Effect of synthesized mustard soap on the scheelite surface during flotation

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.

Laboratory Testing of Scheelite Flotation from Raw Ore in Sangdong Mine for Process Development

Tungsten is an essential metal for the manufacture of special alloys, which is in constant demand due to the development of the industry. The recovery of scheelite from undeveloped tungsten ore in South Korea was investigated to improve the flotation performance for high grade and recovery of concentrate. To investigate the interaction between the flotation reagents and the minerals, the adsorption experiments of oleic acid as a collector on Ca-bearing minerals, such as scheelite, calcite, and fluorite were carried out. This reaction was confirmed chemical adsorption by analysis of zeta potential and FTIR analysis. The batch test was performed using a raw ore to enhance the grade and recovery of the scheelite concentrate. It was obtained at the optimal conditions for high WO3 grade and recovery of scheelite concentrate by using a simple process. In particular, the sodium carbonate used as a pH modifier was investigated to increase scheelite flotation performance by supporting the selective depression of Ca-bearing gangue minerals. Furthermore, a locked cycle test (LCT) was carried out based on batch test results for the design of a continuous pilot plant.

New Combined Depressant/Collectors System for the Separation of Powellite from Dolomite and the Interaction Mechanism

The flotation beneficiation of powellite from dolomite was achieved with a new reagent system that consists of a mixed collector of sodium oleate (NaOl) and benzohydroxamic acid (BHA) and a depressant sodium hexametaphosphate (SHMP). The interaction mechanism of the reagent regime with minerals was studied using zeta potential and X-ray photoelectron spectroscopy (XPS) detection together with crystal chemistry and interaction energy analysis. The matching features of O–O distance in BHA with that in saline minerals and active site density/activity were used as methods to explain the reagent/mineral interaction. The results of microflotation finally established the new reagent regime at pH 8–12: 2.5 × 10−4 M SHMP, 2 × 10−4 M mixed collector containing 1.5 × 10−4 M NaOl and 0.5 × 10−4 M BHA. SHMP selectively depresses the adsorption of NaOl and BHA onto dolomite but minimally affects the adsorption of NaOl and BHA on the powellite surface.

Utilization of Sodium Hexametaphosphate for Separating Scheelite from Calcite and Fluorite Using an Anionic–Nonionic Collector

This study presents a highly selective reagent system that utilizes sodium hexametaphosphate (SHMP) to improve the separation of scheelite from calcite and fluorite using an anionic–nonionic collector. The recoveries of calcite and fluorite decreased to 20% as the SHMP dose exceeded 6 × 10−6 mol/L, whereas that of scheelite remained at 85%. The interaction mechanisms of minerals with SHMP were investigated through equilibrium speciation, Zeta potential, Fourier transform infrared spectrometry, and X-ray photoelectron spectroscopy analyses. SHMP exists as hydrogen phosphate anion in the aqueous solution with a pH of 7–12. Moreover, it may be adsorbed intensively on the positively charged surfaces of calcite and fluorite via electrostatic force or chelation with calcium ion to impede further adsorption of the assembled collector. By comparison, the adsorption of SHMP is feeble on the scheelite surface because of its negative charge. The roughing grade of low-grade scheelite ore is substantially improved from 0.74% to 1.65% compared with that in the contrast test in the absence of SHMP.

Use of Sodium Hexametaphosphate and Citric Acid Mixture as Depressant in the Flotation Separation of Scheelite from Calcite

The floatability of scheelite and calcite in the presence of single depressant (SHMP or H3Cit) and mixed depressant (SHMP/H3Cit) was studied by microflotation experiments and artificial mixed mineral experiments. Solution chemical calculation, zeta potential tests, thermodynamic analysis and XPS analysis were used to explain the relevant depressive mechanism. Mixed depressant (SHMP/H3Cit) exhibited excellent selective depressive effect on calcite. The optimal molar ratio of SHMP to H3Cit was 1:4. The depressant SHMP and H3Cit can be chemically bonded with Ca2+ to form CaHPO4 and Ca3(Cit)2 at pH 8. The CaHPO4 was more easily formed than Ca3(Cit)2 on the mineral surface, which indicated that the depressive effect of SHMP was stronger than H3Cit. The SHMP and H3Cit of the mixed depressant were co-adsorbed on the calcite surface, while the H3Cit of the mixed depressant was weakly adsorbed on the scheelite surface. The mixed depressant can significantly improve the separation efficiency of scheelite from calcite.

Prediction of Hydrophobic Reagent for Flotation Process Using Molecular Modeling

The interaction or nonbonded energies of base organic ions and water molecules during the flotation process of minerals have important meanings for organizing hydrophobic and stable collectors. Furthermore, the interaction, cross-term, and valence energies of optimized structures are important for understanding the properties and structures of selective collectors. The simulation of pure scheelite mineral (PSM) surfaces with four different negative ions, using an adsorption locator module is demonstrated. The interaction energies for base organic ions and water molecules were resolved and detected by shaping the best hydrophobic interaction and the most stable suspension over the PSM surface (112) and (101). The adsorption locator results for base organic ions and water molecules on PSM surfaces (112) and (101) using buffer width 0.5 Å and temperature range from 318.15 to 283.15 K confirmed the results obtain from Forcite calculations. The results have demonstrated that the possibilities of using consistent valence force field implemented by Forcite and adsorption locator modules in the selection of flotation reagents are cost saving. Furthermore, hydrophobicity of the main negative ions in soaps were solved by the simulation methods and results are in a good agreement with the experimental methods that proved that mustard soap is more selective on the mineral surfaces than sunflower soap when used as a collector. Increasing the molecular weight of negative ions increases the interaction energy between base collector ions and PSM surfaces (112) and (101) significantly.