XRF Measurements Research Articles

In-situ X-ray Fluorescence Analysis of In-plane Cerium-ion Distribution Under Humidity Gradients in Proton Exchange Membrane

For the wide application of polymer electrolyte fuel cells, durability of more than 50,000 hours is necessary. Chemical degradation of the perfluorosulfonic acid (PFSA) membrane electrolyte is one of the degradation factors. Hydrogen peroxide generated from crossover gas reacts with impurities, and the resulting radicals break the chemical bonds in the electrolyte membrane. To quench the radicals, cerium ions are added to the membrane electrode assembly (MEA) as a radical quencher. However, cerium ions are known to move in the in-plane direction due to the humidity gradient during fuel cell operation. In areas where cerium ions are depleted, the chemical bonds of the PFSA are attacked by radicals. Therefore, it is necessary to understand the in-plane transport phenomena of cerium ions under fuel cell operating conditionsand incorporate into the development of MEAs. In this study, we developed an operando measurement cell that can track the change of cerium ion distribution over time by X-ray fluorescence spectroscopy (XRF) using high energy X-rays under fuel cell operation while controlling the in-plane humidity gradient. The in-plane transport of cerium ions, driven by the humidity and concentration gradients, was analyzed.Two gas inlets were connected to an end plate with an X-ray transmission window to control two humidity environments on the left and right sides with in-plane direction of MEA. For MEA, Pt/C catalyst layer was coated on PFSA membranes in which a part of sulfonic acids were exchanged with cerium ions. GDL without cerium was used. Operando XRF measurements were performed at beamline BL37XU on SPring-8. The incident energy was 60 keV X-rays, and Ce-Kα fluorescence X-rays were counted. The beam size was 0.5×0.5 mm2. The cell temperature was 60°C, the different relative humidity (RH) in the in-plane direction was set to 90% and 50% using N2 gas, then the RH of the whole MEA was set to 95% to measure the relaxation behavior of cerium.Fig. 1 shows the Ce intensity variation at the vertical center of the MEA under the condition of humidity difference with in-plane direction. The x-axis corresponds to the horizontal position of the MEA, with RH 90% on the left side and RH 50% on the right side. The y-axis corresponds to the time under the humidity gradient. The darker blue indicates weaker intensity of the Ce-Kα fluorescence X-ray and the white indicates stronger Ce intensity. This suggests that cerium ions move from the high humidity side to the low humidity side with the humidity gradient as the driving force. The time scale for this movement of a few millimeters was shown to be about tens of minutes. Acknowledgments The authors would like to thank M. Toida (Toyota Motor Corporation) for providing samples and for in-depth discussions. Figure 1

Azadirachta indica seed oil epoxidation process using carbonized melon seed peel catalyst; genetic algorithm coupled artificial neural network approach

The study used ANN-GA and RSM to predict the best process parameters for generating epoxide from Azadirachta indica seed oil (AISO). This procedure used carbonized sulphonated melon seed peel catalyst. FTIR, SEM, XRD, BET, and XRF measurements confirm the -SO3H group's attachment to the solid catalyst. The dependant variable was relative conversion to oxirane (RCO), while the independent parameters were catalyst dosage (0.6, 1.2, 1.8 wt %), time (4, 6, 8 h), and temperature (50°C, 60°C, 70°C). The ANN was evaluated using 11 backpropagation (BP) methods. Each method was examined with three input layer neurons for catalyst dosage, duration, and temperature. Ten neurons were in the hidden layer and one was in the output layer signifying RCO. The AISO epoxidation process forecast was most accurate using Bayesian regularisation. Simulated RSM and ANN models were built using experimental and algorithmic designs. The 3D plots showed that process parameters significantly affected RCO. R2 and MSE were used to evaluate model performance. For process forecasting, the ANN model (R2=0.9999, MSE=2.3404E-13) outperforms the RSM model (R2=0.9979, MSE=0.4688). Under the best RSM circumstances, RCO yield was 78.03 %. Additionally, the ANN and ANN-GA yielded 85.84 % and 92.51 %, respectively at optimal conditions of 0.6 wt % catalyst, 50°C temperature, and 6 h reaction time. However, all techniques optimized AISO and matched experimental results (RCO-77.41 %). FT-IR and GCMS characterizations of epoxy AISO corroborated the oxirane ring's attachment. The results show that ANN-GA is a reliable method for modelling and optimizing AISO epoxide production utilizing CSMSPC, encouraging sustainable development.

Modeling soil moisture from in situ portable X-ray spectrometer measurements: A novel approach for correcting geochemical data across different environments and climatic conditions

The portable X-ray fluorescence (pXRF) spectrometer is widely employed for in situ analysis of both contaminated and uncontaminated soils. However, the accuracy of the measurements can be significantly affected by soil moisture, resulting in unreliable soil pollution monitoring. This effect has already been studied and quantified, but this is ineffective if the soil moisture in the field is unknown. Given the considerable variability of soil moisture conditions across time and space, significant bias during in situ investigations remains a main issue. This study introduces a novel method to estimate soil moisture directly from pXRF field measurements, enabling its reliable use in almost any field condition. The study was conducted using soil samples and in situ pXRF soil surface measurements in Estarreja (Portugal) and Vicdessos (France). In the first experiment, the innovative approach involved modeling soil moisture directly from the raw XRF measurement errors obtained in moist soils using multiple regression. In the second experiment, metal concentrations were modeled as an exponential function of the moisture content. The final model integrates both approaches to correct field data from geochemical mapping in diverse environments, including a coastal region in Portugal and a mountainous region in France. Our findings demonstrate that this simple, efficient and cost-effective method accurately predicts soil moisture (U) using pXRF, as shown by the equation Umeasured = 1.0028 x Uestimated (r2 = 0.9715). The model effectively corrected up to 70% of moisture-induced errors in metal concentrations in the wettest soils and produced more reliable soil Fe, Pb, and Zn maps. Specifically, the accuracy improvement was at least 32% in drier soils (Portugal) and at least 55% in wetter soils (France). This study offers a cost-effective, efficient solution for employing pXRF in geochemical mapping across different climatic conditions and soil environments.

Investigating Microbial Biosignatures in Aeolian Environments Using Micro-X-Ray: Simulation of PIXL Instrument Analyses at Jezero Crater Onboard the Perseverance Mars 2020 Rover.

Assessing the past habitability of Mars and searching for evidence of ancient life at Jezero crater via the Perseverance rover are the key objectives of NASA's Mars 2020 mission. Onboard the rover, PIXL (Planetary Instrument for X-ray Lithochemistry) is one of the best suited instruments to search for microbial biosignatures due to its ability to characterize chemical composition of fine scale textures in geological targets using a nondestructive technique. PIXL is also the first micro-X-ray fluorescence (XRF) spectrometer onboard a Mars rover. Here, we present guidelines for identifying and investigating a microbial biosignature in an aeolian environment using PIXL-analogous micro-XRF (μXRF) analyses. We collected samples from a modern wet aeolian environment at Padre Island, Texas, that contain buried microbial mats, and we analyzed them using μXRF techniques analogous to how PIXL is being operated on Mars. We show via μXRF technique and microscope images the geochemical and textural variations from the surface to ∼40 cm depth. Microbial mats are associated with heavy-mineral lags and show specific textural and geochemical characteristics that make them a distinct biosignature for this environment. Upon burial, they acquire a diffuse texture due to the expansion and contraction of gas-filled voids, and they present a geochemical signature rich in iron and titanium, which is due to the trapping of heavy minerals. We show that these intrinsic characteristics can be detected via μXRF analyses, and that they are distinct from buried abiotic facies such as cross-stratification and adhesion ripple laminations. We also designed and conducted an interactive survey using the Padre Island μXRF data to explore how different users chose to investigate a biosignature-bearing dataset via PIXL-like sampling strategies. We show that investigating biosignatures via PIXL-like analyses is heavily influenced by technical constraints (e.g., the XRF measurement characteristics) and by the variety of approaches chosen by different scientists. Lessons learned for accurately identifying and characterizing this biosignature in the context of rover-mission constraints include defining relative priorities among measurements, favoring a multidisciplinary approach to the decision-making process of XRF measurements selection, and considering abiotic results to support or discard a biosignature interpretation. Our results provide guidelines for PIXL analyses of potential biosignature on Mars.

Sustainable reuse of waste ceramic tiles powder and waste brick powder as a replacement for cement on green high strength concrete properties

Nowadays, reducing construction waste has grabbed the attention. As bricks and ceramic tiles represent more than 50% of the ceramic waste in many European countries. Thus, the recycling of this waste type is one of the most significant challenges within the paradigm of the circular economy. This paper investigated the impact of substitution levels of cement by waste ceramic powder (WCP) and waste brick powder (WBP) at 0%, 5%, 10% and 15%, on the HSC characteristics. The WBP and WCP materials were characterized in detail by laser granulometry, XRF and XRD measurements, followed by standard mixing, production, and curing of concrete samples. The experiments on dry density, modulus of elasticity, flexural strength, splitting tensile strength, compressive strength, resistance to sulfate attack, water absorption and ultrasonic pulse velocity were conducted to evaluate the hardened properties of concrete. It was demonstrated that the durability and strength of concrete containing WBP and WCP as partial replacements for cement are marginally inferior to those of the control sample. On the other hand, samples containing WBP had a lesser negative effect on HSC properties in comparison with samples containing WCP. However, employing a 5% WBP with 10% WCP mixture enhanced the characteristics of the HSC in comparison to samples containing various percentages of WCP individually. In addition, the microstructure analyses revealed that the addition of 10% WCP and 5%WBP to HSC specimens resulted in higher hydration products and a slightly denser concrete matrix compared to samples containing various percentages of WCP individually. Research findings indicate that a 15% substitution of cement with WCP or WBP illustrated an environmental benefit in concrete production due to a 13.1% reduction in specific energy consumption.

Lead-based paint detection using perovskite fluorescence and X-ray fluorescence

BackgroundIngestion of flakes of Pb-based paint by infants remains a global health hazard with life-long consequences. Pb-based paint was banned for residential use in the US and Western Europe decades ago but is still sold in many countries. This study evaluates the performance of a new kit for detecting exposed Pb-based paint relying on the formation of Pb-halide perovskite that fluoresces bright green under a UV flashlight after spraying a non-toxic reagent. ResultsTests with the Lumetallix kit were conducted in parallel with X-fluorescence and inductively-coupled plasma atomic emission analysis upon acid digestion using paint currently sold in Côte d'Ivoire and samples of older US paint. Comparison of the three different methods indicates a detection limit for the Lumetallix kit of approximately 500 mg kg−1 (ppm) Pb in paint, with a sensitivity of 95 % and selectivity of 94 % relative to that threshold (n = 76). This detection limit is an order of magnitude below the US definition of Pb-based paint of 0.5 % (5,000 ppm) Pb by weight. SignificanceBecause the kit is easy to use, exposed paint posing a risk could reliably be screened at scale by the general public. Any follow-up for confirmation and mitigation based on XRF measurements will need to consider that Pb-based paint covered with low-Pb paint will not respond to the kit but will be detected by XRF through the overpainted layer.

Benchtop x-ray fluorescence to quantify elemental content in nails non-destructively

Metals continue to impose health issues among world populations. A non-invasive alternative biomarker for assessment of metals and other elements has been explored in other studies using toenail samples. Some benefits of using toenails as biomarkers over blood samples include cost efficiency, ease of collection, and a longer biological half-life within samples. The objective of this study was to employ desktop XRF for the purpose of measuring metal concentrations in human nail samples, thus conducting a non-destructive assessment. These benefits paired with comparable accuracy in exposure detection could prove toenail samples to be a preferred biomarker for many studies. Current elemental quantification techniques in toenail samples could be improved. The standard practice for measuring metal exposure in toenails, inductively coupled plasma mass spectrometry (ICP-MS), has a counterpart in x-ray fluorescence. While maintaining similar quantification capabilities, x-ray fluorescence could provide decreased cost, preservation of samples, and ease of operation. Portable XRF machines have been tested for measuring toenail samples, but they have drastically increased detection limits in comparison to ICP-MS. New benchtop XRF systems should give comparable detection limits to ICP-MS. This study compares the benchtop XRF measurements of lead (Pb), copper (Cu), iron (Fe), and Selenium (Se) levels to that of ICP-MS measurements of toenail samples and calculates estimated detection limits for 23 other elements. We found strong correlations for the toenail lead (R2 = 0.92), copper (R2 = 0.95), selenium (R2 = 0.60), and iron (R2 = 0.77) comparison between desktop XRF and ICP-MS measurements. Median minimum detection limits over the 23 elements were found to be 0.2 μg/g using a 7.5-min measurement. Benchtop XRF provides a lower detection limit than previously studied portable XRF machines, which gives it the capability of accurately detecting almost any desired element in nail samples. Benchtop XRF provides a non-destructive alternative to ICP-MS in surveillance of nail samples.

Extremely high resolution XRF core scanning reveals the Early Triassic depositional history of the Montney Formation in northeastern British Columbia, Canada

The Montney Formation is a laterally extensive, fine-grained sedimentary unit in western Alberta and northeastern British Columbia, and a major target of hydrocarbon exploration. It also retains a complete record of the Early Triassic epoch, a time when the biosphere was recovering from the effects of the end-Permian mass extinction. An industry well provides a full-diameter core of the complete distal Montney Formation in northeastern British Columbia (over 350 m thick), with stratigraphic age control provided by conodont biostratigraphy and regional correlations. For this study, the core was scanned using an ITRAX X-ray fluorescence spectrometer, at centimeter-scale resolution. The resulting dataset (over 37,000 individual measurements) provides an extremely high level of resolution for a deep-time geochemical study. While the data generated by this instrument are semiquantitative, they can be calibrated by correlating them with more conventional ICP-MS and XRF measurements of select samples. Using this method, we assessed the reliability of each of the elemental data series, and where possible converted them to quantitative geochemical measurements. These calibrated measurements serve as the basis for our detailed reconstruction of the Montney Formation's depositional history.The distal Montney depositional basin, including the location of the c-65-F core, was euxinic immediately following the end-Permian mass extinction, and accumulated sediments from the rapidly eroding margin of western North America. Conditions stabilized somewhat in the Dienerian, with oxic bottom water and a trend toward more compositionally mature sediment, but conditions of widespread euxinia and rapid erosion of the North American craton recurred in the early Smithian, earlier than this global crisis has been recognized elsewhere. Above the middle-upper Montney sequence boundary, in the overlying Spathian succession, local effects predominate. Coastal upwelling resumed in the basal Spathian, though the Montney depositional basin was soon cut off from the global ocean by uplift of the Yukon-Tanana arc bounding the basin to the west. Restricted conditions, with euxinic bottom water, were punctuated by oxic intervals, when rising sea level allowed the basin to freely exchange water with the open ocean. Intervals of restriction became progressively less acute in the upper Spathian.

A Study of Color Palettes and Painting Techniques of Prayat Pongdam: Oil on Board Painting “Cats and Birds (1957)” Using Micro-XRF Scanning Technique

This work presents the characterization of the pigments in the painting by Prayat Pongdam, one of the most essential artists in the history of Thai contemporary art. The painting that was studied is named “Cats and Birds (1957),” oil on board, from the collection of a private collector. XRF measurements were carried out utilizing a portable system and mapping scanning. XRF revealed substantial information about the pigments in the painting and the artist’s technique. Lead white (Pb) was presented in or near the ground layer. A mixture of barium (Ba) and titanium (Ti) was applied in almost all areas but less in the blue areas, presumably because these two pigments were used on top of the ground layer. Zinc (Zn) white was mixed with the cerulean blue (Co, Sn) for the blue regions. Chromium-based green (Cr) and red ochre (Fe) were in the palette in green and red areas, respectively. A layer of gold was applied to some areas, assuming the artist wanted to make it a highlight. Metallic pigments containing copper (Cu) were also revealed.

Investigating the impact of sample desiccation on Itrax XRF core scanner signal reproducibility

AbstractSediment samples tend to dry out during storage and are, therefore, stored refrigerated at about 4°C after wrapping in plastic foil. During XRF core scanning however, the samples must be taken out of their cover, increasing the risk of drying and formation of desiccation cracks on the surface. Because scan times can often amount to several hours and at highest resolution may take over a day to complete, the core will progressively dry out during scanning. With this study we aim to increase our understanding of how this slow drying of the samples during scanning and storage influences the XRF signal because of changes in water content, sediment surface topography, and the development of small, but slowly expanding cracks in the sediment core. Results show that the desiccation of samples during scanning and storage influence the XRF measurements in several ways. Most importantly, slow desiccation of the cores results in both a general lowering of the sample surface, and a shortening of the core due to shrinkage. Larger distance between sediment surface and detector leads to increased noise levels and poor reproducibility for many elements, while the shrinking of cores may shift individual data points between runs, resulting in poor reproducibility and offsets between datasets obtained at different times. Moreover, the loss of light elements, such as hydrogen and oxygen, can influence the matrix effect, especially for organic‐rich sediment. Because the XRF signals of individual elements are affected to different degrees, these changes may induce artificial shifts and biases in many elemental ratios commonly used for paleoenvironmental reconstruction.

Detection of Silica in Rice Husks Using Laser-Induced Plasma and Studying the Effect of Laser Energy on the Parameters of the Produced Plasma

This study aims to analyze the spectral properties of plasma produced from rice husk(Rh) using the laser breakdown spectroscopy (LIBS) method. The plasma generation process used the fundamental harmonic (1064 nm) of a Q-switched Nd:YAG laser. Yttrium aluminum garnet (YAG) is a man-made crystalline material. The laser fired pulses with a duration of 10 ns and a repetition rate of 6 Hz. Thus, the energy outputs achieved were 50–200 mJ at the wavelength of 1064 (nm). The silica content in the rice hulls was verified using an XRF measurement, which revealed the presence of silica in the rice hulls in a high percentage. Precise beam focusing was achieved by focusing the laser on the target material. This target material is placed within an atmospheric environment at standard pressure settings. The electron temperature was derived using the Boltzmann diagram method by harnessing experimental data for the linear properties associated with the neutral lines (Si II), (O II), and ion lines (Si I). The use of analytical methodology led to the determination of electron temperature values from 0.79 eV to 1.16 eV for the fundamental harmonic of the laser. At the same time, the electron (ne) density was determined by analyzing the Stark broadening profile associated with the neutral silica line. Furthermore, the study included an additional dimension by determining the plasma properties (electron temperature and electron density) by adjusting the laser energy on the target surface longitudinally along the path of the plasma plume.

A comprehensive study on the fire resistance properties of ultra-fine ceramic waste-filled high alkaline white cement paste composites for progressing towards sustainability

The most practical sustainable development options to safeguard the local ecology involve reducing the use of raw materials and guaranteeing proper recycling of the principal destroyed solid wastes. Preventing the creation of hazardous waste and the subsequent pollution that results from improper disposal is a top priority. Based on this, the study's authors recommend reusing the ultra-fine ceramic shards (CW). High-alkaline white cement (WC) has been partially replaced by ultra-fine CW because it is a cheaper, more abundant, and more lasting environmental material used in the production of trendy blended white cement pastes composites. In this context, we look at ultra-fine CW, a material that has been suggested for use as a hydraulic filler due to its high performance, physicomechanical qualities, and durability. XRF, XRD, FTIR, and SEM measurements are used to characterize the microstructure, thermal characteristics, and thermodynamics. Because of the effect of ultra-fine ceramic waste, the firing test reduces the mechanical strength by default, but with active filler, decreases slowly and increase its physicomechanical features and compressive strength compared to the control sample (WC), setting a new benchmark. The maximum amount of crystallization formed in the presence of ultra-fine ceramic waste in WC-matrix, resulting in a decrease in total porosity and early cracking. Together, the improved workability and energy-saving features of cement blends with ultra-fine ceramic waste, reflect their economic and environmental benefits, which may reduce building costs and boost the durability of the raw materials used in the mix.

Lunar elemental abundances as derived from Chandrayaan-2

The distribution of Mg, Al, Si, Ca and Fe on the lunar surface are important to understand the petrological characteristics of the Moon and its geological evolution. We derived new elemental distribution maps using the Chandrayaan-2 Large Area Soft X-ray Spectrometer (CLASS) experiment onboard the Chandrayaan-2 Orbiter. These are the first set of maps derived from three years of CLASS data (2019–2022) at a spatial resolution of 150 km × 12.5 km. These maps are free of the topographic shadow effects and space weathering effects because the elemental abundances are derived only using X-ray spectra in the 0.5 to 20 keV energy range. CLASS derived abundances are compared to the elemental maps obtained using the Lunar Prospector Gamma Ray Spectrometer, with abundances of the lunar soil samples, and with XRF measurements of Chandrayaan-1 mission to establish its credibility. These maps derived using X-ray fluorescence spectroscopy are a new resource for lunar geochemical studies based on the most direct detection technique.

Exploring organo-bentonite adsorption properties for biphenyl removal from organic-aqueous media: kinetic study and industrial perspective

Biphenyl, a frequently encountered and resilient compound in wastewater, proves resistant to conventional treatment methods because of its enduring nature. It forms the structural basis for persistent organic pollutants such as PCBs. In this study, we explored the adsorption of biphenyl in an organo-aqueous medium using both natural (Bent) and organomodified (CTAB-Bent) bentonite clay. Our objective was to highlight its potential for biphenyl wastewater treatment. We analyzed the physicochemical and textural properties of these clays through FTIR, XRF, XRD, SEM, BET method, and Zeta potential measurements. Impressively, these materials exhibited remarkable biphenyl adsorption capacity under acidic conditions, with Bent achieving 60% removal and CTAB-Bent an impressive 91%. We investigated the adsorption kinetics using first-order and pseudo-second-order models and assessed isotherm data with the Langmuir, Freundlich, and Langmuir-Freundlich (sips) equations. The Langmuir model, at pH 3, proved optimal, with high accuracy (R²) and minimal error (RMSE) values (0.997 and 1.20, respectively). Clay nature significantly influenced pollutant uptake efficiency, confirming the efficacy of the selected bio-based clay. We propose a protocol adaptable for industrial-scale applications.

Surface Quality Control by X-Ray Fluorescence

Elemental analysis by X-ray fluorescence, XRF, is a well-known technique, widely used in laboratories and industrial plants. XRF equipment manufacturers offer accessories and programs to integrate their equipment into automated plants and use it as quality control tools. The relationshipbetween the surface roughness of the samples and the quality of the measurement is studied and its physical principles are known. In this work it is proposed to use an XRF equipment to analyze the surface roughness of the elements produced in chain, and establish a pass/do not pass control of a batch.By integrating the XRF equipment into the chain, and comparing the measurement with a previous measurement considered reference (which can be done with other equipment such as a roughness meter or confocal microscope) it can be determined if the surface roughness of the samples conforms to the established tolerance limits. The advantages of using an XRF equipment are: using equipment that is already in the plant, automating the control process, integrating an XRF into a flexible manufacturing environment and non-contact roughness analysis (surface texture).In this work the authors start from different machined specimens of aluminium alloy perfectly known by spark emission spectrometry to the appropriate dimensions to be measured in an XRF spectrometer. The surface to be evaluated is machined until the desired order of roughness is achieved, its surface finish is determined by optical methods and subsequently measured in the XRF equipment. Different specimens, are produced to determine the changes in the XRF measurements. The intensity of selected elements in each specimen is related to the surface finish and conclusions are drawn.

DETECTION AND CHARACTERIZATION OF SOME GLAZE FAULTS ENCOUNTERED IN SANITARYWARES

The use of suitable glaze compositions, which enable ceramic sanitaryware (such as sink, toilet bowl, toilet bowl, etc.) to have better hygienic, aesthetic and technical properties, is of great importance as in other ceramic products. Glaze compositions, which provide durability to sanitaryware materials, reduce impact resistance and give ceramic material a hygienic appearance, are produced as ~97% white color depending on the preferences of the consumers, therefore, surface defects attract more attention in glazing and post-glazing process applications. When faults occurred during the different stages of manufacture detected on the final product, failure to detect faults on the final product by passing many production stages poses a problem in terms of intervention in the process. Faults that occur during glaze preparation are important in terms of cost. Since it is a stage in which many economic evaluations have been made in production, eliminating the faults caused from glaze preparation prevents further financial loss. In this study, the appearance of the faults in the sanitaryware items and the change in their regions (occured as a result of the oils contaminations from the machinery and components used in the preparation of glaze, the pipes of the tanks used in the glaze transport tanks and the glaze transfer or the impurities contaminated from the environment, the splashing of the impurities by the colored glazes in the glazing cabinets etc.) were characterized by means of SEM (Scanning Electron Microscopy), XRF (X-ray fluorescence spectrometry), XRD (X-Ray Diffractometry) and color measurement (L a* b*) analyses. According to the data derived from the final defected products, the faulty products were imitated by using the same components and methods on the plates under the laboratory conditions. Finally, the solutions for the problems were determined on the basis of faulty products obtained in the laboratory.

IrxNb1-XO2 Mixed Metal Oxides As Anode Catalyst for PEM Electrolysis: From Fundamentals to Application

Summary. Here we describe the synthesis of IrxNb1-xO2 (mixed) metal oxides powders with several compositions. The catalysts are characterized with a variety of techniques to achieve a structure – activity relation. Furthermore, the effect of annealing temperature is addressed. Promising catalysts were tested in a full electrolysis cell as well. . Electrochemical water splitting will play a crucial role in future industries and will contribute to a more sustainable economy. Hydrogen produced by electrolysis is suitable to replace hydrogen produced by fossil fuels, enables the electrification of multiple sectors and can be used as long- and short-term chemical energy storage system [1].Here we describe the synthesis of IrxNb1-xO2 (mixed) metal oxides powders. Several compositions regarding the Ir/Nb ration are synthesized and studied. The study is based on previous experimental and theoretical findings using model films of IrxNb1-xO2 [2]. We address fundamental properties like crystal structure and composition and furthermore, test the catalysts in full electrolysis cell measurements. The synthesized materials are analysed using a variety of techniques, like XRF, XRD, RDE, BET, SEM, TEM, TGA and conductivity measurements to determine the activity and stability, crystal structure, morphology and conductivity. Furthermore, the effect of the annealing temperature on the above mentioned properties was studied. The optimal composition was determined based on activity and stability measurements in a three-electrode setup and physical properties like the powder conductivity.The synthesized catalysts could outperform commercial catalysts in terms of activity and stability and can be used with lower Ir loadings. XRD measurements reveals an IrO2 rutile structure with very broad peaks, indicating an amorphous crystal structure.The most promising catalysts were evaluated in a full electrolysis cell with different loadings.[1] Getting Hydrogen to the Gigaton Scale; B. S. Pivovar, M. F. Ruth, A. Nakano, H. Furutani, C. Hebling, T. Smolinka; Electrochem. Soc. Interface. 2021, 30, 85.[2] Molecular Analysis of the Unusual Stability of an IrNbOx Catalyst for the Electrochemical Water Oxidation to Molecular Oxygen (OER); C. Spöri, L. J. Falling, M. Kroschel, C. Brand, A. Bonakdarpour, S. Kuhl, D. Berger, M. Gliech, T. E. Jones, D. P. Wilkinson, P. Strasser

A New Albite Microanalytical Reference Material from Piz Beverin for Na, Al and Si Determination, and the Potential for New K‐Feldspar Reference Materials

Determination of alkali elements is important to Earth scientists, yet suitable and reliable microanalytical reference materials are lacking. This paper proposes a new albite reference material and evaluates the potential for future K‐feldspar reference materials. The proposed Piz Beverin albite reference material from Switzerland yields a homogeneous composition at the centimetre‐ to micrometre‐scale for Si, Al and Na with < 2000 μg g‐1 total trace elements (mostly heterogeneously distributed Ca, K and Sr). EPMA and LA‐ICP‐MS measurements confirm a composition of 99.5(2)% albite component, which is supported further by bulk XRF measurements. A round robin evaluation involving nine independent EPMA laboratories confirms its composition and homogeneity for Si, Al and Na. In addition, a set of five distinct clear K‐feldspar samples was evaluated as possible reference materials. The first two crystals of adular and orthoclase yield unacceptable inhomogeneities with > 2% relative local variations of Na, K and Ba contents. The three other investigated sets of K‐feldspar crystals are yellow sanidine crystals from Itrongay (Madagascar). Despite distinct compositions, EPMA confirms they are each homogeneous at the centimetre to micrometre scale for Si, Al and K and have no apparent inclusions; further investigation to find larger amounts of these materials is therefore justified.

Acid-base treatment of lightweight expanded clay aggregate (LECA) for removal of paraquat from aqueous media

This study focuses on the modification of lightweight expanded clay aggregate (LECA) with sulfuric acid, potassium hydroxide, and sulfuric acid-potassium hydroxide to enhance the removal efficiency of the highly hazardous herbicide (paraquat) from the aqueous solution. The modification results showed that samples activated with sulfuric acid before KOH yielded higher removal efficiency (70.8%) than those activated with acid or base (25.6% and 35.8%, respectively). The paraquat uptake mechanism by LECA was investigated using XRD, XRF, FTIR, FESEM, BET, and zeta potential measurements. Batch adsorption tests were conducted under different conditions using LECA and acid-base-modified LECA. The results indicated the maximum removal efficiency for PQ at 240 min contact time, adsorbent dose of 3.5 g L−1, and pH 9 was achieved with the acid-base treated sample. Experimental data were evaluated with different isothermal, thermodynamic, and kinetic models. The pseudo-second-order model with a correlation coefficient of R2 > 0.99 was congruent with experimental results for LECA and acid-base-activated LECA through kinetic investigations. The highest adsorption capacities for the LECA and acid-base-activated LECA samples, respectively, were 6.12 mg g−1 and 21.23 mg g−1 according to the Langmuir equilibrium isotherm, which offered greater agreement with the experimental results. A negative standard enthalpy change (−21.09 kJ mol−1) and Gibbs free energy change for PQ uptake at 15, 25, and 35 °C indicated an exothermic and spontaneous process. Reusability studies confirmed that the treated adsorbent could successfully remove paraquat even after four regeneration cycles.

Raman spectroscopy and XRF identification: First step in industrial wastewater management

Considering the environmental risk, industrial facilities should strive to maximise the effectiveness of on-site treatment processes. It is important to detect the types of pollutants in wastewater and their concentrations, which can be challenging in industrial conditions. In this study, industrial wastewater samples from pickling and electropolishing of stainless steel were analyzed through Raman spectroscopy and XRF techniques using portable instruments. A 3-step procedure for the rapid identification of type of wastewater was proposed. The identification and analysis of peaks present in the Raman spectroscopy at 900, 990, 1050, 1380 cm−1allows for the differentiation of wastewater type and dilution. The final step is to employ XRF measurements to determine the approximate content of the investigated elements. The use of portable analytical instruments for the estimation of contamination levels is essential for the management of the industrial wastewater neutralization process as well as during emergency operations in cases of accidents.