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Fine Particle Flotation: Experimental Study and Modelling

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A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Processing and Extractive Metallurgy".

Deadline for manuscript submissions: closed (23 April 2021) | Viewed by 36494

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Special Issue Editors

Prof. Dr. Lev Filippov

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Guest Editor

GeoResources Laboratory, University of Lorraine, F-54505 Vandœuvre-lès-Nancy, France
Interests: flotation general; surface chemistry; modeling of reagent adsorption; synergistic effects of reagents in flotation; calcium mineral separation; process intensification; fine particle flotation; flotation machine; sonication
Special Issues, Collections and Topics in MDPI journals

Assoc. Prof. Daniel Fornasiero

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Co-Guest Editor

Future Industries Institute, University of South Australia, Adelaide, Australia
Interests: surface chemistry; kinetics of flotation; fine and coarse particle flotation; modeling of particle flotation

Special Issue Information

Dear Colleagues,

Froth flotation is the most economical method to separate minerals in ores. However, the complexity of new ore bodies requires fine grinding to liberate valuable minerals, which produces particles with sizes too fine for an efficient mineral flotation and separation. In addition, fine grinding has produced undesirable effects, where gangue minerals too often dilute the valuable mineral concentrates. Although the main causes for the low flotation and separation of fine particles are known and different methods have been developed in the laboratory to overcome these problems, none or only a few of these methods have been successfully implemented in the industry. Therefore, this Special Issue will bring together studies from all areas of fine particle flotation and mineral separation, from fundamental studies on fine particle–bubble interactions (experimental and modeling) in different hydrodynamic conditions, the development of new flotation machines, to the use of more complex mineral systems where mineral separation is the key issue. The hope is that this Special Issue will bring together studies from academic and industry experts, which will contribute to a better understanding of particle–bubble interaction in a complex system and provide solutions to the problem of the low flotation and separation of fine mineral particles in the industry.

Prof. Dr. Lev Filippov
Assoc. Prof. Daniel Fornasiero
Guest Editors

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Keywords

particle–bubble interaction
flotation rate
particle size
bubble size
hydrodynamics
flotation machines
mineral separation
numerical modeling
micro-bubbles
nano-bubbles
slime coating

Published Papers (11 papers)

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Research

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22 pages, 9502 KiB

Open AccessArticle

Iron Ore Slimes Flotation Tests Using Column and Amidoamine Collector without Depressant

by Lev O. Filippov, Klaydison Silva, Alexandre Piçarra, Neymayer Lima, Iranildes Santos, Leandro Bicalho, Inna V. Filippova and Antonio Eduardo Clark Peres

Minerals 2021, 11(7), 699; https://doi.org/10.3390/min11070699 - 29 Jun 2021

Cited by 14 | Viewed by 3785

Abstract

This work describes the concentration of iron ore slimes on a pilot scale by using a 500-mm diameter flotation column and a novel collector, which renders the use of a depressant unnecessary. The pilot column was operated in series with the industrial plant Vargem Grande 2 (Iron Quadrangle, Brazil) receiving, as feed, part of the underflow from the desliming thickener. These pilot tests represented only the rougher stage of a flotation circuit. The novel collector used was an amidoamine (average collector dosage of 160 g/t), and the tests were carried out in the absence of starch, at pH 10.5 and with bubbles/microbubbles generated by cavitation tube. It was possible to achieve a concentrate, by reverse flotation, with an average iron content of 53% and an average metallurgical recovery of 91.5% The recovery of the silica in the froth was 53.1% in average for one stage of flotation. The high variability of the slime characteristics rendered difficult the stabilization of the SiO₂ recovery; however, the applicability of the amidoamine collector was proven. In an industrial scale circuit, the use of online analyzers for Fe and SiO₂ content and the adoption of control logics based on the adjustment of parameters such as reagents dosage and washing water flow rate adjustment should contribute to the optimization of the results obtained in the pilot scale tests. Further studies adding a cleaner concentration stage should be performed. Full article

(This article belongs to the Special Issue Fine Particle Flotation: Experimental Study and Modelling)

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18 pages, 3328 KiB

Open AccessArticle

A Hybrid Device for Enhancing Flotation of Fine Particles by Combining Micro-Bubbles with Conventional Bubbles

by Polyxeni K. Tsave, Margaritis Kostoglou, Thodoris D. Karapantsios and Nikolaos K. Lazaridis

Minerals 2021, 11(6), 561; https://doi.org/10.3390/min11060561 - 25 May 2021

Cited by 12 | Viewed by 2962

Abstract

Flotation in the mining industry is a very significant separation technique. It is known that fine and ultra-fine particles are difficult to float, leading to losses of valuable minerals, mainly due to their low collision efficiency with bubbles. Flotation of fine particles can be enhanced either by increasing the apparent particle size or by decreasing the bubble size. Literature review reveals that electroflotation resulted in higher recoveries of ultrafine particles as compared with dispersed-air flotation, because electrolytic bubbles are smaller in size. To this end, the best practical approach is to combine conventional air bubbles and micro-bubbles from water electrolysis. Therefore, the design, fabrication, and operation of a bench-scale micro-bubble generator through water electrolysis is proposed. Moreover, this electrolysis unit is adapted in a mechanical Denver-type flotation cell. The resulting hybrid flotation device is capable of producing bubbles within a wide range of diameters. The significance of this process is that micro-bubbles, attached tothe surface of fine particles, facilitate the attachment of conventional-sized bubbles and subsequently increase the flotation recovery of particles. Experimental flotation results so far on the hybrid device indicate the enhancement of fine particle recovery by approximately 10% with the addition of micro-bubbles. Full article

(This article belongs to the Special Issue Fine Particle Flotation: Experimental Study and Modelling)

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20 pages, 6574 KiB

Open AccessArticle

Impact of Sodium Hexametaphosphate on the Flotation of Ultrafine Magnesite from Dolomite-Rich Desliming Tailings

by Duong Huu Hoang, Doreen Ebert, Robert Möckel and Martin Rudolph

Minerals 2021, 11(5), 499; https://doi.org/10.3390/min11050499 - 8 May 2021

Cited by 5 | Viewed by 3167

Abstract

The depletion of ore deposits, the increasing demand for raw materials, the need to process low-grade, complex and finely disseminated ores, and the reprocessing of tailings are challenges especially for froth flotation separation technologies. Even though they are capable of handling relatively fine grain sizes, the flotation separation of very fine and ultrafine particles faces many problems still. Further, the flotation of low-contrast semi-soluble salt-type minerals with very similar surface properties, many complex interactions between minerals, reagents and dissolved species often result in poor selectivity. This study investigates the flotation beneficiation of ultrafine magnesite rich in dolomite from desliming, currently reported to the tailings. The paper especially focuses on the impact of the depressant sodium hexametaphosphate (SHMP) on the following: (i) the froth properties using dynamic froth analysis (DFA), (ii) the separation between magnesite and dolomite/calcite, and (iii) its effect on the entrainment. As a depressant/dispersant, SHMP has a beneficial impact on the flotation separation between magnesite and dolomite. However, there is a trade-off between grade and recovery, and as well as the dewatering process which needs to be considered. When the SHMP increases from 200 g/t to 700 g/t, the magnesite grade increases from 67% to 77%, while recovery decreases massively, from 80% to 40%. The open circuit with four cleaning stages obtained a concentrate assaying 77.5% magnesite at a recovery of 45.5%. The dolomite content in the concentrate is about 20%, where 80% of dolomite was removed and importantly 98% of the quartz was removed, with only 0.3% of the quartz in the final concentrate. Furthermore, the application of 1-hydroxyethylene-1,1-diphosphonic acid (HEDP) as a more environmentally friendly and low-cost alternative to SHMP is presented and discussed. Using only 350 g/t of HEDP can achieve a similar grade (76.3%), like 700 g/t of SHMP (76.9%), while obtaining a 17% higher magnesite recovery as compared to 700 g/t of SHMP. Interestingly, the proportion of hydrophilic quartz minerals ending up in the concentrate is lower for HEDP, with only 1.9% quartz at a recovery of 21.5% compared to the 2.7% of quartz at a recovery of 24.9% when using SHMP. The paper contributes in general to understanding the complexity of the depressant responses in froth flotation. Full article

(This article belongs to the Special Issue Fine Particle Flotation: Experimental Study and Modelling)

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16 pages, 3256 KiB

Open AccessArticle

Adsorption Kinetics of Various Frothers on Rising Bubbles of Different Sizes under Flotation Conditions

by Khandjamts Batjargal, Onur Guven, Orhan Ozdemir, Stoyan I. Karakashev, Nikolay A. Grozev, Feridun Boylu and Mehmet Sabri Çelik

Minerals 2021, 11(3), 304; https://doi.org/10.3390/min11030304 - 16 Mar 2021

Cited by 10 | Viewed by 2506

Abstract

This paper studies the effect of the type and concentration of selected frothers, the gas flowrate, and the pore size of the porous frit on the bubble sizes (Sauter mean diameter, SMD) of bubbling flow produced in a micro-flotation cell, and the determination of bubble size distribution (BSD) in the presence of the frothers. The commercial frothers polypropylene glycols (PPG 200, 400, and 600), tri propylene glycol (BTPG), triethylene glycol (BTEG), dipropylene glycol (BDPG), and Methyl Isobutyl Carbinol (MIBC) were used in the present investigation. The frother concentration varied from 1 to 1000 ppm. The flow rate varied in the range of 25 to 100 cm³/min. The pore sizes of the frit were selected as 10–16 μm, 16–40 μm, and 40–100 μm. Each frother exhibited its own unique ability in preventing coalescence of the bubbles in the order of BTEG < BDPG < PPG 200 < MIBC < BTPG < PPG 400 < PPG 600. The factorial experiments established that the type of the frother and its concentration have a major effect on the size of the bubbles. The bubbles decreased twice their size when the frother concentration was increased from 1 ppm to 1000 ppm. The pore size of the frit is a significant factor as well. The size of the bubbles can be reduced from about 10% to about 40% by decreasing the pores from 40–100 μm to 10–16 μm but the level of this decrease depends on the type of the frother. The increase of the flowrate from 25 cm³/min to 100 cm³/min produced bubbles smaller by 25% to 50% for the case of BTEG, BDPG, PPG 200, MIBC, BTPG, while a minimum of the bubble sizes was reached for the case of PPG 400 and PPG 600, beyond which the bubbles enlarged their size. The BSD in the presence of PPG 600 varied around 0.3 mm, whereas BTEG gave a wider BSD which indicated that the type of frother affected the bubble production. Our analysis shows that the first group of frothers adsorbs instantly on the bubbles, once they leave the porous frit, thus reaching equilibrium. PPG 400 and PPG 600 adsorb significantly slower on the bubbles, possibly not reaching equilibrium during their resident time. Full article

(This article belongs to the Special Issue Fine Particle Flotation: Experimental Study and Modelling)

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12 pages, 22938 KiB

Open AccessFeature PaperCommunication

A Model Structure for Size-by-Liberation Recoveries in Flotation

by Paulina Vallejos, Juan Yianatos and Luis Vinnett

Minerals 2021, 11(2), 194; https://doi.org/10.3390/min11020194 - 12 Feb 2021

Cited by 6 | Viewed by 2704

Abstract

This communication presents a model structure for the flotation recovery of middling particles (10–90% liberation). Fourteen datasets from the literature were studied (galena flotation), which involved different flotation systems and operating conditions. The flotation responses allowed the model flexibility to be evaluated under a range of recovery profiles. The modelling results showed that galena recovery can be characterized by the interaction between a linear function and a concave function (e.g., Gamma model), to account for the liberation and particle size effects, respectively. Liberation also impacts the location and dispersion of the recovery dependence on particle size. The proposed model structure showed there was adequate flexibility with five parameters, leading to adjusted coefficients of determination ranging from 0.863 to 0.998 for the studied datasets. Thus, an alternative approach for modelling the recovery of middling particles is proposed, which represents the liberation and particle size dependence with a few parameters. Full article

(This article belongs to the Special Issue Fine Particle Flotation: Experimental Study and Modelling)

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Graphical abstract

13 pages, 3816 KiB

Open AccessArticle

Reverse Combined Microflotation of Fine Magnetite from a Mixture with Glass Beads

by Nickolaj N. Rulyov, Lev O. Filippov, Dmytro Y. Sadovskyi and Vitalina V. Lukianova

Minerals 2020, 10(12), 1078; https://doi.org/10.3390/min10121078 - 30 Nov 2020

Cited by 2 | Viewed by 1722

Abstract

Magnetite is an essential iron-bearing mineral. The primary method of magnetite ore beneficiation involves successive steps of crushing, grinding, and magnetic separation. Reverse cationic flotation is used at the final stage to remove silicate and aluminosilicate impurities from the magnetite concentrate and reduce silica content to 1–3%, depending on metallurgical processing route (electrometallurgy, direct iron reduction). In view of the stringent demands of the magnetite concentrate grade, before flotation, the ore is currently routinely ground down to a particle size below 35 µm, and magnetite particles are ground to a size below 10 µm. This significantly reduces the efficiency of flotation and increases iron loss in the tailings due to the hydraulic report in froth being up to 15–25%. Combined microflotation (CMF) looks to be a promising method of increasing fine-particle flotation efficiency, as it uses relatively small amounts of microbubbles alongside conventional coarse bubbles. Microbubbles act as flotation carriers, collecting gangue particles on their surface, which then coarse bubbles float. The purpose of this study is to explore the effectiveness of CMF for processing a model mixture that contained magnetite particles smaller than 10 µm and glass beads (Ballotini) below 37 µm in size when the initial iron content in the mixture was 63.76%. Commercial reagent Lilaflot 821M was used as both collector and frother. The flotation procedure, which included the introduction of 15 g/t of the collector before the start of flotation, and the addition of 5 g/t of the collector in combination with a microbubble dose of 0.018 m³/t 6 min after starting flotation, ensured an increase in the concentrate grade to 67.63% Fe and iron recovery of 91.16%. Full article

(This article belongs to the Special Issue Fine Particle Flotation: Experimental Study and Modelling)

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16 pages, 4177 KiB

Open AccessArticle

Hydrophobic Agglomeration of Fine Pyrite Particles Induced by Flotation Reagents

by Wanli Cheng, Zhengbin Deng, Xiong Tong and Tianshen Lu

Minerals 2020, 10(9), 801; https://doi.org/10.3390/min10090801 - 11 Sep 2020

Cited by 15 | Viewed by 3473

Abstract

Flotation reagents can change the surface properties of minerals, leading to differences in the interaction between mineral particles and affecting the mutual aggregation or dispersion of particles. In this work, we studied the role of activator copper sulfate, collector butyl xanthate and frother terpineol in adjusting the potential energy of pyrite particles from the perspective of the interfacial interaction. We evaluated the surface characteristics using contact angle analysis and zeta potential measurements under different reagents. A microscope was used to observe aggregation state of particles. The hydrophobic agglomeration kinetics of pyrite was studied through the turbidity meter measurement, and the interaction energy between pyrite particles was calculated using the extended-Derjaguin-Landau-Verwey-Overbeek (extended-DLVO) theory. The results showed that the repulsive potential energy is dominant among pyrite particles in aqueous suspensions and that the particles are easy to disperse. Flotation reagents can effectively reduce the repulsive energy between pyrite particles and increase the attraction energy between particles, which is conducive to the hydrophobic agglomeration of fine pyrite. Reagent molecules can greatly reduce the electrostatic repulsion potential energy of the pyrite particles’ interface, increase the hydrophobic attraction potential energy between the particle interfaces, and its size is 2 orders of magnitude larger than the van der Waals attraction potential energy, which is the main reason for induced the agglomeration of fine pyrite and is conducive to the flotation recovery of fine pyrite. Generally, the order in which the reduction of pyrite agglomeration was affected by the additions of flotation reagents was butyl xanthate > terpineol > copper sulfate. Full article

(This article belongs to the Special Issue Fine Particle Flotation: Experimental Study and Modelling)

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7 pages, 786 KiB

Open AccessCommunication

Semi-Continuous Froth Discharge to Reduce Entrainment of Fine Particles in Flotation Cells Subject to Low-Mineralized Froths

by Juan Yianatos, Paulina Vallejos, Luis Vinnett and Sebastián Arriagada

Minerals 2020, 10(8), 695; https://doi.org/10.3390/min10080695 - 5 Aug 2020

Cited by 1 | Viewed by 1895

Abstract

An operational strategy is proposed to improve the metallurgical performance of flotation cells subject to low-mineralized froths. This strategy consists of using a semi-continuous discharge into the concentrate, in which the froth is operated under loading and unloading periods. A transient model is developed to evaluate the proposed approach. The model is calibrated using experimental data from two industrial flotation banks. The metallurgical performances of the last cells of these banks are then simulated, considering the semi-continuous froth discharge. The results show that the semi-continuous mode significantly reduces gangue entrainment, improving the concentrate grade while maintaining approximately the same recovery. The semi-continuous strategy demonstrates good potential to enhance the metallurgical indexes under low-mineralized froths, as those in the last cells of rougher flotation banks. Full article

(This article belongs to the Special Issue Fine Particle Flotation: Experimental Study and Modelling)

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14 pages, 1899 KiB

Open AccessArticle

The Depressing Effect of Kaolinite on Molybdenite Flotation in Seawater

by Andres Ramirez, Leopoldo Gutierrez, Dennis Vega-Garcia and Lorenzo Reyes-Bozo

Minerals 2020, 10(6), 578; https://doi.org/10.3390/min10060578 - 26 Jun 2020

Cited by 16 | Viewed by 3423

Abstract

Copper-molybdenum grades of important mining deposits have progressively decayed, which is associated with high levels of clay minerals which affect froth flotation. The depressing effect of clay minerals on copper sulfides was previously reported but there are no systematic studies on the effect on molybdenite flotation in seawater. The objective of this work was to study the effect of kaolinite on molybdenite flotation in seawater and to evaluate the use of sodium hexametaphosphate (SHMP) as dispersant. The results of this work show that kaolinite depresses molybdenite flotation which is more significant in seawater at pH > 9. All the experimental data validate the hypothesis that kaolinite covers molybdenite, reducing its flotation recovery. The depressing effect of kaolinite on molybdenite flotation in seawater is enhanced by the magnesium and calcium hydroxo complexes at pH > 9, which induce heterocoagulation between kaolinite and molybdenite, thus reducing recovery. The attachment of the positively charged hydroxo complexes of magnesium and calcium to the molybdenite and kaolinite surfaces is diminished by SHMP. This reagent increases the repulsive forces between molybdenite and precipitates and as a result, molybdenite becomes more hydrophobic and recovery increases. Full article

(This article belongs to the Special Issue Fine Particle Flotation: Experimental Study and Modelling)

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10 pages, 4655 KiB

Open AccessArticle

Carrier Flotation of Low-Rank Coal with Polystyrene

by Gen Huang, Jiaqi Xu, Pengyue Geng and Jihui Li

Minerals 2020, 10(5), 452; https://doi.org/10.3390/min10050452 - 18 May 2020

Cited by 16 | Viewed by 2581

Abstract

The problem of low-rank coal flotation continues to be a challenge due to the poor hydrophobicity and abundant oxygenated functional groups on particle surfaces. In this study, carrier flotation was used to improve the flotation performance of low-rank coal with polystyrene as a carrier material. Kerosene was used as a collector and played a role in the adhesion of fine low-rank coal to polystyrene due to its hydrophobic properties. The carrier feature of polystyrene was demonstrated by Turbiscan Lab Expert stability analysis and scanning electron microscopy analysis. The flotation experiments revealed that the optimum conditions were: collector dosage 5000 g/t, pulp concentration 40 g/L, and the ratio of low-rank coal to polystyrene 100:10. Under these conditions, the combustible recovery by carrier flotation was obtained as 70.59% when the ash content was 12.32%, which increased by 25.68 points compared with the combustible recovery of conventional flotation under almost the same ash content. The fine coal particles coated the coarse polystyrene particles through hydrophobic interactions between the polystyrene and hydrocarbon chains of the kerosene adsorbed on coal particles. The results suggested that the flotation performance of low-rank coal was significantly improved by carrier flotation with polystyrene, especially for fine particles. Full article

(This article belongs to the Special Issue Fine Particle Flotation: Experimental Study and Modelling)

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Review

Jump to: Research

17 pages, 2742 KiB

Open AccessFeature PaperReview

by Kirsten C. Corin, Belinda J. McFadzean, Natalie J. Shackleton and Cyril T. O’Connor

Minerals 2021, 11(5), 533; https://doi.org/10.3390/min11050533 - 18 May 2021

Cited by 13 | Viewed by 6029

Abstract

In order to increase the recovery of PGMs by flotation, it is necessary to optimise the liberation of the key minerals in which the platinum group elements (PGEs) are contained which include sulphides, arsenides, tellurides, and ferroalloys among others, while at the same time ensuring the optimal depression of gangue minerals. In order to achieve this, comminution circuits usually consist of two or three stages of milling, in which the first stage is autogeneous, followed by ball milling. Further liberation is achieved in subsequent stages using ultra-fine grinding. Each comminution stage is followed by flotation in the so-called MF2 or MF3 circuits. While this staged process increases overall recoveries, overgrinding may occur, hence creating problems associated with fine particle flotation. This paper presents an overview of the mineralogy of most of the more significant PGM ores processed in South Africa and the various technologies used in comminution circuits. The paper then summarises the methodology used in flotation circuits to optimise recovery of fine particles in terms of the collectors, depressants, and frothers used. The effect of entrainment, slimes coating, changes in rheology caused by the presence of a significant amount of fines and of chromite recovery is addressed. Full article

(This article belongs to the Special Issue Fine Particle Flotation: Experimental Study and Modelling)

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