Sarah Harmer

Synchrotron XPS studies of solution exposed chalcopyrite, bornite, and heterogeneous chalcopyrite with bornite

Publisher: Elsevier BV

Date: 02-2010

DOI: 10.1016/J.MINPRO.2009.11.006

Synchrotron-based XPS and NEXAFS study of surface chemical species during electrochemical oxidation of chalcopyrite

Publisher: Elsevier BV

Date: 07-2015

DOI: 10.1016/J.HYDROMET.2015.05.011

Characterisation of the Material and Mechanical Properties of Atomic Force Microscope Cantilevers with a Plan-View Trapezoidal Geometry

Publisher: MDPI AG

Date: 27-06-2019

DOI: 10.3390/APP9132604

Abstract: Cantilever devices have found applications in numerous scientific fields and instruments, including the atomic force microscope (AFM), and as sensors to detect a wide range of chemical and biological species. The mechanical properties, in particular, the spring constant of these devices is crucial when quantifying adhesive forces, material properties of surfaces, and in determining deposited mass for sensing applications. A key component in the spring constant of a cantilever is the plan-view shape. In recent years, the trapezoidal plan-view shape has become available since it offers certain advantages to fast-scanning AFM and can improve sensor performance in fluid environments. Euler beam equations relating cantilever stiffness to the cantilever dimensions and Young’s modulus have been proven useful and are used extensively to model cantilever mechanical behaviour and calibrate the spring constant. In this work, we derive a simple correction factor to the Euler beam equation for a beam-shaped cantilever that is applicable to any cantilever with a trapezoidal plan-view shape. This correction factor is based upon previous analytical work and simplifies the application of the previous researchers formula. A correction factor to the spring constant of an AFM cantilever is also required to calculate the torque produced by the tip when it contacts the s le surface, which is also dependent on the plan-view shape. In this work, we also derive a simple expression for the torque for triangular plan-view shaped cantilevers and show that for the current generation of trapezoidal plan-view shaped AFM cantilevers, this will be a good approximation. We shall apply both these correction factors to determine Young’s modulus for a range of trapezoidal-shaped AFM cantilevers, which are specially designed for fast-scanning. These types of AFM probes are much smaller in size when compared to standard AFM probes. In the process of analysing the mechanical properties of these cantilevers, important insights are also gained into their spring constant calibration and dimensional factors that contribute to the variability in their spring constant.

Identification of pyrite valence band contributions using synchrotron-excited X-ray photoelectron spectroscopy

Publisher: Mineralogical Society of America

Date: 02-2004

DOI: 10.2138/AM-2004-2-319

The role of mineral surface chemistry in modified dextrin adsorption

Publisher: Elsevier BV

Date: 05-2011

DOI: 10.1016/J.JCIS.2011.02.017

Abstract: The adsorption of two modified dextrins (phenyl succinate dextrin--PS Dextrin styrene oxide dextrin--SO Dextrin) on four different mineral surfaces has been studied using X-ray photoelectron spectroscopy (XPS), in situ atomic force microscopy (AFM) imaging, and captive bubble contact angle measurements. The four surfaces include highly orientated pyrolytic graphite (HOPG), freshly cleaved synthetic sphalerite (ZnS), and two surfaces produced through surface reactions of sphalerite: one oxidized in alkaline solution (pH 9, 1 h immersion) and one subjected to metal ion exchange between copper and zinc (i.e. copper activation: exposed to 1×10(-3) M CuSO(4) solution for 1 h). XPS measurements indicate that the different sphalerite surfaces contain varying amounts of sulfur, zinc, oxygen, and copper, producing substrates for polymer adsorption with a range of possible binding sites. AFM imaging has shown that the two polymers adsorb to a similar extent on HOPG, and that the two polymers display very different propensities for adsorption on the three sphalerite surface types, with freshly cleaved sphalerite encouraging the least adsorption, and copper activated and oxidized sphalerite encouraging significantly more adsorption. Contact angle measurements of the four surfaces indicate that synthetic sphalerite has a low contact angle upon fracture, and that oxidation on the timescale of one hour substantially alters the hydrophobicity. HOPG and copper-activated sphalerite were the most hydrophobic, as expected due to the carbon and di oly-sulfide rich surfaces of the two s les, respectively. SO Dextrin is seen to have a significant impact on the wettability of HOPG and the surface reacted sphalerite s les, highlighting the difficulty in selectively separating sphalerite from carbonaceous unwanted minerals in flotation. PS Dextrin has the least effect on the hydrophobicity of the reacted sphalerite surfaces, whilst still significantly increasing the wettability of graphite, and thus has more potential for use as a polymer depressant in this separation.

High resolution XPS study of the large-band-gap semiconductor stibnite (Sb2S3): Structural contributions and surface reconstruction

Publisher: Elsevier BV

Date: 2006

DOI: 10.1016/J.SUSC.2005.10.034

ARXPS and SXPS Evidence for Surface Stabilization of Sphalerite Zn_1-xFe_xS (110) Surfaces

Publisher: The Electrochemical Society

Date: 16-04-2010

DOI: 10.1149/1.3367904

Abstract: Angle resolved X-ray photoelectron spectroscopy (ARXPS) and synchrotron XPS (SXPS) have been used to study the (110) surface of two Fe containing sphalerites cleaved in vacuo. The ARXPS S 2p and Zn 2p spectra collected from a low Fe (0.02 wt.%) sphalerite revealed a low binding energy peak when collected at low take off angles (20°). These peaks have been assigned as surface core-level shifts of ~ -0.46 eV and ~ +0.34 eV, respectively. The ARXPS and SXPS S 2p spectra collected from a high Fe (14.79 wt.%) sphalerite indicated the presence of a low binding energy peak resulting from a core level shift ~ -0.42 eV below the bulk S 2p line. A higher binding energy contribution, attributed to a second surface species, was found +0.47 eV above the bulk S 2p doublet. Comparison of the S 2p spectra collected from the two sphalerites, suggested that high Fe concentrations might induce surface reconstruction in the form of surface S dimers. The surface S dimers are likely to be concentrated at high energy step edges and defects.

Synchrotron PEEM and ToF-SIMS study of oxidized heterogeneous pentlandite, pyrrhotite and chalcopyrite

Publisher: International Union of Crystallography (IUCr)

Date: 28-07-2010

DOI: 10.1107/S0909049510026749

Cu(II) removal by Anoxybacillus flavithermus–iron oxide composites during the addition of Fe(II)aq

Publisher: Elsevier BV

Date: 2016

DOI: 10.1016/J.GCA.2015.09.031

The effect of different pyrolysis temperatures on the speciation and availability in soil of P in biochar produced from the solid fraction of manure

Publisher: Elsevier BV

Date: 02-2017

DOI: 10.1016/J.CHEMOSPHERE.2016.11.058

Abstract: Biochar application to agricultural land has been proposed as a means for improving phosphorus (P) availability in soil. The purpose of the current study was to understand how pyrolysis temperature affects P speciation in biochar and how this affects availability of P in the amended soil. Biochar was produced at different temperatures from digestate solids. The primary species of P in digestate solids were simple calcium phosphates. However, a high co-occurrence of magnesium (Mg) and P, indicated that struvite or other magnesium phosphates may also be important species. At low temperatures, pyrolysis had little effect on P speciation however, as the temperature increased above 600 °C, the P gradually became more thermodynamically stable in species such as apatite. At very high temperatures above 1000 °C, there were indications of reduced forms of P. Biochar production decreased the immediate availability of P in comparison with the original digestate solids. However, for biochar produced at low temperatures, availability quickly increased to the same levels as in the digestate solids. For biochar produced at higher temperatures, availability remained depressed for much longer. The low availability of P in the biochar produced at high temperatures can probably be explained by the formation of less soluble P species in the biochar. In contrast, the transient decrease of availability of the P in the biochar produced at low temperatures can be explained by mechanisms, such as sorption on biochar, which gradually decreases because of oxidation of the biochar surfaces or changes in pH around the biochar particles.

Sulfur K-edge XANES spectroscopy

Publisher: Mineralogical Association of Canada

Date: 10-2005

DOI: 10.2113/GSCANMIN.43.5.1605

Local and electronic structure of FeS, CoS, NiS: Ultrasoft sulfur L2,3 X-ray absorption spectra analysis

Publisher: Elsevier BV

Date: 06-2005

DOI: 10.1016/J.ELSPEC.2005.01.014

Stabilization of pyrite (FeS2), marcasite (FeS2), arsenopyrite (FeAsS) and loellingite (FeAs2) surfaces by polymerization and auto-redox reactions

Publisher: Elsevier BV

Date: 08-2004

DOI: 10.1016/J.SUSC.2004.06.199

Synchrotron FTIR microscopy of Langmuir-Blodgett monolayers and polyelectrolyte multilayers at the solid-solid interface

Publisher: American Chemical Society (ACS)

Date: 12-01-2012

DOI: 10.1021/LA2045543

Electronic structure of MeS (Me = Ni,Co,Fe): x-ray absorption analysis

Publisher: IOP Publishing

Date: 02-10-2004

DOI: 10.1088/0953-8984/16/41/031

Selective Attachment of Leptospirillum ferrooxidans for Separation of Chalcopyrite and Pyrite through Bio-Flotation

Publisher: MDPI AG

Date: 27-02-2018

DOI: 10.3390/MIN8030086

Scanning Auger Microscopy Studies of Silane Films Grown on Plasma-Modified HOPG Surfaces

Publisher: MDPI AG

Date: 12-02-2019

DOI: 10.3390/POLYM11020307

Abstract: The growth of silane films on plasma oxidized highly oriented pyrolytic graphite (HOPG) surfaces has been studied using wet chemical deposition of propyltrimethoxysilane (PTMS) and propyldimethylmethoxysilane (PDMMS). Scanning Auger microscopy (SAM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the chemical composition and morphology of the silane films. The effects of several deposition parameters were examined, including the necessity of oxidation of the HOPG surface, addition of water with the silane, and rinsing before curing. The optimal conditions needed to create a complete uniform film differ for the two silanes due to differences in their structures. Both silanes require an oxidized HOPG surface for a film to grow, the addition of water with PTMS results in a thicker film, while the addition of water with PDMMS decreases the film growth. Rinsing of both s les before curing removes physisorbed species, leaving only the covalently bonded film on the surface.

Orientation and mutual location of ions at the surface of ionic liquids

Publisher: Royal Society of Chemistry (RSC)

Date: 2010

DOI: 10.1039/C0CP00683A

Abstract: The structure of the liquid-vacuum interface in room temperature ionic liquids (ILs) is investigated using angle-resolved X-ray photoelectron spectroscopy (ARXPS) and synchrotron X-ray photoelectron spectroscopy (SXPS). By varying the polar angle and comparing the results for the chosen ionic liquids, we identify the presence of a surface layer that is chemically different to the bulk. In particular, this layer: (i) is enriched by aliphatic carbon atoms from the saturated carbon chains of the anions and cations, and (ii) contains an unequal distribution of cations and anions in a direction normal to the surface. This unequal distribution creates a potential gradient which extends from the surface into the liquid. We show unequivocally that this layer is not due to the presence of impurities.

Sulfur species at chalcopyrite (CuFeS₂) fracture surfaces

Publisher: Mineralogical Society of America

Date: 07-2004

DOI: 10.2138/AM-2004-0713

The oscillatory adsorption of self‐assembled organosilane films on aluminium oxide surfaces

Publisher: Wiley

Date: 22-06-2018

DOI: 10.1002/SIA.6483

Reconstruction of pyrrhotite fracture surfaces

Publisher: Elsevier BV

Date: 06-2022

DOI: 10.1016/J.MINENG.2022.107666

The Oscillatory Adsorption of Organosilane Films on Aluminium Oxide: Film Morphology using Auger Electron Spectromicroscopy

Publisher: Elsevier BV

Date: 05-2019

DOI: 10.1016/J.APSUSC.2019.01.015

Oxidative Dissolution of Sulfide Minerals in Single and Mixed Sulfide Systems under Simulated Acid and Metalliferous Drainage Conditions

Publisher: American Chemical Society (ACS)

Date: 28-01-2021

DOI: 10.1021/ACS.EST.0C07136

Synchrotron XPS, NEXAFS, and ToF-SIMS studies of solution exposed chalcopyrite and heterogeneous chalcopyrite with pyrite

Publisher: Elsevier BV

Date: 10-2010

DOI: 10.1016/J.MINENG.2010.03.007

A direct observation of bacterial coverage and biofilm formation by Acidithiobacillus ferrooxidans on chalcopyrite and pyrite surfaces

Publisher: Informa UK Limited

Date: 09-08-2015

DOI: 10.1080/08927014.2015.1073720

Abstract: To obtain a fundamental understanding of the population behaviour of Acidithiobacillus ferrooxidans at chalcopyrite and pyrite surfaces, the early stage attachment behaviour and biofilm formation by this bacterium on chalcopyrite (CuFeS2) and pyrite (FeS2) were studied by optical microscopy, Raman spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS) and electron backscatter diffraction (EBSD). The results indicate there was no significant difference in selectivity of bacterial attachment between chalcopyrite and pyrite. However, the result of ToF-SIMS analysis suggests that the surface of the pyrite was covered more extensively by biofilm than that of the chalcopyrite, which may indicate more extracellular polymeric substances (EPS) formation by bacterial cells growing on pyrite. EBSD and optical image analysis indicated that selectivity of bacterial attachment to chalcopyrite was not significantly affected by crystal orientation. The results also suggest that the bacterial population in defective areas of chalcopyrite was significantly higher than on the polished surfaces.

Influence of Co:Fe:Ni ratio on cobalt Pentlandite’s electronic structure and surface speciation

Publisher: Elsevier BV

Date: 12-2022

DOI: 10.1016/J.MINENG.2022.107935

CHEMICAL STATE OF SULFUR IN NATURAL AND SYNTHETIC LAZURITE BY S K-EDGE XANES AND X-RAY PHOTOELECTRON SPECTROSCOPY

Publisher: Mineralogical Association of Canada

Date: 10-2005

DOI: 10.2113/GSCANMIN.43.5.1589

Atomic Force Microscopy and Raman Microspectroscopy Investigations of the Leaching of Chalcopyrite (112) Surface

Publisher: MDPI AG

Date: 26-05-2020

DOI: 10.3390/MIN10060485

Abstract: The aim of this study was to determine the reactivity of the chalcopyrite (112) surface under industrially relevant leaching conditions. Leaching of the chalcopyrite (112) surface was carried out at approximately pH 1 and in the presence of 0.01 M ferric or ferrous. The atomic force microscopy (AFM) and Raman microspectroscopy analyses suggested that the chalcopyrite (112) surface was relatively inert, with no formation of elemental sulfur observed over 42 days of leaching. In addition, it was found that the distribution of Fe-S and Cu-S bonds was always negatively correlated, as revealed by Raman analysis. This suggested that the breakage of the Fe-S and Cu-S bonds did not occur concurrently at a specific reaction site. The rate of variation of surface roughness, as reflected by AFM data, also suggested that leaching of the chalcopyrite (112) surface in the ferric or ferrous solution medium likely occurred more rapidly in the initial stage (fewer than seven days) than in the later stage (after seven days).

Spectroscopic study of ionic liquid adsorption from solution onto gold.

Publisher: Royal Society of Chemistry (RSC)

Date: 2015

DOI: 10.1039/C4CP05558F

Abstract: HMIM NTf 2 adsorbs on gold from ethanol to form a patchy bilayer. ‘Bound’ anion (filled anion) and ‘bound’ cation (filled blue) sit underneath a layer of cation (empty blue) and anion (empty orange). The IL regions are separated by oxidised gold (darker colour).

Species formed at cuprite fracture surfaces; observation of O 1s surface core level shift

Publisher: Elsevier BV

Date: 02-2009

DOI: 10.1016/J.SUSC.2008.12.024

Synchrotron scanning photoemission microscopy of homogeneous and heterogeneous metal sulfide minerals

Publisher: International Union of Crystallography (IUCr)

Date: 27-04-2011

DOI: 10.1107/S0909049511007175

Abstract: Scanning photoemission microscopy (SPEM) has been applied to the investigation of homogeneous and heterogeneous metal sulfide mineral surfaces. Three mineral s les were investigated: homogeneous chalcopyrite, heterogeneous chalcopyrite with bornite, and heterogeneous chalcopyrite with pyrite. Sulfur, copper and iron SPEM images, i.e. surface-selective elemental maps with high spatial resolution acquired using the signal from the S 2 p and Cu and Fe 3 p photoemission peaks, were obtained for the surfaces after exposure to different oxidation conditions (either exposed to air or oxidized in pH 9 solution), in addition to high-resolution photoemission spectra from in idual pixel areas of the images. Investigation of the homogeneous chalcopyrite s le allowed for the identification of step edges using the topography SPEM image, and high-resolution S 2 p spectra acquired from the different parts of the s le image revealed a similar rate of surface oxidation from solution exposure for both step edge and a nearby terrace site. SPEM was able to successfully distinguish between chalcopyrite and bornite on the heterogeneous s le containing both minerals, based upon sulfur imaging. The high-resolution S 2 p spectra acquired from the two regions highlighted the faster air oxidation of the bornite relative to the chalcopyrite. Differentiation between chalcopyrite and pyrite based upon contrast in SPEM images was not successful, owing to either the poor photoionization cross section of the Cu and Fe 3 p electrons or issues with rough fracture of the composite surface. In spite of this, high-resolution S 2 p spectra from each mineral phase were successfully obtained using a step-scan approach.

Synchrotron X-ray photoelectron spectroscopic study of the chalcopyrite leached by moderate thermophiles and mesophiles

Publisher: Elsevier BV

Date: 12-2014

DOI: 10.1016/J.MINENG.2014.08.011

Microbial induced corrosion of 3D printed stainless steels: a surface science investigation

Publisher: MDPI

Date: 08-05-2021

DOI: 10.3390/CMDWC2021-09973

Microencapsulation of bacterial strains in graphene oxide nano-sheets using vortex fluidics

Publisher: Royal Society of Chemistry (RSC)

Date: 2015

DOI: 10.1039/C5RA04415D

Abstract: Microencapsulation of bacterial cells with different shapes in graphene oxide (GO) layers is effective using a vortex fluidic device, with the bacterial cells showing restricted cellular growth with their biological activity sustained.

Electronic environments in carrollite, CuCo2S4, determined by soft X-ray photoelectron and absorption spectroscopy

Publisher: Elsevier BV

Date: 08-2009

DOI: 10.1016/J.GCA.2009.05.030

The Role of Physisorption and Chemisorption in the Oscillatory Adsorption of Organosilanes on Aluminium Oxide

Publisher: MDPI AG

Date: 04-03-2019

DOI: 10.3390/POLYM11030410

Abstract: The effect of physisorbed and chemisorbed species on the time-dependent self-assembly mechanism of organosilane films has been investigated on aluminium oxide using X-ray Photoelectron Spectroscopy. The role of physisorbed species was determined through their removal using a simple rinsing procedure while monitoring film substrate coverage. Removing physisorbed species from Propyldimethylmethoxysilane films, shown to follow a Langmuir-type adsorption profile, reduces the substrate coverage initially but quickly results in coverages equivalent to films that did not undergo a rinsing procedure. This indicates that all Propyldimethylmethoxysilane molecules are covalently bound to the substrate following 15 s of film growth. Removing physisorbed species from films, which have been shown to follow an oscillatory adsorption profile, Propyltrimethoxysilane and Propylmethyldimethoxysilane, reveal the persistence of these oscillations despite a reduction in silane substrate coverage. These results not only confirm the presence of two thermodynamically favourable phases in the condensation equilibrium reaction as physisorbed and chemisorbed species, but also indicate that the desorption of species during film growth involves both states of chemical binding.

The evolution of surface layers formed during chalcopyrite leaching

Publisher: Elsevier BV

Date: 09-2006

DOI: 10.1016/J.GCA.2006.06.1555

Probing Molecular Mechanisms during the Oscillatory Adsorption of Propyl Chain Functionalized Organosilane Films with Sum Frequency Generation Spectroscopy

Publisher: American Chemical Society (ACS)

Date: 16-02-2021

DOI: 10.1021/ACS.JPCB.0C09715

Surface characterisation of pyrite exposed to A. brierleyi

Publisher: Elsevier BV

Date: 07-2021

DOI: 10.1016/J.MINENG.2021.106934

The influence of particle shape properties and associated surface chemistry on the flotation kinetics of chalcopyrite

Publisher: Elsevier BV

Date: 07-2011

DOI: 10.1016/J.MINENG.2011.02.019

Polarized X-ray absorption spectroscopy and XPS of TiS3: S K- and Ti L-edge XANES and S and Ti 2p XPS

Publisher: Elsevier BV

Date: 06-2005

DOI: 10.1016/J.SUSC.2005.03.048

RECONSTRUCTION OF FRACTURE SURFACES ON BORNITE

Publisher: Mineralogical Association of Canada

Date: 10-2005

DOI: 10.2113/GSCANMIN.43.5.1619

Surface structure of sphalerite studied by medium energy ion scattering and XPS

Publisher: Elsevier BV

Date: 2007

DOI: 10.1016/J.SUSC.2006.10.001

Classification of time-of-flight secondary ion mass spectrometry spectra from complex Cu–Fe sulphides by principal component analysis and artificial neural networks

Publisher: Elsevier BV

Date: 2013

DOI: 10.1016/J.ACA.2012.11.001

Abstract: Artificial neural network (ANN) and a hybrid principal component analysis-artificial neural network (PCA-ANN) classifiers have been successfully implemented for classification of static time-of-flight secondary ion mass spectrometry (ToF-SIMS) mass spectra collected from complex Cu-Fe sulphides (chalcopyrite, bornite, chalcocite and pyrite) at different flotation conditions. ANNs are very good pattern classifiers because of: their ability to learn and generalise patterns that are not linearly separable their fault and noise tolerance capability and high parallelism. In the first approach, fragments from the whole ToF-SIMS spectrum were used as input to the ANN, the model yielded high overall correct classification rates of 100% for feed s les, 88% for conditioned feed s les and 91% for Eh modified s les. In the second approach, the hybrid pattern classifier PCA-ANN was integrated. PCA is a very effective multivariate data analysis tool applied to enhance species features and reduce data dimensionality. Principal component (PC) scores which accounted for 95% of the raw spectral data variance, were used as input to the ANN, the model yielded high overall correct classification rates of 88% for conditioned feed s les and 95% for Eh modified s les.

XPS andab initiocalculation of surface states of sulfide minerals: pyrite, chalcopyrite and molybdenite

Publisher: Informa UK Limited

Date: 25-03-2009

DOI: 10.1080/08927020601081616

X-PEEM, XPS and ToF-SIMS characterisation of xanthate induced chalcopyrite flotation: Effect of pulp potential

Publisher: Elsevier BV

Date: 05-2015

DOI: 10.1016/J.SUSC.2014.12.012

The effect of bulk iron concentration and heterogeneities on the copper activation of sphalerite

Publisher: Elsevier BV

Date: 11-2008

DOI: 10.1016/J.MINENG.2008.02.014

High-resolution XANES S L_3,2 edge spectra collected from a series of iron-bearing sphalerite(Zn,Fe)S minerals

Publisher: Canadian Science Publishing

Date: 10-2007

DOI: 10.1139/V07-072

Abstract: High-resolution S L 3,2 -edge XANES spectra have been collected from a series of high-quality sphalerite s les. Each of the sphalerite s les examined has a characteristic iron concentration, and the range is from .01 to 14.79 wt% Fe. The structures of the S L 3,2 -edges are investigated by comparing ab initio calculated spectra with experimentally measured S L 3,2 -edge spectra collected from synthetic ZnS sphalerite. The theoretical and experimental data provide evidence that S 2p electron transitions to empty S 3s and S 3d states can occur across an energy range above the absorption edge. A chemical shift, associated with iron to sulphur bonds, is identified, and for the first time, a pre-edge feature associated with S–Fe bonding in sphalerite is observed.Key words: XANES, zincblende, sphalerite, characteristic iron content, S L-edge structure, ab initio calculated spectra, density of states, pre-edge peak.

New interpretation and approach to curve fitting synchrotron X-ray photoelectron spectra of (Fe,Ni)9S8 fracture surfaces

Publisher: Elsevier BV

Date: 02-2020

DOI: 10.1016/J.APSUSC.2019.144458

Chemometric and Multivariate Statistical Analysis of Time-of-Flight Secondary Ion Mass Spectrometry Spectra from Complex Cu–Fe Sulfides

Publisher: American Chemical Society (ACS)

Date: 02-03-2012

DOI: 10.1021/AC202971Y

Abstract: Time-of-flight secondary ion mass spectrometry (TOF-SIMS) spectra of mineral s les are complex, comprised of large mass ranges and many peaks. Consequently, characterization and classification analysis of these systems is challenging. In this study, different chemometric and statistical data evaluation methods, based on monolayer sensitive TOF-SIMS data, have been tested for the characterization and classification of copper-iron sulfide minerals (chalcopyrite, chalcocite, bornite, and pyrite) at different flotation pulp conditions (feed, conditioned feed, and Eh modified). The complex mass spectral data sets were analyzed using the following chemometric and statistical techniques: principal component analysis (PCA) principal component-discriminant functional analysis (PC-DFA) soft independent modeling of class analogy (SIMCA) and k-Nearest Neighbor (k-NN) classification. PCA was found to be an important first step in multivariate analysis, providing insight into both the relative grouping of s les and the elemental/molecular basis for those groupings. For s les exposed to oxidative conditions (at Eh ~430 mV), each technique (PCA, PC-DFA, SIMCA, and k-NN) was found to produce excellent classification. For s les at reductive conditions (at Eh ~ -200 mV SHE), k-NN and SIMCA produced the most accurate classification. Phase identification of particles that contain the same elements but a different crystal structure in a mixed multimetal mineral system has been achieved.

Surface Chemical Characterisation of Pyrite Exposed to Acidithiobacillus ferrooxidans and Associated Extracellular Polymeric Substances

Publisher: MDPI AG

Date: 24-03-2018

DOI: 10.3390/MIN8040132

Examination of the proposition that Cu(II) can be required for charge neutrality in a sulfide lattice — Cu in tetrahedrites and sphalerite

Publisher: Canadian Science Publishing

Date: 10-2007

DOI: 10.1139/V07-078

Abstract: Synchrotron XPS and Cu L 2,3 -edge NEXAFS spectroscopic data for a natural tetrahedrite surface prepared by fracture under UHV were in accord with the composition of the mineral and its expected semiconductivity. The 2p binding energy for the 6-coordinate S atoms was found to be not detectably greater than that for the 4-coordinate S atoms, and surface species were not clearly discernible in either surface-optimized S 2p or Cu 2p spectra. The Cu 2p and Cu L 2,3 -edge spectra indicated that all Cu in the mineral was indisputably Cu(I). The Cu L 2,3 -edge spectra of relatively pure natural sphalerite treated with mildly acidic aqueous cupric solution revealed the presence of Cu(II) in the outermost layer of the fracture surfaces, but it was concluded that most of the Cu near the surface of the mineral was in formal oxidation state Cu(I), albeit with higher than normal d 9 character. The Cu(I) absorption peak was at an energy much lower than for the tetrahedrite absorption edge, but still consistent with Cu(I) in 4-fold coordination by S. The Cu(II) was consistent with Cu bonded both to S atoms in the outermost layer of the sphalerite and to O atoms in chemisorbed water. S 2p spectra determined at different photon energies revealed high binding energy components arising from oligosulfide-like environments in the outermost layers, but not necessarily in a completely restructured lattice and not in a Cu oligosulfide only. The data indicated some loss of Zn in addition to the Zn that had been replaced by Cu in the outermost layers of the sulfide lattice. The presence of these oligosulfide-like environments precluded the detection of S with formal oxidation state greater than (-II) that might have arisen only from Cu(I) in the S lattice. No evidence was obtained for the presence of Cu(II) in a sulfide lattice, but it was not possible to exclude the possibility of a very low concentration because of the presence of the Cu(II) bonded to both S and O at the surface of the treated sphalerite.Key words: tetrahedrite, sphalerite, copper uptake, XPS, NEXAFS.

Flinders University

Location: Australia

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