X-ray Diffraction Fluorescence Research Articles

Study on the preparation and properties of high-belite cementitious materials from shield slag and calcium carbide slag

With the continuous increase in subway construction in China, a large amount of shield slag is produced. The piling and transportation of shield slag seriously affect the urban environment. Therefore, it is necessary to study the recycling technology of shield muck to reduce its environmental pollution and realize its resource utilization. Jinan shield muck contains a large amount of calcareous muck and clayey muck. It is feasible to prepare silica-aluminum cementitious materials through the reasonable combination of these mucks. In this study, calcareous slag and clayey slag were used as the main raw materials, and calcium carbide slag, iron powder, silica fume and alum soil were used as correction materials to prepare high-belite cementitious materials based on the residue. By measuring the content of free calcium oxide and using X-ray fluorescence diffraction, scanning electron microscopy and differential thermal analysis, the formation mechanism of high-belite cementified materials under different doping conditions was studied. The results show that the addition of CaSO4 and CF2 can significantly improve the burnability of raw materials when the saturation coefficient of lime holding time has a great influence on the formation of clinker. According to the Rietveld quantitative phase analysis, under the doping state, the content of belite can reach more than 50%. The content of this mineral can effectively overcome the problem of the low short-term strength of high belite cementite materials. Through the above research, it was confirmed that the shield mule of Jinan metro can form high-belite cementitious material.

Synchronized Esterification and Transesterification of Jatropha Curcas Using Ferric Sulfate Modified Snail Shells As a Bi-Functional Catalyst: A Box-Behken Optimization Approach

The study is focused on modelling and optimizing the process parameters on the production of biodiesel from Jatropha Curcas oil using achantinoidea shell catalyst. Shells of achantinoidea were sourced, crushed, sieved, and subject to temperatures of 900°C for 4 h to convert CaCO3 present to CaO and further doped with ferric sulfate. Characterization of the catalyst was conducted via Fourier transform infrared (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray fluorescence diffraction (XRF). Optimization was done using response surface methodology (RSM) based on the Box–Behken design. The parameters optimized in the production process are methanol to oil molar ratio, catalyst concentration, temperature, and time. A second order quadratic model (p < 0.0001) was developed for predicting the methyl-ester yield. The model predicted maximum yield of 84.74% under the following optimum process conditions: methanol to oil molar ratio 15 : 1, catalyst concentration 8.90 wt %, temperature 62.36 and reaction time 3 h, while for the acid value the model predicted minimum 1.11 under same conditions.

Enhanced Immobilization of Arsenic from Acid Mine Drainage by Detrital Clay Minerals

Arsenic (As) is a potent carcinogen and the most common metal(loid) contaminant in drinking water sources globally. In acidic, Fe-rich systems, nanocrystalline Fe(III) precipitates (Fe(III)NP) are the main scavengers of As. However, the redox cycling of Fe(III)NP highly enhances As mobility and bioavailability. Notably, the irreversible release of As in runoff resulting from reductive dissolution of Fe(III)NP makes the effective remediation of As an ongoing environmental challenge. Here, we show for the first time that detrital clay minerals originating from the partial weathering of coal mining waste substantially increased total As uptake by acid mine drainage (AMD) sediments. The As immobilization mechanisms by the AMD sediments were investigated by the combined use of microbial community structure characterization (16S rRNA), chemical extractions, and synchrotron-based X-ray fluorescence (XRF), diffraction (XRD), and absorption (XANES). The use of an X-ray spot size as small as one micrometer allowed a detailed examination of the heterogeneous AMD sediments. Our results suggest that during sustained redox cycling of iron in Fe(III)NP-clay mixed-mineral systems, the clays controlled As mobility by (1) enhancing heterogeneous precipitation of Fe(III)NP under oxic conditions, which then adsorbed or incorporated As; and (2) facilitating the transfer of As from Fe(III)NP to clay during microbially mediated reduction of Fe(III)NP coatings under anoxic conditions. Designing remediation strategies that incorporate clay could become a promising low-cost strategy for As remediation in mining-impacted areas.

Improved Dispersion and Ultradeep Activity of HDS Catalyst by New Synthesis Approach

AbstractThe syntheses of highly dispersed NiMoS catalysts for ultradeep hydrodesulfurization (HDS) of refractory organosulfur compounds is carried out by adopting different metal deposition strategies on mesoporous silica: (i) single‐pot approach (SP), (ii) modified‐single‐pot approach (MSP); and (iii) addition of chelating agent (CA) with MSP (MSP‐CA). The characteristics of catalysts were evaluated by means of N2‐physisorption, chemisorption by thermal desorption and reduction (TPD and TPR), scanning electron microscopy (SEM), High resolution transmission electron microscope (HRTEM), and spectroscopy techniques; X‐ray diffraction (XRD), fluorescence (XRF), photoelectron (XPS), Fourier transform infrared (FTIR) and with pyridine adsorption (FTIR‐pyridine). Simultaneous desulfurization activity of dibenzothiophene (DBT) and dimethyl‐dibenzothiophene (4,6‐DMDBT) was carried out in a batch autoclave reactor at 350 °C and 5 MPa. MSP approach showed notable improvement in the Ni loading, textural properties and dispersion of active metals compared to the SP method. Consequently, MSP catalyst outperformed for the HDS rate of refractory organosulfur compounds (DBT and 4,6‐DMDBT) by both the direct desulfurization and hydrogenation routes. The addition of CA further improved the performance of MSP, especially for the HDS of 4,6‐DMDBT.

Formation of the background component of the analytical signal in the long-wavelength region of X-ray fluorescence spectrum

Components of X-ray background in the long-wavelength spectral region of a crystal diffraction X-ray fluorescence spectrometer were calculated. The calculations took into account the bremsstrahlung radiation of free electrons, diffuse scattering and fluorescence of the crystal analyzer, and high-order reflections of the scattered radiation of the fluorescent sample by the crystal analyzer. The results of calculations were compared with the intensities of background samples measured in the region of the NaKα fluorescence line on an SRM-25 wave X-ray spectrometer. The experimental background intensities (response function) well correlate with those found by the regression equation with calculated factors. The importance of particular processes in the formation of X-ray background was assessed.

Zinc mobility and speciation in soil covered by contaminated dredged sediment using micrometer-scale and bulk-averaging X-ray fluorescence, absorption and diffraction techniques

The mobility and solid-state speciation of zinc in a pseudogley soil (pH = 8.2–8.3) before and after contamination by land-disposition of a dredged sediment ([Zn] = 6600 mg kg −1) affected by smelter operations were studied in a 50 m 2 pilot-scale test site and the laboratory using state-of-the-art synchrotron-based techniques. Sediment disposition on land caused the migration of micrometer-sized, smelter-related, sphalerite (ZnS) and franklinite (ZnFe 2O 4) grains and dissolved Zn from the sediment downwards to a soil depth of 20 cm over a period of 18 months. Gravitational movement of fine-grained metal contaminants probably occurred continuously, while peaks of Zn leaching were observed in the summer when the oxidative dissolution of ZnS was favored by non-flooding conditions. The Zn concentration in the <50 μm soil fraction increased from ∼61 ppm to ∼94 ppm in the first 12 months at 0–10 cm depth, and to ∼269 ppm in the first 15 months following the sediment deposition. Higher Zn concentrations and enrichments were observed in the fine (<2 μm) and very fine (<0.2 μm) fractions after 15 months (480 mg kg −1 and 1000 mg kg −1, respectively), compared to 200 mg kg −1 in the <2 μm fraction of the initial soil. In total, 1.2% of the Zn initially present in the sediment was released to the environment after 15 months, representing an integrated quantity of ∼4 kg Zn over an area of 50 m 2. Microfocused X-ray fluorescence (XRF), diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopy techniques were used to image chemical associations of Zn with Fe and Mn, and to identify mineral and Zn species in selected points-of-interest in the uncontaminated and contaminated soil. Bulk average powder EXAFS spectroscopy was used to quantify the proportion of each Zn species in the soil. In the uncontaminated soil, Zn is largely speciated as Zn-containing phyllosilicate, and to a minor extent as zincochromite (ZnCr 2O 4), IVZn-sorbed turbostratic birnessite (δ-MnO 2), and Zn-substituted goethite. In the upper 0–10 cm of the contaminated soil, ∼60 ± 10% of total Zn is present as ZnS inherited from the overlying sediment. Poorly-crystalline Zn-sorbed Fe (oxyhydr)oxides and zinciferous phyllosilicate amount to ∼20–30 ± 10% each and, therefore, make up most of the remaining Zn. Smaller amounts of franklinite (ZnFe 2O 4), Zn-birnessite and Zn-goethite were also detected. Further solubilization of the Zn inventory in the sediment, and also remobilization of Zn from the poorly-crystalline neoformed Fe (oxyhydr)oxide precipitates, are expected over time. This study shows that land deposition of contaminated dredged sediments is a source of Zn for the covered soil and, consequently, presents environmental hazards. Remediation technologies should be devised to either sequester Zn into sparingly soluble crystalline phases, or remove Zn by collecting leachates beneath the sediment.