•The conversion of used nuclear-grade graphite with O2 and CO2 was investigated.•Kinetic parameters were determined covering different reaction regimes.•The pore structure resistance with a rising ...degree of conversion was established.•The mechanism of particle conversion was shown.•The behavior of trace elements during the gasification of graphite was determined.
The study on the thermochemical conversion of release-measured nuclear-grade graphite recovered from the thermal column of a shut-down nuclear research reactor focuses on kinetic processes of gasification and oxidation of this graphite. More specifically, the kinetic parameters were determined and the evolution of the graphite structure during carbon conversion was investigated. For oxidation, the three conversion regimes of heterogeneous reactions in the temperature range of 500 °C to 950 °C were observed. The activation energy is approx. 288 kJ/mol in the kinetic regime limited by the chemical reaction (Regime I), approx. 185 kJ/mol in the pore diffusion regime (Regime II) and approx. 10 kJ/mol in the mass transfer regime (Regime III). With an increase of the partial pressure of oxygen, an increase of the pre-exponential factor in Regime I from 6.6 × 1012 1/s at 0.2 bar to 1.8 × 1013 1/s at 0.5 bar and to 2.0 × 1013 at 0.8 bar of oxygen was determined. A similar effect was observed in Regime II. A reaction order of 0.96 ± 0.16 was obtained for the oxidation reaction. In case of CO2 gasification at temperatures of 900 °C to 1400 °C, two regimes were identified. In Regime I, an activation energy of approx. 294 kJ/mol and a pre-exponential factor of 3.5 × 107 1/s were determined, the corresponding parameters being approx. 156 kJ/mol and 8.3 × 102 1/s for Regime II, respectively. Similar activation energy values for both oxidation and gasification reactions indicate that the structure of the nuclear graphite remains stable with proceeding carbon conversion. From the analysis of the development of the inner surface area and particle size distribution at increasing conversion rates, it can be concluded that the gasification of nuclear graphite mainly takes place on the outer surface. Using the ETV-ICP-OES analysis, it was found that the trace elements, Ca, Fe, S, V and Zn, were evaporated and no longer detectable in partially gasified nuclear graphite, whereas elements such as Ba, Cr or Mn are being accumulated in the solid residue.
•The major mineral elements of red garlic were determined using ICP-OES analysis.•Geographical classification of Italian red garlic was performed.•We built and validated efficient class models for ...four red garlic varieties.
Sixty-five samples of red garlic (Allium sativum L.) coming from four different production territories of Italy were analysed by means of inductively coupled plasma optical emission spectrometry. The garlic samples were discriminated according to the geographical origin using the content of seven elements (Ba, Ca, Fe, Mg, Mn, Na and Sr). Both classification and class modelling methods by using linear discriminant analysis (LDA) and soft independent model class analogy (SIMCA), respectively, were applied. Classification ability and modelling efficiency were evaluated on an external prediction set (21 garlic samples) designed by application of duplex Kennard-Stone algorithm. All the calibration and prediction samples were correctly classified by means of LDA. The class models developed using SIMCA exhibited high sensitivity (almost all the calibration and external samples were accepted by the respective classes) and good specificity (the majority of extraneous samples were refused by each class model).
The paper presents an independent application of two hyphenated techniques, wherein an identical chromatographic system i.e. high performance liquid chromatography (HPLC) was coupled to microwave ...induced plasma optical emission spectrometry (MIP OES) or inductively coupled plasma optical emission spectrometry (ICP OES). A cation–exchange column and a mobile phase based on pyridine–2,6–dicarboxylic acid (PDCA) were employed to separate Fe(II) and Fe(III) within 300 s. Additionally, two methods of sample preparation were employed. Optimization and validation of both methods were conducted parallel. The applicability was presented with different sample matrix types: post–glacial sediments, archaeological pottery, soils located in the proximity of industry wastes disposal site, river sediments and yerba mate (Ilex paraguariensis). Obtained results were compared in terms of the excitation source (microwave induced or inductively coupled) and supplied gas (nitrogen or argon). The research introduces HPLC–MIP OES for iron speciation analysis and its applicability were critically evaluated with HPLC–ICP OES.
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•The optical emission detectors with different plasma sources has been applied for iron species determination.•The hyphenated techniques HPLC–MIP–OES and HPLC–ICP–OES has been optimized and validated.•The application of speciation analysis has been elaborated for different matrixes.
Drought-induced forest dieback is causing reductions in productivity, increasing tree mortality and impairing terrestrial carbon uptake worldwide. However, the role played by long-term nutrient ...imbalances during drought-induced dieback is still unknown. To improve our knowledge on the relationships between dieback and nutrient imbalances, we analysed wood anatomical traits (tree-ring width and wood density), soil properties and long-term chemical information in tree-ring wood (1900–2010) by non-destructive Micro X-ray fluorescence (μXRF) and destructive (ICP-OES) techniques. We studied two major European conifers with ongoing drought-induced dieback in mesic (Abies alba, silver fir) and xeric (Pinus sylvestris, Scots pine) sites. In each site we compared coexisting declining (D) and non-declining (ND) trees. We used dendrochronology and generalized additive and linear mixed models to analyse trends in tree-ring nutrients and their relationships with wood traits. The D trees presented lower growth and higher minimum wood density than ND trees, corresponding to a smaller lumen area of earlywood tracheids and thus a lower theoretical hydraulic conductivity. These differences in growth and wood-anatomy were more marked in silver fir than in Scots pine. Moreover, most of the chemical elements showed higher concentrations in D than in ND trees during the last two-five decades (e.g., Mn, K and Mg), while Ca and Na increased in the sapwood of ND trees. The Mn concentrations, and related ratios (Ca:Mn, Mn:Al and P:Mn) showed the highest differences between D and ND trees for both tree species. These findings suggest that a reduced hydraulic conductivity, consistent with hydraulic impairment, is affecting the use of P in D trees, making them more prone to drought-induced damage. The retrospective quantifications of Mn ratios may be used as early-warning signals of impending dieback.
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•110-Year long series of wood-chemistry to understand drought-induced dieback.•Declining trees showed lower growth and higher minimum wood density than non-declining trees.•Alterations in wood nutrient concentrations are coherent with hydraulic failure hypothesis.•Mn, Ca:Mn and P:Mn rings content may serve as early-warning signals of dieback.
Fatigue is a sudden failure of components below the maximum strength of the material when subjected to repeated loading. This paper studies the fatigue behavior of basalt, carbon, and glass ...fibers/epoxy hybrid composites under three‐point flexural loading and a saltwater environment. Five different composite panels were manufactured using the VARTM. The samples were then immersed in a saltwater solution for 60, 120, and 180 days before conducting the tests. Three‐point static and fatigue tests were conducted using UTM as per ASTM D7264‐07 and ASTM D7774‐12. The S‐N and stiffness degradation curves were plotted, and the morphology of the fatigue samples was investigated using SEM. In addition, the ion penetration in the solution was detected with ICP‐OES analysis. The result shows that bending fatigue properties of all composite samples show a degradation as the immersion period increases. This might be due to micro‐hole formation as the ions move from the sample to the saltwater solution.
Highlights
Composite specimens were immersed in a saltwater solution for 2, 4, and 6 months.
Three‐point bending fixture is used for fully reversed fatigue loading (T‐C).
Percentage degradation of fatigue life and stiffness loss increases with the immersion period
SEM image shows delamination, fiber pullout, debonding, and fiber and matrix breakage.
The accumulation of heavy metals in fish has been extensively studied and well documented. However, the research has been mainly focused on the muscle tissue, while the distribution patterns among ...other tissues, such as liver and gills, have been mostly neglected. Within the present study, the concentrations of Ag, Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se, Sr, Zn and Li in the muscle, gills, liver and intestine of the sterlet (Acipenser ruthenus) from the Danube River have been assessed by using the inductively-coupled plasma optical spectrometry. The analysis has revealed a high degree of differential accumulation of the studied heavy metals and trace elements in the tissues of the Danube sterlet. Liver appeared to be the main heavy metal storage tissue, while the lowest levels of analyzed metals were found in muscles. Heavy metal concentrations in the muscle were at acceptable levels for human consumption, except partly for cadmium. We conclude that, in order to enable a more efficient control of contaminants in fish products, there is an apparent need to resolve the problem of lack of legal limits for many metals in European legislation.
A new GO/Fe3O4@β-lactoglobulin sorbent was prepared for selective extraction of trace Pb(II). The GO/Fe3O4@β-lactoglobulin packed column advantageously permeates samples faster than nascent GO column ...ca. 5 fold. We experimentally demonstrated the developed SPE method for the enrichment of Pb(II) from real samples (tap, river and packaged drinking water) before ICP-OES determination. The sulfhydryl groups of the vicinal cysteine and the carboxylic groups were led to successful chelate formation with Pb(II) ions. The method shows a detection limit of 0.30 ng mL−1 for Pb(II) ion. The prepared sorbent has a surface area and pore volume of 1460.37 m2g−1 and 1.36 ccg−1, respectively. The preconcentration limit and preconcentration factor for Pb(II) was found to be 0.37 μg L−1 and 900, respectively using 3 mL of eluent. At 95% confidence level, the Student's t-test was less than the critical Student's t value (4.303). A coefficients of variation for five replicate measurements is 3.45%, indicates good precision of the method.
•Graphene Oxide/Fe3O4@β-lactoglobulin composite was prepared.•The composite shows good adsorption of Hg(II) i.e. 150 mg/g.•Effectively extract trace Pb (II) ions from complex matrix.•Selectively quantify Pb(II) in real sample analysis.
This study introduces a novel method for preconcentrating As, Cu, and Pb from seawater samples using manganese oxide octahedral molecular sieve (OMS-2), as a sorbent, and the analysis by Inductively ...Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The OMS-2 nanomaterial was synthesized and characterized using X-ray diffraction and scanning electron microscopy, revealing a crystallite size of 20.9 nm and a typical needle-like morphology of cryptomelane structure. To optimize the ICP-OES operating conditions and the preconcentration process, a central composite design was used. The optimal conditions for ICP-OES analyses were 1200 W and 0.7 L min−1 for the levels of the radio frequency potential (RF) and nebulization gas flow rate, respectively. The optimal conditions for the adsorption process were achieved at a pH of 6.5, 30 mg of OMS-2, and 35 min of stirring time, in the presence of the sample matrix. The enrichment factors obtained were 66, 45, and 21, and a limit of detection of 0.3, 0.1, and 2.1 μg L−1 for As, Cu, and Pb, respectively. The recovery tests ranged from 80 % to 120 %. The method was successfully applied to determine As, Cu, and Pb in seawater samples.
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•A new material was applied for the determination of As, Cu, and Pb.•The factors affecting the separation were optimized using chemometrics.•Very sensitive method was achieved for As, Cu, and Pb determination.
•Multi-elemental contents of Sechium edule fruits were determined.•LDA, kNN, PLS-DA and SVM were used for classification.•Chemometric analysis is effective in distinguishing the origin of fruits.•LDA ...classification model was simplified by forward stepwise selection of variables.•Ca, Ba, Cu, Mn, Na, Sr, and Zn contents allowed above 90% correct classification.
This paper describes the determination and evaluation of the major and trace element composition (Al, As, Ba, Ca, Cd, Co, Cu, Fe, K, Mg, Mn, Na, Pb, Sr and Zn) of Sechium edule (Jacq) Swartz fruits collected from four different places of production in Corrientes province, Argentina. Element concentrations were determined by using inductively coupled plasma optical emission spectrometry (ICP OES) after microwave digestion. The accuracy was confirmed with standard reference material of spinach leaves (NIST, 1570a) and spiking tests. Principal component analysis (PCA), linear discriminant analysis (LDA), k-nearest neighbors (kNN), partial least square-discriminant analysis (PLS-DA) and support vector machine (SVM) were applied to the results for discriminating the geographical origin of S. edule fruits. Finally, the LDA method was found to perform best with up to 90% accuracy rate based on the following elements: Ca, Ba, Cu, Mn, Na, Sr, and Zn.
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