Search Results (20)

Rare earth elements (REE) are critical to 21st-century technology, from electronics and defense applications to renewables and beyond. The processing of REE is primarily based on minerals (bastnasite, monazite, and xenotime), but alternative resources (coal ash, E-waste, and permanent magnets) are also gaining increasing interest. Adsorption remains one of the most efficient, environmentally friendly extraction methods despite its lengthy mixing time. In the present research article, a hemp biochar prepared by vacuum pyrolysis at 700 °C was examined for its applicability in the adsorption of selected REE (La³⁺, Nd³⁺, Dy³⁺) from synthetic solutions. An innovative technique, Resonant Vibratory Mixing (RVM), was applied to improve adsorption kinetics, with factors including time (5–30 min) and intensity (30–70%) at room temperature. Using the Thermo Scientific 4000 M shaker for mixing, the maximum adsorption capacities were 77.56 mg/g for Dy³⁺, 75.85 mg/g for La³⁺, and 72.65 mg/g for Nd³⁺ using 100 mg of hemp biochar and 10 mL solutions (1000 mg/L). The adsorption capacity of 100 mg hemp biochar was 79.79 mg/g for Dy³⁺, followed by 77.61 mg/g for La³⁺ and 75.75 mg/g for Nd³⁺, using RVM for only 40 min at 70% intensity. RVM increased the adsorption capacities of all REE in only 40 min. Surface and structural analyses were carried out using Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer-Emmett-Teller analysis (BET), Zeta Potential, and Carbon/Hydrogen/Nitrogen (CHN) methods. The adsorption recoveries of all REE in the single-element system were higher than 98.5%. However, in a multi-element system, the adsorption recoveries of La³⁺, Nd³⁺, and Dy³⁺ were 83.7%, 96.2%, and 99.2%, respectively, demonstrating that hemp biochar has low selectivity for Dy³⁺ and Nd³⁺. The adsorption process could be well described by the Langmuir isotherm and the pseudo-second-order kinetic model, indicating monolayer adsorption and chemical process involvement. Based on the characterization analysis of hemp biochar, electrostatic interaction was the dominant mechanism in this study. REE desorption using 0.5 M nitric acid was the most efficient, with >80% of REE recovered. The combination of hemp biochar as an adsorbent and RVM as a mixing technique demonstrated excellent performance in synthetic solutions; the reusability and application of hemp biochar to natural solutions require further study. Full article

Marine transportation and storage of liquid hydrogen (LH2) has gained increasing interest, while potential LH2 membrane-type tanks could utilize 316L corrugated austenitic stainless-steel sheets. The corrugation process results in a strain-induced martensitic transformation in the material, introducing rapid diffusion pathways for hydrogen atoms and promoting the formation of hydrogen-trapping sites that alter hydrogen transport and reduce the material’s resistance to hydrogen embrittlement. In this study, 316L sheets were subjected to different levels of uniaxial pre-strain (10, 20, 30, and 40%) with two different strain-rates, to replicate the varying degrees of pre-deformation caused by the corrugation. Microstructural analysis using Electron Backscatter Diffraction (EBSD) (Thermo Fisher Scientific, Waltham, MA, USA) and X-Ray Diffraction (XRD) (Bruker, Billerica, MA, USA) combined with quantitative phase analysis using the Rietveld Method on XRD data, provided valuable insights into the induced phase transformations. Cathodic hydrogen charging method was implemented on as-received and pre-strained material, followed by slow strain rate tensile testing (SSRT) and thermal desorption spectroscopy (TDS) to examine the hydrogen effect on each condition. Experimental results indicated that although 316L exhibits considerable phase stability, it undergoes strain-induced phase transformation resulting in a significant amount of martensite, reaching 5% in the 40% pre-strained condition. Pre-deformation increased hydrogen embrittlement, as evidenced by fractographic analysis which indicated a Relative Reduction of Area (RRA) of 0.83, and by increased hydrogen uptake. These findings contribute to a better understanding of phase transformations and the role of hydrogen in austenitic stainless steels. Full article

International efforts are being made to reduce environmental pollution caused by microplastics (MPs). Microplastics are released into the environment through sewage treatment sludge, and the use of sludge as a soil improvement agent is increasing rapidly, emphasising the importance of controlling microplastics in sewage treatment facilities. The release of microplastics into the environment is an increasingly significant concern, with sources including sewage treatment sludge. This study focuses on the analysis of microplastics in sewage sludge using optical (Fourier-transform infrared spectroscopy, FTIR) and thermal (Thermo Extraction Desorption–Gas Chromatograph–Mass Spectroscopy, TED-GC-MS) processing-based analytical equipment. The average amount of MPs in the sewage sludge analysed using FTIR was 228.5 microplastics/g of sludge (MPs/g), primarily of the polypropylene type. Approximately 75% of the MPs were 0.1 mm in size or smaller. However, the average amount of MPs in the sewage sludge determined using TED-GC-MS was 95.79 µg-MPs/g. For the systematic management of microplastics, it is important to estimate the amount of microplastics generated by sewage treatment plants. Therefore, a microplastic generation calculation formula was proposed and used to estimate the potential microplastic generation in sewage treatment plants. The total amount of MPs generated from sewage treatment plants in South Korea, calculated using the equation, was approximately 364 ton/yr; we further divided the total amount by administrative regions. The findings of this study can be applied to assess global trends in MP research. Full article

Bioactive glass is currently considered a material with a high biocompatibility and has been used both in the field of bone regeneration and in the preparation of cosmetic products with the controlled release of active compounds. The present work involved a study on the synthesis of bioglass using the sol–gel process. The study aims to evaluate the influence of the treatment of bioglass with Polyethylene glycol 4000 (PEG 4000) on its main characteristics. The surface characteristics of this material were obtained by nitrogen adsorption/desorption analysis, using the standard BET (Brunauer–Emmett–Teller) equation, the crystallinity by XRD (X-ray diffraction) analysis, the surface structure by SEM (Scanning Electron Microscope), thermal stability by TGA (ThermoGravimetric Analyses), and chemical bonds changes by FTIR (Fourier transform infrared) spectroscopy. After treatment with PEG 4000, the average diameter of the pores increased insignificantly, the crystallinity peak disappeared, and the SEM analysis highlighted several clusters of very small sizes. Full article

In order to study the synergistic effects of exogenous catalysts and in situ minerals in the reservoir during heavy oil aquathermolysis, in this paper, a series of simple supported transition metal complexes were prepared using sodium citrate, chloride salts and bentonite, and their catalytic viscosity reduction performances for heavy oil were investigated. Bentonite complex catalyst marked as B@Zn(II)L appears to be the most effective complex. B@Zn(II)L was characterized by scanning electron microscopy (SEM), Fourier-Transform Infrared (FTIR) spectroscopy, thermo-gravimetric analysis (TGA) and N2 adsorption–desorption isotherms. Under optimized conditions, the viscosity of the heavy oil was decreased by 88.3%. The reaction temperature was reduced by about 70 °C compared with the traditional reaction. The results of the group composition analysis and the elemental content of the heavy oil indicate that the resin and asphaltene content decreases, and the saturated and aromatic HC content increases. The results of TGA and DSC of the heavy oil show that the macromolecular substances in the heavy oil were cracked into small molecules with low boiling points by the reaction. GC-MS examination of water-soluble polar compounds post-reaction indicates that B@Zn(II)L can diminish the quantity of polar substances in heavy oil and lower the aromatic nature of these compounds. Thiophene and quinoline were utilized as model compounds to investigate the reaction mechanism. GC-MS analysis revealed that C-C, C-N and C-S bonds were cleaved during the reaction, leading to a decrease in the viscosity of heavy oil. Full article

In this paper, the synthesis, characterization, and properties of crosslinked poly(ε-caprolactone)-based polyurethanes as potential tissue replacement materials are reported. The polyurethane prepolymers were prepared from poly(ε-caprolactone)diol (PCD), polyethylene glycol (PEG)/polylactic acid diol (PLAD), and 1,6-hexamethylene diisocyanate (HDI). In these segmented polyurethanes, the role of PEG/PLAD was to tune the hydrophobic/hydrophilic character of the resulting polymer while sucrose served as a crosslinking agent. PLAD was synthesized by the polycondensation reaction of D,L-lactic acid and investigated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and nuclear magnetic resonance spectroscopy (NMR). The crosslinked polyurethane samples (SUPURs) obtained were characterized by attenuated total reflectance Fourier-transform infrared spectroscopy (AT-FT-IR), swelling, and mechanical (uniaxial tensile tests) experiments. The thermo and thermomechanical behavior were studied by differential scanning calorimetry (DSC) and dynamical mechanical analysis (DMA). The viability of dental pulp stem cells was investigated in the case of polyurethanes composed of fully biocompatible elements. In our studies, none of our polymers showed toxicity to stem cells (DPSCs). Full article

In this study, a V₂O₅-Sb₂O₃/TiO₂ monolithic catalyst was modified by introducing WO₃. The WO₃-modified catalyst exhibited enhanced catalytic activity in the measuring temperature range of 175–320 °C. The changes in dispersion of vanadia species were investigated by ultraviolet-visible (UV-Vis) spectroscopy and H₂ temperature-programmed reduction (H₂-TPR). A durability test was conducted in a wet SO₂-containing atmosphere at 220 °C for 25 h. The sulfate deposition was estimated by temperature-programmed decomposition (TPDC) of sulfates, thermo-gravimetric (TG) analysis, and temperature-programmed desorption (TPD) of NH₃. Isothermal SO₂ oxidation and temperature-programmed surface reaction (TPSR) of NH₄HSO₄ with NO were performed. Based on these characterizations, effects of WO₃ modification on the sulfate tolerance of the catalyst were explored. Full article

An aqueous impregnation method using manganese (II) nitrate precursor, followed by calcination at 400 °C, was carried out for the preparation of manganese doped hydroxyapatite catalysts (MnxHap; x = Mn wt.%: 2.5, 5.0, 10, 20, and 30 based on MnO₂). Methods of characterization including inductively coupled plasma spectroscopy (ICP), N₂ physisorption, X-ray Diffraction (XRD), Fourier-Transform Transmission Infrared (FT-IR), Raman, and Thermal gravimetric analysis (TGA/MS) analysis were used for the identification of Mn species and its surrounding environment. Raman spectroscopy indicated the presence of the ε-MnO₂ phase for Mn20Hap and Mn30Hap in agreement with the XRD results and the presence of β-MnOOH species for Mn5Hap and Mn10Hap. The formaldehyde total oxidation was investigated on these catalysts and it was shown that Mn5Hap was the most active catalyst, achieving a normalized rate of formaldehyde (HCHO) conversion into CO₂ per mole of Mn of 0.042 h⁻¹ at a temperature of 145 °C. The well dispersed oxidized manganese species on Hap with a medium Mn AOS (average oxidation state) were mainly responsible for this performance. Since HCHO was retained on the surface of all catalysts during the catalytic test, the combined Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFT) experiment at room temperature and thermodesorption (TD)-FTIR identified formate species as their oxidation consumed surface OH groups. A stability test and moisture effect study showed that the presence of water vapor has a beneficial effect on the performances of the catalyst. Full article

A series of Mn_0.15Fe_0.05/fly-ash catalysts have been synthesized by the co-precipitation method using coal fly ash (FA) as the catalyst carrier. The catalyst showed high catalytic activity for low-temperature selective catalytic reduction (LTSCR) of NO with NH₃. The catalytic reaction experiments were carried out using a lab-scale fixed-bed reactor. De-NO_x experimental results showed the use of optimum weight ratio of Mn/FA and Fe/FA, resulted in high NH₃-SCR (selective catalytic reduction) activity with a broad operating temperature range (130–300 °C) under 50000 h⁻¹. Various characterization methods were used to understand the role of the physicochemical structure of the synthesized catalysts on their De-NO_x capability. The scanning electron microscopy, physical adsorption-desorption, and X-ray photoelectron spectroscopy showed the interaction among the MnO_x, FeO_x, and the substrate increased the surface area, the amount of high valence metal state (Mn⁴⁺, Mn³⁺, and Fe³⁺), and the surface adsorbed oxygen. Hence, redox cycles (Fe³⁺ + Mn²⁺ ↔ Mn³⁺ + Fe²⁺; Fe²⁺ + Mn⁴⁺ ↔ Mn³⁺ + Fe³⁺) were co-promoted over the catalyst. The balance between the adsorption ability of the reactants and the redox ability can promote the excellent NO_x conversion ability of the catalyst at low temperatures. Furthermore, NH₃/NO temperature-programmed desorption, NH₃/NO- thermo gravimetric-mass spectrometry (NH₃/NO-TG-MS), and in-situ DRIFTs (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) results showed the Mn_0.15Fe_0.05/FA has relatively high adsorption capacity and activation capability of reactants (NO, O₂, and NH₃) at low temperatures. These results also showed that the Langmuir–Hinshelwood (L–H) reaction mechanism is the main reaction mechanism through which NH₃-SCR reactions took place. This work is important for synthesizing an efficient and environmentally-friendly catalyst and demonstrates a promising waste-utilization strategy. Full article

To reveal the nature of SO₂ poisoning over Cu-SSZ-13 catalyst under actual exhaust conditions, the catalyst was pretreated at 200 and 500 °C in a flow containing NH₃, NO, O₂, SO₂, and H₂O. Brunner−Emmet−Teller (BET), X-ray diffraction(XRD), thermo gravimetric analyzer (TGA), ultraviolet Raman spectroscopy (UV Raman), temperature-programmed reduction with H₂ (H₂-TPR), temperature-programmed desorption of NO+O₂ (NO+O₂-TPD), NH₃-TPD, in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS), and an activity test were utilized to monitor the changes of Cu-SSZ-13 before and after in situ SO₂ poisoning. According to the characterization results, the types and generated amount of sulfated species were directly related to poisoning temperature. Three sulfate species, including (NH₄)₂SO₄, CuSO₄, and Al₂(SO₄)₃, were found to form on CZ-S-200, while only the latter two sulfate species were observed over CZ-S-500. Furthermore, SO₂ poisoning had a negative effect on low-temperature selective catalytic reduction (SCR) activity, which was mainly due to the sulfation of active sites, including Z₂Cu, ZCuOH, and Si-O(H)-Al. In contrast, SO₂ poisoning had a positive effect on high-temperature SCR activity, owing to the inhibition of the NH₃ oxidation reaction. The above findings may be a useful guideline to design excellent SO₂-resistant Cu-based zeolite catalysts. Full article

Carbon-based solid acid catalysts were prepared using rice straw (RS) waste, and the effects of carbonization temperature and sulfonation temperature on the catalytic activity were investigated. The properties of the catalysts were characterized using thermo gravimetric (TG), scanning electron microscope (SEM), Brunauer–Emmet–Teller (BET), Fourier transform infrared spectroscopy (FT-IR), temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS), and their activities were investigated through the hydration of α-pinene. The conversion of α-pinene and the selectivity of α-terpineol reached 67.60% and 57.07% at 80 °C and atmospheric pressure in 24 h, respectively. The high catalytic capacity of the catalyst is attributed to the high acid site density and high porosity of the catalyst. TPD analysis and FT-IR spectroscopy showed that the catalyst produced by low-temperature carbonization at 300 °C followed by low-temperature sulfonation at 80 °C had abundant strong acid sites (0.82 mmol/g), which can effectively inhibit the side reactions of hydrated α-pinene. The total acidity reached 2.87 mmol/g. N₂-physisorption analysis clearly indicated that the obtained catalysts were mesopore-predominant materials, and the S_BET and V_Total of catalysts reached 420.9 m²/g and 4.048 cm³/g, respectively. Preparation of the catalyst involves low energy consumption, and its cheap raw materials make the whole process simple, economical, and environmentally friendly. Full article

In this work, the thermo-sensitive materials N-isopropylacrylamide (NIPAM) and acrylic acid (AA) were crosslinked with carboxymethyl cellulose (CMC) (CMC/P (NIPAM-co-AA)) via a free radical polymerization method for the removal of U(VI) from aqueous solution. The L16 (4⁵) orthogonal experiments were designed for the optimization of the synthesis condition. The chemical structures of the crosslinking hydrogel were confirmed by FTIR spectroscopy. The microstructural analyses were conducted though scanning electron microscopy (SEM) to show the pore structure of the hydrogel. The adsorption performance of the CMC/P (NIPAM-co-AA) hydrogel for the uptake of U(VI) from simulated wastewater was also investigated. The adsorption reached equilibrium within 1 h. Under the reaction of pH = 6 and a temperature of 298 K, an initial concentration of U(VI) of 5 mg·L⁻¹, and 10 mg of the CMC/P(NIPAM-co-AA) hydrogel, the maximum adsorption capacity was 14.69 mg g⁻¹. The kinetics fitted perfectly with the pseudo-second-order model, and the isotherms for the composite hydrogel adsorption of U(VI) was in accordance with the Langmuir model. The chemical modification confirmed that the acylamino group played an important role in uranium adsorption. The desorption and reusability study revealed that the resolution rate was still available at approximately 77.74% after five alternate heating cycles at 20 and 50 °C of adsorption-desorption. Full article

While the overwhelming number of papers on multi-principal-element alloys (MPEAs) focus on the mechanical and microstructural properties, there has been growing interest in these alloys as solid-state hydrogen stores. We report here the synthesis optimization, the physicochemical and the hydrogen sorption properties of Ti_0.325V_0.275Zr_0.125Nb_0.275. This alloy was prepared by two methods, high temperature arc melting and ball milling under Ar, and crystallizes into a single-phase bcc structure. This MPEA shows a single transition from the initial bcc phase to a final bct dihydride and a maximum uptake of 1.7 H/M (2.5 wt%). Interestingly, the bct dihydride phase can be directly obtained by reactive ball milling under hydrogen pressure. The hydrogen desorption properties of the hydrides obtained by hydrogenation of the alloy prepared by arc melting or ball milling and by reactive ball milling have been compared. The best hydrogen sorption properties are shown by the material prepared by reactive ball milling. Despite a fading of the capacity for the first cycles, the reversible capacity of the latter material stabilizes around 2 wt%. To complement the experimental approach, a theoretical investigation combining a random distribution technique and first principle calculation was done to estimate the stability of the hydride. Full article

In this study, oxide materials La_1−xCa_xScO_3−α (x = 0.03, 0.05 and 0.10) were synthesized by the citric-nitrate combustion method. Single-phase solid solutions were obtained in the case of calcium content x = 0.03 and 0.05, whereas a calcium-enriched impurity phase was found at x = 0.10. Water uptake and release were studied by means of thermogravimetric analysis, thermodesorption spectroscopy and dilatometry. It was shown that lower calcium content in the main phase leads to a decrease in the water uptake. Conductivity was measured by four-probe direct current (DC) and two-probe ascension current (AC) methods at different temperatures, pO₂ and pH₂O. The effects of phase composition, microstructure and defect structure on electrical conductivity, as well as correlation between conductivity and water uptake experiments, were discussed. The contribution of ionic conductivity of La_1−xCa_xScO_3−α rises with decreasing temperature and increasing humidity. The domination of proton conductivity at temperatures below 500 °C under oxidizing and reducing atmospheres is exhibited. Water uptake and release as well as transport properties of La_1−xCa_xScO_3−α are compared with the properties of similar proton electrolytes, La_1−xSr_xScO_3−α, and the possible reasons for their differences were discussed. Full article

In this study, a novel green adsorbent material prepared by the esterification of bacterial cellulose (BC) and graphene oxide (GO), richly containing hydroxyl, alkyl, and carboxylate groups was characterised by FTIR (Fourier Transform infrared spectroscopy), XRD (X-ray diffraction), SEM (Scanning electron microscopy) and TGA (Thermo-graphimetric analysis). The specific surface area (SSA) and pore size distribution (PSD) analysis of materials were also analysed. Batch experiments–adsorption studies confirmed the material to have a very high Pb²⁺ removal efficiency of over 90% at pH 6–8. Kinetic studies showed that the uptake of metal ions was rapid with equilibrium attained after 30 min and fitted well with the pseudo-second-order rate model (PSO). Isotherm results with a maximum adsorption capacity (Q_max) of 303.03 mg/g were well described by Langmuir’s model compared to Freundlich. Desorption and re-adsorption experiments realised that both adsorbent and adsorbates could be over 90–95% efficiently recovered and reused using 0.1 M HNO₃ and 0.1 M HCl. Full article