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Applications of Atomic Force Microscopy in Mineral Flotation
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Applications of Atomic Force Microscopy in Mineral Flotation

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 (30 September 2018) | Viewed by 30219

Special Issue Editors

Dr.-Ing. Martin Rudolph

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Guest Editor
Helmholtz Institute Freiberg for Resource Technology, Chemnitzer Str. 40, 09599 Freiberg, Germany
Interests: minerals; flotation; ultra-fine particle processing; fluid dynamics; interface science; surface free energy; AFM; IGC
Mr. Yaowen Xing

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Guest Editor
1. Physics at Interfaces, Max Planck Institute for Polymer Research, 55128 Mainz, Germany
2. School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China
Interests: flotation; surface force; thin water film drainage; bubble–particle interaction; AFM; XPS; flotation intensification (including high-efficiency process and reagents design)

Special Issue Information

Dear Colleagues,

Mineral flotation, belonging to the family of hetero-coagulation separation techniques, is based on the differences in surface hydrophobicity of dispersed mineral particles. It plays an important role in providing raw materials for various industries. Currently, more than two billion tons of minerals and fine coals are processed annually by using froth flotation worldwide. Up to now, the flotation mechanisms at the nanoscale are still not well understood due to the difficulty in experimental verification. In the past years, atomic force microscopy (AFM) has matured to be an indispensable tool to characterize nanomaterials in colloid and interface science. For imaging, a sharp probe mounted near to the end of a cantilever scans over the sample surface providing a high resolution three-dimensional topographic image. In addition, the AFM tip can be used as a force sensor to detect local properties like adhesion, stiffness, charge, etc. After the invention of the colloidal probe technique it has also become a major method to measure surface forces. In the last two decades, AFM has also been widely used by flotation scientists, greatly assisting the fundamental understanding of flotation. This Special Issue aims to publish papers focusing on recent advances in applications of AFM in mineral flotation field. Contributions reporting on surface imaging, water at mineral surface (water structure, surface nanobubbles, etc.), reagent adsorption, inter-particle force, and bubble–particle interaction (including film drainage) are especially welcome.

Dr.-Ing. Martin Rudolph
Mr. Yaowen Xing
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Atomic Force Microscopy
  • Mineral flotation
  • Surface imaging
  • Water at mineral surface (water structure near the interface, surface nanobubbles, etc.)
  • Reagent adsorption (structure of adsorbed reagent, force between reagent and minerals, etc.)
  • Inter-particle force
  • Bubble–particle interaction and film drainage

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Published Papers (7 papers)

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Research

9 pages, 6520 KiB  
Article
Effect of Acidithiobacillus ferrooxidans on Humic-Acid Passivation Layer on Pyrite Surface
by Hongying Yang, Wenjie Luo and Ying Gao
Minerals 2018, 8(10), 422; https://doi.org/10.3390/min8100422 - 22 Sep 2018
Cited by 14 | Viewed by 3512
Abstract
The effect of Acidithiobacillus ferrooxidans on the humic-acid passivation layer on pyrite surfaces was studied by atomic-force microscopy, leaching experiments, and adsorption experiments. Atomic-force-microscopy results showed that humic-acid was adsorbed onto the pyrite surface. The bacteria grew and reproduced on the humic-acid layer. [...] Read more.
The effect of Acidithiobacillus ferrooxidans on the humic-acid passivation layer on pyrite surfaces was studied by atomic-force microscopy, leaching experiments, and adsorption experiments. Atomic-force-microscopy results showed that humic-acid was adsorbed onto the pyrite surface. The bacteria grew and reproduced on the humic-acid layer. Leaching experiments showed that the humic-acid passivation layer prevented the oxidation of pyrite by Fe3+ under aseptic conditions. Bacteria destroyed the humic-acid layer, promoted pyrite oxidation, and increased the oxidation of pyrite from 1.64% to 67.9%. Bacterial adsorption experiments showed that the humic-acid passivation layer decreased the speed of bacterial adsorption on the pyrite surface but had no effect on the number of bacteria adsorbed on the pyrite surface. The maximum number of bacteria adsorbed by pyrite with and without the humic-acid layer was 4.17 × 1010 cells∙mL−1 and 4.4 × 1010 cells∙mL−1, respectively. Extracellular polymeric stratum layer of bacteria cultured at different concentrations of humic-acid was extracted and analyzed. This layer could destroy the humic-acid layer and promote pyrite oxidation. Full article
(This article belongs to the Special Issue Applications of Atomic Force Microscopy in Mineral Flotation)
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10 pages, 6561 KiB  
Article
Flotation Behavior of Diatomite and Albite Using Dodecylamine as a Collector
by Ying Gao, Yuexin Han and Wenbo Li
Minerals 2018, 8(9), 371; https://doi.org/10.3390/min8090371 - 27 Aug 2018
Cited by 8 | Viewed by 3934
Abstract
The flotation behaviors of diatomite and albite using dodecylamine (DDA) as a collector were investigated and compared. The pure mineral flotation results indicate that the flotability difference between albite and diatomite is above 87% at pH 5.5 to 10.5. The recovery of albite [...] Read more.
The flotation behaviors of diatomite and albite using dodecylamine (DDA) as a collector were investigated and compared. The pure mineral flotation results indicate that the flotability difference between albite and diatomite is above 87% at pH 5.5 to 10.5. The recovery of albite improves with increasing DDA dosage at pH 5.5 to 10.5. In the same pH range, diatomite has weaker flotability than albite, particularly in alkaline pH pulp. Zeta potential measurements indicate that diatomite has a higher negative surface charge than albite at pH 7 to 12, DDA interacts strongly with albite and weakly with diatomite. Thus, DDA preferentially absorbs on albite surface rather than diatomite under alkaline conditions. Fourier transform infrared spectra (FTIR) indicate that the amount of DDA adsorbed to albite is greater than that adsorbed to diatomite, under the same conditions. The adsorption of DDA on the surface of diatomite is investigated by using atomic force microscopy (AFM) for the first time. The adsorption of the collector DDA on the surface of albite per unit area is greater than that on diatomite. This accounts for the lower recovery of diatomite than that of albite. Full article
(This article belongs to the Special Issue Applications of Atomic Force Microscopy in Mineral Flotation)
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14 pages, 4750 KiB  
Article
Effects of Xanthate on Flotation Kinetics of Chalcopyrite and Talc
by Limei Bai, Jie Liu, Yuexin Han, Kai Jiang and Wenqing Zhao
Minerals 2018, 8(9), 369; https://doi.org/10.3390/min8090369 - 25 Aug 2018
Cited by 23 | Viewed by 4293
Abstract
This paper investigated the effects of using or not using potassium butyl xanthate (PBX) as a collector on the flotation kinetics of talc and chalcopyrite. By means of atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR), a contact angle measuring instrument and particle [...] Read more.
This paper investigated the effects of using or not using potassium butyl xanthate (PBX) as a collector on the flotation kinetics of talc and chalcopyrite. By means of atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR), a contact angle measuring instrument and particle size analyzer, the underlying causes behind the flotation rate changes of talc and chalcopyrite are analyzed. Experimental results showed that in collectorless flotation, the law of change in the flotation rate constant (k) of the two minerals over time is independent of pH, and k values of chalcopyrite are much smaller than those of talc. In the presence of PBX, the flotation speed of chalcopyrite greatly increases, and the k values of chalcopyrite are far larger than those of talc. This is mainly because the amount of xanthate adsorbed on the surface of chalcopyrite is large and the adsorption is in the form of chemisorption, while the adsorption of xanthate on the talcum surface is in very small amounts and in the form of physical adsorption. Simulation results indicated that the collectorless flotation of chalcopyrite conform to the classical first-order kinetics model and the Kelsall model, whereas that of talc only conform to the latter, which is due to the layered structure of talc. In the presence of the collector, talc flotation conforms to the two model, because talc has a higher floatability and particle morphology has less influence on the flotation rate. Full article
(This article belongs to the Special Issue Applications of Atomic Force Microscopy in Mineral Flotation)
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10 pages, 3831 KiB  
Article
Role of DTAB and SDS in Bubble-Particle Attachment: AFM Force Measurement, Attachment Behaviour Visualization, and Contact Angle Study
by Yaowen Xing, Mengdi Xu, Ming Li, Wei Jin, Yijun Cao and Xiahui Gui
Minerals 2018, 8(8), 349; https://doi.org/10.3390/min8080349 - 13 Aug 2018
Cited by 14 | Viewed by 4176
Abstract
Atomic force microscopy (AFM) and contact angle measurements were used to study the role of dodecyltrimethylammonium bromide (DTAB) and sodium dodecyl sulphate (SDS) in bubble-particle attachment. The results show that the forces between bubbles and the hydrophilic glass particle were always repulsive in [...] Read more.
Atomic force microscopy (AFM) and contact angle measurements were used to study the role of dodecyltrimethylammonium bromide (DTAB) and sodium dodecyl sulphate (SDS) in bubble-particle attachment. The results show that the forces between bubbles and the hydrophilic glass particle were always repulsive in the absence of DTAB and SDS. An attractive hydrophobic force was induced when the particles became hydrophobic, and the force was proportional to the water contact-angle. In the presence of DTAB and SDS, the cationic head group of DTAB adsorbed onto the negative hydrophilic glass surface as a monolayer and thus induced a hydrophobic force. However, at a high DTAB concentration, the DTAB molecules began to adsorb as a bilayer, reverting back to a hydrophilic surface. The hydrophobic force disappeared and the water film between the bubble and particle was stabilised under the repulsive double-layer force. The anionic SDS molecules could not adsorb onto the hydrophilic glass surface. The repulsive force always dominated the bubble-particle interaction. In the case of hydrophobic glass, the hydrophobic force decreased, and even disappeared, with the addition of DTAB and SDS. All the findings from the AFM force curves were consistent with the attachment behaviour and contact angle results. Full article
(This article belongs to the Special Issue Applications of Atomic Force Microscopy in Mineral Flotation)
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11 pages, 5991 KiB  
Article
Effect of Al (III) Ions on the Separation of Cassiterite and Clinochlore Through Reverse Flotation
by Yumeng Chen, Xiong Tong, Dongxia Feng and Xian Xie
Minerals 2018, 8(8), 347; https://doi.org/10.3390/min8080347 - 11 Aug 2018
Cited by 14 | Viewed by 3956
Abstract
Most hydrophobic clay minerals, such as clinochlore, are known to cause problems in the recovery of cassiterite. In this study, a new reagent scheme, i.e., sodium oleate (NaOL) as a collector and Al (III) ions as a depressant, for reverse flotation separation of [...] Read more.
Most hydrophobic clay minerals, such as clinochlore, are known to cause problems in the recovery of cassiterite. In this study, a new reagent scheme, i.e., sodium oleate (NaOL) as a collector and Al (III) ions as a depressant, for reverse flotation separation of cassiterite and clinochlore was investigated. The flotation performance and interaction mechanism were studied by microflotation tests, adsorption tests, contact angle measurements, and X-ray photoelectron spectroscopy (XPS) analysis. Results of single mineral flotation experiments showed that NaOL had a different flotation performance on cassiterite and clinochlore, and the addition of Al (III) ions could selectively inhibit the floatability of cassiterite. Reverse flotation tests performed on mixed minerals indicated that the separation of cassiterite and clinochlore could be achieved in the presence of NaOL and Al (III) ions. Adsorption experiments demonstrated that Al (III) ions hindered the adsorption of NaOL on cassiterite surfaces but exerted little influence on the adsorption of NaOL on clinochlore surfaces. Results of contact angle measurements indicated that Al (III) ions could impede the hydrophobization process of cassiterite in NaOL solution. XPS results showed that aluminum species were adsorbed onto the cassiterite surfaces through the interaction with O sites. Full article
(This article belongs to the Special Issue Applications of Atomic Force Microscopy in Mineral Flotation)
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12 pages, 5445 KiB  
Article
Near-Field Optical Examination of Potassium n-Butyl Xanthate/Chalcopyrite Flotation Products
by Tamás Firkala, Frederik Kuschewski, Tobias Nörenberg, J. Michael Klopf, Alexej Pashkin, Harald Foerstendorf, Martin Rudolph, Susanne C. Kehr and Lukas M. Eng
Minerals 2018, 8(3), 118; https://doi.org/10.3390/min8030118 - 19 Mar 2018
Cited by 6 | Viewed by 4278
Abstract
The present study introduces scattering-type scanning near-field infrared optical nanospectroscopy (s-SNIM) as a valuable and well-suited tool for spectrally fingerprinting n-butyl xanthate (KBX) molecules adsorbed to chalcopyrite (CCP) sample surfaces. The collector KBX is well known to float CCP and is used [...] Read more.
The present study introduces scattering-type scanning near-field infrared optical nanospectroscopy (s-SNIM) as a valuable and well-suited tool for spectrally fingerprinting n-butyl xanthate (KBX) molecules adsorbed to chalcopyrite (CCP) sample surfaces. The collector KBX is well known to float CCP and is used in beneficiation. We thus identified KBX reaction products both by IR optical far- and near-field techniques, applying attenuated total internal reflection Fourier-transform infrared spectroscopy (ATR FT-IR) in comparison to s-SNIM, respectively. The major KBX band around 880 cm−1 was probed in s-SNIM using both the tunable free-electron laser FELBE at the Helmholtz-Zentrum Dresden-Rossendorf facility, Germany, and table-top CO2 laser illumination. We then were able to monitor the KBX agglomeration in patches <500 nm in diameter at the CCP surface, as well as nanospectroscopically identify the presence of KBX reaction products down to the 10−4 M concentration. Full article
(This article belongs to the Special Issue Applications of Atomic Force Microscopy in Mineral Flotation)
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11 pages, 7503 KiB  
Article
Effect of Dodecane and Oleic Acid on the Attachment between Oxidized Coal and Bubbles
by Mengdi Xu, Yaowen Xing, Yijun Cao and Xiahui Gui
Minerals 2018, 8(2), 29; https://doi.org/10.3390/min8020029 - 23 Jan 2018
Cited by 25 | Viewed by 4182
Abstract
The objective of this study is to explain the different flotation responses observed in oxidized coal flotation when using a nonpolar flotation collector, dodecane, versus a polar flotation collector, oleic acid. Particularly, the effect of each flotation collector on bubble–coal particle attachment was [...] Read more.
The objective of this study is to explain the different flotation responses observed in oxidized coal flotation when using a nonpolar flotation collector, dodecane, versus a polar flotation collector, oleic acid. Particularly, the effect of each flotation collector on bubble–coal particle attachment was investigated. Colloidal probe atomic force microscopy (AFM) was used to directly measure the force between a model coal surface and a model bubble in the presence of either dodecane or oleic acid. Pyrolytic graphite (PG) treated with oxygen plasma and a polymethylmethacrylate (PMMA) particle were selected to represent the model oxidized coal surface and model bubble. High speed visualization for bubble–oxidized coal attachment was used to monitor the attachment behavior between bubble and oxidized coal in presence of dodecane and oleic acid, respectively. It was found that the force between the oxidized PG and the PMMA particle in Milli-Q water was monotonically repulsive, illustrating that oxidized coal particles attach onto bubble surface with difficulty. The flotation recovery using a traditional hydrocarbon oil, dodecane, was always lower than when oleic acid was used at a low dosage (300–1100 g/t). The force measurements showed that an attractive hydrophobic force was introduced when a 0.01 mM oleic acid solution was used, while the force was still repulsive in presence of a 0.01 mM dodecane solution. The minimum contact time for successful attachment between oxidized coal surface and bubbles in the presence of 0.01 mM oleic acid is much shorter than that in 0.01 mM dodecane. However, a high flotation recovery of 85.81% was obtained when dodecane concentration was further increased to 1700 g/t. The significant jump into contact effect observed in the AFM force curves and the short induction time in the presence of 1 mM dodecane solution was responsible for this high flotation recovery. Full article
(This article belongs to the Special Issue Applications of Atomic Force Microscopy in Mineral Flotation)
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