The XRF-CT technique continues to gain attention with respect to both its development and applications. The emergence of fast scanning approaches in conjunction with ED-detectors of high counting ...rate capability has allowed XRF-CT to evolve towards a truly 3D elemental imaging technique. At SR sources, the technique is regularly applied at sub-μm resolution together with complementary imaging modalities such as absorption and phase-contrast CT, XRD-CT, 2D/3D XAS and ptychography. The TXRF spectrometric analysis of suspensions and undigested samples (
e.g.
clay, cosmetics and nanoparticles) continues to receive much attention. In the analysis of fly ash samples, elemental sensitivities were affected by the angle of the measurement. In the use of TXRF spectrometry for the analysis of particle-like large specimens, the influence of the standing wave field was considered to be negligible. However, more work needs to be done on this source of uncertainty to improve our understanding of the influence of the standing wave field on these kind of samples. Novel equipment capable of very good angle resolution will be useful for such studies. Pre-concentration procedures are becoming more sophisticated with the introduction of new substrates for ligands capable of binding heavy metals and, in some cases, of being applied directly on the TXRF spectrometry reflector for immediate analysis. A sophisticated explanation of the excitation spectrum reported for μ-XRF spectrometry included a new description of the energy distribution of electrons in the target. Another highlight was the application of high-resolution monochromatic μ-XRF spectrometry using DCC optics for excitation and focusing as well as for increasing the spectral resolution of the Pu and U L-lines. Although the use of portable XRF spectrometry systems is now well established, new dedicated systems continue to be developed including those with a triaxial configuration. The focus is now primarily on the development and use of portable TXRF spectrometry systems for an expanding range of applications. In the area of cultural heritage applications, macroXRF spectrometry is a well-established imaging technique for the analysis of paintings that is now also being used to image stained-glass panels. The extensive study using a number of micro- and macro-techniques of Vermeer's painting of The Girl with a Pearl Earring illustrated the power of this approach. Not only could the different shades of blue in the painting be characterised but also the materials and techniques used to achieve various effects in the painting.
This review covers developments in and applications of XRF techniques such as EDXRF, WDXRF, TXRF, XRF microscopy using technologies such as synchrotron sources, X-ray optics, X-ray tubes and detectors in laboratory, mobile and hand-held systems.
That the boundaries of analysis using XRF spectrometry performed at SR sources continues to be pushed back is evidenced by the nanoscale spatial resolution with near single-atom sensitivity for the ...most efficiently detected elements in nanobeam applications and high speed 2D/3D imaging capabilities. The 4
th
generation SR facilities currently under development, such as the ESRF Extremely Brilliant Source (EBS), will be at the forefront of these advances. A clear trend is that SR-XRF spectrometry is increasingly applied with complementary X-ray spectroscopic/imaging techniques to combine spatially resolved elemental information with speciation and structural/morphological imaging. The wide range of applications of scanning (sub)microXRF spectrometry for elemental imaging published in the period covered by this review included biomedical, environmental, materials science and cultural heritage studies. Most applications involved XAS and XRD methods at hard X-ray micro- and nano-probe facilities. Full field microXRF spectrometry has made very promising advances with respect to the optics used. Coded apertures have potential for overcoming the low count rates that often restrict the full potential of laboratory-based full-field setups. The availability of commercial full-field detectors will increase the user community and thereby foster advancement in full field microXRF spectrometry. The TXRF spectrometry of ambient air is becoming more and more sophisticated and the advantages of this micro analytical tool over ICP-MS in terms of short sampling times with high particle size resolution are becoming ever more apparent. For example, the optimal sampling time for aerosols for TXRF analysis was well below 12 hours, whereas that for ICP-MS analysis was about 24 hours. High-quality grazing incidence XRF analysis in the laboratory has become more feasible with the development of prototype TXRF instrumentation and the availability of commercial XRD setups with energy dispersive detectors. Portable XRF spectrometry has undergone significant technological improvements in recent years and is now applied in a wide range of applications. This is reflected in a significant number of valuable review papers dealing with different aspects of the portable XRF technique. The growth in the use of macroXRF scanning systems in cultural heritage investigations has required development of new software and methodologies for efficient handling of the huge data files generated. In several contributions the possibilities of a new scanning station equipped with real time macroXRF spectrometry was demonstrated.
This review covers developments in and applications of XRF techniques such as EDXRF, WDXRF, TXRF, XRF microscopy using technologies such as synchrotron sources, X-ray optics, X-ray tubes and detectors, in laboratory, mobile and hand-held systems.
The utilisation of SR sources has significantly enhanced the analytical capabilities of XRF spectrometry techniques. With the latest generation of facilities, SR-XRF spectrometry achieves remarkably ...high nm-scale resolution with excellent LODs at ppb levels. A noteworthy trend is the increasing use of SR-XRF spectrometry together with other X-ray spectroscopic and imaging techniques. This provides complementary information on elemental speciation as well as structural and morphological characteristics of samples. Sub-μm SR-XRF spectrometry has been extensively applied in diverse fields such as environmental and planetary studies, biomedical research, materials science and cultural heritage investigations. Methods for handling the huge datasets produced by macroXRF spectrometry have become essential for processing and classifying the element distributions collected from the analysis of paintings. Machine-learning-based correlations of element maps have been developed for the automatic identification of patterns as an alternative method of processing macroXRF spectrometry data from cultural heritage samples. The microanalytical capabilities of TXRF spectrometry have led to a steep increase in applications to biomedical problems with successful analyses of minute amounts of samples (
ca.
20 mg) of,
e.g.
, blood, placenta and heart tissue. The suspension-assisted preparation of theses samples and of mineralogical materials was improved in many studies by extending the common internal standard calibration with uni- and multivariate approaches. The development of a scan-free grazing-exit XRF spectrometer improved accuracy in the analysis of periodic surface structures. The degree of protonation of different thiol- or hydroxyl-bearing organic monolayers was successfully determined using grazing-incidence XRF and TXRF spectrometries in combination with other techniques.
This review covers developments in and applications of XRF techniques such as EDXRF, WDXRF, TXRF, XRF microscopy using technologies such as synchrotron sources, X-ray optics, X-ray tubes and detectors in laboratory, mobile and hand-held systems.
This review describes advances in the XRF group of techniques published approximately between April 2018 and March 2019. The review is selective with the aim of providing a critical insight into ...developments in instrumentation, methodologies and data handling that represent a significant advance in XRF spectrometry. It is not the intention of the review to cover comprehensively the applications of XRF techniques except in those cases where the non-destructive and remote sensing nature of XRF analysis makes it particularly valuable and the method of choice. These applications concern samples which are irreplaceable and of great cultural value such as works of art and archaeological artefacts.
This 2019 review covers developments in and applications of XRF techniques such as EDXRF, WDXRF, TXRF, XRF microscopy using technologies such as synchrotron sources, X-ray optics, X-ray tubes and detectors in laboratory, mobile and hand-held systems.
Imidazolium salts were prepared which possess 2-ethoxyethyl pivalate or 2-(2-ethoxyethoxy)ethyl pivalate groups as amphiphilic side chains with oxygen donors as well as
n
-butyl substituents as ...hydrophobic groups. The N-heterocyclic carbenes of the salts, characterized by
7
Li and
13
C NMR spectroscopy as well as by Rh and Ir complex formation, were used as starting materials for the preparation of the corresponding imidazole-2-thiones and imidazole-2-selenones. Flotation experiments in Hallimond tubes under variation of the air flow, pH, concentration and flotation time were performed. The title compounds proved to be suitable collectors for the flotation of lithium aluminate and spodumene for lithium recovery. Recovery rates up to 88.9% were obtained when the imidazole-2-thione was used as collector.
The title compounds are effective collectors for the flotation of lithium aluminate and spodumene for lithium recycling, respectively.
A highlight this year was the construction of elemental maps of microalgae cells at the organelle level using XRF-CT with a beam size of just 15 nm. These probably represent the highest ever spatial ...resolution achieved for XRF-CT images. An innovative approach for reconstruction algorithms used a deep convolutional neural network to correct for the self-absorption effects in the XRF-CT sinogram domain. Such corrections will enable the use of conventional tomographic reconstruction algorithms for XRF-CT analysis. A remarkable advantage of the proposed method was that it could correct for self-absorption effects without any prior knowledge of the scanning setups. A particularly innovative dual-energy X-ray-beam ptycho-fluorescence imaging method combined XRF spectrometry and X-ray ptychography scanning with simultaneous data-collection. To overcome the incompatibility of the different excitation and scanning conditions required for fast ptychography and high spatial resolution XRF spectrometry, two coaxial beams of different sizes were used on the sample simultaneously. In comparison to sequential scans, this combined approach has the potential to reduce the data collection time by a factor of 25. The very good performance of laboratory 2D-XRF spectrometry for the analysis of minute amounts of radioactive material has made it a potential alternative to TXRF spectrometry. Reconstruction algorithms are now capable of significantly enhancing imaging resolution in μXRF spectrometry. The forensic classification of incredibly small amounts of samples such as single fibres was accomplished using elemental profiles determined by TXRF spectrometry. Although characterisation of the low-Z matrix in milk and polymers by conventional TXRF spectrometry is challenging, it was successfully achieved by studying the Compton and Rayleigh scatter with both univariate and multivariate approaches. Portable XRF spectrometry is a well-established technique for a wide range of applications. Emphasis continues to be placed on improving calibration and reducing matrix and inter-element effects. The sample type remains a challenge for portable XRF analysis. Computer vision and statistical methods such as spectral angle mapper are being increasingly applied to maximise the information that can be extracted from the data. For example, an innovative approach exploited the elemental features from XRF spectra to improve the interpretation of molecular information provided by reflectance spectroscopy, and
vice versa
.
This review covers developments in and applications of XRF techniques such as EDXRF, WDXRF, TXRF, XRF microscopy using technologies such as synchrotron sources, X-ray optics, X-ray tubes and detectors in laboratory, mobile and hand-held systems.
Derivatives of the natural product punicine 1-(2′,5′-dihydroxyphenyl)pyridinium chloride were developed as switchable collectors for the flotation of lithium-containing engineered artifical minerals ...(EnAMs). These EnAMs are
e.g.
formed by pyrometallurgical processing of end-of-life lithium-ion batteries. Depending on the pH value and the lighting conditions, punicines exist in water as cations, two different electrostatically neutral mesomeric betaines, anionic tripoles, radical cations or radical anions. The radical species form by photochemically induced disproportionation reactions. We prepared punicine derivatives introducing alkyl chains in the pyridinium moiety (4-methyl, 4-ethyl, 4-octyl and 4-undecanyl) to install hydrophobic groups and examined the recovery rates of the flotation of lithium aluminate (LiAlO
2
). We varied the lighting conditions (darkness, daylight, LED irradiation at
λ
= 390-400 nm) and the pH value, the collector's and frother's concentration, and the flotation time. With our collectors, recovery rates of lithium aluminate up to 90% were accomplished when the flotation was conducted in Hallimond tubes exposed to daylight at pH 11 in water.
Punicines were used as light-switchable collectors for flotation of the engineered artificial mineral lithium aluminate.
Pyrometallurgical processes produce slags that may contain valuable elements because of their high oxygen affinity. However, the concentration is extremely low, which causes losses. In fact, these ...elements, for example, tantalum and rare earth elements, are less than 1% recycled. To return such technologically important elements to the material cycle, pyrometallurgically is used to enrich them in the simplest possible compounds within the slag, which have favorable properties for recovery (morphology, crystal size, magnetic properties), allowing further mechanical separation. The purpose of modification of the slag system is to obtain engineered artificial minerals” (EnAM), a process in which targeted minerals with high element concentration are formed. In this article, this approach is investigated using tantalum-rich fayalitic slag, since this slag is commonly found in the industry for the pyrometallurgical treatment of waste electric and electronic equipment. Synthetic fayalitic slags in reducing environment under different cooling rates were produced with Ta addition. The characterization of the produced samples was carried out using powder X-ray diffraction (PXRD) and electron probe microanalysis (EPMA). Additionally, the speciation of Fe and Ta was accessible through X-ray absorption near-edge structure (XANES) spectroscopy. EPMA also provided a semiquantitative assessment of the Ta distribution in these individual compounds. In these slags, tantalum accumulated in perovskite-like oxidic and silicate compounds as well as in magnetic iron oxides. The enrichment factor is highest in tantalite/perovskite-type oxides (FexTayO6, CaxFeyTazO3) with up to 60 wt.% Ta and ‘tantalomagnetite’ (FeII(FeIII(2-5/3x)Tax)O4) with a maximum of ~30 wt.% Ta (only fast cooling). This is followed by a perovskite-like silicon containing oxide (XYO3) with 12–15 wt.% Ta (only slow cooling), and a hedenbergite-like compound (XYZ2O6) with a varying content of 0.3–7 wt.%. The Ta concentration in pure Fe, Fe(1-x)O, hercynitic spinel and hematite is negligible. Despite the very low phase fraction, the most promising EnAM compound is nevertheless perovskite-like tantalum oxide, as the highest enrichment factor was obtained. Tantalum-rich magnetite-like oxides also could be promising.
Pyrometallurgical slags are a valuable secondary resource for several technologically important critical materials/elements. A promising cost-efficient recovery currently under research depends on ...the incorporation of the element of interest into a specific compound. This new approach under research to recover these elements from the slag is called the "Engineered Artificial Minerals" (EnAM) concept. Optimization of slag system and cooling conditions potentially allow enrichment of a desired element in only one phase. Studying EnAM-formation requires multi model characterization of the slag at different states of formation. This includes bulk as well as microscopic elemental, structural, and species analytical tools and modeling approaches. Here, a characterization strategy mainly studying the formation of potential EnAMs for the recovery of lithium from battery recycling slags is reviewed. LiAlO
2
as well as lithium manganates were identified as promising EnAMs. The manganese oxidation state was identified a decisive parameter. For a knowledge-based design of slags, it is necessary to understand the processes leading to oxidation state variability. Hence, besides structural, compositional characterization, speciation of redox active elements is discussed here using molecular dynamics simulations, powder X-ray diffraction, electron probe microanalysis, X-ray absorption near edge structure, micro-X-ray fluorescence, micro-X-ray diffraction, and micro-X-ray absorption near edge structure.
Due to the increasing demand for electromobility, the recovery of technologically relevant elements from spent Li-ion batteries is becoming increasingly important. Pyrometallurgical processing can ...deal with a broad range of input materials. Unfortunately, ignoble elements such as Li and Mn enter the slag. A novel approach to facilitate this processing is the Engineered Artificial Minerals (EnAM) strategy for the recovery of critical elements. The aim of this study is to investigate whether it is possible to stabilize Li in Li-manganates as the first crystallizate. For this purpose, synthetic oxide slags (Li, Mg, Al, Si, Ca, Mn) of varying compositions were made. The constituting compounds were identified using inductively coupled plasma optical emission spectrometry, powder X-ray diffraction, X-ray absorption near-edge structure analysis, and electron probe microanalysis. These results provide an understanding of the solidification process and the behavior of the elements of concern. Lithium-manganate(III) (LiMnO2) crystallized first, next to hausmannite (Mn2+Mn3+2O4) in a matrix consisting of wollastonite (CaSiO3) and larnite (Ca2SiO4). Within the structure of LiMnO2, Li and Mn can replace each other in certain proportions. By adding Al and Mg spinel, solid solutions between Mn2+Mn3+2O4, MnAl2O4, MgAl2O4 and LiMnO2 are expected and described by the stoichiometry formula: (Li(2x),Mg(1x),Mn(2+(1–x)))1+x(Al(2–z),Mn3+(z))2O4.
