X-ray Fluorescence Spectrometry Research Articles

The Role of Iron Impurities on Nickel Cathodes for Hydrogen Evolution Reaction (HER)

Over the last decades, several studies have reported the effect of traces of iron species on the improvement of the oxygen evolution reaction (OER) kinetics for nickel-based anode materials in alkaline media. [1] However, the effect of iron impurities on the hydrogen evolution reaction (HER) is still a subject to debate. For instance, at low iron concentrations (0.03 – 0.5 ppm) a loss of the HER activity for Ni surface is observed due to the electrochemical deposition of less active Fe. [2,3] Other studies showed less deactivation behavior of the Ni cathode at 3 and 14 ppm iron ion concentration over time. [2,4] This improvement of the lifetime of the Ni electrode in the presence of iron cations is very likely related to the increased surface roughness by Fe electrodeposition and thereby the decrease in the formation of inactive NiH species. [2] Systematic investigations on Fe sputtered Ni surfaces with different coverages showed that ≥ 60% of Fe coverage stabilizes the Ni cathode by preventing hydrogen diffusion through the Ni lattice at constant current density of -100 mA cm-2. [5] Generally, the role of Fe impurities on the HER activity for nickel cathode surface in alkaline environments is still unclear to date.In this work, we comprehensively evaluated the influence of the iron ion concentration on the long-term HER performance for a polycrystalline Ni electrode by using rotating disc electrode (RDE) setup. The changes in HER activity as a function of the iron ion concentration was correlated with resulting surface roughness and layer thickness/coverage of the electrodeposited iron. Highly purified 0.1 M KOH was used as basic electrolyte solution and mixed with iron ion concentrations in the range of <1, 6 and 14 ppm. The initial HER activity on the Ni surface is unchanged irrespective of the iron ion concentration added into the electrolyte. However, at iron ion concentrations of <1 ppm and 6 ppm, the chronopotentiometric (CP) experiments at -10 mA cm-2 for 24 hours show a potential drop of ~70 mV and ~53 mV, respectively, resulting in a deactivation of the Ni surface by forming NiH species. Very interestingly, high iron ion concentrations (e.g. ~14 ppm) lead to an almost constant potential (~ 1 - 7 mV drop) during the CP experiment, by reducing the formation of inactive NiH. The electrochemically treated Ni electrodes were then characterized by X-ray fluorescence spectroscopy (XRF) and scanning electron microscopy in combination of energy dispersive X-ray spectroscopy (SEM-EDX). The SEM micrographs show iron particles electrodeposited uniformly on the polycrystalline Ni surface after the CP experiments with < 1, 6 and 14 ppm of iron ion concentrations in 0.1 M KOH. The analysis of the EDX maps reveals a coverage of 17, 54 and 58 % on the Ni surface at iron ion concentrations of < 1, 6 and 14 ppm, respectively. Obviously, iron ion concentrations of 6 and 14 pm show very similar coverages on the Ni surface, indicating their minor role on the HER activity. We suggest that during the HER the hydrogen bubbles suppress the formation of a dense and complete iron layer on the Ni electrode surface. The spatial distribution and thickness of the electrodeposited Fe particles were also evaluated after 1 h and 24 h of CP experiments with < 1, 6 and 14 ppm iron ion concentrations by using micro-XRF equipped with a polycapillary lens of 20 µm. Thicker iron layers after 24 hours are formed at high iron ion concentrations, preventing the hydrogen diffusion into Ni lattice to form inactive NiH species and to maintain the HER activity over time under alkaline conditions.In summary, we show that traces of iron impurities have a huge impact on the long-term durability of polycrystalline Ni electrodes for HER in alkaline environments. A critical iron ion concentration is required to suppress the formation of inactive NiH species during the HER at -10 mA cm-2 for 24 h and/or to electrodeposite enough iron for maintaining the HER kinetics on the polycrystalline Ni electrodes in alkaline environments.

Unveiling the Origins of “Memory Effects” in Thick Electrodes through 2D XRF-XANES Mapping and Modeling

Making electrodes much thicker than the current commercial lithium-ion batteries is a promising approach to further increase the energy density of rechargeable batteries by reducing the weight/volume fraction of inactive components at the battery cell level. However, thick electrodes suffer inferior rate performance as non-uniform reaction develops within the electrode due to the increased ionic and electronic transport distances, which reduces the capacity utilization. In this work, we demonstrate yet another challenge faced by the application of thick electrodes (>100 µm), that is, they exhibit pronounced “memory effect” that is not seen in their thin electrode counterpart. While “memory effect” was initially observed in nickel-cadmium and nickel metal-hybrid batteries, which experience capacity reduction upon repeated shallow discharging, here we use the terminology to refer to the phenomenon that the (dis)charging performance of a lithium-ion battery depends on its cycling history. An example is illustrated in Figure 1, which shows the 2C discharge capacity of a 150μm-thick LiFePO4 electrode in a half cell when it starts from an initial state of charge (SoC) at 50%. Our experiment reveals that the discharge capacity has a strong dependence on how the electrode was first brought to the initial state. When it is charged to 50% SoC at 1.5C, the subsequent discharge capacity is 137% larger compared to when it is discharged to the same SoC at 1.5C. Similar phenomenon is also observed in another mainstream cathode NMC622. We show that such memory effect is caused by the reaction polarization present in the thick electrodes. To this end, 2D X-ray fluorescence (XRF) spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) were employed to characterize the reaction distribution within the electrodes, and its correlation to the (dis)charging kinetics and OCV relaxation were investigated by electrochemical testing and pseudo-2D battery simulation. Our study highlights the issues created by the memory effect on the capacity prediction and SoC determination, which need to be addressed to develop a better battery management system for thick-electrode-based battery cells and packs. Figure 1

Electrodeposited Ni-Fe-TiO2 Alloy Composites for the Hydrogen Evolution Reaction

Hydrogen is a carbon-free alternative energy source that is environmentally friendly, has high energy density, and is a promising fuel for future generations. Water splitting is an efficient way to produce hydrogen, requiring a catalyst with a small overpotential and Tafel slope, and good stability. However, only 4 % of global hydrogen is produced by water electrolysis due to high cost and lack of inexpensive replacements of the active platinum electrocatalyst.1 However, replacing these noble metal electrocatalysts with those comprised of lower, earth-abundant elements remains challenging as these materials impart a higher overpotential and thus require higher energy. Guided by the recognised enhancements of TiO2 particles in Co-Mo alloys for HER, earth-abundant, low-cost Ni and Fe metals are examined as composite electrocatalysts Ni-Fe-TiO2 towards HER.2 Nano-scale TiO2 particles were embedded into Ni-Fe alloys by using galvanic and pulse-reverse electrodeposition, onto rotating cylinder electrodes. Pulse-reverse electrodeposition considerably increased the concentration of the particles incorporated into the alloy. The composition and morphology were characterized by X-ray fluorescence (XRF) spectroscopy and scanning electron microscopy (SEM), respectively. The addition of particles to the electrolyte affected both the deposit composition and morphology. The alloy composites were then used as electrocatalysts in 1 M KOH to characterize HER via linear sweep voltammetry on the resulting hydroxide surface. The surface area was examined in a ferri/ferrocyanide electrolyte. The polarization data in 1 M KOH shows a significant reduction in the HER overpotential when TiO2 particles are present in the Ni-Fe deposit. The surface analysis of Ni-Fe and Ni-Fe-TiO2 confirmed that the improvement in HER activity is not due to surface roughness but an intrinsic one. The stability of the electrocatalysts under an electrolysis for HER was examined at -10 mA/cm2 for 24 hr and the working electrode potential remained stable over time; Tafel polarization curves after electrolysis were similar to those prior to electrolysis. References Le, P. A., Trung, V. D., Nguyen, P. L., Phung, T. V. B., Natsuki, J., & Natsuki, T. RSC advances, 13(40), 28262-28287 (2023).C. Wang, H. K. Bilan, and E. J. Podlaha. J. Electrochem. Soc. 166 F661 (2019). C. Wang and E. J. Podlaha, J. Electrochem. Soc. 167, 132502 (1~4) (2020).

Operando X-Ray Fluorescence Analysis of Dynamic Cerium Radical Quencher Motion Perpendicular to MEA

Polymer electrolyte fuel cells (PEFCs) are required to have a durability of over 50,000 hours. One of the degradation factors is chemical degradation of perfluorosulfonic acid (PFSA) electrolyte membrane. The reaction of hydrogen peroxide with iron impurities produces hydroxyl radicals that break the chemical bonds in the PFSA membrane. Cerium ions are added to electrolyte membranes to absorb these radicals and act as a radical quencher, contributing to improved membrane durability.1 However, cerium ions have been shown to move in both the planar and through-plane directions under fuel cell operating conditions.2,3 The spatial scale of migration in the membrane planar direction is large, and therefore the time scale is also large, where analysis of end-of-life samples has been reported. On the other hand, the observation of the movement in the membrane direction is not easy because the thickness of the electrolyte membrane is 10 micrometers, and it is estimated to be significantly different between the post-disassembly condition and the operating condition. Therefore, it is necessary to establish operando measurement technique for cerium ion concentration with high spatial and temporal resolution in the direction perpendicular to the membrane. We developed an operando X-ray fluorescence spectroscopy technique using a combination of high-energy X-rays and a focused microbeam, and analyzed the behavior of cerium concentration change under current-applied conditions.4 The distribution behavior of cerium ions in the membrane is significantly different depending on the current and humidity. In a high-humidity environment, the ions move in the membrane in the vertical direction in about 1 second. Therefore, in this study, we developed a method to continuously measure the cerium ion concentration in the membrane on a sub-second scale and were able to estimate the effective cerium diffusion coefficient. It was also found that cerium ions migrate to the cathode layer under current-applied conditions. This behavior is accelerated in low humidity environments. This is because the diffusion coefficient of cerium ions is smaller at lower humidity and the back-diffusion flux is smaller.This work is based on results obtained from the project commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.[1] E. Endoh, ECS Trans., 16, 1229–1240 (2008).[2] Y. Lai, K. M. Rahmoeller, J. H. Hurst, R. S. Kukreja, M. Atwan, A. J. Maslyn,C. S. Gittleman, J. Electrochem. Soc., 165, F3217-F3229(2018).[3] S.M. Stewart, D. Spernjak, R. Borup, A. Datye, F. Garzon, ECS Electrochem. Lett., 3, F19-F22 (2014).[4] Y. Orikasa, A. Takezawa, K. Amemiya, Y. Tsuji, T. Asaoka, M. Ohki, O. Sekizawa, K. Nitta, ECS Trans., 109 109 (2022).

Chemical characterization of bitumen-derived pyrolysis oil

The objective of this study is to characterize the elemental and functional group analysis of oils obtained from the pyrolysis of oil sand bitumen with the aim of determining oil quality. For this purpose, the present study extracted bitumen from oil sand using toluene, thermally cracked the bitumen using a fixed bed reactor, chromatographically separated the derived oil into saturate and aromatic fractions, and employed Energy dispersive x-ray fluorescence and Fourier transform-infrared spectroscopy to characterize them. The results of the elemental analysis indicated that potassium had the highest mean concentration of about 531 mg/L and 552 mg/L in the saturate and aromatic fractions respectively. The mean elemental concentrations of the aromatic fraction were relatively higher than the saturate fraction. The functional group analysis showed the predominant presence of C-H (CH3) and C-H (CH2) groups, indicating the presence of aliphatic compounds in the pyrolytic oils, in addition to the presence of sulfur reflected by the sulphoxide index. The findings of the study provide valuable information on the feedstock potential of the pyrolysis oil in the petrochemical industry. This study provides baseline information required for exploitation of the heavy oil resource which is yet to be commercially mined in Nigeria.

Assessment of Human Health Risk Caused by Heavy Metals in Kiln Dust from Coal-Fired Clay Brick Factories in Türkiye

AbstractHeavy metal (HM) pollution from natural processes and different anthropogenic activities pose significant human and environmental health risks because of their stability, non-degradable properties, and high toxicity. HM released into the air in the form of dust can enter the human body via ingestion, inhalation, and dermal contact. Keeping in mind the significance of estimating the risk from HM in different environments, the carcinogenic and non-carcinogenic health risks to workers caused by HM in kiln dust (KD) samples collected from coal-fired clay brick factories in the Western Black Sea Region of Türkiye were assessed for the first time in this study. The concentrations of major and minor oxides and HMs in the collected KD samples were analyzed using energy-dispersive X-ray fluorescence spectrometry. The average concentrations of Fe, Mn, Cr, Ni, V, Zn, Cu, As, Co and Pb analyzed in thirty-three KD samples were determined as 65444, 768, 251, 249, 248, 122, 60, 52, 42 and 16 mg/kg dw, respectively. The average levels of Ni, As, Cr, Co and Cu exceed the maximum contaminant levels recommended in the Turkish Regulation on Control of Soil Pollution. Carcinogenic and non-carcinogenic human health risk assessments for workers via three exposure pathways were carried out, estimating the hazard index (HI) and total carcinogenic risk (TCR) index, respectively. The HI values (&lt; 1) revealed no possible non-carcinogenic health risk due to exposure to all HMs in the studied KD samples. The average TCR value revealed that the potential cancer risks for Ni, As, Cr, and Pb were slightly above the safe limit and required monitoring and further investigation for these HMs.

Preparation of high-purity magnetite from iron ore concentrate

In pursuit of environmental protection and green, low-carbon economic development, China has proposed the dual-carbon strategies of carbon peak and carbon neutrality. To achieve the dual-carbon goals, traditional steel metallurgical production processes are gradually shifting towards green and low-carbon hydrogen metallurgical processes. However, hydrogen metallurgical processes have strict requirements for raw materials and typically require the utilization of high-grade iron concentrates. The scarcity of high-grade iron ore in China severely constrains the development of hydrogen metallurgical processes. Therefore, this study proposes the utilization of ordinary magnetite concentrate to produce high-grade magnetite. Comprehensive analytical methods, including chemical analysis, X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD) analysis, laser particle size testing, optical microscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), and mineral liberation analysis, were employed to elucidate the mineralogical characteristics of the iron concentrate. The analysis revealed that the iron concentrate had a total iron (TFe) grade of 65.56 %, with SiO2 and Al2O3 contents of 8.28 % and 0.38 %, respectively. Subsequently, a combined beneficiation process involving magnetic separation, flotation, and chemical leaching was conducted. Experimental results showed that a single magnetic separation obtained an iron concentrate grade of 67.52 % with an overall recovery of 86.18 %. Following magnetic separation, flotation was conducted to increase the concentrate grade. With one roughing and four cleaning flotation stages, a concentrate grade of 72.19 % and a 36.36 % overall recovery were achieved. A subsequent leaching operation after flotation yielded high-purity magnetite with a Fe grade of 72.30 % and an overall recovery of 35.68 %. The high-purity magnetite was confirmed to have a purity of up to 99.9 % based on chemical titration, XRD analysis, magnetic susceptibility measurement, and SEM analysis. Furthermore, detailed kinetics studies on leaching were conducted to elucidate the reaction mechanism, revealing an apparent activation energy of 25.70 kJ/mol. The successful implementation of this process will provide a benchmark for producing similar high-purity magnetite concentrates and contribute to China’s dual-carbon goals.

Synergistic effects of zinc and cadmium on phytoremediation potential of Christmas moss (Vesicularia montagnei)

The hyperaccumulation potential of zinc (Zn) and cadmium (Cd) and their synergistic effects were examined in relation to Christmas moss (Vesicularia montagnei (Bél) Broth., Hypnaceae), an aquatic and terrestrial moss, dosed with Cd (Cd1 and Cd2), Zn (Zn1 and Zn2) and combined Zn and Cd (Cd1Zn1 and Cd2Zn2). Zinc promoted plant growth and development, particularly in the highest Zn and combined Zn/Cd treatments (Zn2 and Cd2Zn2). The Zn treatment resulted in substantial moss chlorophyll content and highest percentage relative growth rate in biomass value (0.23 mg L−1 and 106.8%, respectively); however, the Cd2Zn2 treatment achieved maximal production of chlorophyll a and total chlorophyll (0.29 and 0.51 mg L−1, respectively) due to synergistic effects. These findings suggest that Christmas moss is a highly metal-tolerant and adaptable bryophyte species. Zinc was essential for reducing the detrimental effects of Cd while simultaneously promoting moss growth and biomass development. Furthermore, Christmas moss exhibited hyperaccumulation potential for Cd and Zn in the Cd2Zn2 and Zn alone treatments, as evidenced by highest Cd and Zn values in gametophores (1002 and 18,596 mg per colony volume, respectively). Using energy dispersive X-ray fluorescence (EDXRF) spectrometry, atomic percentages of element concentrations in moss gametophores in the Zn2, Cd2 and combined Zn/Cd treatments were generally in the order: K > Ca > P > Zn > Cd. When comparing the atomic percentages of Zn and Cd in gametophores, it is likely that the higher atomic percentage of Zn was because this element is essential for plant growth and development.

ZnO/TiO2 photocatalytic nanocomposite for dye and bacteria removal in wastewater

This study investigates ZnO/TiO2 nanocomposites synthesized by the sol–gel method for their potential application in textile wastewater treatment. The physicochemical properties of these materials were comprehensively characterized using various analytical techniques, including transmission electron microscopy (TEM), x-ray diffraction (XRD) analysis, x-ray fluorescence (XRF) spectroscopy, Brunauer–Emmett–Teller (BET) surface area analysis, and UV–visible (UV-Vis) spectroscopy. XRD and XRF analyses confirmed the formation of a ZnO/TiO2 heterostructure. TEM images revealed a quasi-spherical morphology with slight agglomeration. The ZnO/TiO2 nanocomposite with a 1:5 molar ratio of Zn(II):Ti(IV) showed the highest BET surface area (91.345 m2 g−1) and the narrowest band gap (Eg = 3.06 eV). This composite demonstrated efficient degradation of methylene blue dye under sunlight irradiation and exhibited 100% antibacterial activity against S. typhi and S. aureus at concentrations ≥5 mg ml−1, indicating its potential for treating textile wastewater.

Geochemical Evaluation of Itakpe Iron Ore Mine Tailings, Itakpe, Nigeria

The study focus on the characterisation of the tailings attributes with a view to understanding the geotechnical properties, leaching potential and possible major oxides. The samples were composited into five. The composited samples were subjected to both physical and chemical tests. The physical tests include particle size distribution, specific gravity, density, residual humidity and Atterberg limits. The chemical tests include pH, organic matter, and Energy Dispersive X-Ray Fluorescence Spectrometry (ED-XRFS). Mineralogical analyses were also carried out on the composited samples using the Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDX). The results from the physical tests show that the tailings are mostly fine-medium sands, having high specific gravity and bulk density, with low residual humidity. The chemical analyses show that the tailings are weakly acidic and neutral with low organic matter. The energy dispersive x-ray fluorescence spectroscopy analysis of the samples shows that they contain high concentrations of Fe2O3, SiO2, and other trace compounds. The Fe2O3 of the samples ranged from 15.03 to 20.12% and SiO2 ranged from 57.26 to 60.10%. SEM micrographs obtained revealed the interlocking nature of the minerals constituting the ore matrix. EDX analysis of the regions within the ore matrix revealed the presence of Si, Fe, Al, K, Ca, Nb, Y, Ag, Zn, Mg, Cl, P, S, Na, Ti, Zr; such that silicon and iron are the major elemental constituents of the ore matrix while other elements exists in trace form.

Detection of Protective Coatings Applied on Baroque Amber Artworks: Case Studies

Amber has been used to create decorative items for centuries, but its degradation presents challenges for conservators. This study identifies substances historically used to protect amber objects, especially those from 17th and 18th century Gdansk workshops. Despite their historical value, information on amber conservation is scarce. Traditional substances are noted, but their exact compositions and effects on amber remain unclear. Synthetic resins, introduced in the late 19th century, also degrade, complicating conservation due to their removal difficulty and interference with amber identification. This research aimed to develop methods for detecting and analyzing protective coatings on amber objects using macroscopic and microscopic techniques. Initial methods included analytical photography under visible and UV light and reflectance imaging spectroscopy (RIS) to assess the surface. Raman spectroscopy (RS) and X-ray fluorescence spectroscopy (XRF) were used for detailed analysis. RS provided precise layer-specific information but was sensitive to surface conditions, while XRF quickly identified inorganic compounds but not organic materials. Examining amber objects from Polish collections using this methodology revealed various protective substances, including synthetic resins and nitrocellulose varnishes. This research contributes to amber conservation by proposing a comprehensive material analysis approach, essential for developing effective conservation strategies for these historic objects.

Multiple approaches for heavy metal contamination characterization and source identification of farmland soils in a metal mine impacted area

Heavy metal and metalloid contamination of farmland soils are closely related to human health. Soil contamination caused by small-scale mining activities has been largely neglected, especially in developing countries. This research studies the characteristics and the source of heavy metals and metalloids in farmland soils in the Bailing Cu–Zn deposit area in Northeastern China through multiple approaches. Geochemical mapping conducted by portable X-ray fluorescence (pXRF) spectrometry and elemental fractionation analysis (sequential extraction) revealed the spatial variations in elemental concentration and fractionation of the farmland soils. The elemental variations in the sediment and water samples in a stream passing by the farmland were determined by inductively coupled plasma mass spectroscopy (ICP-MS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis. Results indicate elevated As, Zn, Fe, and Mn concentrations in the west bank of the farmland and the associated environmental risks caused by extremely high As concentrations (>500 mg kg−1). The upstream mining activities are identified as a dominated source of contamination in the studied farmland based on the variations of elemental concentrations and fractionations, as well as multivariate analysis results. This study revealed potential ecological risks caused by heavy metal and metalloid contamination in farmland soils in the metal mine impacted area and the stream as a primary pathway for the migration of pollutants associated with mining activities.

Evaluating the portable X-ray fluorescence reliability for metal(loid)s detection and soil contamination status.

Marginalized communities experience barriers that can prevent soil monitoring efforts and knowledge transfer. To address this challenge, this study compared two analytical methods: portable X-ray fluorescence spectroscopy (pXRF, less time, cost) and inductively coupled plasma mass spectrometry (ICP-MS, "gold standard"). Surface soil samples were collected from residential sites in Arizona, USA (N = 124) and public areas in Troy, New York, USA (N = 33). Soil preparation differed between groups to account for community practice. Statistical calculations were conducted, paired t test, Bland-Altman plot, and a two-way ANOVA indicated no significant difference for As, Ba, Ca, Cu, Mn, Pb, and Zn concentrations except for Ba in the t test. Iron, Ni, Cr, and K were statistically different for Arizona soils and V, Ni, Fe, and Al concentrations were statistically different for New York soils. Zinc was the only element with high R2 and low p value. Pollution load index (PLI), enrichment factors (EF), and geo-accumulation index (Igeo) were calculated for both methods using U.S. Geological Survey data. The PLI were > 1, indicating soil pollution in the two states. Between pXRF and ICP-MS, the Igeo and EF in Arizona had similar degree of contamination for most elements except Zn in garden and Pb in yard, respectively. For New York, the Igeo of As, Cu, and Zn differed by only one classification index between the two methods. The pXRF was reliable in determining As, Ba, Ca, Cu, Mn, Pb, and Zn in impacted communities. Therefore, the pXRF can be a cost-effective alternative to using ICP-MS techniques to screen soil samples for several environmentally relevant contaminants to protect environmental public health.

Paleoclimate Controls on West African Dust Inferred from Rb/Sr and Si/Al of Sediments in an Eastern Equatorial Atlantic Marine Core

Increased dust emissions from dryland areas and their effects on human health, ecosystem viability, and environmental change are a global concern in the face of the growing climate crisis. Dust plume emissions from the West African landmass, Sahara, and Sahel areas comprise a major fraction of the global aerosol budget. Dust plume intensity is closely related to regional winds (e.g., Harmattan, Sahara Air Layer), the Intertropical Convergence Zone, monsoonal seasonality, marine currents, and physiography. To study terrigenous material emitted from the continent over the last ~260 kyr (late Quaternary), we used X-ray fluorescence spectroscopy (XRF) to analyze a ~755 cm long marine sediment core from the eastern equatorial Atlantic Ocean, resulting in nearly 1400 discrete measurements. Spectral analysis results suggest that concentrations of elements (Rb, Sr, Si, Al) preserved in the sediments are correlated to different types of orbital climate forcing. Chemical weathering intensity indicated by the Rb/Sr ratio was sensitive to seasonal insolation variations controlled by precession cycles (23–18 kyr), which presumably reflects the relationship between monsoonal rainfall and sensible heating of the continent. Spectral analysis of silicate mineral grain size (Si/Al) showed significant 40 kyr cycles that were paced by obliquity. Based on these data, we infer that winter tradewind activity accelerated in response to the intertropical insolation gradient induced by high obliquity. High Rb/Sr ratios during the last glacial maximum and penultimate glacial maximum may have been due to a predominance of mechanical weathering over chemical weathering under dry/cool climates or the dissolution of Sr-bearing carbonates by corrosive glacial bottom waters.

In vitro tungsten bioaccessibility in Chinese residential soils: Implications for human health risk assessments and soil screening level derivation

Tungsten (W) contamination presents emerging environmental challenges, necessitating the need to establish soil screening levels (SSLs), especially for residential soils. This study assessed the health exposure risk and derived national and regional residential SSLs for W in Chinese residential soils, incorporating machine-learning prediction of in-vitro soil W bioaccessibility. We analyzed 204 residential soil samples collected across 24 provinces, recording a wide range of W concentrations (0.01–3063.2 mg/kg). Synchrotron-based X-ray fluorescence spectroscopy, chemical extractions, and random forest modeling indicated that the key determinants of soil W bioaccessibility were soil pH, cation exchange capacity, organic matter, and clay contents. Monte Carlo simulations demonstrated that soil W contamination predominantly results in noncarcinogenic health risks to residents via oral exposure, especially in mining-affected regions. A national residential SSL (NRSSL) of 35.5 mg/kg and regional residential SSLs (RRSSLs) of 34.5–49.2 mg/kg were established. Incorporating predicted bioaccessibility increased the NRSSL to 73.8 mg/kg and the RRSSLs to 69.8–112.5 mg/kg. Southern China, which is rich in W ore, exhibited lower RRSSLs, underscoring a need for enhanced safety management. Our framework and findings provide a robust scientific foundation for future soil contamination risk assessment studies, and we present customized SSLs that can guide targeted W risk control strategies.

Revealing ancient yellow colorants in painted artworks along the silk Road (6th-10th century AD)

A comprehensive analytical protocol was undertaken to elucidate the yellow colorants employed in wall paintings from the Kizil Grottoes, the Taojia Tomb, the Baiyangzhai Tomb, and polychrome figurines from the Astana Tombs, all positioned along the historical Silk Road and dating to the 6th-10th centuries AD. To unequivocally identify these colorants, multi-analytical techniques were deployed, encompassing digital microscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray fluorescence spectroscopy (XRF), micro-Raman spectroscopy, and ultra-performance liquid chromatography triple quadrupole time-of-flight mass spectrometry (UPLC-Triple TOF-MS/MS). This comprehensive approach facilitated the unambiguous identification of both inorganic pigments, specifically vanadinite, and plant-derived colorants, including gamboge (Garcinia sp.) and Chinese cork tree (Phellodendron chinense), within these archaeological artifacts. These findings not only significantly enhance our scientific understanding of the materials and techniques utilized in the creation of these wall paintings and polychrome figurines, but also shed light on the vibrant exchange of materials and technological advancements that flourished along the ancient Silk Road.

Comparison of Quantitative and Qualitative EDXRF Analysis for Provenance Study of Archaeological Ceramics.

The most common scientific analysis of archaeological ceramics aims to determine the raw material source and/or production technology. Scientists and archaeologists widely use XRF-based techniques as a tool in a provenance study. After conducting XRF analysis, the results are often analyzed using multivariate analysis in addition to interpretation and conclusions. Various multivariate techniques have already been applied in archaeological ceramics provenance studies to reveal different raw material sources, identify imported pieces, or determine different production recipes. This study aims to evaluate the results of multivariate analysis in the provenance study of ceramics that belong to three cultures that settled in the same area during various prehistoric periods. Portable energy-dispersive X-ray fluorescence spectrometry (pEDXRF) was used to determine the elemental composition of the ceramic material. The ceramic material was prepared in two different ways. The ceramic body material was ground into powder, homogenized, and then pressed into tablets. After that, the same fragments are polished in suitable places. Quantitative and qualitative analyses were performed on the tablets and polished pieces. The results were subjected to both unsupervised and supervised multivariate analysis. Based on the results, it was concluded that qualitative analysis of the well-prepared shards' surface using EDXRF spectrometry could be utilized in provenance studies, even when the ceramic assemblages were made of similar raw materials.

It is not crystal clear: “nuances” in the selection of raw materials for Iron Age translucent glass revealed by chemical analyses of beads from central Italy

The Iron Age was a period of change, with many innovations in the glass-making technology. The chemical composition of the set of objects considered in the present study demonstrates the diversity of the raw materials used and the depth of knowledge about the manipulation of glass appearance in the eighth-sixth centuries BCE. The study was carried out using fibre optics reflection spectroscopy and portable X-ray fluorescence spectrometry at the museums’ premises to examine a large number of glass beads and preliminarily group them on the basis of their composition and spectral characteristics. In addition, a smaller set of selected samples was analysed by laser ablation inductively coupled plasma mass spectrometry to provide a comprehensive chemical characterisation of the material. The compositional data indicated that the samples belonged to the high magnesium and low magnesium glass compositional types. Only one sample was recognised as low magnesium medium potassium glass. Glasses within each group were made from different sands, suggesting different provenances. Some of the samples were suggested to be of local origin, while the others were interpreted as imported glass. Evidence of glass colouring, decolouring and recycling are also discussed.

Biosynthesized and chemically synthesized Ag/TiO2 nanocomposites: Effect of reaction parameters on synthesis using watermelon rind extract and comparative analysis

This work synthesized Ag/TiO2 nanocomposite via an aqueous reduction method using a green and chemical reducing agent. Citrullus lanatus (watermelon) rind extract (WMRE) and sodium borohydride (NaBH4) were used as the reducing agents during green synthesis and chemical synthesis, respectively. During green synthesis, a pH of 12, a reaction time of 45 min, and an operating temperature of 100 °C yielded the best visible light activity. The biosynthesized and chemically-synthesized Ag/TiO2 were compared using UV–Vis spectroscopy, X-ray fluorescence spectroscopy (XRF), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), energy dispersive spectroscopy-scanning electron microscopy (EDS-SEM) and transmission electron microscopy (TEM). Synthesis using WMRE yielded spherical Ag nanoparticles modified on the surface of TiO2 nanoparticles. The Ag nanoparticles had enhanced monodispersity with an average diameter of 7.48 ± 4.06 nm. Therefore, the developed WMRE green synthesis method provides a simple, less chemical-intensive, and effective alternative to chemical synthesis.

Tracking the quality of graphene oxide suspension during long-term storage

Graphene oxide is a popular material because of not only its cost–efficient production but also its unique properties. However, after long-term storage, several changes occur in the structure of graphene oxide obtained using the modified Hummers’ method, affecting its stability and physicochemical properties. Despite the obvious problem, there is only a limited number of works devoted to ageing factors, their impact on the properties and structure of graphene oxide itself, and operational modes of materials and devices based on graphene oxide. Therefore, to facilitate the widespread industrial application of graphene oxide, it is crucial to establish standardized protocols for storage and quality assessment of graphene oxide. In this paper, the prepared samples were extensively characterized using various techniques, including transmission electron microscopy, X-ray photoelectron spectroscopy, UV–Vis and fluorescence spectroscopy techniques. Among the various analytical methods, comprehensive spectroscopic analysis of the absorption and fluorescence properties has proven to be the most sensitive to sample ageing. We investigated the change in optical and physicochemical properties of graphene oxide during its long-term storage under various conditions. It was found that graphene oxide precipitated during storage, and the O/C ratio in graphene oxide decreased slightly from 0.49 to 0.47. Still, the type of oxygen-containing functional groups did not change, which might indicate possible intra-structural changes. Using transmission electron microscopy, molecular dynamic and density functional theory simulation, we showed that the rearrangement of functional groups on the surface leads to the formation of large sp2 domains that interact with each other, leading to aggregation of the graphene oxide.