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Physical soil organic matter (SOM) fractions provide increased insight into the biogeochemical functioning of soils. Several fractionation methodologies have been developed to separate particulate (POM) from mineral-associated organic matter (MAOM) fractions either by particle size, particle density, or some combination of these two properties. The proliferation of approaches to separation has led to ambiguity regarding what these methodologically defined fractions should be understood to conceptually represent, hindering robust data synthesis analyses and model development. Here we attempt to identify chemical similarities and differences amongst POM and MAOM fractions separated by different physical approaches, with the aim of guiding fractionation choices for future research. We obtained soils from 11 farms across the United States with variable parent materials, textures, and pHs, and fractionated them using 4 methods. We tested two single-step methods: a size fractionation (53 µm cutoff) and a density separation (1.85 g cm−3 cutoff), and two multi-step methods: a combined size and density separation after full dispersion, which isolates a third pool of organic matter associated with coarse, heavy particles (coarse heavy associated organic matter; CHAOM), and a combined method with delayed dispersion to separate the free POM from the occluded POM + CHAOM fraction. We analyzed all fractions for C and N concentrations, their isotopic composition, and for their chemical composition via mid-infrared spectroscopy. We found that MAOM fractions tended to be very homogenous in character regardless of fractionation schemes, while POM varied widely. In particular, to POM isolated by density floatation was distinct in both isotopic and spectroscopic signature compared to POM isolated by size fractionation alone. Indeed, our results indicated that POM isolated by size is a composite fraction of light POM and CHAOM, and does not map well onto a conceptual pool. We found the CHAOM fraction to be more similar to MAOM in terms of chemical and spectroscopic composition, indicating that one-step density separations may be the most effective means of isolating contrasting SOM pools in a time and cost-efficient matter. However, our analysis highlights that POM, CHAOM and MAOM exhibit distinct features, and the three fractions are worth separating via a combined size-density fractionation when possible.

Recently, the influence of Nb addition in the oxide solid solution of Sn and Ti was investigated with regard to the morphological, structural and electrical properties for the production of chemoresistive gas sensors. (Sn,Ti,Nb)xO2-based sensors showed promising features for ethanol monitoring in commercial or industrial settings characterized by frequent variation in relative humidity. Indeed, the three-metal solid solution highlighted a higher response level vs. ethanol than the most widely used SnO2 and a remarkably low effect of relative humidity on the film resistance. Nevertheless, lack of knowledge still persists on the mechanisms of gas reaction occurring at the surface of these nanostructures. In this work, operando Diffuse Reflectance Infrared Fourier Transform spectroscopy was used on SnO2- and on (Sn,Ti,Nb)xO2-based sensors to combine the investigations on the transduction function, i.e., the read-out of the device activity, with the investigations on the receptor function, i.e., compositional characterization of the active sensing element in real time and under operating conditions. The sensors performance was explained by probing the interaction of H2O and ethanol molecules with the material surface sites. This information is fundamental for fine-tuning of material characteristics for any specific gas sensing applications. [ABSTRACT FROM AUTHOR]

Catalysts with no hazardous or toxic components are required for the selective hydrogenation of acetylenic bonds in the synthesis of pharmaceuticals, vitamins, nutraceuticals, and fragrances. The present work demonstrates that a high selectivity to alkene can be reached over a Pd-Fe-O/SiO2 system prepared by the co-impregnation of a silica support with a solution of the metal precursors (NH4)3[Fe(C2O4)3] and [Pd(NH3)4]Cl2 followed by thermal treatment in hydrogen or in air at 400 °C. A DRIFT spectroscopic study of CO adsorption revealed large shifts in the position of the Pdn+-CO bands for this system, indicating the strong effect of Fen+ on the Pd electronic state, resulting in a decreased rate of double C=C bond hydrogenation and an increased selectivity of alkyne hydrogenation to alkene. The prepared catalysts consisted of mono- and bimetallic nanoparticles on an SiO2 carrier and exhibited a selectivity as high as that of the commonly used Lindlar catalyst (which contains such hazardous components as lead and barium), while the activity of the Fe-Pd-O/SiO2 catalyst was an order of magnitude higher. The hydrogenation of a triple bond over the proposed Pd-Fe catalyst opens the way to selective hydrogenation over nontoxic catalysts with a high yield and productivity. Taking into account a simple procedure of catalyst preparation, this direction provides a rationale for the large-scale implementation of these catalysts. [ABSTRACT FROM AUTHOR]

NO2 is one of the main greenhouse gases, which is mainly generated by the combustion of fossil fuels. In addition to its contribution to global warming, this gas is also directly dangerous to humans. The present work reports the structural and gas sensing properties of the CaCu3Ti4O12 compound prepared by the sol-gel technique. Rietveld refinement confirmed the formation of the pseudo-cubic CaCu3Ti4O12 compound, with less than 4 wt% of the secondary phases. The microstructural and elemental composition analysis were carried out using scanning electron microscopy and X-ray energy dispersive spectroscopy, respectively, while the elemental oxidation states of the samples were determined by X-ray photoelectron spectroscopy. The gas sensing response of the samples was performed for different concentrations of NO2, H2, CO, C2H2 and C2H4 at temperatures between 100 and 300 °C. The materials exhibited selectivity for NO2, showing a greater sensor signal at 250 °C, which was correlated with the highest concentration of nitrite and nitrate species on the CCTO surface using DRIFT spectroscopy. [ABSTRACT FROM AUTHOR]

The surface characteristics of the zeolites need to be known for their effective use especially, as ion exchanger, catalyst, and adsorbent. In this study, the morphological, mineralogical and surface properties of zeolites were investigated by some instrumental analyses such as X-ray diffraction pattern (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) methods. FTIR spectra proved the presence of silanol and bridged hydroxyls on the zeolite surface. The pore properties including surface area, pore volume, pore size distribution, and average pore diameter of the zeolites were determined by N2 adsorption at 77 K using the BET t-plot and density functional theory (DFT) methods. The pore size distribution showed that the zeolites include both micro and mesopores. The specific surface area of zeolites with different SiO2/Al2O3 ratios decreased as the Si/Al ratio increased. XRD Method was used to examine the crystal structures of zeolites and SEM was used to examine the particle structures. Surface acidity of heat activated zeolites was determined using two different methods. Information about the total amount of acid sites on the zeolites was provided by the n-Butylamine titration method. and FTIR spectra provided information about surface acidity. [ABSTRACT FROM AUTHOR]

Catalytic conversion of ethanol to 1-butanol was studied over MgO–Al2O3 mixed oxide-based catalysts. Relationships between acid-base and catalytic properties and the effect of active metal on the hydrogen transfer reaction steps were investigated. The acid-base properties were studied by temperature-programmed desorption of CO2 and NH3 and by the FT-IR spectroscopic examination of adsorbed pyridine. Dispersion of the metal promoter (Pd, Pt, Ru, Ni) was determined by CO pulse chemisorption. The ethanol coupling reaction was studied using a flow-through microreactor system, He or H2 carrier gas, WHSV = 1 g E t O H · g c a t. − 1 · h − 1 , at 21 bar, and 200–350 °C. Formation and transformation of surface species under catalytic conditions were studied by DRIFT spectroscopy. The highest butanol selectivity and yield was observed when the MgO–Al2O3 catalyst contained a relatively high amount of strong-base and medium-strong Lewis acid sites. The presence of metal improved the activity both in He and H2; however, the butanol selectivity significantly decreased at temperatures ≥ 300 °C due to acceleration of undesired side reactions. DRIFT spectroscopic results showed that the active metal promoted H-transfer from H2 over the narrow temperature range of 200–250 °C, where the equilibrium allowed significant concentrations of both dehydrogenated and hydrogenated products. [ABSTRACT FROM AUTHOR]

Boron carbide powders were synthesized from elemental powders and studied using X‐ray diffraction (XRD) and UV–visible diffuse reflectance, Raman, and diffuse reflectance IR spectroscopies. Following reaction at 1400°C for 6 h, synthesized powders exhibited possible faulting as suggested by XRD patterns. B3C, B4.3C, and B5C powders contained graphitic carbon whereas the boron carbides with higher B/C ratios contained no residual carbon, suggesting that the carbon rich phase boundary is likely temperature dependent. Analysis by Raman and IR spectroscopy suggested that Raman spectra are influenced by excitation frequency due to resonance. We suggest that measurement of boron carbides with resonant Raman lifts the selection rules to allow measurement of Raman silent modes that are present in the IR spectra. Optical reflectance of the boron carbide powders revealed that the B/C ratio governed the indirect and direct optical band gaps of the faulted powders. B3C and B4.3C powders were light gray in spite of the presence of the carbon, whereas B5C, B6.5C, B10C, and B12C were gray, green, brown, and dark brown, respectively. Increasing carbon content increased the optical indirect band gap from 1.3 eV for B12C to 3.2 eV for B3C, causing the observed color changes. [ABSTRACT FROM AUTHOR]

Recently, the influence of Nb addition in the oxide solid solution of Sn and Ti was investigated with regard to the morphological, structural and electrical properties for the production of chemoresistive gas sensors. (Sn,Ti,Nb)xO2-based sensors showed promising features for ethanol monitoring in commercial or industrial settings characterized by frequent variation in relative humidity. Indeed, the three-metal solid solution highlighted a higher response level vs. ethanol than the most widely used SnO2 and a remarkably low effect of relative humidity on the film resistance. Nevertheless, lack of knowledge still persists on the mechanisms of gas reaction occurring at the surface of these nanostructures. In this work, operando Diffuse Reflectance Infrared Fourier Transform spectroscopy was used on SnO2- and on (Sn,Ti,Nb)xO2-based sensors to combine the investigations on the transduction function, i.e., the read-out of the device activity, with the investigations on the receptor function, i.e., compositional characterization of the active sensing element in real time and under operating conditions. The sensors performance was explained by probing the interaction of H2O and ethanol molecules with the material surface sites. This information is fundamental for fine-tuning of material characteristics for any specific gas sensing applications.

Catalysts with no hazardous or toxic components are required for the selective hydrogenation of acetylenic bonds in the synthesis of pharmaceuticals, vitamins, nutraceuticals, and fragrances. The present work demonstrates that a high selectivity to alkene can be reached over a Pd-Fe-O/SiO2 system prepared by the co-impregnation of a silica support with a solution of the metal precursors (NH4)3[Fe(C2O4)3] and [Pd(NH3)4]Cl2 followed by thermal treatment in hydrogen or in air at 400 °C. A DRIFT spectroscopic study of CO adsorption revealed large shifts in the position of the Pdn+-CO bands for this system, indicating the strong effect of Fen+ on the Pd electronic state, resulting in a decreased rate of double C=C bond hydrogenation and an increased selectivity of alkyne hydrogenation to alkene. The prepared catalysts consisted of mono- and bimetallic nanoparticles on an SiO2 carrier and exhibited a selectivity as high as that of the commonly used Lindlar catalyst (which contains such hazardous components as lead and barium), while the activity of the Fe-Pd-O/SiO2 catalyst was an order of magnitude higher. The hydrogenation of a triple bond over the proposed Pd-Fe catalyst opens the way to selective hydrogenation over nontoxic catalysts with a high yield and productivity. Taking into account a simple procedure of catalyst preparation, this direction provides a rationale for the large-scale implementation of these catalysts.

NO2 is one of the main greenhouse gases, which is mainly generated by the combustion of fossil fuels. In addition to its contribution to global warming, this gas is also directly dangerous to humans. The present work reports the structural and gas sensing properties of the CaCu3Ti4O12 compound prepared by the sol-gel technique. Rietveld refinement confirmed the formation of the pseudo-cubic CaCu3Ti4O12 compound, with less than 4 wt% of the secondary phases. The microstructural and elemental composition analysis were carried out using scanning electron microscopy and X-ray energy dispersive spectroscopy, respectively, while the elemental oxidation states of the samples were determined by X-ray photoelectron spectroscopy. The gas sensing response of the samples was performed for different concentrations of NO2, H2, CO, C2H2 and C2H4 at temperatures between 100 and 300 °C. The materials exhibited selectivity for NO2, showing a greater sensor signal at 250 °C, which was correlated with the highest concentration of nitrite and nitrate species on the CCTO surface using DRIFT spectroscopy.

Catalytic conversion of ethanol to 1-butanol was studied over MgO–Al2O3 mixed oxide-based catalysts. Relationships between acid-base and catalytic properties and the effect of active metal on the hydrogen transfer reaction steps were investigated. The acid-base properties were studied by temperature-programmed desorption of CO2 and NH3 and by the FT-IR spectroscopic examination of adsorbed pyridine. Dispersion of the metal promoter (Pd, Pt, Ru, Ni) was determined by CO pulse chemisorption. The ethanol coupling reaction was studied using a flow-through microreactor system, He or H2 carrier gas, WHSV = 1 gEtOH·gcat.−1·h−1, at 21 bar, and 200–350 °C. Formation and transformation of surface species under catalytic conditions were studied by DRIFT spectroscopy. The highest butanol selectivity and yield was observed when the MgO–Al2O3 catalyst contained a relatively high amount of strong-base and medium-strong Lewis acid sites. The presence of metal improved the activity both in He and H2; however, the butanol selectivity significantly decreased at temperatures ≥ 300 °C due to acceleration of undesired side reactions. DRIFT spectroscopic results showed that the active metal promoted H-transfer from H2 over the narrow temperature range of 200–250 °C, where the equilibrium allowed significant concentrations of both dehydrogenated and hydrogenated products.

Our recent study in this journal highlighted misassignments of surface intermediates of diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements of published Cu/ZnO (CZ) catalyst systems for methanol synthesis. Here we investigate a recent and very active CZ system, in part promoted by oxidative fluorination (i. e. a Cu/ZnO1–x/ZnF2 system), with realistic operando‐DRIFTS measurements of a 3H2/CO2 gas feed (30 bar, 513 K). This DRIFTS setup is linked to an online GC analysis system and the catalytic performance of the Cu/ZnO1–x catalyst showed a similar performance of the catalysis process in the DRIFTS cell as in the catalyst test station. In the DRIFTS measurements, a very broad absorption band with a maximum at about ∼ 1500 cm−1 (=I1500) is evident. This I1500 band is absent in nitrogen; its intensity increases in pure hydrogen and is particularly high during methanol synthesis. I1500 results from photoionization of an electron residing in a mono‐ionized oxygen vacancy VO+ in the ZnO1–x part of the Cu/ZnO1–x catalyst. Consequently, the I1500 band intensity provides information on the extent of the strong metal‐support interaction SMSI. Therefore, measurement of the I1500 band intensity could be a novel and efficient tool to characterize any CZ‐based catalyst systems online. Mechanistically, the maximum VO+ photoionization I1500 band intensity in a 3H2/CO2 gas stream is coupled to the reaction of CO2 giving the CO2−. radical anion intermediate that is rapidly trapped in the VO2+ site formed. This trapped intermediate may react by hydrogen migration to the well‐known surface formate (1603, 1371, and 1314 cm−1). However, the long‐lived formate with this spectroscopic signature is only a spectator. It is also visible by DRIFTS in catalyst samples that in the same setup do not produce methanol (GC). By contrast, the band intensities of the surface species at 1759, 1691, 1457 and 1398 cm−1 are directly connected to methanol production and the applied WHSV. Therefore, only these surface species are relevant for CO2 hydrogenation to methanol at higher pressure and likely represent true reaction adsorbates/intermediates. [ABSTRACT FROM AUTHOR]

[Display omitted] In the course of the treatment of Pd3Ag/α-Al2O3 in 0.5%CO + He at 200 °C, intense transformation of single atom Pd1 surface sites isolated from each other by Ag atoms to multiatomic Pdn (n ≥ 2) ensembles occurs, as revealed by a rapid increase in the intensity of multibonded CO bands in FTIR spectra. The structure of intermetallic Pd3In nanoparticles is significantly more stable, and the formation of new multiatomic adsorption centers was not observed even after extended CO exposures. [ABSTRACT FROM AUTHOR]

Water‐extractable organic matter (WEOM) drives many fundamental functions which determine soil equilibria, acting as a useful probe to highlight the effect of land management on overall C cycling. The ecological importance of WEOM is emphasized in tropical environments characterized by humid climate and short OC turnover. The low OC concentration and the physical–chemical conditions associated to water dissolved compounds determine an analytical issue for the characterization of WEOM. The present experiment aimed to test the diffuse reflectance infrared Fourier transformation (DRIFT) spectroscopy as a rapid tool to evaluate the dynamic of WEOM in tropical soils under different soil organic matter (SOM) managements. The influence of SOM composition on WEOM fraction was evaluated in a laboratory incubation of two tropical soils treated with different organic amendments. The superficial layers of forest and sugarcane Ultisol were incubated for 1 year with 10 mg C g−1 soil of litter from either native tropical forest or sugarcane crop residues. The sugarcane residues promoted a fast increase of dissolved organic carbon (DOC) followed by a subsequent decrease in both soils, whereas the soils amended with forest litter showed DOC dynamics similar to control samples. The DRIFT analysis unveiled changes in the chemical profile of WEOM mainly reflected on the preservation of dissolved hydrophobic compounds. The results indicate the DRIFT technique as an efficient tool to monitor the chemical changes of WEOM f as related to soil use and organic inputs, and to support a comprehensive understanding of the interaction of WEOM in agro‐ecological and environmental processes. [ABSTRACT FROM AUTHOR]

• Density separations isolated a POM fraction distinct from size separations. • Size fractionated POM represented a composite fraction. • Both size- and density-based separations isolated similar MAOM fractions. • Soil properties did not affect fractionation results in a consistent manner. • Fractionations employing a density separation step are recommended for future research. Physical soil organic matter (SOM) fractions provide increased insight into the biogeochemical functioning of soils. Several fractionation methodologies have been developed to separate particulate (POM) from mineral-associated organic matter (MAOM) fractions either by particle size, particle density, or some combination of these two properties. The proliferation of approaches to separation has led to ambiguity regarding what these methodologically defined fractions should be understood to conceptually represent, hindering robust data synthesis analyses and model development. Here we attempt to identify chemical similarities and differences amongst POM and MAOM fractions separated by different physical approaches, with the aim of guiding fractionation choices for future research. We obtained soils from 11 farms across the United States with variable parent materials, textures, and pHs, and fractionated them using 4 methods. We tested two single-step methods: a size fractionation (53 µm cutoff) and a density separation (1.85 g cm−3 cutoff), and two multi-step methods: a combined size and density separation after full dispersion, which isolates a third pool of organic matter associated with coarse, heavy particles (coarse heavy associated organic matter; CHAOM), and a combined method with delayed dispersion to separate the free POM from the occluded POM + CHAOM fraction. We analyzed all fractions for C and N concentrations, their isotopic composition, and for their chemical composition via mid-infrared spectroscopy. We found that MAOM fractions tended to be very homogenous in character regardless of fractionation schemes, while POM varied widely. In particular, to POM isolated by density floatation was distinct in both isotopic and spectroscopic signature compared to POM isolated by size fractionation alone. Indeed, our results indicated that POM isolated by size is a composite fraction of light POM and CHAOM, and does not map well onto a conceptual pool. We found the CHAOM fraction to be more similar to MAOM in terms of chemical and spectroscopic composition, indicating that one-step density separations may be the most effective means of isolating contrasting SOM pools in a time and cost-efficient matter. However, our analysis highlights that POM, CHAOM and MAOM exhibit distinct features, and the three fractions are worth separating via a combined size-density fractionation when possible. [ABSTRACT FROM AUTHOR]

Using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy to study surface species of reaction intermediates on heterogeneous catalysts requires particular precautions, when assigning IR bands to intermediates apparently resulting from the reaction of H2, CO, and CO2. In accordance with earlier work, it is shown that in the investigation of the heterogeneous methanol synthesis, several gas phase bands of CO2 were misassigned in previous studies as adsorbates on the catalyst surface. Thus, several combination bands and overtones of CO2 in the 2200–750 cm−1 range – notably those at 2130, 2112, 2107, 2094, 2077, ∼2056, 1933, ∼1920, ∼1079, ∼1050, ∼973, and ∼948 cm−1 – were already misinterpreted as adsorbates/intermediates. Some of these bands exhibit similar (low) intensities as surface species and are in the range of typical adsorbed CO or methoxy/methanol vibrations. Higher pressures and temperatures, which are necessary to study industrial catalysts by in situ IR spectroscopy, even amplify this effect. In addition, due to a Fermi resonance at a CO2 partial pressure above ∼10 bar, two further bands appear at 1388 and 1285 cm−1. This is also within the range typically associated with surface adsorbates. In order to avoid misassignments of IR bands for in situ or operando DRIFT spectroscopy, those occurring at CO2 pressures up to 30 bar in the widely used Praying MantisTMHigh Temperature Reaction Chamber are presented here and assigned to their origin as combination bands and overtones of gaseous CO2. [ABSTRACT FROM AUTHOR]

Water repellency related to organic matter (OM) of coatings along the earthworm burrows (EB) walls can facilitate preferential flow due to limiting the water exchange with the soil matrix. The objectives of this work were (i) to characterize the hydraulic behavior of EB wall and the surrounding matrix using a miniaturized infiltrometer; (ii) to compare standard infiltration analyses with BEST-W R algorithm; and (iii) to determine the local spatial distribution of water repellency at the EB wall surface in relation to that of the OM composition. Infiltration experiments were carried out on intact sample surfaces, including the EB wall and the surrounding matrix. Soil samples were collected from Bt and C horizons in a characteristic Haplic Luvisol. Hydraulic conductivity (K) at different water pressure heads (h) and water and ethanol sorptivity (Sw and Se, respectively), water repellency index (RI) and water repellency cessation time (WRCT) were determined from infiltration data. The adapted Beerkan Estimation of Soil Transfer parameters (BEST) algorithm for water-repellent soils (BEST-W R) was used for analysing infiltration data. The potential water repellency index (PWRI), relating C-H with C O functional groups in OM, was determined at the same locations using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Lower values of K and Sw in the coatings as compared to the soil matrix were found related to higher PWI values. Water repellency was also reflected in the shape of the cumulative infiltration curves and in the RI-values. The latter were significantly higher for EB as compared to matrix surfaces. The fittings provided by the BEST-W R algorithm characterizing the hydraulic properties of the macropore surfaces were comparable to those obtained with standard method. The tested methods could help to improve the estimation of parameters for macropore-matrix mass exchange in two-domain models. • Mini-infiltration was used for hydraulic characterization of earthworm macropore. • Organic matter (OM) composition was determined with DRIFT spectroscopy. • OM's hydrophobic functional groups reduce hydraulic conductivity and sorptivity. • BEST-W R could be used for macropore-matrix mass exchange parameters estimation. [ABSTRACT FROM AUTHOR]

• Activity, selectivity and H 2 O resistance of Mn–Ce/TiO 2 catalyst was improved by Co. • Operation temperature window of Mn–Ce/TiO 2 catalyst was broadened by Co. • The Co–Mn–Ce/TiO 2 with Co/Ti molar ratio of 0.4 exhibits the best performance. • NH 3 -SCR reaction of the (Co)Mn–Ce/TiO 2 catalysts follows L-H and E-R mechanisms. • Detailed structure-performance relationships of investigated catalysts are obtained. The promotional effect of cobalt (Co) modification on MnCeO x /TiO 2 catalyst for selective catalytic reduction of NO with NH 3 (NH 3 -SCR) was investigated extensively in this study. A series of CoMnCeO x /TiO 2 catalysts with different Co contents were prepared by the facile impregnation method and characterized by XRD, N 2 sorption, XPS, H 2 -TPR, NH 3 /NO-TPD, and in situ DRIFT spectroscopy. The results indicate that the modification of MnCeO x /TiO 2 by Co could significantly improve its low-temperature activity and N 2 selectivity, and broaden operation temperature window (>95% NO conversion at 100–225 °C), and that the optimal mole ratio of Co to Ti in the catalyst is 0.4. Furthermore, the introduction of Co to MnCeO x /TiO 2 could obviously enhance H 2 O resistance. The characterization results reveal that the addition of Co to the MnCeO x /TiO 2 catalyst could enhance the dispersion of MnO x and CeO x , and increase the relative ratio of Mn4+ and Ce3+ on the catalyst surface. In addition, the surface area of MnCeO x /TiO 2 is enlarged evidently after doping of Co. From the results of H 2 -TPR, NH 3 /NO-TPD, and NO oxidation, CoMnCeO x /TiO 2 exhibits stronger reducibility, larger adsorption capacity for NH 3 and NO, and higher NO to NO 2 conversion than MnCeO x /TiO 2 , thus obtaining the higher SCR activity, N 2 selectivity, and H 2 O tolerance. In situ DRIFT spectroscopy tests indicate that the NH 3 -SCR reaction on both MnCeO x /TiO 2 and CoMnCeO x /TiO 2 follow simultaneously the Langmuir-Hinshelwood and Eley-Rideal mechanisms. [ABSTRACT FROM AUTHOR]

Knowledge about the thermal properties of zeolites is extremely important due to their potential application in the chemical industry. In this work, the thermal stability and the dehydration process of zeolite A were investigated by in situ high temperature Fourier transform infrared spectroscopy. The progress of thermal decomposition that zeolite A underwent during the controlled temperature increase in the range of 25–600 °C was determined by the DRIFT spectroscopic method. Infrared spectra are presented and discussed for this compound on the basis of the crystal structure. Based on the courses of the obtained DRIFT spectra, it was found that, during heating, water was gradually removed from the structure of the material, followed by dehydration and formation of hydrogen bonds. It was established that the process of thermal degradation began as early as 550 °C. The analysis of the obtained results of structural tests can be repeated on other materials from the zeolite group and complements the research work on the thermal analysis of these materials.

Carbon fiber reinforced polymer composites are a dynamically developing group of lightweight composites for applications in the automotive, wind energy, aerospace, and sports sectors. Interfacial connection is the weakest place in these materials. In this study, an attempt was made to improve adhesion between carbon fiber and epoxy resin. For this purpose, nanoparticles of graphene oxide were added to a polymer matrix. The results of the three-point bend test showed that the strength of samples with added graphene oxide increased. Improvement of adhesion between components, reduction of the pull-out effect and change in the method of crack propagation were observed. An attempt was made to explain this effect using spectroscopic methods, both IR and Raman. On the basis of the obtained results, chemical bonds between the individual components of the composites were identified.

• GVL hydroconversion proceeds over oxide-supported metal catalysts. • Selectivity is controlled together by acidic and metallic catalytic functions. • Hydroconversion of GVL can be steered to get either 2-MTHF or PA. • 2-MTHF formation proceeds via 2-hydroxy-5-methyl-THF intermediate. • The GVL ring is opened to pentenoic acid over Brønsted acid sites. The hydroconversion mechanism of γ-valerolactone (GVL) was studied over a Co/SiO 2 and a Pt/aluminosilicate catalyst. The reaction was carried out at 250 °C, 30 bar, and WHSV = 1 g GVL ·g cat. -1 h-1. The Co/SiO 2 catalyst had moderate hydrogenation activity and Lewis acidity, whereas the Pt/aluminosilicate catalyst had high hydrogenation activity and Brønsted acidity. Diffuse Reflectance Fourier Transform Spectroscopic (DRIFTS) results suggested that the GVL ring was bounded more strongly to the stronger acid Pt/aluminosilicate than to the weaker acid Co/silica catalyst. The Pt/aluminosilicate catalyst was substantiated to open the GVL ring in a protonation/deprotonation process giving pentenoic acid (PE) intermediate and pentanoic acid (PA) as main final product. Over Co/SiO 2 catalyst 2-methyl-tetrahydrofuran (2-MTHF) and pentanol were the major products of GVL conversion. It was substantiated that latter transformation proceeded in consecutive hydrogenation and dehydration steps via 2-hydroxy-5-methyl-tetrahydrofuran and 1,4-pentanediol (1,4-PD) intermediates. The oxygen atoms of GVL were shown to establish H-bonds with the silanol groups of the Co/SiO 2 catalyst. The ν CO frequency of the adsorbed GVL depends on the adsorption interaction of the GVL and the silica surface. Three distinct ν CO bands were distinguished by DRIFTS. Quantum chemical calculations gave the structures of the three adsorbed GVL species. Operando DRIFTS examination of the catalytic reaction suggested that in the structure that was activated for hydrogenation/hydrogenolysis both the ring and the carbonyl oxygen were bound to silanol groups. [ABSTRACT FROM AUTHOR]

Colluvisols form a significant part of the erosion–deposition soil catena mainly in undulating, agriculturally managed landscapes. Due to their sedimentary origin, they are soils with highly variable properties. For such diverse and often extremely deep soils, it is essential to capture the vertical distribution of properties in as much detail as possible. This study demonstrates the potential of the diffuse reflectance infrared spectroscopy (DRIFT) to derive accurate information on the stratigraphy and selected soil properties (soil organic carbon and calcium carbonate contents and aluminium and iron concentrations) of deep colluvial profiles in three regions in the Czech Republic with different dominant soil types (Chernozem, Luvisol, and Cambisol). The normalization of the spectrum using the quartz spectral band was found to be suitable for assessing the carbonate content in Chernozems and Luvisols (coefficients of determination (R2) were 0.89 and 0.88, respectively). The amount of organic carbon can be predicted from such normalized spectra with less confidence (R2 = 0.64). Organic matter quality as an indicator of their stability and maturity was computed from aliphatic compounds spectral bands (2930 cm–1) and aromatics and C O groups band around 1640 cm–1. The highest values of this indicator were found in Colluvisols in the Chernozem region (> 6, while, e.g., in the Cambisol region it is < 1), especially in the layers corresponding to the oldest sediments or buried in-situ horizons. In the Cambisol region, the buried B horizon was identified based on normalized (i) clays and Fe oxides bands and (ii) wider band of OH groups, which in this case is related to the content of iron oxyhydroxides. The study proved that the applied set of spectral parameters is an effective tool for the description of diverse soil parameters and for identification of the boundaries of individual soil layers. It is equally suitable for carbonate-free soils as well as for soils with higher carbonate contents, which usually cause difficulties in the interpretation of soil organic matter spectral parameters. It provides a comprehensive view of the soil and its mineral and organic components and can provide information that is difficult to measure by other methods. • Spectral parameters set usable for describing soil properties was proposed. • Proposed spectral parameters are suitable for both carbonate and non-carbonate soils. • Content of carbonates and organic matter can be deduced from adjusted soil spectra. • Spectra provides information about soil organic matter quality (composition). • Soil spectral parameters identify layers of Colluvisols and describe their properties. [ABSTRACT FROM AUTHOR]

The organo-mineral coatings of soil aggregates, cracks, and biopores control sorption and macropore-matrix exchange during preferential flow, in particular in the clay-illuvial Bt-horizon of Luvisols. The soil organic matter (SOM) composition has been hypothesized to explain temporal changes in the hydraulic properties of aggregate surfaces. The objective of this research was to find relations between the temporal change in wettability, in terms of droplet infiltration dynamics, and the SOM composition of coated and uncoated aggregate surfaces. We used 20 to 40 mm sized soil aggregates from the Bt2 horizon of a Haplic Luvisol from loess that were (i) coated, (ii) not coated (both intact), and (iii) aggregates from which coatings were removed (cut). The SOM composition of the aggregate surfaces was characterized by infrared spectroscopy in the diffuse reflection mode (DRIFT). A potential wettability index (PWI) was calculated from the ratio of hydrophobic and hydrophilic functional groups in SOM. The water drop penetration times (WDPT) and contact angles (CA) during droplet infiltration experiments were determined on dry and moist aggregate samples of the three types. The decrease in the CA with time was described using the power function (CA(t) = at−b). For dry aggregates, the WDPT values were larger for coated as compared to uncoated regions on the aggregate surfaces, and increased with increasing PWI value (R2 = 0.75). The a parameter was significantly related to the WDPT (R2 = 0.84) and to the PWI (R2 = 0.64). The relations between the b parameter and the WDPT (R2 = 0.61) and the PWI (R2 = 0.53) were also significant. The WDPT values of wet soil aggregates were higher than those of dry aggregates due to high water contents, which limited the droplet infiltration potential. At the wet aggregate surfaces, the WDPT values increased with the PWI of the SOM (R2 = 0.64). In contrast to dry samples, no significant relationships were found between parameters a or b of CA(t) and WDPT or PWI for wet aggregate surfaces. The results suggest that the effect of the SOM composition of coatings on surface wettability decreases with increasing soil moisture. In addition to the dominant impact of SOM, the wettability of aggregate surfaces could be affected by different mineralogical compositions of clay in coatings and interiors of aggregates. Particularly, wettability of coatings could be decreased by illite which was the dominant clay type in coatings. However, the influence of different clay mineral fractions on surface wettability was not due to small number of measurements (2 and 1 samples from coatings and interiors, respectively) quantified.

Diffuse reflection infrared Fourier transform (DRIFT) spectra have been quantitatively evaluated to determine unknown extinction coefficients as well as the number of active surface centers and the amount of adsorbed species. Sulfated zirconia with n-butane as probe gas was used as model system. For quantitative evaluation of n-butane adsorption at 323 K, the sulfate band S=O at 1400 cm−1 was chosen. During adsorption, this band is red-shifted to lower wavenumbers accompanied by a structural change of the band indicating isomerization reaction. By analyzing difference spectra and determining the areas of the selected band, the extinction coefficients as well as the number of active centers and the amount of chemisorbed n-butane were calculated. The quantitative evaluation results in a mean internal decadic extinction coefficient of 60 cm−1 µmol−1, an average amount of n-butane adsorbed to the sulfated zirconia of about 4 μmol, and a number of active centers of around 21 μmol/g. These results correspond very well with values from the literature obtained by microcalorimetry. Thus, this method is suggested to be transferred also to unknown systems of interest.

Mucilage is receiving increasing attention because of its putative effects on plant growth, but so far no method is available to measure its spatial distribution in the rhizosphere. We tested whether the C-H signal related to mucilage fatty acids is detectable by infrared spectroscopy and if this method can be used to determine the spatial distribution of mucilage in the rhizosphere. Maize plants were grown in rhizoboxes filled with soil free of organic matter. Infrared measurements were carried out along transects perpendicular as well as axially to the root channels. The perpendicular gradients of the C-H proportions showed a decrease of C-H with increasing distance: 0.8 mm apart from the root center the C-H signals achieved a level near zero. The measured concentrations of mucilage were comparable with results obtained in previous studies, which encourages the use of infrared spectroscopy to quantitatively image mucilage in the rhizosphere.

This work aims at obtaining comprehensive information on the corrosion behaviour of AA2024-T3 in oxalic acid solutions under different concentrations (0.007-0.2 M) and pH (2-6). Various tests to characterise the corrosion behaviour are performed, including weight loss and electrochemical tests. Coupon surfaces are examined using infinite-focus microscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, Raman spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy. Corrosion rates, anodic and cathodic reaction kinetics are detailed to provide a fundamental understanding of the electrochemical behaviour of AA2024-T3 as a function of pH and oxalate concentration. The synergistic effect of pH and oxalate concentration on corrosion of AA2024-T3 is evaluated for both AA2024-T3 matrix and main intermetallics (i.e. Al-Cu-Mg and Al-Cu-Fe-Mn) and the electrochemical behaviour of each constituent element in AA2024-T3 is systematically studied. [ABSTRACT FROM AUTHOR]

Abstract: By applying the newly developed flow cell (FC) concept, this study investigated the impact of small‐scale spatial variations (millimetre to centimetre) in organic matter (OM) composition (diffusive reflectance infrared Fourier transform spectroscopy), biological activity (zymography), and wettability (contact angle [CA]) on transport processes (tracer experiments, radiography). Experiments were conducted in five undisturbed soil slices (millimetre apart), consisting of a sandy matrix with an embedded loamy band. In the loamy band increased enzyme activities and OM (10 mm apart) were found compared with the sand matrix, with no interrelations although spatial autocorrelation ranges were up to 7 cm. CAs were increased (0–110°) above the loamy band and were negatively correlated with acid phosphatase. Missing correlations were probably attributed to texture variations between soil slices. A general correlation between CA and C content (bulk) were confirmed. Variability in texture and hydraulic properties led to the formation of heterogeneous flow patterns and probably to heterogeneously distributed interfacial properties. The new FC concept allows process evaluation on the millimetre scale to analyse spatial relations, that is, between small‐scale textural changes on transport processes and biological responses. The concept has been proved as a versatile tool to analyse spatial distribution of biological and interfacial soil properties in conjunction with the analysis of complex micro‐hydraulic processes for undisturbed soil samples. The concept may be improved by additional nondestructive imaging methods, which is especially challenging for the detection of small‐scale textural changes. [ABSTRACT FROM AUTHOR]

Abstract: The deposition of organic matter (OM), which is known for its high potential water repellency, on biopore walls can enhance preferential flow through these pores. In this study, OM composition determined with diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was related to soil water repellency (SWR) determined with sessile drop method, Wilhelmy plate method, and sorptivity tests. We hypothesized that the chemical composition (in terms of potential wettability index; a) is related to the physical properties (i.e., contact angle) of biopore walls, (b) depends on the history of the biopore, and (c) differs from the bulk soil matrix. Thus, the main objective was to identify the relation between OM composition determined with DRIFT spectroscopy and SWR in structured soils. The experiments were carried out on biopores and their surrounding soil matrices, excavated from 2 depths of a haplic Luvisol, with 3 different biopore histories (i.e., root channels, earthworm burrows, and root channels that were short‐term colonized by an earthworm). All measurements at intact biopore surfaces indicated a larger SWR at the surface of biopore walls as compared with the surrounding matrices and showed a higher proportion of hydrophobic functional groups. The OM composition determined with DRIFT spectroscopy correlated (R2 > .7) with contact angles (sessile drop method) that is in line with results of both water sorptivity and Wilhelmy plate method for soils with reduced wettability. The surfaces of short‐term colonized earthworm burrows had the most varying hydrophobic to hydrophilic components (A/B)‐ratio of all investigated biopore surfaces depending on soil depth. For biopore surfaces at this depth, contact angles >90° were frequently observed. The results also indicate that earthworms can lower SWR by aggregate disruption. [ABSTRACT FROM AUTHOR]

A non-invasive method has been carried out to show the capabilities and limitations of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for identifying of colourants and binders in modern reverse glass paintings. For this purpose, the reverse glass paintings “Zwei Frauen am Tisch” (1920–22), “Bäume” (1946) (both by Heinrich Campendonk), “Lofoten” (1933) (Edith Campendonk-van Leckwyck) and “Ohne Titel” (1954) (Marianne Uhlenhuth), were measured. In contrast to other techniques (e.g. panel and mural painting), the paint layers are applied in reverse succession. In multi-layered paint systems, the front paint layer may no longer be accessible. The work points out the different spectral appearance of a given substance (gypsum, basic lead white) in reverse glass paintings. However, inverted bands, band overlapping and derivative-shaped spectral features can be interpreted by comparing the spectra from the paintings with spectra from pure powders and pigment/linseed oil mock-ups. Moreover, the work focuses on this method's capabilities in identifying synthetic organic pigments (SOP). Reference spectra of three common SOP (PG7, PY1, PR83) were obtained from powders and historical colour charts. We identified PR83 and PY1 in two reverse glass paintings, using the measured reference spectra. The recorded DRIFTS spectra of pure linseed oil, gum Arabic, mastic, polyvinyl acetate resin and bees wax can be used to classify the binding media of the measured paintings. [ABSTRACT FROM AUTHOR]

This article analyses the role of gold nanoparticles supported on TiO 2 for the gas-phase ethanol condensation. Previously, the original P25 surface was modified for increasing the Au-Ti interaction, in order to minimize the thermal deactivation. Catalysts were tested both in absence and presence of hydrogen (523–673 K, WHSV = 7.9 h −1 ; y EtOH = 0.32; y H2 = 0-0.1; 0.1 MPa). Parent TiO 2 is mainly selective for dehydration reactions yielding diethyl ether (favoured at low temperatures) and ethylene (favoured at higher temperatures). The presence of Au in the catalyst promotes dehydrogenation pathways, yielding acetaldehyde, as well as condensation products (mainly butanol, with selectivities close to 10%). According to DRIFT spectroscopy results, the strong ethanol adsorption on the TiO 2 surface justifies the low yields and the high relevance of side-reactions produced by inter- or intra- molecular dehydration routes (diethyl ether, and ethylene formation). The gold addition minimizes this adsorption and enhances the main route by a double role: an improvement in the dehydrogenation rate (yielding more acetaldehyde) and an enhancement in the hydrogenation steps. [ABSTRACT FROM AUTHOR]

Soils on riverine floodplains in Central Europe are commonly enriched in soil organic matter (SOM). We analyzed the quantity and qualitative aspects of SOM in three soil profiles with mollic horizons along the Elbe River (Germany) after physical fractionation by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy to gain deeper insights into the composition of SOM and the formation of these soils. In all horizons, the majority of SOM was recovered in the fraction of particulate OM and in that of sand and aggregates, while SOM in the silt and clay fraction always made up < 20% of soil organic carbon. The C:N ratios of most fractions did not decrease with depth, indicating less decomposed or pyrogenic OM or both. The presence of pyrogenic OM, as a characteristic feature of floodplain soils, was indicated in almost all physical fractions. As derived from DRIFT spectroscopy, SOM was less qualitatively differentiated among the fractions in the soil with the longest duration of flooding, while qualitative differences of SOM were more pronounced in the more aerated ones. The soils have developed from stratified fluviatile sediments and fulfil the criteria of a mollic horizon, irrespective of differences in the composition of SOM. From a soil-genetic point of view, we strongly suggest to classify these soils as Mollic Fluvisols instead of Fluvic Phaeozems, which would accord to the latest WRB classification. [ABSTRACT FROM AUTHOR]

Tungsten oxide is a renowned material for resistive type gas sensors with high sensitivity to nitrogen oxides. Most studies have been focused on sensing applications of WO3 for the detection of NO2 and a sensing mechanism has been established. However, less is known about NO sensing routes. There is disagreement on whether NO is detected as an oxidizing or reducing gas, due to the ambivalent redox behavior of nitric oxide. In this work, nanocrystalline WO3 with different particle size was synthesized by aqueous deposition of tungstic acid and heat treatment. A high sensitivity to NO2 and NO and low cross-sensitivities to interfering gases were established by DC-resistance measurements of WO3 sensors. Both nitrogen oxides were detected as the oxidizing gases. Sensor signals increased with the decrease of WO3 particle size and had similar dependence on temperature and humidity. By means of in situ infrared (DRIFT) spectroscopy similar interaction routes of NO2 and NO with the surface of tungsten oxide were unveiled. Analysis of the effect of reaction conditions on sensor signals and infrared spectra led to the conclusion that the interaction of WO3 surface with NO was independent of gas-phase oxidation to NO2.

In this study, we demonstrate the preparation and characterization of small palladium nanoparticles (Pd NPs) on modified ceria support (Pd/CeO2) using wet impregnation and further reduction in an H2/Ar flow. The obtained particles had a good dispersion, but their small size made it difficult to analyze them by conventional techniques such as transmission electron microscopy (TEM) and X-ray powder diffraction (XRPD). The material demonstrated a high catalytic activity in the CO oxidation reaction: the 100% of CO conversion was achieved at ~50 °C, whereas for most of the cited literature, such a high conversion usually was observed near 100 °C or higher for Pd NPs. Diffuse reflectance infrared Fourier-transform (DRIFT) spectroscopy in combination with CO probe molecules was used to investigate the size and morphology of NPs and the ceria support. On the basis of the area ratio under the peaks attributed to bridged (B) and linear (L) carbonyls, high-dispersion Pd NPs was corroborated. Obtained results were in good agreement with data of X-ray absorption near edge structure analysis (XANES) and CO chemisorption measurements.

The ethanol condensation catalyzed by mixed oxides is studied in this work, considering not only the activity but also the stability of these materials. Concerning to the activity, different weight hourly space velocities (WHSV) were tested, obtaining the highest conversion and 1-butanol selectivity with Mg-Al, mainly at 673 K and a WSHV of 7.9 h −1 . On the other hand, dehydration products, observed with Mg-Zr in relevant amounts, limit the results obtained with this material. Deactivation studies were carried out by combining the measurement of reactant and products in the gas phase and in the catalytic surface using spectroscopic techniques (DRIFT). Good stability was observed with both materials at low temperatures (lower than 673 K), whereas at the highest one, Mg-Zr suffers relevant deactivation justified by the permanent adsorption of aldehydes and oxygenated oligomers on the active sites. It has been demonstrated that Mg-Al mixed oxides are promising catalyst for 1-butanol production from ethanol not only in terms of activity, but also in terms of catalyst stability. [ABSTRACT FROM AUTHOR]

During the last years the need for non-invasive and non-destructive analytical methods brought to the development and application of new instrumentation and analytical methods for the in-situ analysis of cultural heritage objects. In this work we present the application of a portable diffuse reflectance infrared Fourier transform (DRIFT) method for the non-invasive characterization of colorants prepared according to ancient recipes and using egg white and Gum Arabic as binders. Approximately 50 colorants were analyzed with the DRIFT spectroscopy: we were able to identify and discriminate the most used yellow (i.e. yellow ochres, Lead-tin Yellow, Orpiment, etc.), red (i.e. red ochres, Hematite) and blue (i.e. Lapis Lazuli, Azurite, indigo) colorants, creating a complete DRIFT spectral library. The Principal Component Analysis–Discriminant Analysis (PCA–DA) was then employed for the colorants classification according to the chemical/mineralogical composition. The DRIFT analysis was also performed on a gouache painting of the artist Sutherland” and the colorants used by the painter were identified directly in-situ and in a non-invasive manner. [ABSTRACT FROM AUTHOR]

This article describes an in-progress research project that looks to investigate the use of supercritical carbon dioxide (scCO) for the addition of water to historic and modern, softwood and hardwood samples. The experiments were carried out at 20 MPa and 50 °C, the effects of co-solvent addition, methanol (MeOH), were examined. A three point bend test provided mechanical data for the wood samples treated with both pure and modified scCO. All the wood samples, with only one exception, saw an increase in Modulus of Rupture (MOR) after being treated with scCO. Thereby indicating an increased resistance to force in the treated samples. Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy was performed to help deduce if any trends in the OH/CH and OH/Cellulose peak area ratios could be established with the nature of the treatment and the type of wood used. The development of this technique seeks to be relevant and safe for applications within modern conservation practices, where dry and fragile materials are prevalent. [ABSTRACT FROM AUTHOR]

Operando DRIFT analysis of the surface species observed on Fischer Tropsch catalysts at work has been performed under H 2 /CO syngas at 503 K. Decomposition of the evolution in the IR operando spectra has been done by chemometric analysis in order to depict the modifications occurring on the surface of the nanoparticles as a function of time on stream. Results obtained on three catalysts with different reducibility determined from temperature programmed reduction experiments are confronted in order to correlate the spectral observations to the cobalt surface atoms speciation. Attribution of the IR components in the 2100–1750 cm −1 range is confirmed on the basis of the chemometric decomposition. The component falling in the 2068–2064 cm −1 range is assigned to CO sorbed onto Co° surface atoms of partially H 2 -reduced nanoparticles. This component is found to progressively decrease as a function of catalyst time on stream which indicates a progressive reduction of the nanoparticles under syngas at 503 K. [ABSTRACT FROM AUTHOR]

Riverine floodplain soils contain large stocks of soil organic matter (SOM) also in larger depth. Qualitative characterization of SOM, especially in the subsoil horizons of floodplain soils, is scarce. To gain deeper insights into the composition of SOM and the driving parameters of SOM processing, we studied 121 horizons of 18 soil profiles along the Central Elbe River (Germany) by determining permanganate-oxidizable carbon (POXC) and a stability parameter derived from diffuse reflectance infrared (DRIFT) spectroscopy. The absolute and relative amounts of POXC varied between the horizons. While the topsoil horizons contained the largest total contents of POXC (average 923 mg kg − 1 soil), the largest relative proportions were detected in subsoil horizons characterized by reducing conditions and water saturation (up to 19% of total organic C), which exceeded those reported for terrestrial soils. The absolute contents of POXC were positively and partially highly significantly correlated with those of total organic, hot-water extractable and microbial-biomass C, confirming its nature as slightly processed and relatively labile fraction of SOM. The correlations were distinctly weaker for the reduced horizons, indicating hampered decomposition. The contents of POXC were also positively correlated with the DRIFT stability parameter, expressing the ratio of aliphatic to aromatic C. Our results suggest the presence of a large fraction of less processed SOM in the subsoils of floodplain soils, originating from inputs of particulate organic matter that was buried and weakly decomposed at water saturation, and partially from charcoal particles, also transported by the river water. The results point to a possible limitation of POXC as an indicator of decomposition to soils lacking an aquic moisture regime. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dry grinding and aging of arsenides produced thin heterogeneous oxide and hydroxide layers. • Arsenides conditioning under alkaline conditions enhanced the oxidation effect on surfaces. • CuSO 4 activation improves the adsorption of xanthate on the arsenide surfaces, mainly under alkaline conditions. • PAX adsorption effectiveness depends on arsenides surface physico-chemistry. Skutterudite ((Co,Ni,Fe)As 3), gersdorffite (NiAsS), and nickeline (NiAs) are some common arsenic- and nickel-bearing minerals often encountered worldwide in mine ores and mine wastes. These arsenides can be the source of arsenic- and nickel-contaminated neutral drainage (CND) when subjected to atmospheric conditions. Environmental desulphurization by froth flotation is a promising technique used to prevent this contamination. This study fills a knowledge gap in the evolution of the surface physicochemistry of these arsenides under different conditions, in order to determine the best conditions for flotation and successful environmental desulfurization. This work evaluates the impact of grinding, air-oxidation (aging), and conditioning on the mineral surfaces, as well as their interaction with potassium amyl xanthate (PAX) as a flotation collector. The effect of activation by copper sulphate (CuSO 4) was also examined. The adsorption of PAX was analyzed by ultraviolet–visible (UV–Vis) spectrophotometry and zeta potential measurements, and the surface was characterized using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) allowing the speciation of the oxidation layer across the different mineral surfaces. Dry grinding and aging of the minerals produces thin heterogenous oxide and hydroxide layers that are mainly enriched in arsenic oxides, especially in the form of arsenate (as an oxidation product of arsenite), and arsenic, cobalt, and nickel sulphates and hydroxides. Arsenides conditioning under alkaline conditions enhances the oxidation effect on the mineral surfaces compared to natural conditions. Copper sulfate activation was found to be effective on the arsenides and improves the adsorption of xanthate on the oxidized arsenide surfaces, especially under alkaline conditions. The results of this study provide a better understanding of the surface chemistry of these minerals before and after collector adsorption, which should impact their flotation behavior. [ABSTRACT FROM AUTHOR]

In order to increase their stability and tune-sensing characteristics, metal oxides are often surface-loaded with noble metals. Although a great deal of empirical work shows that surface-loading with noble metals drastically changes sensing characteristics, little information exists on the mechanism. Here, a systematic study of sensors based on rhodium-loaded WO3, SnO2, and In2O3—examined using X-ray diffraction, high-resolution scanning transmission electron microscopy, direct current (DC) resistance measurements, operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, and operando X-ray absorption spectroscopy—is presented. Under normal sensing conditions, the rhodium clusters were oxidized. Significant evidence is provided that, in this case, the sensing is dominated by a Fermi-level pinning mechanism, i.e., the reaction with the target gas takes place on the noble-metal cluster, changing its oxidation state. As a result, the heterojunction between the oxidized rhodium clusters and the base metal oxide was altered and a change in the resistance was detected. Through measurements done in low-oxygen background, it was possible to induce a mechanism switch by reducing the clusters to their metallic state. At this point, there was a significant drop in the overall resistance, and the reaction between the target gas and the base material was again visible. For decades, noble metal loading was used to change the characteristics of metal-oxide-based sensors. The study presented here is an attempt to clarify the mechanism responsible for the change. Generalities are shown between the sensing mechanisms of different supporting materials loaded with rhodium, and sample-specific aspects that must be considered are identified.

We investigate the relationship between the H $$_2$$ :NO ratio and NH $$_3$$ formation over alumina supported Pt and Pd catalysts. By kinetic studies and in situ infrared spectroscopy, we report that NH $$_3$$ formation is not only sensitive to the catalyst formulation but equally dependent on the feed gas composition and temperature. Specifically, we identify that hydrogen plays an important role in the dissociation of NO at low temperature. We also show that the support material itself plays a vital role in the ammonia formation mechanism due to the redox behaviour of NO adsorption at low temperature. This was unexpected as the noble metal is generally considered to be the active phase for the reaction of NO and H $$_2$$ . [ABSTRACT FROM AUTHOR]

In order to meet the legislative emission requirements for NO x -containing exhaust gases, SCR catalysts, in particular zeolites, are used. To improve catalysts and the catalytic processes, an in-depth understanding of the reaction mechanisms is required as well as an analysis of the physicochemical properties of the SCR catalysts, preferably in real-time. Here, we introduce a setup combining impedance spectroscopy and infrared spectroscopy in diffuse reflection mode for in situ measurements on zeolites under SCR-related conditions. This setup allows for the first time to simultaneously monitor both, the proton conductivity of zeolites and the vibration modes of the molecules involved in the catalytic conversion of NO by NH 3 . We studied both, pure and Fe-promoted H-form zeolites, as sensors and model catalysts at the same time, and found out that weakly bound NH 3 is dominating the proton conductivity of both zeolites in a temperature range below the desorption temperature of NH 3 . When a part of the weakly bound NH 3 is consumed by the SCR reaction, proton conductivity and thus the sensing effect gets dominated by strongly bound NH 3 . This allows applying impedance spectroscopy to assess the degree of NH 3 loading and the state of the SCR conversion process in zeolite catalyst. [ABSTRACT FROM AUTHOR]

This paper is focused on soil organic matter quality assessment in acid forest soils. Soil samples were collected in the Jizera Mountains region. Vegetation cover of sampling sites was formed by spruce or beech monocultures. Humus quality was assessed by the ratio of absorbances of pyrophosphate soil extract at the wavelengths of 400 and 600 nm (A400/A600). Humus fractionation was performed on selected soil samples. DRIFT spectra of individual fractions were measured. Higher pH and lower C and N contents were found in beech forest than in spruce forest. A400/A600 well correlates with C and N contents (r = 0.510*** and 0.615***, respectively). C and N content increases as to humus quality decreases. DRIFT spectra of fulvic acids turned out to be unsuitable for describing differences in humus quality. DRIFT spectra of humic acids and humin were hence more suitable. The difference between spruce and beech forest was found in 1514.cm-1 (C=C bounds of benzene rings) and 1550 cm-1 (N-H bounds in monosubstituted amides) bands intensities. Humic acids and humin coming from the O horizons of beech forest are relatively enriched by nitrogen functional groups. Values of humic acids aromaticity index did not differ between beech and spruce forests. DRIFT spectroscopy was shown as a possible method for detailed humus quality studying.

The polymeric nanoparticles are prepared from biocompatible polymers in size between 10-1000 nm. Chitosan is a biocompatible polymer that - can be utilized as drug delivery systems. In this study, chitosan nanoparticles were synthesized using an optimized spontaneous emulsification method. Determining particle size and morphology are two critical parameters in nanotechnology. The aim of this study is to introduce methodology based on relation between particle size and diffuse reflectance infrared fourier transform (DRIFT) spectroscopy technique. Partial least squares (PLS) technique was used to estimate the average particle size based on DRIFT spectra. Forty two different chitosan nanoparticle samples with different particle sizes were analyzed using DRIFT spectrometry and the obtained data were processed by PLS. Results obtained from the real samples were compared to those obtained using field emission scanning electron microscope(FE-SEM) as a reference method. It was observed that PLS could correctly predict the average particle size of synthesized sample. Nanoparticles and their morphological state were determined by FE-SEM. Based on morphological characteristics analyzing with proposed method the samples were separated into two groups of «appropriate» and «inappropriate». Chemometrics methods such as principal component analysis, cluster analysis (CA) and linear discriminate analysis (LDA) were used to classify chitosan nanoparticles in terms of morphology. The percent of correctly classified samples using LDA were 100%and 90% for training and test sets, respectively. [ABSTRACT FROM AUTHOR]

We present 77 K isotherms of krypton adsorption on bundles of closed highly-pure HiPco single-walled carbon nanotubes (SWCNTs). Two volumetric adsorption protocols were used, one with an increasing Kr dose per injection (IAD), one with a constant dose (CAD). Detailed microstructural examination showed that the SWCNTs combine into small bundles (of 25-30 SWCNTs) which are heterogeneous in diameter with a consequential range of interstitial channel (IC) shapes and sizes. The IC-sites are the subnanoscaled pores with alternating enlargements and constrictions along the tube axes. This results in adsorption dosing (AD) dependent characteristics of the low-pressure region of the isotherm. In the IAD protocol the switch-back behavior of the isotherm stemmed from metastable adsorption. Using the CAD protocol, different branches are observed. Well-pronounced substeps were established which we interpret as corresponding to the formation of various phases of confined Kr with different atoms arrangement. The height of a given substep obtained in different measurements depends on the AD value which can strongly influence the population of the site. Some substeps existing only for certain values of AD suggests the existence of a certain selectivity or of a preferential phase formation according to this value. [ABSTRACT FROM AUTHOR]

Results from lab scale flotation show that when process water was re-used copper and cobalt recovery from an oxidized ore decreased respectively with 25% and 30% at the rougher stage bringing lower grade concentrate as well. The presence of thiosulphate ions contributed to slow down of NaHS consumption during sulphidisation of pure malachite and hindered collector adsorption. Elevated concentration of thiosulphate ions affected malachite surface properties and induced dissolution effects. DRIFT spectroscopy on activated malachite enabled to reveal the effects of thiosulphate ions presence with hydrophilic species being identified. [ABSTRACT FROM AUTHOR]

Abstract: Spectral variable selection is an important step in spectroscopic data analysis, as it tends to parsimonious data representation and can result in multivariate models with greater predictive ability. In this study, we used VIS-NIR (visible to near-infrared) diffuse reflectance and DRIFT (diffuse reflectance infrared Fourier transform in the mid-infrared range, MIR) spectroscopy to determine a series of chemical and biological soil properties. Multivariate calibrations were performed with partial least squares regression (PLSR) using the full absorbance spectra (VIS-NIR: 400–2500nm with 5-nm intervals; MIR: 4000–800cm−1 with 4-cm−1 intervals) and with a combination of PLSR and CARS (competitive adaptive reweighted sampling) to integrate only the most informative key variables. The CARS procedure has as yet not been applied in the field of soil spectroscopy. As set heterogeneity is crucial for an optimal calibration, we tested these approaches to a sample set of 60 agricultural samples covering a broad range of different parent materials, soil textures, organic matter contents and soil pH values. Soil samples were taken from the Ap horizon (0–10cm depth), air-dried and pulverised before the lab spectroscopic measurements were performed. In a cross-validation approach, the CARS–PLSR method was markedly more accurate than full spectrum-PLSR for all investigated soil variables and both spectral regions. With MIR data and CARS–PLSR, excellent results (indicated by a residual prediction deviation (RPD) greater than 3.0) were obtained for organic carbon (OC), nitrogen (N), microbial biomass-C (Cmic) and pH values; for hot water extractable C (Chwe), RPD was 2.60. The accuracies obtained with VIS-NIR data were considerably lower than those with the MIR spectra; best results were retrieved for pH and Cmic (approximately quantitative as indicated by RPD values between 2.0 and 2.5). The information content of the MIR data was substantially different from the VIS-NIR information, as indicated by 2D correlation analysis. We found an overall blurred 2D correlation pattern between both spectral regions with moderate to low correlation coefficients, which suggested that the heterogeneity of the studied soil sample population had led to a very complex blurring of overtones and combination bands in the NIR region. Statistical CARS selections were physically reasonable. MIR key wavenumbers for the studied C fractions were inter alia identified at the bands at 2920cm−1 and 2850cm−1 (both aliphatic CH-groups) and the region between 1740 and 1600cm−1 (CO-groups) and represent hydrophobic and hydrophilic compounds of soil organic matter. Important VIS-NIR wavelengths for assessing C fractions and N were located nearby the prominent water absorption band at 1915nm and the hydroxyl band at 2200nm. The simplicity of the approach, parsimony of the multivariate models, accuracy levels in the cross-validation and physically reasonable selections indicated a successful operation of the CARS procedure. It should be further examined with a larger number of samples using separate calibration and validation sets. [Copyright &y& Elsevier]

Tri‐salts added: Pt on alumina catalysts can be used for converting methanol and water into hydrogen and carbon dioxide (see picture), for applications such as hydrogen storage. Both the activity and selectivity could be enhanced by coating these materials with a thin layer of a molten salt mixture of Li/K/Cs acetate. Potassium doping was identified by DRIFTS measurements to be an important factor for the boost in catalyst performance. [ABSTRACT FROM AUTHOR]

Abstract: There is a limited knowledge on the role of soil texture and clay mineralogy in governing the content and composition of organic matter (OM) associated with physically-separated fractions in major Thai soils. To extend the understanding in this context, we sampled a range of Thai soils representing four major mineralogy groups, i.e. siliceous, mixed mineralogy, kaolinitc, and smectitic soils. The clay fraction and four density fractions [two particulate OM, free-light (fPOM) and occluded (oPOM), <1.85gcm−3; and two heavy fractions, 1.85–2.60gcm−3 (HFOM1.85–2.60) and >2.60gcm−3 (HFOM>2.60)] of soils from the top- and sub-soil horizons with varying clay content (58–967gkg−1) and mineralogy were analyzed for organic carbon (OC) and total nitrogen (N) contents. Additionally, chemical composition of the OM in the clay fraction of soils from 0–20cm, 20–40cm and 40–70cm and the four density fractions from soils at 20–40cm depth was characterized using diffuse reflectance infrared Fourier transformed (DRIFT) spectroscopy. The OM associated with oPOM (OC only) and HFOM1.85–2.60 (OC and total N) fractions was significantly increased with increasing clay content among soil groups and the degree of association depended on the dominating clay mineral (albeit significantly at P <0.05 for some soil groups only). The relative proportion (%rA) of aliphatic-C in the clay and HFOM1.85–2.60 fractions significantly increased with increasing sand content, and significantly decreased with increasing clay content. Whereas, opposite relationships were observed for the aromatic-C and amide N (amide-II) with sand and clay contents, respectively. The organic-mineral fractions (clay or HFOM1.85–2.60) of the coarse-textured siliceous soils were enriched with aliphatic-C and depleted in amide N, whereas the organo-mineral fractions of the fine-textured soils were enriched with aromatic-C and amide N. Aliphatic-C represented the dominating organic structure in the siliceous soils, whereas aromatic-C and amide N represented typical forms of OM in the fine-textured soil groups. The present study provided insights into the role of soil texture and clay mineralogy in governing the content and composition of OM pools in Thai soils with relevance for sustaining soil fertility and mitigating C emissions. [Copyright &y& Elsevier]