Flotation Practice Research Articles

О влиянии «гидрофобности» газовой фазы на образование флотокомплексов в процессах флотации

Introduction. A model of a three-phase system in which, as a result of hetero coagulation from a bulk liquid, its thin layer has formed, the surfaces of which separate the gas and condensed phases with different potentials, is a wetting film. The study of wetting films adds to the knowledge of the nature of the structure-induced surface forces acting in them, which serves to develop the theory of hetero coagulation and is of interest for solving various topical problems of the theory and practice of flotation. The purpose of the work is to study the influence of “hydrophobic” properties of the gas phase on the separation of minerals by flotation with a vapor-air mixture in flotation schemes with jet countercurrent flow of feed and rough concentrate. Materials and Methods. Methods and installations have been developed to investigate the temperature dependence of the equilibrium thickness of wetting films and wetting edge angles. Studies of wetting films are supplemented by measurements of induction time at adhesion of minerals to each other and to an air bubble on a specially designed installation. In-situ flotation experiments were performed on a sample of apatite-nepheline ores. Results. The temperature dependence of the equilibrium thickness of the wetting film has been revealed, which does not contradict the experimentally established decrease of the exponentially decreasing (non-oscillating) part of the cleavage pressure with increasing temperature. It is shown that the temperature dependence of the boundary angles formed by the wetting film on the hydrophobic and hydrophilic surface is multidirectional. The connection between the temperature dependence of the boundary angle and the temperature dependence of the spreading coefficient obtained from Young’s law and determined by multiplication of parameters characterizing the magnitude and long-range action of forces caused by the difference between the structure and properties of the liquid in the boundary layers and their values in the volume is shown. “Hydrophobicity” of the bubble is associated with a smaller range effect of structural repulsion forces compared to hydrophobic attraction forces. By measuring the induction time, it is shown that the “hydrophobicity” of air manifests itself in the difference in the stability of wetting (when hydrophobic and hydrophilic particles adhere to the air bubble) and symmetric (when particles of the same hydrophobicity/hydrophilicity adhere to each other) films as the temperature increases. Discussion. In the framework of the phonon mechanism of surface forces, the dynamic structure of the liquid in the boundary layers (the sign and magnitude of the phonon component of the bowing pressure) determines the selectivity of aggregation and completeness of particle extraction, as well as the stability of symmetric and wetting films from temperature. Conclusion. When discussing the stability of disperse systems, the concepts of additional (to dispersive (van der Waals) and ionic-electrostatic interactions) forces associated with the overlap of boundary layers of liquids with structure parameters changed compared to their bulk values are fruitfully used. Such differences are understood as static deviations of the structure and properties of the liquid induced by the surface. However, the main reason for changes in the stability of wetting films at increasing temperature may be the high sensitivity to temperature of the entire set of rotational and vibrational motions of atoms and molecules of the liquid, i. e., its dynamic structure and the associated phonon component of the wedging pressure. Resume. The results of the study can be used to improve the technological performance of ores enriched by flotation. Consideration of the influence of linear tension on the system with the line of threephase contact will be useful for revealing the peculiarities of flotation of micro-dispersions of minerals by the developed technology.

Lead species formation on pure hemimorphite surface and its performance for subsequent sulfidization

Hemimorphite is important-supplementary resource for the commercial zinc production, but it easy loses into tailings due to extreme difficulty for its surface sulfidization. Adding active metal ions after sulfidization have been widely proposed for enhancing hemimorphite floatability, but its desired efficiency in flotation practice has not yet been completely achieved caused by the instability of sulfide layer. Whereas pre-adsorption of active metal ions to modify the hemimorphite surface has strong potential to make up for this shortcoming. Herein, the feasibility and appropriate environment of free Pb<sup>2+</sup> for modifying the pure hemimorphite surface was evaluated. Subsequently, the performance of Pb<sup>2+</sup> adsorption for enhancing sulfidization stability and floatability of hemimorphite were investigated. The X-ray photoelectron spectroscopy results indicated that the Pb<sup>2+</sup> adsorption on hemimorphite surface was achieved through the Pb ions displacement for Zn ions, and it was bond to oxygen-containing groups on hemimorphite surface. Such adsorption was strengthened with the increasing of solution pH, owing to the abundant Pb hydroxyl species precipitated on mineral under alkaline conditions, in term of the results of visual MINTEQ modeling and time-of-flight secondary-ion mass spectrometry. In addition, the X-ray photoelectron spectroscopy results showed dominant Pb hydroxyl species further reacted with sulfur during subsequent sulfidization to generate much more S species than that of without Pb<sup>2+</sup> pre-modification. Meanwhile, such sulfide layer composed by Pb<sup>2+</sup> on the mineral surface presented much higher stability than Zn-S species, which was verified via adsorption and desorption tests. As a result, the sulfidization and flotation recovery of hemimorphite increased after Pb<sup>2+</sup> pre-adsorption.

Flotation separation of chalcopyrite from molybdenite with sodium thioglycolate: Mechanistic insights from experiments and MD simulations

The pivotal roles of Cu and Mo in industrial applications accentuate the importance of effectively separating and recovering chalcopyrite and molybdenite. They commonly exist together in natural environments, necessitating their segregation prior to engaging in smelting processes. The separation is mainly accomplished through flotation. The inadequate comprehension of the mechanisms of thiol depressants, commonly used in the separation of chalcopyrite and molybdenite, poses challenges to both resource recovery and the development of depressants. Based on the bulk flotation practice of copper-molybdenum sulfide minerals, this study investigated the separation effect and mechanism of sodium thioglycolate (STG) on xanthate-treated chalcopyrite and molybdenite. Flotation and contact angle tests validate that STG enhances the hydrophilicity of chalcopyrite surfaces, leading to an 83.79% flotation separation efficiency for molybdenite. Various methodologies were employed to explore the mechanism of the depressant, encompassing open-circuit potential measurements, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, infrared and ultraviolet spectroscopy, time-of-flight secondary ion mass spectrometry, classical molecular dynamics and ab initio molecular dynamics simulations. The stable adsorption layer of STG is established by the interaction of thiol groups from STG with Cu and Fe sites on the chalcopyrite surface, resulting in the formation of Cu(I)-S and Fe(III)-S structures. The adsorption density of STG layer on the chalcopyrite surface is four times greater than that on molybdenite. Additionally, following the adsorption of STG, the previously adsorbed xanthate chalcopyrite surface is desorbed with an efficiency of 65.88%. These findings contribute to the elucidation of the mechanistic understanding of thiol-containing depressants in the flotation separation process of copper-molybdenum sulfide minerals and establish a basis for the prospective advancement of mineral processing reagents.

Eco-friendly approach for enhancing the floatability of non-metallic components in waste printed circuit boards: Adding gutter oil during dry grinding

Waste printed circuit boards (WPCBs) are an attractive secondary resource that is challenging to dispose of due to its complexity. Reverse flotation is an effective method to remove non-metallic particles (NMPs) to obtain metals from WPCBs. Nevertheless, the removal of NMPs is usually inadequate in the present flotation practice. Thus, to provide a clean approach to improve the removal efficiency of NMPs, the method of adding gutter oil during dry grinding process was adopted to enhance the hydrophobic sites on the surface of NMPs to improve the floatability. The surface morphology of NMPs was analyzed by SEM, the results show that the rough morphology inhibited the adhesion of bubbles, while water occupied the cracks and pores, making it challenging for collector adsorption, which result in unstable particle-bubble adhesion. The results of FTIR indicate that both NMPs and gutter oil have –CH3, –CH2, -C = O, -C-O functional groups, which promotes the adsorption of gutter oil on the surface of NMPs. The contact angle (CA) results show that the adsorption of gutter oil on the particle surface is conducive to the formation of enhanced CA. Furthermore, the flotation enhancement effect was verified by flotation kinetic experiments. The accumulated floats yield of NMPs conditioned by gutter oil during grinding is increased from 67.05% (NMPs without conditioning) to 95.02%, and the resin recovery is increased by 31.10%. It is demonstrated that dry grinding with gutter oil can strengthen the floatability of NMPs, which provides a potential approach to increase the flotation efficiency of WPCBs.

Mechanistic study on the depression of calcite by sodium hexametaphosphate in sodium oleate system

Sodium hexametaphosphate (NaHMP), a common depressant for calcium-containing minerals, is widely used in flotation practice. In this work, the depression mechanism of NaHMP on calcite was thoroughly investigated by using experiments and DFT calculations. Accordingly, the micro-flotation results revealed that NaHMP possessed noticeable depression effect on calcite, with the calcite recovery decreasing from 94.21% without NaHMP to 17.29% with NaHMP concentration of 1 mg/L at pH 8. The surface Zeta potential suggested that NaHMP could be strongly adsorbed on calcite, while no absorption band of hexametaphosphate was detected in the FTIR spectra of calcite treated by NaHMP, but a remarkable weakening of the absorption peak of sodium oleate (NaOL) was detected in the presence of NaHMP, which was also reflected in the XPS spectra. In addition, the significant chemical shifts in the binding energies of Ca 2p and P 2p electrons observed from the XPS high-resolution spectra suggested that the hexametaphosphate groups (HMP) were chemisorbed on calcite. DFT calculations further revealed that the sorption of HMP on calcite was more preferable than that of oleate ion (OL) in thermodynamics, which explained the beneficiation practice that NaOL was difficult to float calcite in the presence of NaHMP.

Utilization and Mechanisms of Tannic Acid as a Depressant for Chalcopyrite and Pyrite Separation.

Current flotation practices using lime or cyanide as depressants in chalcopyrite and pyrite separation have significant disadvantages, such as substantial reagent consumption, high slurry pH, and environmental hazards. This work aimed to explore the utilization and mechanisms of tannic acid (TA) as an eco-friendly alternative to lime or cyanide in chalcopyrite-pyrite separation. Flotation results showed that TA selectively depressed pyrite yet allowed chalcopyrite to float at neutral or alkaline pH. Adsorption density and zeta potential results indicated that TA adsorbed intensely on pyrite but minorly on chalcopyrite. Besides, potassium ethyl xanthate was still largely adsorbed on chalcopyrite but not on pyrite after TA adsorption. Surface analysis by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy further showed that the oxidation species of FeOOH and Fe2 (SO4)3, particularly FeOOH were the main active sites for TA chemical adsorption. Owing to the greater and faster oxidation of pyrite, more FeOOH and Fe2 (SO4)3 were generated on the pyrite surface, and the chemical adsorption of TA was more pronounced on the pyrite surface than on the chalcopyrite surface.

Progressive Hydrophilic Processes of the Pyrite Surface in High-Alkaline Lime Systems.

Pyrite, as a disturbing gangue mineral in the beneficiation of valuable sulfide minerals and coal resources, is usually required to be depressed for floating in flotation practice. Specifically, the depression of pyrite is achieved by causing its surface to be hydrophilic with the assistance of depressants, normally with inexpensive lime used. Accordingly, the progressive hydrophilic processes of the pyrite surface in high-alkaline lime systems were studied in detail using density functional theory (DFT) calculations in this work. The calculation results suggested that the pyrite surface is prone to hydroxylation in the high-alkaline lime system, and the hydroxylation behavior of the pyrite surface is beneficial to the adsorption of monohydroxy calcium species in thermodynamics. Adsorbed monohydroxy calcium on the hydroxylated pyrite surface can further adsorb water molecules. Meanwhile, the adsorbed water molecules form a complex hydrogen-bonding network structure with each other and with the hydroxylated pyrite surface, which makes the pyrite surface further hydrophilic. Eventually, with the adsorption of water molecules, the adsorbed calcium (Ca) cation on the hydroxylated pyrite surface will complete its coordination shell surrounded by six ligand oxygens, which leads to the formation of a hydrophilic hydrated calcium film on the pyrite surface, thus achieving the hydrophilization of pyrite.

Flotation kinetics of aluminum powders derived from waste crystalline silicon solar cells and its comparison between batch, continuous and column flotation practices

Flotation kinetics of aluminum powders derived from waste crystalline silicon solar cells and its comparison between batch, continuous and column flotation practices

Pilot tests of gravity-flotation technology for processing industrial waste from alluvial gold mining

Large-scale development of technogenic resources with low recoverable value is constrained by the lack of technologies that ensure their break-even development. Most of the gold from dumps can be extracted using the least costly gravity methods. In the pilot industrial processing of this raw material, screw separators were used in the main metal concentration operation. The finishing of their heavy fractions was carried out on concentration tables. With the light fraction of gravitational apparatus, 28.7% of the gold was lost. The light fraction material (with gold in the form of thin leaves and scales) has a low contrast in density. Gold of hard-to-recover morphotype was isolated from light fractions of gravitational apparatus by flotation. It was found that with an increase in the content of gold in the feedstock, its recovery into concentrate by flotation increases. In the practice of flotation, the required increase in the metal content in the separation operation is achieved through the turnover of middlings. However, in this case, the gold content of the resulting mixture increases and the separability decreases. This result is due to the fact that grains with reduced flotation properties are returned with the middlings. During flotation, the rough concentrate separated from 1/2 part of the initial feed is mixed with another 1/2 part of the initial feed. As a result, in the main flotation operation, the metal content and the ability of the material to be separated by flotation increase. In this case, the pulp is aerated with a mixture of air with hot steam. Condensation of steam in bubbles is the reason for the increase in completeness of gold recovery and selectivity of the flotation process. The technological efficiency of the developed technology has been proven by the results of its pilot tests. The assessment of economic efficiency was carried out by extraction of metal from the waste of alluvial gold mining and by the amount of capital costs and operating costs associated with its production. When processing man-made raw materials with a low gold content and switching from gravity to gravity-flotation technology due to the profit from additionally obtained gold, the payback period for the discounted cash flow decreases by one year, the value of the net discounted income increases by more than an order of magnitude, and the profitability index by 12.5% (rel.), EBITDA margin — from 31.4 to 42.5%.

Improvement of coal flotation by exposure of the froth to acoustic sound

Simultaneously improving coal flotation performance and the subsequent froth breakdown is challenging. The present work addresses this challenge by developing and evaluating a non-chemical approach based on the stabilization effect of acoustic sound on flotation froth. The effectiveness of this approach for improving coking coal flotation at different frother concentrations (10–25 ppm MIBC), collector dosages (0–400 g diesel/t) and aeration rates (1.2–2.2 cm/s) was demonstrated at laboratory scale and in batch mode, with a loudspeaker being placed in air above the flotation cell lip. It was found that at any operating condition tested, the use of sound could improve the flotation performance including the final combustible recovery, apparent flotation rate constant and separation efficiency rate. There was no statistically significant difference in product ash content between the flotation tests with and without applying sound, except at the highest MIBC concentration tested. The images of the product froth taken before and 5-min after being discharged from the flotation cell indicated that the froth stabilization effect induced by sound would occur only within the sound field, demonstrating the potential of the approach in mitigating the overfrothing issue without sacrificing the flotation performance. The possible mechanisms of the improvement of flotation performance with applying sound and its potential of improving coal flotation practice through reducing reagent and air consumption were discussed.

СОВЕРШЕНСТВОВАНИЕ РЕАГЕНТНЫХ РЕЖИМОВ ФЛОТАЦИИ СФАЛЕРИТА И ПИРИТА ИЗ МЕСТОРОЖДЕНИЙ КОЛЧЕДАННЫХ МЕДНО-ЦИНКОВЫХ И ПОЛИМЕТАЛЛИЧЕСКИХ РУД

Pyrite copper-zinc (sulfide) and polymetallic ores in Russia are complex and refracto-ry mineral raw materials. The main processing technology for such ores is flotation. Currently, the improvement of the flotation technology of such mineral raw materials is carried out in several directions. It has been established by the practice of enrichment of copper-zinc ores that obtaining high-quality zinc and pyrite concentrates is impossible without the use of various modifiers in the practice of flotation of sphalerite and pyrite. Such reagents are copper (II), zinc and iron (II) sulfates in an alkaline lime environment. Therefore, studies were carried out to float sphalerite and pyrite in an alkaline lime medium with the addition of one of the indicat-ed sulfates to the mineral flotation operation. The effect of each of the sulfates of copper (II), zinc and iron (II) on the flotation of sphalerite and pyrite was studied during flotation of the mineral with butyl xanthate and dithiophosphate at pH = 8, 10, and 12. The aim of this work was to study the effect of sulfhydryl collectors in the presence of copper sulfates , zinc and iron for flotation of sphalerite and pyrite with a size class (-0.074 + 0.044 mm) from one of the Rus-sian deposits.

Towards the efficient flotation of monazite from silicate-rich tailings with fatty acids collectors using a lanthanum salt as a selective phosphate activator

The exploitation of massive rare-earth element (REE) deposits is frequently contested because of the pollution generated by the heavy mining operations and REE extractive metallurgy operations. In an effort to minimise the environmental footprint of the REE production and meet the increasing demand for these elements, mine wastes and extractive metallurgy tailings are attracting attention as alternative primary sources. However, these residues frequently contain small amounts of monazite [(Ce,La,Nd)PO4] in silicate-rich gangues, rendering the efficient and selective recovery via current flotation routes difficult. Herein, we investigated the use of LaCl3 as an activator to promote the selective adsorption of fatty acid collectors on the surface of phosphate minerals, thus improving the monazite flotation performance. Bench-scale flotation tests were performed on a low monazite-grade, silicate-rich residue and revealed that a low LaCl3 dosage (about 1 g t−1) selectively enhanced the floatability of monazite and gangue phosphate minerals. We found that the influence of LaCl3 on the monazite flotation performance depends on the LaCl3 dosage, collector dosage, and method of addition of these reagents to the pulp. The mineral composition of the flotation products was determined by mineral liberation analysis (MLA), which indicated that higher concentrations of lanthanum ions promote the adsorption of the collector on rutile and aluminium-rich minerals, thus reducing the selectivity of the monazite flotation separation. This study is a stepping stone towards the development of a new practice of monazite flotation with environmentally friendly collectors and may render low REE-grade residues a commodity.

Effect of Transition Metal Impurities on the Adsorption of Flotation Reagents on Pyrite Surface

Pyrite is one of the most common sulfide minerals on earth, which is usually grown with chalcopyrite and other sulfide minerals. In flotation practice, pyrite from different mines or different sections in a same mine may have different flotation behaviors. This is because the pyrite crystal contains lattice defect, including ionic vacancy and lattice impurity. The present work investigates the effects of three typical 3d transition metal (Co, Ni, and Fe) on the adsorption of CH3OCS2−, OH−, and CN− on pyrite surface by density functional theory (DFT) calculations. Calculated results show that Co impurity reduces the adsorption energies of CH3OCS2− and CN− on the surface of pyrite, while Ni and Cu impurities significantly increase the adsorption energies of CH3OCS2− and CN− on the surface of pyrite. Co impurity has small influence on the adsorption of OH−, but Ni and Cu impurities significantly increase the adsorption energies. Calculations on Mulliken charge population of Co2+, Ni2+, and Cu2+ indicate that the Mulliken charges of Co2+, Ni2+, and Cu2+ after OH− adsorption are more than those after CN− adsorption. This suggests that the ionic property of the M-OH- coordination bond is greater than that of M-CN- coordination bond, while covalent bonding of M-CN- coordination bond is greater than that of M-OH- coordination bond. The adsorption results are discussed based on coordination field theory (CFT).

Influences of electronic spin structures on the magnetic properties of Fe, Co and Ni ions and the adsorption of collectors

The electronic spin properties of Fe, Co and Ni metal ions in the octahedral field formed by S and O ligands were studied by density functional theory (DFT). It is found that in MO octahedral field, the metal exhibits a high spin nature, whereas in MS octahedral field, the metal exhibits a low spin nature. This suggests that O atom is a weak-field ligand and S atom is a strong-field ligand. It is found that MO atoms are mainly ionicly bonded, whereas MS atoms are mainly covalently bonded. This result is consistent with the MO and MS bonds in the real metal oxide and sulfide minerals. Hence, MO and MS coordination compound models can be used to simulate the crystals of the real oxide and sulfide minerals. Then the adsorption of O- and S-containing flotation collectors on these two mineral models was studied. It is indicated that S-containing collectors could not effectively collect oxide minerals, but O-containing collectors have strong collecting ability to oxide minerals. In addition, the collecting ability of S- and O-containing collectors to sulfide minerals is nearly the same. These are consistent with the flotation practice that O-containing collectors have no selective collecting capacity on oxide and sulfide minerals but S-containing collectors have strongly selectively collecting capacity to sulfide minerals.

New Insights into the Role of Surface Nanobubbles in Bubble-Particle Detachment.

It is well recognized that an improved flotation recovery can be achieved by introducing nanobubbles to common flotation practice due to the increased capture efficiency between bubbles and particles. However, the specific role of nanobubbles in bubble-particle interactions (collision, attachment, and detachment) is not well understood. In the present study, we explore the role of surface nanobubbles in bubble-particle detachment. Surface nanobubbles were introduced via ethanol-water exchange and their presence was confirmed using laser scanning confocal microscopy (LSCM). The effect of surface nanobubbles on bubble-particle detachment behavior was then investigated using an oscillating bubble apparatus. Bubble-particle aggregate stability was evaluated using critical detachment amplitude. Further, bubble-particle detachment forces in the absence and presence of nanobubbles were measured directly using a micro-nano mechanical testing system. Using LSCM, numerous surface nanobubbles were observed on a glass surface after ethanol-water exchange, regardless of wettability. The number and lateral dimensions of generated nanobubbles on the hydrophilic surface were significantly smaller than that on the hydrophobic surface. Surface nanobubbles increased the stability of bubble-particle aggregates. Macroscopic air bubbles coalesce with the nanobubbles on the particle surface, increasing the pinning effect of the three-phase contact line and advancing contact angle. As a result, the capillary force between bubbles and particles increased in the presence of surface nanobubbles.

Application of ultrasonic pretreatment for coking coal flotation and its mechanism

ABSTRACT This paper focuses on enhancing the flotation of coking coal with ultrasonic pretreatment and the corresponding improving mechanism. The effects of ultrasound on the coal surface properties and the dispersion of oil collector in flotation slurry were fully studied. The SEM, FTIR and XRF analyses indicated that, after the ultrasonic pretreatment, the fine particles covered on coarse coal particles were removed and the elements forming gangue minerals were decreased, which improved the surface hydrophobicity of the coal sample. What’s more, the optical microscope measurements for collector dispersion showed that the size of diesel oil droplets was greatly reduced after the ultrasonic treatment, suggesting the enhanced dispersion of collector in flotation pulp. As a result of synergistic effects of ultrasonic treatment on the coal surface cleaning and promotion of collector dispersion in pulp, a maximum combustible matter recovery of 79.79% was attained with the flotation process 2 (i.e., the ultrasonic treatment was performed after the addition of collector to the pulp). Furthermore, the enhanced collector dispersion in pulp caused by the ultrasonic treatment may be conducive to reduce the collector consumption in actual flotation practice.

Selective flotation of chalcopyrite from pyrite using diphosphonic acid as collector

Ethyl xanthate (EX) is a widely used collector in the flotation of sulfide minerals. However, it also has the disadvantages of low selectivity and harm to human health. Screening and/or designing more selective and green collectors is a ‘hot topic’ in mineral processing field. In this work, 1-Hydroxyethylidene-1, 1-diphosphonic acid (HEDP), a cheap green reagent widely used in water treatment, was for the first time, applied in the flotation separation of chalcopyrite from pyrite. In addition, a comparative test of the traditional EX collector was also carried out. Flotation results of single mineral and binary mineral mixture showed that HEDP possessed a better selectivity for the separation of chalcopyrite from pyrite than EX. Zeta potential measurement results indicated that HEDP exhibited a stronger adsorption on chalcopyrite and a weaker interaction with pyrite. Hence, HEDP is a promising collector that possesses the potential to replace EX in future chalcopyrite flotation practice.

A density functional based tight binding (DFTB+) study on the sulfidization-amine flotation mechanism of smithsonite

Sulfidization-amine is the most effective method for the recovery of smithsonite (ZnCO3), however the interface interaction details remain unclear. The sulfidization-amine flotation mechanism of smithsonite has been studied by Density Functional based Tight Binding (DFTB+) method in this paper. The slab model of ZnCO3 (1 0 1) surface was built and the adsorptions of a monolayer of OH−, HS− and S2− ions were conducted to model the hydration effect of water and the sulfidization effect on the ZnCO3 (1 0 1) surface adsorption. On the primitive smithsonite surface, the adsorption of dodecylamine (DDA) is stronger than dodecyl secondary amine (DSA) and dodecyl tertiary amine (DTA). However, DDA hardly interacts with the hydrated ZnCO3 (1 0 1) surface. Under the low concentration of Na2S, HS− ions form a ZnSHSH structure on the ZnCO3 (1 0 1) surface, which hinders the interaction between DDA and surface Zn atoms. Under the high concentration of Na2S, a layer of ZnS is formed on ZnCO3 (1 0 1) surface, which is favorable for the adsorption of DDA on the surface. This is consistent with the flotation practice where smithsonite flotation requires a large amount of sodium sulfide. The results could provide a microscopic investigation into the sulfidization-amine flotation mechanism of smithsonite.

Magnetic conditioning of sulfide minerals to improve recovery of fines in flotation � a plant practice

In flotation practices, as particles become finer, such as smaller than 20 µm, process efficiency declines markedly. Selective agglomeration of fine particles is a technique to enhance the recovery of fine valuable minerals in flotation circuits. Different agglomerating methods have been introduced and tested. One method that has recently received much attention is to make use of magnetic force to aggregate fine particles. A selective aggregation of fine paramagnetic particles, such as sulfide minerals, can be achieved in the high-intensity magnetic field prior to or during flotation. The method is simple, selective and effective for fine particles and has low operational cost, though a minimum magnetic susceptibility for fine grains is required to promote the process. In this paper, the implementation of the ProFlote magnetic conditioning device in Boliden’s Garpenberg old concentrator in Sweden, where a complex massive sulfide ore is treated, is presented and discussed based on Boliden’s Garpenberg plant. The results showed an increase in the flotation recovery of fine valuable minerals. Zinc (Zn) production was increased by between 1,100 and 1,500 t/a, while salable yearly silver (Ag) production was increased by 1,500 kg. The copper (Cu) grade in the final concentrate was increased by 1 percent, while reductions in its Zn and lead (Pb) grades were obtained. Moreover, considerable reduction in Zn deportment to the final tail was observed.

Physical Methods and Flotation Practice in the Beneficiation of a Low Grade Tungsten-Bearing Scheelite Ore

In this paper, beneficiation studies were carried out on a low-grade tungsten-bearing scheelite from Nezam Abad ore with total WO3 grade of 0.11%. Mineralogical studies showed that scheelite is mainly distributed in the ore and gangue minerals include Quartz and Tourmaline. Liberation degree (d80) of tungsten- bearing scheelite is achieved around particles size 150 μm. Gravity concentration, magnetic and flotation methods were conducted by using experimental designs including fractional factorial and response surface methodology. Gravity concentration results indicated that jig separator could not be able to improve tungsten grade in size fraction +600–1750 μm; however, shaking table increased feed grade up to 27.05% with total recovery more than 50% by using four stages concentration in the size range of +125–600 μm. Multi Gravity Separator (MGS) applied on the intermediate products, improved efficiently the total tungsten recovery of the circuit. The results of flotation practice on the pre-concentrated product demonstrated that WO3 grade could be increased up to 9.2% with total recovery of 27.04% by using one stage rougher and four stages of cleaning. Different methods including MGS, wet and dry magnetic separation were considered for upgrading fines from grinding stages; however, only MGS result was satisfactory. The MGS produced a product with WO3 grade 0.64% and total recovery 93%.