Reverse Flotation Of Iron Ore Research Articles

Electrochemical action on the flotation beneficiation of ordinary iron ore concentrate

One of the main challenges in processing fresh ferruginous quartzites is to obtain high-quality iron ore concentrates containing more than 70% total iron and less than 1.8% silica to produce DR pellets and hot Briquetted Iron (HBI). Currently, it is widely recognized that the most effective methods to achieve high-quality iron ore concentrates is through reverse flotation using cationic amine collectors in an alkaline medium. However, due to the very fine impregnation of magnetite in quartz, the insufficiently complete release of magnetite even with fine grinding, and the proximity of the flotation (surface) behavior of the separated minerals, high-quality concentrates are not always achievable in the flotation process. Consequently, exploring methods to enhance the efficiency of flotation separation of minerals and improve concentrate quality remains a pertinent issue. Historical studies have shown that electrochemical treatment can adjust the properties of reagents, enhance their effect on specific minerals, and thus control the flotation process. The efficiency of quartz and other silicates flotation by amines significantly depends on the ratio of ionic and molecular forms of the reagent in aqueous solutions of the collector and in the flotation pulp. Altering this ratio can impact the outcomes of reverse cationic flotation of iron ores. It is feasible to change the ratio of the amine forms through electrochemical oxidation or reduction of the reagent solution. Moreover, the electrochemical treatment facilitates the dispersion of the amine in the aqueous medium and its physical adsorption on minerals. Therefore, electrochemical pretreatment of amines can be considered a promising method for intensifying the reverse flotation of iron ore. This paper presents research results aimed at improving the quality of the oversize of the fine screening of ordinary magnetite concentrate from Mikhailovsky GOK, named after A.V. Varichev, through the use of electrochemically treated solutions of cationic amine class collectors in the process of reverse cationic flotation. The research findings confirmed the feasibility of using preliminary diaphragmless electrochemical treatment of reagents Tomamine RA-14 and Lilaflot 811M (esters of monoamine of different composition) for the targeted modification of their properties and for increasing the efficiency of reverse flotation. Consequently, the silica content in the flotation cell product decreased from 1.66–1.7% to 1.51–1.56, with the grade of total iron exceeding 70%.

Effect of Sodium Hexametaphosphate on Flotation of Quartz and Hematite with Starch/Etheramine in the Presence of Ca and Mg Ions

ABSTRACT The aim of this study was to evaluate the effect of sodium hexametaphosphate (SHMP), a complexing reagent for Ca and Mg ions, on iron ore reverse cationic flotation. Quartz and hematite samples contaminated with both Ca and Mg were subjected to microflotation assays at pH 10.5 with starch and etheramine, which showed that SHMP did not provide selectivity in the separation of these minerals. Zeta potential measurements, Fourier transform infrared spectroscopy of quartz and hematite without and with the studied reagents (starch, amine, SHMP, CaCl2/MgCl2) and published studies in the literature indicated that although the HMP anions removed the Ca and Mg ions from both minerals, it also formed complexes with the Fe3+ ions on the hematite surface, which prevented subsequent adsorption of starch and consequently decreased the selectivity for reverse flotation of iron ore.

Effect of dolomite on cationic reverse flotation of iron ore with amide-amine

The reverse cationic flotation of siliceous iron ore containing dolomite is a current challenge in some mines of the Quadrilátero Ferrífero - Brazil, since the starch adsorbs on sites containing Ca and Mg species, previously adsorbed and/or precipitated on the quartz surface, thus preventing the adsorption of the collector (amine), and consequently, affecting the selectivity in the separation between quartz and iron bearing minerals. In previous studies on flotation of siliceous iron ore, using new amide-amine (pKa = 8.2) collector, selectivity was obtained in the process without the use of starch. In this work, the influence of Ca and Mg ions, added as CaCl2 and MgCl2, on the surface properties of quartz and hematite in pH 8 and 10.5, using amide-amine with and without the use of starch, as well as the effect of the collector and depressant on the surface properties of dolomite was evaluated. In bench scale flotation tests with an artificial siliceous iron ore sample containing dolomite (2.5%), it was found that starch (200 g/t) was required for the effective flotation of the ore at pH 8, which produced concentrate with 55% Fe, 25% SiO2 and 17.5% Fe in the tailing with 50 g/t of collector.

Investigation into starch adsorption on hematite and quartz in flotation: Role of starch molecular structure

Various starches have been used as depressants in reverse flotation of iron ores. To date, the effect of molecular structures of starches on the depressing behavior is still not clear using simulation study. In this study, three starches with different ratios of amylose/amylopectin on the molecule (Normal Starch, Waxy Starch and Gelose 50) were used to study their depressing ability on the flotation of hematite and quartz. Microflotation, Zeta potential measurement, XPS analysis and AFM measurement were performed to investigate the interaction between the two minerals and the three starches. It was found that chemisorption occurred between hematite and the starches, while only hydrogen bonding was observed between quartz and the starches. In addition, it was obtained that the chemisorption strength between the starches and hematite under alkaline condition fell in the order: Waxy Starch > Normal Starch > Gelose 50, which was closely related to the ratios of amylose/amylopectin. The underlying mechanism for the different chemisorption strength was revealed via computational chemistry analysis. It is believed that the outcomes of this work could optimize the development of starch-based depressants in iron ore flotation.

Effect of Solid Concentration and Particle Size on the Flotation Kinetics and Entrainment of Quartz and Hematite

Despite the importance of solid concentration in froth flotation, its effect on flotation kinetics and entrainment has rarely been studied. In this study, the flotation kinetics and entrainment in quartz and hematite single-mineral flotation systems as a function of the solid concentration and particle size were investigated using dodecylamine acetate as a collector. Kinetics modeling showed that the Gamma distribution achieved the best agreement with the experimental data, whereas the Classical and Klimpel models poorly fit the data (e.g., RMSE). The flotation rate constants (k) of both quartz and hematite at a higher solid concentration showed a concave shape, with the inflexion point at the middle-size range, whereas this trend altered at lower solid concentrations. Overall, quartz exhibited higher equilibrium recoveries (R∞) than hematite, which indicates its better overall rate constants. The degree of water recovery in both the quartz and hematite systems was higher at higher solid concentrations, but the hematite system exhibited higher water R∞ than the quartz system, meaning that the entrainment of gangue could be higher in direct hematite flotation than the reverse one. Therefore, a higher solid concentration is associated with better overall quartz recovery and can reduce hematite loss by entrainment during reverse flotation. An inverse relationship was identified between the solid concentration and particle size in terms of the ratio of water recovery to the concentrate. In the reverse flotation of iron ore, refraining from achieving equilibrium recovery could help limit entrainment, but this was not necessarily the case in direct flotation. No entrainment model or method other than the Warren and Ross model approximated the overall trends of flotation at the finest size range (−38 µm). However, extending the Warren method to polynomial distribution led to an improved fit with the experimental results. In addition to the solid concentration, particle density and size were revealed to be key to developing new entrainment models. Finally, after the fast recovery period (true flotation) was over, the slow recoveries were mainly driven by the slow-floating water fraction.

Impact of flotation operational parameters on the optimization of fine and coarse Itabirite iron ore beneficiation

This paper investigates the impact of operational parameters on the reverse flotation of Timbopeba itabirite iron ore in a pneumatic (MBE Pneuflot) flotation cell. To this end, the effects of physical and chemical parameters (i.e., collector and depressant dosage, superficial gas velocity (Jg), solids concentration, and feed rate) on the reverse flotation of iron ore are investigated in detail. Results show that increasing collector dosage increases quartz recovery, particularly for the coarser quartz where recovery increases by nearly 30%. Increasing depressant dosage results in a decrease in both quartz recovery and hematite loss, for the coarser hematite particles. In addition, increasing the feed rate does not affect quartz recovery or hematite loss, suggesting that the pneumatic flotation cell is not constrained by residence time. Furthermore, increasing the superficial gas velocity results in an increases in quartz recovery to an optimum at a Jg of around 0.6 cm/s after which it decreases significantly, particularly for the coarser particles where recovery decreases by 50%. Decreasing the solids concentration does not affect quartz recovery but results in a significant reduction in hematite loss. Here, fine and coarse hematite loss decrease from around 25% to 12% and 10% to 2%, respectively. Solids concentration and Jg are operating parameters that have the largest effect on the flotation performance of the pneumatic flotation cell. Overall, the obtained results suggest that this flotation cell should be operated at relatively low superficial gas velocities and solids concentrations. However, these findings are for a pilot scale and would need to be examined at larger scale (e.g., an industrial scale) where different operating conditions may be optimal.

New perspectives in iron ore flotation: Use of collector reagents without depressants in reverse cationic flotation of quartz

The reverse flotation of the iron ore with etheramine collector is significantly impacted when the iron-bearing silicates and the kaolinite are present in the silicates gangue mineral complex. This paper aims to propose a new amidoamine collector N-[3-(Dimethylamino)propyl]dodecanamide for iron ore reverse flotation with a potential of removing the iron oxides depressant. The contact angle and electrophoretic mobility measurements as well as the flotation experiments were performed on the pure quartz, kaolinite and hematite samples to compare its effect with the etheramine which is widely used as collector in reverse flotation of iron ores. Infrared spectroscopy was performed to study the adsorption of the amidoamine collector on the surface of the minerals studied.Amidoamine collector showed a significant selectivity towards quartz while the flotation of hematite and kaolinite were inhibited at pH 10 without the presence of a depressor. A total floatability of quartz was explained by increased contact angle from 10° to about 50° without impacting significantly the contact angle measured on the hematite (9.4° to 17°). Surface hindrance effect caused by the structure of the N-[3-(Dimethylamino)propyl]dodecanamide collector on the hematite surface is the most suitable hypothesis concerning the high selectivity regarding the iron ore reverse flotation process.

Preparation and properties of dodecylamine microemulsion for the flotation of quartz and magnetite

Dodecylamine (DDA) can only be used with acidification in the reverse flotation of iron ore. To solve this problem, this paper proposed a novel water-in-oil microemulsion with DDA prepared using one or two of AEO-3, OP-10, and Tween-80 & Span-80 as the surfactants, 2-octanol as the cosurfactant, and DDA and kerosene as the oil phase. The freezing point, surface tension, droplet size distribution, and zeta potential were determined for the DDA microemulsion. The results showed that the freezing point of the produced DDA microemulsion can be reduced to –12.5 °C. Moreover, the surfaces of its droplets dispersed in aqueous solution are positively charged at pH values less than 10.0. The flotation performance of the DDA microemulsion was investigated by flotation tests. From the results, DDA microemulsion exhibited good dispersibility and surface activity, thereby confirming its ability to effectively reduce air–water interfacial tension. In addition, it was found to have good adaptability to temperature and pulp pH, yielding a magnetite concentrate with 68.54% Fe and 3.60% SiO2 from magnetite with 64.93% Fe and 9.12% SiO2 using 45 g/t DDA microemulsion. Therefore, the proposed DDA microemulsion can be used as an efficient collector in the reverse flotation of magnetite.

Differences in Etheramines Froth Properties and the Effects on Iron Ore Flotation. Part I: Two-Phase Systems

ABSTRACT Etheramines are quartz collectors and also play a role as frothers in cationic reverse flotation of iron ores. While the adsorption of this surfactant on quartz surface has been widely investigated, the impact of its foam/froth properties on the selectivity in iron ore flotation has not yet been addressed in detail. The structural differences between ethermonoamine and etherdiamine result in distinct adsorption and frothing properties, offering versatility in the concentration of hematite. This study addressed the effect of the etheramine type on flotation selectivity, focused on the analysis of frothing properties. The characterization of the surfactants in the pure state and in two-phase systems (liquid/air) was conducted to investigate the behavior of etheramines concerning foam forming and stabilization. The surface tension measurements showed greater activity of etherdiamine at the liquid–air interface in comparison with ethermonoamine, which was more effective to prevent bubble coalescence and produce smaller bubbles, despite the reagent’s higher critical coalescence concentration. Ethermonoamine presented faster foamability for concentrations greater than the observed critical coalescence concentration values as well as greater water recovery in foam, whereas the double CH2 group and higher molecular weight imparted strong lipophilic character to etherdiamines, producing drier, voluminous, and more stable foams, with longer lifetime. These results are fundamental for the evaluation of three-phase systems, which will be presented in a subsequent paper.

Collecting Agent–Mineral Interactions in the Reverse Flotation of Iron Ore: A Brief Review

Froth flotation has been widely used in upgrading iron ores. Iron ore flotation can be performed in two technical routes: direct flotation of iron oxides and reverse flotation of gangue minerals with depression of iron oxides. Nowadays, reverse flotation is the most commonly used route in iron ore flotation. This review is focused on the reverse flotation of iron ores, consisting of reverse cationic flotation and reverse anionic flotation. It covers different types of collecting agents used in reverse iron ore flotation, the surface characteristics of minerals commonly present in iron ores (e.g., iron oxides, quartz, alumina-bearing minerals, phosphorus-bearing minerals, iron-bearing carbonates, and iron-bearing silicates), and the adsorption mechanisms of the collecting agents at the mineral surface. The implications of collecting agent–mineral interactions for improving iron ore flotation are discussed.

A novel miscible collector DDA–2-octanol–kerosene: Properties and flotation performance

A novel combined reagent dodecylamine (DDA)–2-octanol–kerosene was employed to overcome the problems associated with DDA, that is, DDA has a high freezing point and needs to be acidified with hydrochloric or acetic acid when it is used for flotation. The analysis of the basic physical properties of the agent showed that DDA–2-octanol–kerosene had significant advantages in freezing point and dispersibility and its freezing point can be reduced to below 0 °C. From the flotation results of magnetite, it can be seen that DDA–2-octanol–kerosene has a better selectivity. Response Surface Methodology based on a three-level, three-variable Box–Behnken design (BBD) was employed to define the quadratic relationship between the recovery of quartz and the composition of the mixed agent. The results indicated that the recovery of quartz increased with the increase of DDA or 2-octanol dosage, however, kerosene had a marginal positive effect on the recovery of quartz when the amount of kerosene was less than 0.76 times that of DDA and otherwise a negative effect. This study provides a new method and technical support for its industrial application for the reverse flotation of iron ore for the combination of agents in the field of iron ore flotation. And allows for a deeper macro-level understanding of the interaction between the DDA–2-octanol–kerosene ternary mixed agents.

Investigation of the reverse flotation of iron ore in three different flotation cells: Mechanical, oscillating grid and pneumatic

This paper investigates the reverse flotation of iron ore in a laboratory mechanical, oscillating grid (OGC) and pneumatic flotation cell. The main objectives are to investigate the recovery of coarse quartz (+150 µm) by flotation and fine hematite (−25 µm) by entrainment. Agitation/energy input results show that coarse quartz recovery increases with increasing impeller speed to a maximum of ±70%. The recovery of coarse quartz in the OGC is ±10% higher than in the mechanical cell with an optimum at a low energy input of 0.1 W/kg. Froth height results show that coarse quartz recovery and fine hematite loss decrease by over 50% with increasing froth height. Solids concentration results show that coarse quartz recovery remains relatively constant with decreasing solids concentration, but fine hematite loss decreases from 15 to 5% at the maximum froth height due to lower water recoveries. The OGC generally results in the best overall flotation performance at lower energy input. The pneumatic flotation cell achieves better flotation performance than the mechanical flotation cell for most operating conditions.

Investigating the performance of a novel polyamine derivative for separation of quartz and hematite based on theoretical prediction and experiment

This paper presents the effective design method for amine collectors in the reverse flotation of iron ore and a novel polyamine collector N, N-Dimethyl-N′-dodecyl-1,3-propanediamine (DPDA) was designed based on this method. The properties and flotation behaviors of DPDA were evaluated by Density Functional Theory (DFT) calculation and Molecular Dynamics (MD). The properties analysis indicated that DPDA had an excellent collecting ability, which was similar to N-dodecyl-1,3-diaminopropane (NDEA), but it had better selectivity than NDEA and dodecylamine (DDA). The flotation tests showed that DPDA had a strong collecting ability and good selectivity, it could realize the efficient separation of quartz and hematite under neutral and weak alkaline pulp conditions, which was consistent with the theoretical analysis. The analyses of fourier transform infrared spectroscopy (FTIR), zeta potential, and X-ray photoelectron spectroscopy (XPS) indicated that DPDA adsorbed on the surface of minerals mainly via electrostatic force and hydrogen bonding, which also could be noted from the computation calculation results. The excellent flotation performance of DPDA (especially in selectivity) could be ascribed to more active sites and larger polar group sizes. The results indicated that DFT calculation and MD simulation were an effective method to guide the design of the novel cationic collectors with high selectivity.

The nature of hematite depression with corn starch in the reverse flotation of iron ore

The function of corn starch and the significance of the order of addition of corn starch and mono ether amine in the reverse flotation of iron ore has been investigated. Understanding hematite depression with starch and the corresponding hydrophilic state involves consideration of adsorption with amine as well as flocculation of fine hematite. Captive bubble contact angle and micro-flotation experiments indicated that amine has an affinity towards both hematite and quartz, and that the role of starch is to hinder the adsorption of amine at the hematite surface so that flotation is inhibited. Micro-flotation results confirmed that quartz does not have affinity towards starch at pH 10.5. In addition to competitive adsorption, flocculation of fine hematite occurs and images from high resolution X-ray computed tomography (HRXCT) and cryo-SEM reveal further detail regarding floc structure. These results provide substantial evidence that the fine hematite particles are flocculated in the presence of corn starch, and flocculation is dependent on the particle size of hematite, with greater flocculation for finer particles. Thus, starch is playing a dual role in the reverse flotation of iron ore, acting as a depressant by hindering amine adsorption at the hematite surface in order to maintain the hydrophilic surface state of hematite, and acting as a flocculant to aggregate fine hematite particles, which if not flocculated, could diminish the flotation separation efficiency by being transported to the froth phase during reverse flotation.

Influence of attrition variables on iron ore flotation

Abstract The presence of slimes is harmful to the flotation process: the performance and consumption of reagents are negatively affected. Traditionally, the desliming stage has been responsible for removing slimes. However, depending on the porosity of the mineral particles, desliming may not be sufficient to maximize the concentration results. An attrition process before the desliming operation can improve the removal of slime, especially when slimes cover the surface and/or are confined to the cavities/pores of the mineral particles. Attrition is present in the flowcharts of the beneficiation process of phosphate and industrial sand (silica sand). Research has been undertaken for its application to produce pre-concentrates of zircon and iron ore. However, there is still little knowledge of the influence of the attrition variables on the beneficiation process of iron ore. This study presents a factorial design and analysis of the effects of these variables on the reverse flotation of iron ore. The standard of the experimental procedures for all tests included the attrition of pulp, under the conditions of dispersion, desliming and flotation. The parameter analysed (variable response) was the metallurgical recovery in reverse flotation tests. The planning and analysis of the full factorial experiment indicated that with 95% reliability, the rotation speed of the attrition cell impeller was the main variable in the attrition process of the iron ore. The percentage of solid variables in the pulp and the time of the attrition, as well as their interactions, were not indicated to be significant.

Optimization of Reverse Cationic Flotation of Low-Grade Iron Oxide from Fluorspar Tails Using Taguchi Method

Due to gradual depletion of high-grade iron ores, there is a need to investigate the treatment of low-grade iron ores. Current procedures are time and cost intensive. Batch laboratory scale reverse cationic flotation was employed to concentrate low-grade Fe ore, found in fluorspar tails in the form of hematite. This study used two types of depressants (soluble starch and dextrin) and two types of amines (primary mono-amine and tertiary mono-amine). Optimisation of the process investigated parameters such as pH, collector type and dosage, depressant type and dosage, conditioning time, solids content, agitation speed and air flow rate. Owing to the high number of experiments when all possible combinations are investigated, Taguchi design of experiment method was utilised to streamline the number of experiments and optimize parameters using orthogonal array and signal–noise ratio (SN). The SN was used to determine the optimum conditions and analyse the relative significance of parameters studied. The results showed that both depressants were efficient for hematite depression; however, soluble starch produced better results when compared to Betachem 30D. Both Betacol 373 and Dodecylamine collectors were efficient as quartz collectors; however, Dodecylamine produced better results when compared to Betacol 373. Ranking of parameter using SN ratio showed that pH was the most critical parameter in obtaining higher Fe grade concentrate and the optimum pH is 10. De-slimming leads to low recoveries during reverse flotation of iron ores. The main conclusion is that Taguchi method can be used to optimise a reverse cationic flotation process of a low-grade iron ore.

The influence of starch in amine adsorption by quartz in the reverse flotation of iron ore

The influence of starch in amine adsorption by quartz in the reverse flotation of iron ore

XPS study on the mechanism of starch-hematite surface chemical complexation

Polysaccharides are some of the most widely employed flotation reagents in the mineral processing industry. Among several, starch is of particular importance for reverse flotation of iron ores. It is known to behave as an efficient depressant for hematite and, therefore, its interaction is of great relevance. In this paper, we investigate the surface chemistry of starch adsorbed onto hematite by means of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Our results indicate that starch undergoes an important oxidation process under industrial gelatinization conditions, which favors the binding of starch molecules. Meanwhile, the oxide surface is subjected to full hydroxylation, leading to strong polysaccharide-metal hydroxide interaction. Previously proposed starch interaction mechanisms are discussed, and the importance of acid-base interactions is underscored.

Fundamental issues on the influence of starch in amine adsorption by quartz

Apart from being a resource for iron/steel production, the iron oxide mineral, hematite, is used in the paint, cosmetics, and other industries as a pigment. Reverse flotation of quartz from hematite is used extensively in the processing of iron ore containing quartz as the gangue mineral. It has been observed that depression of quartz takes place when excessive starch is used in the reverse flotation of iron ore, thus reducing the grade of the hematite concentrate. In the present work, the reason for the depression of quartz in the presence of excess starch has been investigated. Contact angle, bubble attachment time, quartz crystal micro balance with dissipation (QCM-D), and sum frequency vibrational spectroscopy (SFVS) measurements have been used to examine the interaction between mono ether amine and starch, and molecular dynamics simulation (MDS) was used to visualize the interaction between the amine and starch molecules. On the basis of these measurements it appears that a clathrate interaction takes place in such a way that the starch masks the hydrophobic tail of the mono ether amine, decreasing the contact angle at the quartz surface to 43° from 62° in the presence of excess starch.

Dispersion degree and zeta potential of hematite

The dispersion degree of the mineral particles in the pulp is especially relevant regarding the performance of the cationic reverse flotation of iron ores. The gangue minerals should remain dispersed while hematite particles should be selectively flocculated. The present study addressed determinations of dispersion degree and zeta potential of hematite in the presence of different dispersants, classified as organic polymeric (natural and synthetic), organic monomeric, and inorganic. Special attention was paid to results achieved at pH 10, used in plant practice. For natural organic polymers, correlation was observed between the dispersion degree and the increase in the negative value of zeta potential. Some synthetic organic polymers enhance the dispersion of hematite particles despite not affecting significantly the zeta potential. Sodium silicates, irrespectively of the SiO2/Na2O ratio, at pH 10, did not impact significantly either the dispersion degree or the zeta potential.