Quantitative X-ray Photoelectron Spectroscopy Analysis Research Articles

Ensuring the Global Comparability of XPS Data Through Intensity Scale Calibration: Summary of ISO 5861:2024

ABSTRACTFor quantitative analyses of data acquired from x‐ray photoelectron spectroscopy (XPS) instruments to be globally comparable across industry and academia, a consistent and traceable intensity calibration method is required. ISO 5861 was prepared by Technical Committee ISO/TC 201 Surface Chemical Analysis, Subcommittee 7, Electron Spectroscopies, and describes an intensity calibration method for x‐ray photoelectron spectrometers that use quartz‐crystal monochromated Al Ka x‐rays. The method employs low‐density polyethylene reference spectra that are corrected for any instrument geometry and are traceable to the true reference spectra for gold, silver and copper held by the National Physical Laboratory (NPL), UK. This international standard generates a spectrometer relative response function for use in quantitative XPS analysis that is consistent with NPL's intensity calibration method to within 5% relative error.

A Comprehensive Study on the Effect of Washing on Nickel-Rich Layered Transition Metal Oxides: Surface Characterization after Li+/H+-Exchange

With an increasing demand for high-capacity cathode active materials (CAMs) for lithium-ion batteries, nickel-rich layered lithium nickel cobalt manganese oxides (NCMs, LiNixCoyMnzO2, with x+y+z = 1) are the currently favored CAMs [1]. However, a higher nickel content does not only increase the specific capacity of NCMs, but also the reactivity of the CAM surface, which makes the material more prone to surface contaminants [2]. These contaminants consist of lithium salts from excess synthesis precursors [3], but can also be formed during improper storage [4,5]. During battery cycling, these contaminants decompose during the first charge/discharge cycles, leading to excessive gassing [6], decomposition of electrolyte solvents and salts [7], as well as to impedance build-up and capacity fading [8].Since these contaminants are generally soluble in water, CAMs are usually washed after synthesis. Exposure to liquid or gaseous water, however, is accompanied by a Li+/H+-exchange, whereby protons intercalate into the CAM [9]. Within the framework of this study, we examine the kinetics of the Li+/H+-exchange for a Ni-rich NCM831205 (LiNi0.83Co0.12Mn0.05O2). The amount of protons inserted into the CAM upon washing was characterized by different methods, namely acid/base titration, thermogravimetric analysis, X-ray powder diffraction, and prompt-gamma activation analysis [10]. The effect of ion-exchanged protons on the electrochemistry was then investigated for NCM831205 samples with 1.0 and 1.5 mol% H+. Here it was found that protonated NCMs can be cycled fully reversibly, yet the capacity fading increases with increasing proton concentration while the rate capability decreases [11].In this work, we now particularly focus on the surface and the bulk of differently washed NCM samples by using X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS), respectively. It will be demonstrated that protons intercalate into the near-surface region of the NCM particles, as had only been hypothesized so far [9]. Moreover, the protonated NCM material shows a slightly different Ni-coordination, while maintaining its layered structure. The surface thickness of the protonated layer is determined by quantitative XPS analysis: for example, washing at room temperature for 60 min at a water/CAM mass ratio of 5/1 leads to an approximately 2.5 nm thick protonated surface layer. Lastly, temperature induced phase changes of the protonated surface region are characterized by in-situ by XPS during heating of the sample in vacuum. The data are then correlated with previous results from powder X-ray diffraction. Reference s [1] U. Kim. D. Jun, K. Park, Q. Zhang, P. Kaghazchi, D. Aurbach, D. Major, G. Goobes, M. Dixit, N. Leifer, C. Wang, P. Yan, K. Kim, C. Yoon and Y. Sun, Energy Environ. Sci. 11 1271-1279 (2018).[2] W. Li, E. M. Erickson and A. Manthiram, Nature Energy 5 26 (2020).[3] H.-J. Noh, S. Youn, C.S. Yoon and Y.-K. Sun, J. Power Sources 233 121 (2013).[4]J. Sicklinger, M. Metzger, H. Beyer, D. Pritzl and H.A. Gasteiger,J. Electrochem. Soc. 166 (12) A2322 (2019).[5] L. Hartmann, D. Pritzl, H. Beyer and H.A. Gasteiger, J. Electrochem. Soc. 168 070507 (2021).[6] S. Renfrew and B.D. McCloskey, J. Am. Chem. Soc. 139 17853 (2017).[7] M. Metzger, B. Strehle, S. Solchenbach and H.A. Gasteiger, J. Electrochem. Soc. 163 (7) A1219 (2016).[8] R. Jung, R. Morasch, P. Karayaylali, K. Phillips, F. Maglia, C. Stinner, Y. Shao-Horn and H.A. Gasteiger, J. Electrochem. Soc. 165 (2) A132 (2018).[9] D. Pritzl, T. Teufl, A.T.S. Freiberg, B. Strehle, J. Sicklinger, H. Sommer, P. Hartmann and H.A. Gasteiger, J. Electrochem. Soc. 166 (16) A4056 (2019).[10] S. Oswald, R. Wilhelm, T. Kratky, G. Kieslich, L. Szentmiklósi, B. Maróti, I. Harsányi, M. Piana, S. Günther and H.A. Gasteiger, manuscript in preparation. [11] R. Wilhelm, S. Oswald and H.A. Gasteiger, manuscript in preparation. Acknowledgement This work is financially supported by the German Federal Ministry of Education and Research (BMBF) within the project AQua-POp (grant number 03XP0329B) as well as by the BASF SE Network on Electrochemistry and Battery Research.

Degradation and chemical stability of graphitic carbon nitride during ultraviolet light irradiation

Graphitic carbon nitride (g-C3N4) was synthesized by pyrolysis of urea at 450 °C for 2 h. X-ray diffraction and transmission electron microscopy confirmed the formation of the stacked hexagonal layers and platelet-like structure of g-C3N4. The sample was irradiated by ultraviolet (UV, 370 nm) light for about 62 h and X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), time-of-flight secondary ion mass spectroscopy (ToF-SIMS), Nitrogen adsorption–desorption isotherm, and photoluminescence spectroscopy (PL) were used to investigate the degradation. XPS spectra of C 1s electrons revealed four components associated with adventitious carbon, the –C≡N group, heptazine/triazine and carboxyl/carbonate species. Quantitative XPS analysis indicated an increase in the peak areas associated with the –C≡N group and carboxyl/carbonate species, accompanied by a decrease in the areas of the components associated with the heptazine/triazine and adventitious carbon. XPS spectra of N 1s were fitted using four components which were assigned to pyridinic nitrogen (C–N=C), nitrile group (N≡C), amine groups (NHx) and tertiary nitrogen (N-(C)3). The relative areas of peaks associated with the amine and nitrile groups have slightly increased after UV irradiation whereas the peak associated with pyridinic nitrogen decreased. FTIR spectra suggested a reduction in the C–N and C=N heterocycle bonds and slight variation in the C≡N bonds after UV irradiation. BET analysis revealed that the surface area and pore volume have decreased after irradiation. ToF-SIMS analysis indicate the formation of NOx, CNO, NHx, and C4H3NO2 species after irradiation. PL spectra of the g-C3N4 showed a broad blue-green emission which was fitted using three bands and ascribed to the δ*-LP, π-LP, and π-π* transitions within the bandgap. During UV irradiation, the g-C3N4 powder lost about 22% of its blue-green emission intensity after nearly 45 h and then remained stable for further irradiation time. This study confirmed the degradation of g-C3N4 under UV irradiation, which should be further studied for better integration of this material in photoexcited applications.

Two different approaches to XPS quantitative analysis of polyelectrolyte adsorption layers

X‐ray photoelectron spectroscopy (XPS) was employed to quantify adsorption of polyelectrolytes from aqueous solutions of low ionic strength onto mica, glass, and silica. Silica surfaces were conditioned in base or in acid media as last pre‐treatment step (silica‐base last or silica‐acid last, respectively). Consistency in the determined adsorbed amount, Γ, was obtained independent of the choice of XPS mode and with the two quantification approaches used in the data evaluation. Under the same adsorption conditions, the adsorbed amount, Γ, varied as Γmica > Γsilica‐base last ≈ Γglass > Γsilica‐acid last. In addition, the adsorbed amount increased with decreasing polyelectrolyte charge density (100% to 1% of segments being charged) for all substrates. Large adsorbed amount was measured for low‐charge density polyelectrolytes, but the number of charged segments per square nanometer was low due to steric repulsion between polyelectrolyte chains that limited the adsorption. The adsorbed amount of highly charged polyelectrolytes was controlled by electrostatic interactions and thus limited to that needed to neutralize the substrate surface charge density. For silica, the adsorbed amount depended on the cleaning method, suggesting that this process influenced surface concentration and fraction of different silanol groups. Our results demonstrate that for silica, a higher density and/or more acidic silanol groups are formed using base, rather than acid, treatment in the last step.

Study on dissolution mechanism of mineral/liquid interface during HF acid leaching niobium-tantalum ore

The aim of the research work was to study the specific process of hydrofluoric acid decomposing (Fe,Mn)(Nb,Ta)2O6 mineral structure. In this paper, X-ray photoelectron spectroscopy (XPS), density functional theory (DFT) calculations combining with leaching experiments were used to study the atoms bonding, charge transfer, and energy changes on the mineral/liquid interface and selective dissolution mechanism during the process of leaching (Fe,Mn)(Nb,Ta)2O6 mineral with hydrofluoric acid. DFT calculation results showed that Ta was more easily dissolved than Nb, and Mn was more easily dissolved than Fe. The core energy level spectrum and XPS detection revealed that Nb and Ta at the same site were preferentially leached from the mineral than Fe and Mn at the same site. Therefore, the order of metal dissolution in mineral from difficult to easy was Fe, Mn, Nb, and Ta. ICP results combined with XPS quantitative analysis showed that with the increase of HF concentration, the leaching rate of Nb and Ta increased, and the bridging F existing on the mineral surface would be converted into terminal F, thereby prompting more metal atoms to dissolve away from the mineral surface. Therefore, the dissolution of metals was more likely to occur at higher concentrations of F−.

New insight into the role of microscale residual stresses on initial corrosion behavior of Ti35 alloy

The effect of microscale residual stresses on the initial corrosion behavior of Ti35 alloys in boiling nitric acid solutions was investigated using a combination of electrochemical and immersion tests. The concentration of microscale residual stresses 48 h before corrosion accelerated the dissolution of Ti2+, Ti3+, and Ta5+, as determined by electrochemical impedance spectroscopy measurements and quantitative X-ray photoelectron spectroscopy analysis. After 48 h, the formation of oxide films with consistent compositions and contents (TiO2-51%, Ti2O3-47%, and Ta2O5-1.9%) prevented the corrosion medium from reaching the outer surface of the metal matrix, reducing the effect of residual stresses on the corrosion behavior.

A novel approach to prepare highly oxidized graphene oxide: structural and electrochemical investigations

This research presents two new modified Hummers' methods which include the pre-oxidation of graphite powder by mixtures of H3BO3/H2SO4 and H3BO3/H2SO4/CrO3. Compared to the traditional Hummers’ method, these significant improvements substantially enhanced the number of oxygen functionalities onto graphene oxide (GO) layers. The GO samples were characterized by X-ray photoelectron spectroscopy (XPS), Boehm titration, Raman spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS), and zeta potential analysis. Boehm titration results showed that GO layers contain oxygen functionalities such as phenolic, ketone, lactone, carboxyl, and epoxy. Quantitative XPS analysis reveals that GO obtained using a pre-oxidation step with H2SO4/H3BO3/CrO3 mixture has a higher oxidation degree (C/O = 1.03). Moreover, this sample possessed a greater number of electronegative functional groups, resulting in the decrease of the zeta potential (-43.3 mV). Raman analysis revealed a slightly higher structural disorder in GO layers during the increase in oxidation levels. Further, reduced GO (rGO) obtained from new synthesized GO were tested as label-free H2O2 sensors electrodes. The electrochemical investigations showed that the samples were prospective on H2O2 sensing. Our results suggest that the properties of rGO can be tuned by varying the oxidation degree of GO, which may stimulate new developments in rGO-based sensors.

The Structure of GaSbSe Glasses by High‐Resolution X‐Ray Photoelectron Spectroscopy

To understand the unique physical properties of GaSbSe glasses, high‐resolution X‐ray photoelectron spectroscopy (XPS) studies are performed on representative compositions within the glass‐forming region. The observed peaks in the valence band as well as in Ga, Sb, and Se core‐level XPS spectra are related to the main structural building blocks of the covalent network. On the basis of disproportionality equations and quantitative XPS analysis, the SeSeSe fragments are shown to exist in the glasses with 65 and 68 at% of Se, whereas the samples with lower Se content are shown to contain a significant concentration of SeSe bonds instead. Although the majority of Ga atoms are deemed to form fourfold coordinated units, the existence of Ga atoms in threefold coordination, those bonded to other metal, and forming Ga clusters of undissolved Ga are also plausible on the basis of Ga 3d XPS spectrum analysis. Partial or full destruction of antimony selenide pyramids is found in glasses with low Se content.

Study on the Performance of Titanium Materials Based on Nano Silver Particles in Orthodontic Healing.

Nanomaterials are used as a new type of antibacterial agent in clinical medical research projects due to their unique physical and chemical properties. In this study, silane coupling method was used to coat nano-silver particles on titanium sheets to make the smooth titanium surface have antibacterial properties. Scanning electron microscope to observe the surface morphology of silane coupling modified titanium plate, the shape and size of nano-silver particles, and the adhesion on titanium plate; X-ray energy spectroscopy and line scan analysis of each element on the titanium wafer; X-ray photoelectron spectroscopy quantitative analysis of surface elements on the titanium wafer. The experimental group was nano-silver modified titanium sheet, and the control group was smooth titanium sheet. The experimental results show that the titanium material loaded with nano-silver particles has better antibacterial performance in the orthodontic process than ordinary materials. This material is highly safe and can be promoted for use.

Nitrogen gas interaction on silica aerogel – Effects on hydrophobicity, surface area, porosity, and lithium-ion battery performance

The present study evaluates in-situ pressurized nitrogen gas (N2) purging effect on tuning hydrophobicity of silica aerogel, and the effect on lithium-ion battery applications. The mesoporous silica aerogels are prepared using sol-gel process, followed by supercritical drying with ethanol solvent extraction, and dry nitrogen gas is pressurized and purged to remove the condensed ethanol vapor from the hydrothermal vessel. The pressurized nitrogen gas molecules interact with silica aerogel at 255 °C and remove surface reactive OH groups and increase the surface roughness and hydrophobicity, which is evident from the reduction of Si-OH infrared vibration bands, porous electron microscopic images and increased contact angle. It also increases the surface area, compresses the pores, and carbonizes the organics, which is confirmed from surface area measurements and quantitative X-ray photoelectron spectroscopy analysis. Also, the powder X-ray diffraction patterns confirm the amorphous nature of silica aerogel. The Li-ion battery performance of the obtained amorphous silica aerogel is examined using cyclic voltammogram and charge-discharge studies. The present study enumerates that apart from surface area and in-situ carbon, the pore size is also an important criterion in maintaining better battery performance.

Lithium-based transition-metal oxides for battery electrodes analyzed by x-ray photoelectron spectroscopy. III. LiNi0.6Co0.2Mn0.2O2

X-ray photoelectron spectroscopy (XPS) and x-ray-induced Auger electron spectroscopy were used to analyze untreated LiNi0.6Co0.2Mn0.2O2 powder obtained from Ecopro Company, Ltd. X-ray photoelectron and x-ray-induced Auger electron spectra were obtained using incident monochromatic Al Kα radiation at 0.834 01 nm. A survey spectrum together with Ni 2p, Co 2p, Mn 2p, Ni LMM, O 1s, C 1s, Ni 3s, Co 3s, Mn 3s, Ni 3p, Co 3p, Li 1s, and Mn 3p are presented. The spectra indicate the principal core level photoelectron and Auger electron signals. Making use of the O 1s, Ni 3p, Co 3p, Mn 3p, and Li 1s lines and neglecting the components related to surface contaminants, XPS quantitative analysis reveals an altered stoichiometry of the air-exposed powder surface of LiNi0.2Co0.05Mn0.1O0.7.

Lithium-based transition-metal oxides for battery electrodes analyzed by x-ray photoelectron spectroscopy. IV. LiNi0.5Co0.2Mn0.3O2

X-ray photoelectron spectroscopy (XPS) and x-ray-induced Auger electron spectroscopy (XAES) were used to analyze two lots of untreated LiNi0.5Co0.2Mn0.3O2 powder and one of the two lots of LiNi0.5Co0.2Mn0.3O2 powder recalcined in air at 750 °C obtained from TODA America. X-ray photoelectron and x-ray-induced Auger electron spectra were obtained using incident monochromatic Al Kα radiation at 0.834 01 nm. A survey spectrum together with Ni 2p, Co 2p, Mn 2p, Ni LMM, O 1s, C 1s, Ni 3s, Co 3s, Mn 3s, Ni 3p, Co 3p, Li 1s, and Mn 3p are presented. The spectra indicate the principal core level photoelectron and Auger electron signals and show only minor sulfur contamination. Making use of the O 1s, Ni 3p, Co 3p, Mn 3p, and Li 1s lines and neglecting the components related to surface contaminants, XPS quantitative analysis reveals an altered stoichiometry of the air-exposed powder surfaces for the first lot, the first lot recalcined, and the second lot of LiNi0.3Co0.1Mn0.2O1.2, LiNi0.4Co0.1Mn0.3O1.5, and LiNi0.4Co0.1Mn0.2O1.3, respectively.

Lithium-based transition-metal oxides for battery electrodes analyzed by x-ray photoelectron spectroscopy. VI. LiNi0.4Co0.2Mn0.4O2

X-ray photoelectron spectroscopy (XPS) and x-ray-induced Auger electron spectroscopy were used to analyze untreated LiNi0.4Co0.2Mn0.4O2 powder obtained from TODA America. X-ray photoelectron and x-ray-induced Auger electron spectra were obtained using incident monochromatic Al Kα radiation at 0.834 01 nm. A survey spectrum together with Ni 2p, Co 2p, Mn 2p, Ni LMM, O 1s, C 1s, Ni 3s, Co 3s, Mn 3s, Ni 3p, Co 3p, Li 1s, and Mn 3p are presented. The spectra indicate the principal core level photoelectron and Auger electron signals. Making use of the O 1s, Ni 3p, Co 3p, Mn 3p, and Li 1s lines and neglecting the components related to surface contaminants, XPS quantitative analysis reveals an altered stoichiometry of the air-exposed powder surface of LiNi0.5Co0.2Mn0.5O1.9.

Lithium-based transition-metal oxides for battery electrodes analyzed by x-ray photoelectron spectroscopy. V. LiNi0.4Co0.3Mn0.3O2

X-ray photoelectron spectroscopy (XPS) and x-ray-induced Auger electron spectroscopy were used to analyze untreated LiNi0.4Co0.3Mn0.3O2 powder obtained from TODA America. X-ray photoelectron and x-ray-induced Auger electron spectra were obtained using incident monochromatic Al Kα radiation at 0.834 01 nm. A survey spectrum together with Ni 2p, Co 2p, Mn 2p, Ni LMM, O 1s, C 1s, Ni 3s, Co 3s, Mn 3s, Ni 3p, Co 3p, Li 1s, and Mn 3p are presented. The spectra indicate the principal core level photoelectron and Auger electron signals. Making use of the O 1s, Ni 3p, Co 3p, Mn 3p, and Li 1s lines and neglecting the components related to surface contaminants, XPS quantitative analysis reveals an altered stoichiometry of the air-exposed powder surface of LiNi0.4Co0.2Mn0.3O1.6.

Lithium-based transition-metal oxides for battery electrodes analyzed by x-ray photoelectron spectroscopy. IX. LiCoO2

X-ray photoelectron spectroscopy (XPS) and x-ray-induced Auger electron spectroscopy were used to analyze untreated LiCoO2 powder obtained from BTR New Energy Materials, Inc. X-ray photoelectron and x-ray-induced Auger electron spectra were obtained using incident monochromatic Al Kα radiation at 0.834 01 nm. A survey spectrum together with Co 2p, O 1s, C 1s, Co 3s, Co 3p, and Li 1s are presented. The spectra indicate the principal core level photoelectron and Auger electron signals and show only minor tin contamination. Making use of the O 1s, Co 3p, and Li 1s lines and neglecting the components related to surface contaminants, XPS quantitative analysis reveals an altered stoichiometry of the air-exposed powder surface of LiCo0.9O1.7.

Lithium-based transition-metal oxides for battery electrodes analyzed by x-ray photoelectron spectroscopy. VII. LiNi0.33Co0.33Mn0.33O2

X-ray photoelectron spectroscopy (XPS) and x-ray-induced Auger electron spectroscopy were used to analyze fresh LiNi0.33Co0.33Mn0.33O2 powder obtained from TODA America. X-ray photoelectron and x-ray-induced Auger electron spectra were obtained using incident monochromatic Al Kα radiation at 0.834 01 nm. A survey spectrum together with Ni 2p, Co 2p, Mn 2p, Ni LMM, O 1s, C 1s, Ni 3s, Co 3s, Mn 3s, Ni 3p, Co 3p, Li 1s, and Mn 3p are presented. The spectra indicate the principal core level photoelectron and Auger electron signals and show carbon with only minor fluorine contamination. Making use of the O 1s, Ni 3p, Co 3p, Mn 3p, and Li 1s lines and neglecting the components related to surface contaminants, XPS quantitative analysis reveals an altered stoichiometry of the air-exposed powder surface of LiNi0.4Co0.1Mn0.7O2.0.

Lithium-based transition-metal oxides for battery electrodes analyzed by x-ray photoelectron spectroscopy. X. Li4Ti5O12

X-ray photoelectron spectroscopy (XPS) and x-ray-induced Auger electron spectroscopy were used to analyze untreated Li4Ti5O12 powders obtained from Ishihara Sangyo Kaisha, Ltd. and Samsung Fine Chemicals Company, Ltd. X-ray photoelectron and x-ray-induced Auger electron spectra were obtained using incident monochromatic Al Kα radiation at 0.834 01 nm. A survey spectrum together with O 1s, Ti 2p, C 1s, Ti 3s, Li 1s, and Ti 3p are presented. The spectra indicate the principal core level photoelectron and Auger electron signals and show only minor potassium signal. Making use of the O 1s, Li 1s, and Ti 3p lines and neglecting the components related to surface contaminants, XPS quantitative analysis reveals an altered stoichiometry of the air-exposed powder surfaces from Ishihara Sangyo Kaisha, Ltd. and Samsung Fine Chemicals Company, Ltd. of Li4Ti4.7O14.1 and Li4Ti4.3O13.2, respectively.

Lithium-based transition-metal oxides for battery electrodes analyzed by x-ray photoelectron spectroscopy. I. LiNi0.8Co0.15Al0.05O2

X-ray photoelectron spectroscopy (XPS) and x-ray-induced Auger electron spectroscopy were used to analyze untreated LiNi0.8Co0.15Al0.05O2 powder obtained from TODA America. X-ray photoelectron and x-ray-induced Auger electron spectra were obtained using incident monochromatic Al Kα radiation at 0.83401 nm. A survey spectrum together with Ni 2p, Co 2p, Ni LMM, O 1s, C 1s, Al 2s, Ni 3s, Co 3s, Al 2p, Ni 3p, Co 3p, and Li 1s are presented. The spectra indicate the principal core level photoelectron and Auger electron signals and show carbon with only minor sulfur contamination. Making use of the O 1s, Al 2s, Ni 3p, Co 3p, and Li 1s lines and neglecting the components related to surface contaminants, XPS quantitative analysis reveals an altered stoichiometry of the air-exposed powder surface of LiNi0.2Co0.03Al0.1O0.7.

The use of ionic liquids for the determination of the spectrometer transmission function in X-ray photoelectron spectroscopy (XPS)

The uncertainty of measurement in quantitative XPS analysis can be reduced by using a calibrated spectrometer transmission function T(E), which is usually determined by taking spectra from Au, Ag, Cu and Ge elemental reference materials. However, this approach is quite time-consuming due to required sample preparation steps like sputter cleaning etc., and the relatively big number of samples to be measured. This contribution proposes the use of the ionic liquids [C2C1im][NTf2] and [C3C1im][NTf2] as reference materials for a determination of T(E). These multi-elemental samples deliver five intensive photoemission peaks, F 1s, O 1s, N 1s, C 1s and S 2p, in an energy window from 160 eV to 700 eV which is of specific interest for applications of quantitative XPS for surface chemical analysis of soft matter, one of the major applications of XPS.

XPS analysis of the surface chemistry of sulfuric acid-treated kaolinite and diaspore minerals with flotation reagents

Kaolinite is one of the main associated minerals (gangue) in the processing of diasporic bauxites. Sulfuric acid pretreatment has been shown to have an improving effect on kaolinite-diaspore flotation separation, but the mechanism underpinning this effect is not well known. This study reports the surface chemistry of acid-treated kaolinite and diaspore in the presence of flotation reagents (sodium hexametaphosphate (SHMP) as a depressant and dodecylamine hydrochloride (DAH) as a collector) using X-ray photoelectron spectroscopy (XPS) analysis and zeta potential determinations. Quantitative XPS analysis revealed that the Al/Si atomic ratio on the kaolinite surface was reduced after the acid treatment. Compared with natural kaolinite, acid-treated kaolinite showed weakened adsorption properties for SHMP. Consequently, there was an enhanced DAH adsorption on the acid-treated kaolinite. High-resolution XPS analysis showed formations of “unsaturated Al” components on the diaspore surface after the acid treatment, which were ready to interact with phosphite groups of SHMP to depress diaspore in kaolinite flotation. Zeta potential studies also confirmed extended SHMP adsorption on acid-treated diaspore in comparison with the natural mineral. These findings form a firm knowledge for interpreting the application of kaolinite and diaspore in many adsorption studies, including the efficient separation between kaolinite and diaspore.