP onto the fluorite surface impeded the further adsorption of NaOL. However, because Na2ATP was adsorbed on cassiterite by physisorption, which is relatively weak, the strong chemisorption of NaOL on cassiterite occurred regardless of pre-treatment with Na2ATP. Furthermore, density functional theory calculations revealed that the adsorption mode of Na2ATP to be “horizontal” and to occur at multiple calcium-ion sites on the fluorite surface. In summary, Na2ATP is a suitable high-efficiency depressant for the separation of cassiterite from fluorite by direct flotation.

Activation mechanisms of sodium silicate-inhibited fluorite in flotation under neutral and slightly alkaline conditions

In this study, the activation mechanisms of fluorite inhibited using Na2SiO3 by adjusting the solution pH to neutral and slightly alkaline conditions were investigated. The solution chemistry of sodium silicate and microflotation tests showed that SiO(OH)3− in the Na2SiO3 solution strongly inhibited fluorite flotation, while H4SiO4 and SiO2(am) showed only weak inhibition. By adjusting the solution pH of Na2SiO3-inhibited fluorite flotation to 7–7.5, fluorite flotation was activated. In this pH range, the dominant Na2SiO3 species were H4SiO4 and SiO2(am), and the measured contact angles indicated that the fluorite surface became more hydrophobic. The adsorption tests also indicated that fewer Na2SiO3 species adsorbed on the fluorite surface at pH 7 than 12.3, while in the presence of Na2SiO3, more oleate adsorbed on the fluorite surface under neutral and slightly alkaline conditions.

Intensifying fine-grained fluorite flotation process with a combination of in-situ modification and liquid-gas microdispersion

With the depletion of rich fluorite ore, flotation process suitable for fine-grained fluorite is of great necessity. In this study, such method was preliminarily developed with a combination of in-situ surface modification and gas-liquid microdispersion. By introducing additives into ball-milling, the interaction between reagents and particles was improved. Through exploitation of selective sedimentation of undesired minerals via pH adjustment, the flotation of fine-grained fluorite was achieved with little or even no depressant in this study. Using a well-designed membrane dispersion device, effective interaction between the particles and bubbles was achieved, with massive expansion of the surface area in a limited space, enabling continuous flotation in a miniaturized device. Satisfactory product grade and recovery were obtained while reducing the use of additives, along with significantly decreased costs related to energy consumption, wastewater and flue gas treatment, and facility investments. The mechanism of this flotation separation strategy was summarized on the basis of empirical data. The strategy was effectively and flexibly applied to fluorite ores with different particle sizes and surface properties.

Hydrophobic behavior of fluorite surface in strongly alkaline solution and its application in flotation

Normally fluorite was collected by fatty acid collectors at pH 5–11, rendering the surface to be hydrophobic. In this study, we found that fluorite surfaces are naturally hydrophobic at high pH without any surfactant, which is beneficial for the selective flotation separation of fluorite from calcite. In a flotation test, fluorite recovery showed a decreasing trend at alkalescent pH but increased at high pH. Sum-frequency generation spectroscopy spectrum confirmed that the orientation and hydrogen bonding structure of the water molecules are dramatically changed at fluorite/water interface. Moreover, a new signal peak, wavenumber of 3657 cm−1, appeared under strongly alkaline conditions; this peak is normally attributed to free OH stretching region and indicates a hydrophobic surface. Meanwhile, the results of contact angle and atomic force microscopy measurements show that the hydrophobicity obviously increases at pH 13. Therefore, the surface structure of fluorite must undergo some significant changes, which will play an important role in the flotation of fluorite.

Comparison Between Performance of Fluorite Flotation Under Different Depressants Reagents in Two Pieces of Laboratory Equipment

Fluorite is an important industrial mineral composed of calcium and fluorine (CaF2). This mineral is widely distributed through different deposits. However, in most cases, fluorite is tightly associated with gangue, such as calcite and quartz. In this paper, different depressants are tested in the flotation of fluorite in two different laboratory configurations—cell and column. Quebracho tree (QT) was tested as the main depressant in combination with white dextrin (WD), potato starch (PT), carboxymethyl cellulose (CMC), and sodium hexametaphosphate (SHMP). The optimum pulp pH of the flotation of fluorite was determined as approximately 9.5–10. The best results are obtained using a combination of quebracho and white dextrin as depressants, reaching 74% of fluorite grade for modified column flotation and 70.5% for cell flotation. Additionally, the metallurgical recovery obtained higher values when the flotation was carried out in the modified column and using the same combination of depressant agents—75% for modified column flotation and 60% for flotation cell.

The effect of citric acid in the flotation separation of bastnaesite from fluorite and calcite using mixed collectors

Bastnaesite is a chief natural source of light rare earth elements (LREEs). The effective depression of Ca-containing minerals such as fluorite and calcite in bastnaesite flotation system is normally difficult, and it is imperative to exploit more environmentally-friendly depressants which can inhibit these gangue minerals simultaneously. Hence, we employ citric acid (H3Cit), a green, cheap and commonly available organic acid, to selectively depress the flotation of fluorite and calcite, and use octanohydroxamic acid (OHA) and sodium oleate (NaOL) with a molar ratio of 2:1 as mixed collectors. Micro-flotation results show that H3Cit decreases the recoveries of fluorite, calcite, and bastnaesite by 84.73%, 62.96%, and 9.23%, respectively at pH 8–9. The depression mechanism of H3Cit was investigated through zeta potential measurements, microcalorimetry measurements, solution chemistry and reaction thermodynamic analyses, and X-ray photoelectron spectroscopy (XPS) analyses. These further analyses at the minerals/water interfaces indicate that H3Cit preferentially adsorbs on the gangue mineral surfaces due to the positively charged fluorite and calcite surfaces which interact more easily with citrate ions (Cit3-), and the spontaneous interaction between Cit3- and Ca2+ on the surfaces. Accordingly, H3Cit is supposed to be a potential depressant for Ca-containing minerals in the flotation separation of bastnaesite.

Testing of New Collectors for Concentration of Fluorite by Flotation in Pneumatic (Modified Hallimond Tube) and Mechanical Cells

In this study, two new collectors for fluorite flotation DP-OMC-1033 (DP-I) and DP-OMC-1234 (DP-II) were tested and compared with oleic acid (OA), sodium oleate (SO) and potassium oleate (PO). According to fluorite grade and fluorite metallurgical recovery, the effect of each collector was determined, both in mechanical and pneumatic cell flotation. The effect of temperature on the collectors from 25 to 55 °C was studied. Flotation tests showed that the best results in terms of fluorite metallurgical recovery were 82.8% and 87.9% for new collectors DP-I and DP-II respectively, for a dosage of 100 g/t and using pneumatic cell. Additionally, in terms of fluorite grade, DP-I showed the best results, achieving 79.7% of CaF2 in roughing step for a dosage of 100 g/t. Fluorite metallurgical recovery and grade in concentrate increased for OA, SO and PO with increasing temperature. However temperature did not have a significant effect on both metallurgy recovery and CaF2 grade using DP-I and DP-II, so the process can be effective at 25 °C reducing operating costs.