Scanning Electron Microscopy-energy Dispersive X-ray Spectroscopy Research Articles

Leaching kinetics of ash impurities from aphanitic graphite by combining dual-ultrasound and hydrochloric acid–potassium hydrogen fluoride

The hydrochloric acid-fluoride salt is useful for purifying graphite. Ultrasonic-assisted technique can significantly reduce the leaching time and improve the leaching efficiency. Compared with single-frequency, dual-frequency ultrasound has the advantages of high energy efficiency and wide cavitation area. In this study, the combination of a dual-frequency ultrasound-assisted technique and hydrochloric acid–potassium hydrogen fluoride leaching agent was proposed for the leaching of aphanitic graphite to remove impurity minerals. First, the effects of probe-type ultrasonic power, tank-type ultrasonic power, temperature, HCl concentration, ultrasonication time, and KHF2 concentration on the purification efficiency of impurities from aphanitic graphite with the assistance of dual-frequency ultrasound were investigated. It was found that the combination of dual-frequency ultrasound and hydrochloric acid–potassium hydrogen fluoride can reduce the ash content of aphanitic graphite from 13.02 % to 1.02 % with an ash removal rate of 94.17 %. Second, volumetric reaction models and unreacted shrinkage nucleation models were used to fit the kinetics of impurities from aphanitic graphite with dual-frequency ultrasound-assisted HCl-KHF2 leaching. Kinetic analysis shows that the volumetric reaction model with chemical control was better to fit the leaching process. This is consistent with the calculation results of the activation energy of the reaction (Ea = 58.13 kJ/mol). Finally, laser particle size analyzer, X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), X-ray fluorescence spectroscopy (XRF), transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDS) were used to analyze the fugacity of impurity minerals during the process of dual-frequency ultrasound-assisted HCl-KHF2 leaching. It was revealed that combining ultrasonic cavitation fragmentation with chloric acid–potassium fluoride generated SiF4 with high solubility, thereby removing silica-bearing impurities more efficiently. The challenges in further reducing ash content from 1.02 % in the leached concentrate of aphanitic graphite could be attributed to the existence of titanium-bearing mineral impurities on the surface of graphite particles and the presence of silica-bearing minerals between graphite carbon layers.

Unlocking the power of Inula Viscosa essential oil: A green solution for corrosion inhibition in XC48 steel within acidic environments

A sustainable corrosion inhibitor for XC48 steel in a 1 M HCl environment was effectively formulated using the essential oil of Inula viscosa (IVEO), as corroborated by gas chromatography-mass spectrometry (GC-MS) results. This novel application was assessed via multiple techniques: mass loss, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), Fourier-transform infrared spectroscopy with an attenuated total reflectance accessory (FT-IR/ATR), X-ray diffraction (XRD) and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) and Atomic Force Microscopy (AFM) for surface examination. The plant extract’s inhibitory capacity raised in proportion to its concentration, as confirmed by both mass loss and electrochemical investigations. This trend reached a high point at a 97% inhibitory efficiency at a concentration of 400 ppm at 298 K. FTIR, XRD, SEM/EDS, and AFM analyses further validated the binding of this eco-friendly inhibitor onto the steel surface, which exhibited mixed-type characteristics, thus elucidating its exceptional inhibitory performance. The Langmuir isotherm model aptly fitted the adsorption analysis, indicating the development of an organic protective layer. Advances computational calculations of various quantum chemical parameters for the key ingredients of the essential oil added to the understanding of the link between adsorption and corrosion inhibition.

Designing a Phenalenyl-Based Dinuclear Ni(II) Complex: An Electrocatalyst with Two Single Ni Sites for the Oxygen Evolution Reaction (OER).

A new dinuclear Ni(II) complex 1, [Ni2II(dtbh-PLY)2], is synthesized from 9-(2-(3,6-di-tert-butyl-2-hydroxybenzylidene)hydrazineyl)-1H-phenalen-1-one, dtbh-PLYH2 ligand, and structurally characterized by various analytical tools including the single-crystal X-ray diffraction (SCXRD) technique. In the solid state, both Ni(II) metal centers in complex 1 exist in a distorted square planar geometry and display the presence of rare Ni···H-C anagostic interactions to form a one-dimensional (1-D) linear motif in the supramolecular array. Complex 1 is further stabilized in the solid state by π-π-stacking interactions between the highly delocalized phenalenyl rings. The redox features of complex 1 have been analyzed by the cyclic voltammetry (CV) technique in solution as well as in the solid state, revealing the crucial involvement of both the Ni(II) metal centers for undergoing quasi-reversible oxidation reactions on the application of an anodic sweep. A complex 1-modified glassy carbon electrode, GC-1, is employed as an electrocatalyst for oxygen evolution reaction (OER) in 1.0 M KOH, giving an OER onset at 1.45 V, and very low OER overpotential, 300 mV vs the reversible hydrogen electrode (RHE) to reach 10 mA cm-2 current density. Furthermore, GC-1 displayed fast OER kinetics with a Tafel slope of 40 mV dec-1, a significantly lower Tafel slope value than those of previously reported molecular Ni(II) catalysts. In situ electrochemical experiments and postoperational UV-vis, Fourier transform infrared (FT-IR), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS) studies were performed to analyze the stability of the molecular nature of complex 1 and to gain reasonable insights into the true OER catalyst.

Silver and silicon doped βTCP scaffolds with gentamicin or ceftazidime loaded P(3HB) coatings as multifunctional biomaterials for bone regeneration

The risk of bacterial infections is a significant challenge faced frequently in the use of implants or scaffolds for bone regeneration. Therefore, this study focusses on the development and characterisation of novel β tricalcium phosphate (βTCP) scaffolds co-doped with silver and silicon, along with composites coated with antibiotic-loaded poly(3-hydroxybutyrate) (P(3HB)) layers. The successful incorporation of silver and silicon dopants while maintaining the formation of βTCP phase was confirmed using X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) analysis. The developed materials demonstrated comparable total and open porosity (∼64–70 vol%), suggesting high interconnectivity between pores conducive to nutrient transport and tissue repair. The increase in compressive strength was achieved for both doped (4.73 ± 0.79 MPa) and P(3HB) coated (5.79 ± 0.92 MPa) scaffolds due to the fine bioceramic microstructure and polymeric coating. Silver and silicon-modified βTCP demonstrated enhanced growth inhibition of Gram-negative (Pseudomonas aeruginosa, Escherichia coli) and Gram-positive (Staphylococcus aureus) bacterial strains in vitro compared to the pure βTCP. P(3HB) coatings, enriched with gentamicin or ceftazidime, exhibited burst and sustained release of the antibiotics from the scaffolds up to 120 h further intensifying the bacteria-killing capability, with evident inhibition zones observed in vitro. Moreover, the composites exhibited apatite-forming ability, suggesting their bioactive potential. In vivo evaluation using Caenorhabditis elegans demonstrated the lack of toxicity of the tested materials. The simultaneous incorporation of the dopants and antibiotic-loaded P(3HB) coatings not only offer a dual antibacterial approach but may also facilitate bone regeneration. However, further in vitro and in vivo investigations are needed to assess their potential in clinical application.

In vivo assessment of TiO2 based wear nanoparticles in periprosthetic tissues

A multimodal approach combining inductively coupled plasma mass spectrometry (ICP-MS), single-particle ICP-MS (spICP-MS), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS) and Raman spectroscopy enabled a deeper insight into the balance between total titanium (Ti), the soluble titanium fraction and titanium dioxide based particle fraction levels in periprosthetic tissues collected from patients undergoing revision surgery. Hydrofluoric acid usage in the sample digestion allowed for complete digestion of TiO2 particles, thus enabling accurate estimation of total Ti levels. The TiO2 fraction represents 38–94% of the titanium load in the six samples where particles were detected, and the fraction is present mainly in samples from patients with aseptically loosened total hip arthroplasty. Further attention was given to this fraction determining the elemental composition, particle count, particle size and modification of TiO2. The spICP-MS analysis confirmed the presence of the TiO2-derived (nano)particles (NPs) with a 39- to 187-nm median size and particle count up to 2.3 × 1011 particles per gram of tissue. On top of that, the SEM-EDS confirmed the presence of the TiO2 nanoparticles with 230-nm median size and an anatase crystal phase was determined by Raman spectroscopy. This study presents a novel multimodal approach for TiO2 particle determination and characterization in tissue samples and is the first in vivo study of this character.

Green Flame-Retardant Blend Used to Improve the Antiflame Properties of Polypropylene.

The flammability properties of polymers and polymeric composites play an important role in ensuring the safety of humans and the environment; moreover, flame-retardant materials ensure a greater number of applications. In the present study, we report the obtaining of polypropylene (PP) composites contain a mixture of two green flame retardants, lignin and clinoptilolite, by melt extrusion. These additives are abundantly found in nature. Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), mechanical properties, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), cone calorimetry, UL-94, and carbonized residues analysis were carried out. TGA analysis shows that PPGFR-10 and PPGFR-20 compounds presented better thermal stability with respect to PP without flame retardants. The conical calorimetric evaluation of the composites showed that PPGFR-10 and PPGFR-20 presented decreases in peak heat release rates (HRRs) of 9.75% and 11.88%, respectively. The flammability of the composites was evaluated with the UL-94 standard, and only the PPGFR-20 composite presented the V-0 and 5VB classification, which indicates good flame-retardant properties. Additives in the polymer matrix showed good dispersion with few agglomerates. The PPGFR-20 composite showed an FRI value of 1.15, higher percentage of carbonized residues, and UL-94 V-0 and 5VB rating, suggesting some kind of synergy between lignin and clinoptilolite, but only at high flame-retardant concentrations.

Catalytic upgrading of Naomaohu coal pyrolysis volatiles over NiAl and NiLiAl oxides

Catalytic upgrading of volatiles is an essential technology to improve the product distribution of pyrolysis for the clean and efficient utilization of low-rank coals. In this work, novel acid-base bifunctional catalysts composed of Ni/Li/Al oxides were designed and prepared using LDH precursors with tunable chemical composition and structural properties. The catalysts were systematically characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), physisorption, NH3-temperature programmed desorption (NH3-TPD), CO2-temperature programmed desorption (CO2-TPD), H2-temperature programmed reduction (H2-TPR), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). A two-stage fixed bed reactor was employed to evaluate the performance of the catalysts. Characterization results suggest that the crystal size of NiO and the surface area of the catalyst decreased with increasing Li content and decreasing Ni content in the catalyst, while the pore volume and pore diameter were positively correlated with Li content. Moreover, the addition of Li reduced the amount of weak acid sites and raised the amount of total basic sites. Consequently, the bifunctional catalysts boosted the yield of light tar and the contents of aromatics and phenols in tar. Specifically, with the highest total acid sites (569 μmol/g) promoting the cracking of heavy pitch components, Ni2.5Li0.5Al1 decreased the content of pitch in tar to 23.8 wt%, representing a 42.7 % drop from the corresponding non-catalytic pyrolysis. Accordingly, it improved the light tar yield to 7.2 wt%, which was 18 % higher than non-catalytic pyrolysis. 450 °C is identified as a suitable temperature for the catalytic upgrading of volatiles from Naomaohu coal; higher catalysis temperatures at 500 °C and 550 °C led to lower tar yield and lower phenols content, along with higher gas yield and more carbon deposition.

Enhancing methyl orange discoloration with TiO2/Fe2O3/AC composites: synergistic adsorption-photocatalysis

Fe2O3/TiO2/AC nanocomposites were successfully synthesized via a sol–gel method, and their efficacy in decomposing methyl orange via adsorption-photocatalytic processes was reported for the first time in this study. Systematic exploration of the physicochemical properties impacting photocatalytic activity was conducted through x-ray diffraction, scanning electron microscopy—energy-dispersive x-ray spectroscopy, and Fourier transform infrared spectroscopy (FTIR) characterizations. The study revealed that the discoloration of methyl orange resulted from a synergistic interplay between adsorption and photocatalysis. The incorporation of Fe2O3 nanoparticles significantly elevated photocatalytic activity by 70%, with additional enhancement observed upon the introduction of activated carbon (AC) particles. The synergistic effects of AC adsorption and TiO2/Fe2O3 photocatalysis exhibited remarkable efficiency in degrading methyl orange under visible light irradiation. The trial functioning of Fe2O3 and AC in the TiO2/Fe2O3/AC composite, which serves as an adsorbent, an electron trap, and a co-catalyst providing active sites, significantly improved photocatalytic activity. These findings not only contribute to understanding the crucial role of composite TiO2 in conjunction with metal and carbon-based co-catalysts but also hold valuable implications for advancing research in the development of adsorption-photocatalytic systems for wastewater treatment.

Analytical Study of Polychrome Clay Sculptures in the Five-Dragon Taoist Palace of Wudang, China

During the Ming Dynasty, the Five-Dragon Palace functioned as a royal Taoist temple set atop one of China’s holiest Taoist mountains, Wudang Mountain. Two tower polychrome sculptures with exquisite craftsmanship have remained over the centuries. In this study, the painting materials and the techniques used to construct these sculptures were analyzed through multiple characterization methods, including optical microscope (OM) observations, micro-Raman spectroscopy, scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM−EDS), X-ray diffraction (XRD), micro-Fourier-transform infrared spectroscopy (μ−FTIR), and pyrolysis–gas chromatography/mass spectrometry (Py−GC/MS). The results revealed that the pigments used in these sculptures included red pigments, which were composed of mercury (II) sulfide (cinnabar or vermillion), minium (Pb3O4), and hematite (Fe2O3); green pigments, which included atacamite and botallackite (Cu2Cl(OH)3), and blue pigments, which comprised smalt (CoO·nSiO2) and azurite (Cu3(CO3)2(OH)2). The white base layer was composed of quartz and mica minerals combined with gypsum or plant fiber, and the gold foil was adhered to the surface using heated tung oil. In addition, a special multi−layer technique was applied, with red under the golden gilding, white under the blue layer, and gray and black under the green layer. Drying oil was used as a binder for lead-containing pigments. This study offers substantial proof of reliable techniques to use in the continuing conservation of these sculptures, and it also serves as a foundation to determine if they can be dated to the late Ming or early Qing Dynasty (17th century).

Sustainable production of heavy metal-binding levan by a subarctic permafrost thaw lake Pseudomonas strain 2ASCA

Pseudomonas strain 2ASCA isolated in subarctic Québec, Canada, produced a cell membrane bound levan-type exopolymer (yield 1.17 g/L), after incubation in growth media containing 6 % sucrose (w/v) at temperature of 15 °C for 96 h. The objective of this study was to optimize levan production by varying the growth parameters. Moreover, the polymer's chemical characterization has been studied with the aim of increasing knowledge and leading to future applications in many fields, including heavy metal remediation. Higher levan yields (7.37 g/L) were reached by setting up microbial fermentation conditions based on the re-use of the molasses obtained from sugar beet processing. Spectroscopy analyses confirmed the levan-type nature of the exopolymer released by strain 2ASCA, consisting of a β-(2,6)-linked fructose repeating unit. Gel permeation chromatography revealed that the polymer has a molecular weight of 13 MDa. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) showed that the levan sequestered with a strong affinity Cr(III), which has never been previously reported, highlighting an interesting biosorption potential. In addition, SEM analysis revealed the formation of nanoparticles in acidified water solution.

Provenance of the Bronze Age lapis lazuli pieces from the Early Urban Center of Konar Sandal, Jiroft, Southern Iran

The sources of lapis lazuli objects found in the Bronze Age of the Iranian Plateau and its trade routes have been a subject of interest and a research question. Four archaeological pieces of lapis lazuli recovered from a stone-working workshop in the Bronze Age site of Konar Sandal South (Jiroft Plain), southern Iran, were analyzed using X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) techniques to characterize the mineralogical composition and the possible provenance of raw materials. Results showed that these objects are identical based on their composition, presenting diopside and specific trace element proportions as provenance markers. Comparison with available data from Iranian archaeological sites and ancient resources from Central Asia revealed that these finds may have been imported from lapis lazuli mines located at Badakhshan in Afghanistan, as they were supplied raw materials for ancient lapis lazuli objects of Iran.

Stratified control of chemical crystallization in a pellet fluidized bed for pH-Adjusted fluoride and phosphate reduction: An experimental study

Chemical crystallization granulation in a fluidized bed offers an environmentally friendly technology with significant promise for fluoride removal. This study investigates the impact of stratified pH control in a crystallization granulation fluidized bed for the removal of fluoride and phosphate on a pilot scale. The results indicate that using dolomite as a seed crystal, employing sodium dihydrogen phosphate (SDP) and calcium chloride as crystallizing agents, and controlling the molar ratio n(F):n(P):n(Ca) = 1:5:10 with an upflow velocity of 7.52 m/h, effectively removes fluoride and phosphate. Stratified pH control—maintaining weakly acidic conditions (pH = 6–7) at the bottom and weakly alkaline conditions (pH = 7–8) at the top—facilitates the induction of fluoroapatite (FAP) and calcium phosphate crystallization. This approach reduces groundwater fluoride levels from 9.5 mg/L to 0.2–0.6 mg/L and phosphate levels to 0.1–0.2 mg/L. Particle size analysis, scanning electron microscopy–energy-dispersive X-ray spectroscopy, and X-ray diffraction physical characterizations reveal significant differences in crystal morphology between the top and bottom layers, with the lower layer primarily generating high-purity FAP crystals. Further analysis shows that dolomite-induced FAP crystallization offers distinct advantages. SDP not only dissolves on the dolomite surface to provide active sites for crystallization but also, under weakly acidic conditions, renders both dolomite and FAP surfaces negatively charged. This allows for the effective adsorption of PO43−, HPO42−, and F− anions onto the crystal surfaces. This study provides supporting data for the removal of fluoride from groundwater through induced FAP crystallization in a chemical crystallization pellet fluidized bed.

Optimizing Antimicrobial Efficacy: Investigating the Impact of Zinc Oxide Nanoparticle Shape and Size.

Zinc oxide nanoparticles (ZnO NPs) have been investigated due to their distinct properties, variety of structures and sizes, and mainly for their antimicrobial activity. They have received a positive safety evaluation from the European Food Safety Authority (EFSA) for packaging applications as transparent ultraviolet (UV) light absorbers based on the absence of significant migration of zinc oxide in particulate form. ZnO NPs with different morphologies (spherical, flower, and sheet) have been synthesized via different sol-gel methods and extensively characterized by several solid-state techniques, namely vibrational spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), Fourier Transform Infrared Spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-VIS), electron paramagnetic resonance (EPR), and nitrogen adsorption-desorption isotherms. The ZnO NPs were assessed for their antibacterial activity against Escherichia coli (gram-negative bacteria) and Staphylococcus aureus (gram-positive bacteria) to study the influence of morphology and size on efficacy. ZnO NPs with different morphologies and sizes demonstrated antimicrobial activity against both bacteria. The highest microbial cell reduction rate (7-8 log CFU mL-1 for E. coli and 6-7 log CFU mL-1 for S. aureus) was obtained for the sheet- and spherical-shaped NPs as a result of the high specific surface area. In fact, the higher surface areas of the sheet- and spherical-shaped nanoparticles (18.5 and 13.4 m2 g-1, respectively), compared to the flower-shaped NPs (5.3 m2g-1), seem to promote more efficient bacterial cell reduction. The spherical-shaped particles were also smaller (31 nm) compared with the flower-shaped (233 × 249 nm) ones. The flower ZnO NP resulted in a 4-5 log CFU mL-1 reduction for E. coli and 3-4 log CFU mL-1 reduction for S. aureus. The lower apparent antibacterial activity of the flower-shaped could be associated with either the lack of defects on the particle core or the shape shielding effect. Compared to S. aureus, E. coli seems to be less resistant to ZnO NPs, which may be explained by the characteristics of its cell membrane. With simple synthesis techniques, which do not allow the size and shape of the nanoparticles to be controlled simultaneously, it is a challenge to elucidate the effect of each of these two parameters on antibacterial performance.

Impacts on Urban VOCs and PM2.5 during a Wildfire Episode

This study focuses on the impact of wildfire smoke emissions on regional, urban air quality during a wildfire event. We measured volatile organic compounds (VOCs) and fine particulate matter (PM2.5) in the San Francisco Bay Area to assess air quality during a wildfire event and compared them to those in a later non-wildfire period. VOCs were collected using thermal desorption tubes and quantified using thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS). Elevated concentrations of VOCs such as 1,3,5-trimethylbenzene (0.33 ± 0.01 µg/m3), benzene (1.03 ± 0.02 µg/m3), toluene (2.15 ± 0.04 µg/m3), ethylbenzene (0.60 ± 0.02 µg/m3), and m, p-xylene (0.77 ± 0.07 µg/m3) were observed in the wildfire event. Compared with that in the non-wildfire season, the toluene concentration during the wildfire period was more than three times the non-wildfire concentration. Similarly, the benzene concentration during the wildfire was almost four times higher, and that of p, m-xylene was three times higher. The higher wildfire levels were statistically significant for sec-butylbenzene, 1,2,4-trimethylbenzene, n-propylbenzene, o-xylene, styrene, 1,3,5-trimethylbenzene, benzene, toluene, ethylbenzene, and p,m-xylene (p < 0.00001). These higher VOC levels compared with those for the non-fire period may potentially pose a public health concern. Open face passive sampler (OFPS)-collected PM was analyzed using scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) and revealed organic carbon tar balls. The highest daily average beta-attenuation-monitored PM2.5 during the fire period was 200 µg/m3 and the highest hourly average was 270 µg/m3. Monitoring gas phase species in addition to PM concentrations is useful during wildfire season to inform public health guidance.

Isolation and identification of a high-efficiency hexavalent uranium adsorption strain and preliminary study of the influencing factors and adsorption mechanism.

In this study, a bacterial strain Chryseobacterium bernardetii WK-3 was isolated from the rhizosphere soil of a uranium tailings in Southern China. It can efficiently adsorb hexavalent uranium with an adsorption ratio of 92.3%. The influence of different environmental conditions on the adsorption ratio of Chryseobacterium bernardetii strain WK-3 was investigated, and the adsorption mechanism was preliminarily discussed by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). The results showed that the optimal adsorption conditions for U(VI) by Chryseobacterium bernardetii strain WK-3 were pH = 5, temperature 30 ℃, NaCl concentration 1%, and inoculation volume 10%. When the initial concentration of U was 50 ~ 150mg/L, the adsorption capacity of Chryseobacterium bernardetii strain WK-3 to U(VI) reached the maximum and maintained the equilibrium at 44h. SEM-EDS results showed that phosphorus in cells participates in the interaction of uranyl ions, which may indicate that phosphate was produced during cell metabolism and was further combined to form U(VI)-phosphate minerals. In summary, Chryseobacterium bernardetii strain WK-3 would be a promising alternative for environmental uranium contamination remediation.

Sustainability Evaluation of the Al-Qasab Playa by Integrating Hydrogeochemical and Graphical, ArcGIS Watershed, and Thermodynamic Geochemical Modeling Approaches

Drawing development plans requires evaluating the available resources and assessing their sustainable and subsequent utilization-driven environmental impacts. The current work is concerned with evaluating the sustainability of the halite harvesting process from Al-Qasab Playa, Shaqra, Central Saudi Arabia. The authors integrated, conceptually and quantitatively, ArcGIS-processed SRTM-DEM (Shuttle Radar Topography Mission-Digital Elevation Model) data, hydrogeochemical and thermodynamic-based geochemical modelling, and graphical approaches to achieve the ultimate aims of the study. The watershed is identified as a nonmarine closed basin with a drainage area of 1290 km2, with the slope controlling recharge to the Playa. The Chadha plot including the rainwater exhibits linear regression, with an R2 value of 0.9947, confirming the rainwater origin of the Playa water. The hardness-forming ions are primarily removed in pond 3, eliminating the need for costly and power-consuming steps of softening with ion exchange resins or nanofiltration as it can be used directly as a readily available feed for the chlor-alkali process for producing NaOH, Cl2, and H2 gases through electrolysis. XRD (X-ray diffraction) analysis and the SEM-EDS (Scanning electron microscopy-energy dispersive X-ray spectroscopy) of the harvested halite confirmed its purity. An improved design of the current folkloric harvesting process has been proposed based on the saturation indices calculated thermodynamically to provide a readily available feed intake for the electrolysis chlor-alkali process with or without minimal pretreatment to produce higher value chemicals. The methodological aspects presented here are deemed robust and valid for applications in other study areas, including the assessment of the exploitation of the rejected brine from the desalination plants to achieve the zero liquid discharge approach, as well as other types of sabkhas, regardless of their geographical location.

A study of surface fatigue wear and influence of contaminated lubricant in journal bearing system using tribological and vibration analyses

In the present work, journal bearing performance was evaluated using condition monitoring processes namely wear debris, vibration signal, lubricant oil degradation and temperature analyses. The journal bearing system was operated at 800 rpm and 200 N constant speed and load over a period of 1200 h. The lubricant oil samples were collected for every 300 h of test duration for oil degradation and wear particle analyses by using Fourier transform infrared radiation (FTIR) and scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDS) techniques, respectively. FTIR results provided specific chemical bonds and functional groups contained in the degraded oil. The vibration signals were acquired for every 100 h of operation, and a fast Fourier transform (FFT) frequency spectrum technique was employed for vibration signal analysis. The friction coefficient and specific wear rate parameters were considered to evaluate the tribological performance of the journal-bearing system. Statistical parameters, namely root-mean-square and kurtosis, were evaluated. Wear mechanisms such as abrasive, adhesive and surface fatigue wear were observed on the journal-bearing contact surfaces using a USB optical microscope. The scoring on the bearing element confirmed the fault development and resulted in an increase in vibration amplitudes. Higher mass loss in the bearing material was observed due to high friction and wear rates owing to its being a softer material than that of the journal material. The results obtained from the aforementioned parameter assessment techniques provided a reliable information on the defects which appeared on journal-bearing contact surfaces.

Solvothermal single‐pot synthesis of Pd‐Fe3O4@GO catalyst: Enhanced catalytic performance in Sonogashira coupling reactions

In this study, we present a new approach to synthesizing a magnetically separable Pd‐Fe3O4@GO catalyst using a simple single‐pot method. The catalyst was employed in Sonogashira coupling reactions, demonstrating excellent results. The catalyst was studied using a various characterization method, including X‐ray photoelectron spectroscopy (XPS), scanning electron microscope–energy‐dispersive X‐ray spectroscopy (SEM‐EDS) mapping, TEM, X‐ray diffraction (XRD), FTIR, and inductively coupled plasma mass spectrometry (ICP‐MS). Pd‐Fe3O4@GO exhibited superior catalytic activity compared with its conventional counterparts in phenylacetylene‐iodobenzene coupling reactions under copper co‐catalyzed‐free and ligand‐free conditions, with a higher turnover frequency (TOF) of 118.3 h−1. Optimized conditions yielded high yields for various substrates, including inactive aryl chloride and bromide substrates, emphasizing its versatility. Also, a reaction mechanism was proposed and a kinetic model was developed. The catalyst's green chemistry potential was highlighted because of its high efficiency, purity of products, recoverability, and ease of preparation. Moreover, Pd‐Fe3O4@GO demonstrated impressive stability through multiple recycling rounds without loss of functionality, making it a promising tool for sustainable chemical processes.

Evaluating the effectiveness of coagulation–flocculation treatment on a wastewater from the moroccan leather tanning industry : An ecological approach

The removal of pollutants from tannery wastewaters, which is renowned for its substantial volumes, intricate composition, and considerable hazards to human health and the environment, is a prominent research area in the field of water treatment. The aim of this study is to employ a bio-coagulant derived from Parkinsonia aculeata seeds and a bio-flocculant derived from Hibiscus esculentus to minimise the concentration of pollutants in the combined wastewater originating from tanneries. In the course of the research, a thorough physicochemical analysis of the coagulating and flocculating agents, Parkinsonia aculeata (PA) and Hibiscus esculentus (HE), was performed using techniques such as XRD (X-ray diffraction), FTIR (Fourier-transform infrared spectroscopy), and SEM-EDS (scanning electron microscopy-energy dispersive X-ray spectroscopy). This analysis aimed to determine the composition and characteristics of these biomasses. Subsequently, a comprehensive overview was conducted to summarize the various factors that influence the treatment of tannery wastewater through coagulation/flocculation. This was accomplished by manipulating the target factors and observing their impact on the removal of specific physicochemical parameters such as chemical oxygen demand (COD), electrical conductivity (EC), total chromium (Cr) and Optical density (OD). The variables that were established include pH, dosage of coagulant and flocculant, as well as the speed and duration of agitation in both the fast and slow mixing stages. The experiments were carried out while taking into account the optimal parameters, leading to the near-complete removal of all analyzed pollutants. The optimal requirements for the Parkinsonia aculeata-Hibiscus esculentus Coagulation Flocculation System involve adjusting the pH to 8, choosing concentrations of approximately 1.25 g L−1 and 0.6 g L−1 for the coagulant and flocculant respectively, maintaining a fast speed of 170 rpm for 3 min while keeping the slow agitation at around 30 rpm for 20 min. The removal rates achieved after treating tannery wastewater using the PA-HE coagulant-flocculant combination demonstrate high efficacy, with values reaching approximately 100% for TSS, 98.71% for BOD5, 99.93% for COD, 98.88% for NH4+, 98.21% for NO3−, 90.32% for NO2−, 93.13% for SO42−, 95.44% for PO43−, 96.08% for OD and 60% for total chromium. These results indicate the successful removal of a wide range of pollutants from tannery wastewater through the PA-HE treatment method. In predicting the CF treatment approach, PCA has been employed to preprocess the input data and determine the key variables that impact the process. This can streamline the modeling process and enhance the precision of the predictions.

Microdistribution and Mode of Rare Earth Element Occurrence in the Zhijin Rare Earth Element-Bearing Phosphate Deposit, Guizhou, China

Rare-earth elements (REEs) are often highly concentrated in sedimentary phosphate deposits, and the microdistribution characteristics and occurrence state of rare earth in these deposits play a crucial role in the overall development and utilization of mineral resources. This study aims to analyze the microdistribution of REEs in REE-bearing phosphate deposits in the Zhijin region of Guizhou at the microstructural level and investigate their occurrence modes. Specifically, rock and mineral identification, X-ray diffraction (XRD), scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDS), and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) were utilized to analyze the samples. The correlation between the distribution of REEs and phosphorus was examined. In addition, the microdistribution of REEs in specific mineral phases and the locations of their occurrence were investigated. The analysis revealed that no REEs existed independently in the deposit. Instead, the distribution of REEs was highly consistent and significantly positively correlated with that of phosphorus. In the microarea structure, REEs were predominantly found both in particles, such as bioclasts, sand debris, and agglomerates, and in phosphate cement, where the main mineral components were collophane and apatite. Conversely, the content of REEs in dolomitized sand debris edges, sparry dolomitic cement, and siliceous cement was considerably lower. Based on these findings, it is speculated that REEs primarily occur within the lattice defects of apatite or on the surface of collophanite. There is a notable contrast in the REE content between the unaltered sand debris at the periphery and the dolomitized sand debris, indicating that the dolomitization in the diagenetic stage resulted in a depletion of REE abundance in the ore. Obviously, the dominant gangue mineral, dolomite, does not serve as the primary host for REEs. Furthermore, the highest concentration of REEs was inside organisms. This finding suggests that the high content of REEs in biological soft tissue may remain under the influence of waves and tides, and REE-bearing apatite may be preferentially separated and fill the cavities of deceased organisms. The second highest content of REEs was found in the shells of organisms, indicating that small shelly organisms absorb phosphorus materials through their life activities to construct their shells, resulting in REE enrichment. Quantitative analysis through sequential extraction procedures displayed that most REEs were present in the residual state, with a smaller portion combined with organic matter. These results confirm that REEs in the Zhijin phosphate deposits primarily exist as isomorphic substitutions in the lattice defects of apatite, with a secondary occurrence as organic matter-bound REEs.