Search Results (119)

The alloy Pr${}_2$Fe${}_{16.75}$Ni${}_{0.25}$ has been examined to investigate its structural properties, critical behavior, and magnetocaloric effects. Rietveld’s refinement of X-ray diffraction patterns has revealed a rhombohedral structure with an $R\overline{3}m$ space group. Pr${}_2$Fe${}_{16.9}$Ni${}_{0.25}$ also demonstrates a direct magnetocaloric effect near room temperature, accompanied by a moderate magnetic entropy change ($-\Delta S_M^{\max }$ = 5.5 J kg${}^{-1}$ K${}^{-1}$ at ${\mu }_0\Delta H=5$ T) and a broad working temperature range. Furthermore, the Relative Cooling Power (RCP) is approximately 89% of the widely recognized gadolinium (Gd) for ${\mu }_0\Delta H=2$ T. This compound exhibits a commendable magnetocaloric response, on par with or even surpassing that of numerous other intermetallic alloys. Critical behavior was analyzed using thermo-magnetic measurements, employing methods such as the modified Arrott plot, critical isotherm analysis, and Kouvel-Fisher techniques. The obtained critical exponents ($\beta$, $\gamma$, and $\delta$) exhibit similarities to those of the 3D-Ising model, characterized explicitly by intermediate range interactions. Full article

Industrialization and modernization have significantly improved the quality of life but have also led to substantial pollution. Cost-effective technologies are urgently needed to mitigate emissions from major polluting sectors, such as the automotive and transport industries. In this study, we synthesized naturally derived, kapok-based porous carbon fibers (KP-PCFs) with hollow structures. We investigated their adsorption/desorption behavior for the greenhouse gas n-butane following ASTM D5228 standards. Scanning electron microscopy and X-ray diffraction analyses were conducted to examine changes in fiber diameter and crystalline structure under different activation times. The micropore properties of KP-PCFs were characterized using Brunauer–Emmett–Teller, t-plot, and non-localized density functional theory models based on N₂/77K adsorption isotherm data. The specific surface area and total pore volume ranged from 500 to 1100 m²/g and 0.24 to 0.60 cm³/g, respectively, while the micropore and mesopore volumes were 0.20–0.45 cm³/g and 0.04–0.15 cm³/g, respectively. With increasing activation time, the n-butane adsorption capacity improved from 62.2% to 73.5%, whereas retentivity (residual adsorbate) decreased from 6.0% to 1.3%. The adsorption/desorption rate was highly correlated with pore diameter: adsorption capacity was highest for diameters of 1.5–2.5 nm, while retentivity was greatest for diameters of 3.5–5.0 nm. Full article

The iron and steel industry is a major emitter of carbon. In the context of China’s dual-carbon goals, hydrogen-based reduction ironmaking technology has garnered unprecedented attention. It is considered a crucial approach to reducing carbon dioxide emissions in the steel sector and facilitating the realization of carbon neutrality. This work conducted isothermal thermogravimetric analysis on limonite ore in a N₂/H₂ atmosphere. The influences of reduction temperature, particle size, and hydrogen partial pressure on the hydrogen reduction reaction process of limonite were investigated. Based on the principles of isothermal thermal analysis kinetics and the unreacted core model for flat-plate particles, the mechanism function and kinetic parameters for the reduction of limonite particles were determined. The research results show that the hydrogen reduction process of limonite ore is influenced by multiple factors, including temperature, hydrogen partial pressure, and particle size. Increasing the reduction temperature and hydrogen partial pressure can significantly speed up the reduction reaction rate and enhance the degree of reduction. The kinetic parameters for the hydrogen reduction of limonite particles were obtained as follows: the reaction activation energy was 44.738 kJ·mol⁻¹, the pre-exponential factor was 31.438 m·s⁻¹, and the rate constant for the hydrogen reduction of limonite was $k=31.438\times e^{-{\displaystyle \frac{44.738\times 1000}{RT}}}\mathrm{m}\cdot {\mathrm{s}}^{-1}$. In addition, contour maps were plotted to predict the reaction time and reaction temperature required for a complete reduction of limonite particles of different sizes to iron (Fe) particles under varying hydrogen partial pressures. The research findings can serve as a scientific basis for optimizing hydrogen-based reduction ironmaking technology in the iron and steel industry and achieving carbon neutrality goals. Full article

The inhibitory effect of the alkaloid extract from Chimarrhis cymosa on C38 steel corrosion in 1M HCl was examined through electrochemical investigations. An inhibition efficiency of 90% was achieved with 200 mg/L of the alkaloid extract from Chimarrhis cymosa at 25 °C. Potentiodynamic polarization revealed that the extract acts as a mixed-type inhibitor. Nyquist plots showed that an increase in the concentration of the alkaloid extract from Chimarrhis cymosa led to an increase in charge-transfer resistance and a decrease in double-layer capacitance, resulting in enhanced inhibition efficiency. The adsorption of inhibitor molecules followed the Langmuir adsorption isotherm. XPS analysis confirmed the formation of an inhibitor layer on the steel surface containing the Chimarrhis cymosa alkaloidic extract. Full article

Preventing metal corrosion is one of the most pressing issues in the modern world. One of the most effective ways to combat corrosion is to use inhibitors. Currently, much research is devoted to the study of green corrosion inhibitors obtained from plant extracts and agricultural waste. In this study, banana peel extract, rice straw extract, and their mixture as green corrosion inhibitors of carbon steel samples in 1 M HCl solution were examined by weight loss, electrochemical, and scanning electron microscopy methods. The experimental results showed that the mixture of extracts (40:60 banana peel and rice straw) had a higher inhibitory capacity than the individual inhibitors. At 750 ppm after 24 h of immersion, the inhibition of banana peel, rice extract, and the suggested mixture was 77.87, 95.03, and 96.36%, respectively. Furthermore, the mixture exhibited a maximum synergistic inhibition value of 1.65, indicating a 65% increase in inhibition efficiency when using the mixture instead of the extract alone. Nyquist plots obtained from electrochemical experiments confirmed the optimum concentration value of 750 ppm for banana peel extract, rice extract, and their mixture. These tests also show that the diameter of the semicircles in the presence of the mixture was larger than in the case of the extract alone, indicating a higher inhibitory capacity of the mixture. Moreover, scanning electron microscopy analysis showed the formation of a stable protective film on the metal surface. Finally, adsorption analysis showed the presence of both physical and chemical adsorptions of all the extracts used, which was obtained using the Langmuir isotherm. Full article

Dye wastewater poses significant risks to human health and aquatic ecosystems, necessitating efficient remediation strategies. This study developed a magnetic Fe₂O₃ nanocomposite (MNC) derived from phosphoric acid-treated walnut shell biomass carbon to remove Alizarin red S (AR) dye from polluted water. Characterization techniques confirmed the nanocomposite’s mesoporous structure, superparamagnetic properties (61.5 emu/g), and high crystallinity. Optimization using Response Surface Methodology (RSM) revealed a maximum adsorption efficiency of 94.04% under the following optimal conditions: A pH of 2, AR dye concentration of 85 mg/L, adsorbent dose of 1.5 g/L, and particle size of 448.1 nm. Adsorption followed pseudo-second-order (PSO) kinetics (R² = 0.9999) and Langmuir isotherm models (R² = 0.9983), with thermodynamic studies indicating spontaneous and endothermic chemisorption. The intra-particle diffusion model, Bangham, and Boyd plots describe the adsorption process, and external boundary layer diffusion of AR dye molecules in the aqueous phase limits the adsorbate removal rate. Regeneration tests demonstrated reusability over three cycles, with a desorption efficiency of 50.52% using 30 mM HCl. The MNC exhibited a maximum adsorption capacity (Q_max) of 115.35 mg/g, outperforming other adsorbents, making it an efficient and sustainable alternative solution for AR dye removal from water bodies. Full article

A novel tera-dentate salen ligand and its Fe(III) complex was synthesized and characterized via several spectroscopic and physicochemical techniques. The corrosion rate inhibition of nickel and its alloys inspired the utilization of the L ligand and its FeL complex as vital and eco-friendly inhibitors. To assess their effectiveness, both Tafel plot analysis and electrochemical impedance spectroscopy were employed to examine the electrochemical properties of L and the FeL complex. The results show that corrosion current density (I_corr) steadily drops when the additive concentration is increased, but the inhibition efficiency increases. It has been observed that the efficiency of inhibition rises with temperature, particularly at high temperatures (55 °C) when 1 × 10⁻³ M of L and FeL are present as additives, with η = 90.5% and 92.7%, respectively. Additionally, the findings propose that the adsorption mechanism of both L and FeL additive reptiles follows the Langmuir design isotherm. Electrochemical impedance spectroscopy has also verified these findings. DFT calculations were employed to prove the structure of the investigated FeL complex and its activity as a corrosion inhibitor. Full article

This study evaluates the combined use of mobile transects and fixed stations to analyze atmospheric urban heat islands (UHIs’a) in Temuco, Chile. Data were collected using 23 fixed stations and 3 mobile transects traversing predefined city routes, capturing temperature records at one-minute intervals. Results revealed moderate correlations between methodologies (coefficients: 0.55–0.62) and average temperature differences of 0.72 °C to 1.6 °C, confirming their compatibility for integrated use. UHI intensities ranged from weak (0.5 °C) to extremely strong (13 °C), with the highest urban temperature (33.1 °C) observed in Zone Z-3, contrasting with 25.4 °C at the rural Maquehue station. Simulations and isothermal maps identified four UHI zones, highlighting the influence of impervious surfaces, traffic density, and limited vegetation on temperature distribution. Fluctuation plots revealed rapid cooling in vegetated areas and high heat retention in dense urban zones. These findings validate the methodologies for spatial and temporal UHI analysis and provide actionable insights for urban planning. Targeted interventions, such as increasing vegetation in high-risk zones, are recommended to mitigate extreme heat and enhance thermal comfort in urban areas. Full article

Hydrophobic modification alters the properties of Pluronic F127 to form micelles more efficiently and enhances its drug-loading capacity. However, selecting the appropriate hydrophobic group for modification is laborious. In this paper, we propose an efficient approach for predicting key parameters to select hydrophobic groups for F127 modification prior to synthesis, in order to improve the formability and stability of the micelles. The results of nuclear magnetic resonance and isothermal titration calorimetry were utilized to establish a function for predicting the hydrophile–lipophile balance, critical micelle concentration, and Gibbs free energy of the products based on the structure of raw material. These predicted values can assist us in selecting suitable hydrophobic groups for F127 modification. Subsequently, we successfully tested our method and validated our work using pharmaceutical evaluation methods, such as appearance observation, particle size measurement, drug loading determination, equilibrium binding rate assessment, storage stability testing, and the plotting of accumulation release curves. Therefore, we suggest that our work could provide a model linking the molecular structure to properties, with the purpose of pre-selecting modification products that have advantages in micelle preparation. This can facilitate the application of F127 in preparing nano-micelles. Full article

The textural properties of synthetic and natural clays in the sodium form and exchanged with tetramethylammonium cations (TMA⁺) were characterized using N₂ and Ar physisorption isotherms at cryogenic temperatures. Specific surface areas and micro/mesoporous volumes were determined using the BET and the t-plot models. The t-plot analysis requires the use of reference isotherms measured at the same temperature on the surface of non-porous materials with an identical chemical composition. In order to better assess the effects of chemical heterogeneities in the clay particles, reference isotherms representative of silica surfaces were taken into account in the analysis of the t-curve and corrected to account for variations in curvature at the interface of the film adsorbed in the micropores. In addition, high-resolution Ar adsorption isotherms at 87 K were analyzed using the Derivative Isotherm Summation (DIS) method to quantify the energy contributions of adsorption sites and determine the fractions of basal and lateral surfaces of clay particles. The high-energy adsorption sites, identified in the low-pressure range, were attributed to intra-particle microporosity due to stacking defects and/or open inter-layer spaces. These sites were differentiated from those on the lateral and basal surfaces of the particles. A modification of the DIS method was proposed to measure these contributions and improve the fit with the experimental data. The results show that TMA⁺ cation exchange significantly increases the microporosity of clays compared to their sodic form, which can be attributed to the increased contribution of intra-particle adsorption sites due to interlayer expansion. Full article

Modification of titanium dioxide using ethylenediamine (EDA), diethylamine (DEA), and triethylamine (TEA) has been studied. As the reference material, titanium dioxide prepared by the sol–gel method using titanium(IV) isopropoxide as a precursor was applied. The preparation procedure involved heat treatment in the microwave reactor or in the high-temperature furnace. The obtained samples have been characterized in detail. The phase composition was determined through the X-ray diffraction method, and the average crystallite size was calculated based on it. Values for specific surface areas and the total pore volumes were calculated based on the isotherms obtained through the low-temperature nitrogen adsorption method. The bang gap energy was estimated based on Tauc’s plots. The influence of the type and content of amine, as well as heat treatment on the photocatalytic activity of modified titanium dioxide in the photocatalytic reduction of carbon dioxide, was determined and discussed. It was clear that, regardless of the amount and content of amine introduced, the higher photoactivity characterized the samples prepared in the microwave reactor. The highest amounts of hydrogen, carbon monoxide, and methane have been achieved using triethylamine-modified titanium dioxide. Full article

The cultivation of oil palm (Elaeis guineensis Jaq.) and its production generate large quantities of solid wastes annually. Current strategies adopted for tackling oil palm trunks (OPTs), which account for a significant proportion of oil palm waste (OPW), are considered expensive, inefficient, and unsustainable. Analysts posit this scenario could exacerbate efforts to not only effectively dispose and manage OPT but also lower the carbon footprint of the Oleo industry. Hence, immediate and urgent attention is needed to address the challenges posed by current strategies. Biomass torrefaction has recently gained traction as a practical approach for OPW valorisation into biochar. Therefore, this study seeks to (i) characterise the physicochemical characteristics of OPT through ultimate, proximate, and calorific analyses and (ii) examine the thermochemical, degradation, and temperature profile characteristics of OPT as potential torrefaction feedstock using thermal gravimetric analysis (TGA). TGA was performed at torrefaction temperatures; T_t = 200–300 °C (Δ25 °C stepwise increase) under isothermal/non-isothermal conditions of nitrogen (N₂) flowrate 100 mL/min), heating rate 20 °C/min, and 30-min residence time. The results showed that OPT contains high carbon (>45 wt.%), hydrogen (>6 wt.%), volatile matter (>80 wt.%) but low ash (2 wt.%), fixed carbon (5 wt.%), and moisture (10 wt.%) contents. OPT experienced 14.55–60.82 wt.% weight loss during TGA degradation from 200 to 300 °C. The increase in temperature resulted in a corresponding rise in OPT biochar yields ranging from 85.45 to 39.18 wt.% and higher heating values of 20–23 MJ/kg. The DTG plots showed that the TGA torrefaction process occurred in two stages, (i) 100 °C and (ii) >100 to the selected T_t, which could be ascribed to the drying and devolatilization/depolymerisation of OPT, respectively. Overall, this study demonstrated that OPT is a potentially practical feedstock for torrefaction into biochar. Full article

The thermally stable zirconium-based MOF, UiO-66, was employed for the preparation of bonded porous-layer open-tubular (PLOT) GC columns. The synthesis included the in situ growth of the UiO-66 film on the inner wall of the capillary through a one-step solvothermal procedure. SEM–EDX analysis revealed the formation of a thin, continuous, uniform, and compact layer of UiO-66 polycrystals on the functionalized inner wall of the column. The average polarity (ΔI_av = 700) and the McReynolds constants reflected the polar nature of the UiO-66 stationary phase. Several mixtures of small organic compounds and real samples were used to evaluate the separation performance of the fabricated columns. Linear alkanes from n-pentane to n-decane were baseline separated within 1.35 min. Also, a series of six n-alkylbenzenes (C₃–C₈) were separated within 3 min with a minimum resolution of 3.09, whereas monohalobenzene mixtures were separated at 220 °C within 14s. UiO-66 PLOT columns are ideally suited for the isothermal separation of chlorobenzene structural isomers at 210 °C within 45 s with R_s ≥ 1.37. The prepared column featured outstanding thermal stability (up to 450 °C) without any observed bleeding or significant impact on its performance. This feature enabled the analysis of various petroleum-based samples. Full article

The results of an experimental and mathematical study into the MmNi_4.2Mn_0.8 compound’s hydrogen storage properties are presented in the present research. Plotting and discussion of the experimental isotherms (P-C-T) for different starting temperatures (288 K, 298 K, 308 K, and 318 K) were carried out first. Then, the enthalpy and entropy of formation (ΔH₀, ΔS₀) were deduced from the plot of van’t Hoff. Following that, the P-C-T were contrasted with a mathematical model developed via statistical physics modeling. The steric and energetic parameters, such as the number of the receiving sites (n₁, n₂), their densities (N_m1, N_m2), and the energy parameters (P₁, P₂) of the system, were calculated thanks to the excellent agreement between the numerical and experimental results. Therefore, plotting and discussing these parameters in relation to temperature preceded their application in determining the amount of hydrogen in each type of site per unit of metal ([H/M]₁, [H/M]₂) as well as for the entire system [H/M] versus temperature and pressure besides the absorption energies associated with each kind of site (ΔE¹, ΔE²) and the thermodynamic functions (free energy, Gibbs energy, and entropy) that control the absorption reaction. Full article

The effect of the partial substitution of Cr with Fe on the thermodynamic parameters of vanadium-rich Ti₁₆V₆₀Cr_24-xFe_x alloys (x = 0, 4, 8, 12, 16, 20, 24) was investigated. For each composition, a pressure–concentration isotherm (PCI) was registered at 298, 308, and 323 K. The PCI curves revealed a reduction in plateau pressure and a decrease in desorbed hydrogen capacity with an increasing amount of Fe. For all alloys, about 50% or less of the initial hydrogen capacity was desorbed for all chosen temperatures. Entropy (ΔS) and enthalpy (ΔH) values were deducted from corresponding Van’t Hoff plots of the PCI curves: the entropy values ranged from −150 to −57 J/K·mol H₂, while the enthalpy values ranged from −44 to −21 kJ/mol H₂. They both decreased with an increasing amount of Fe. Plotting ΔS as function of ΔH showed a linear variation that seems to indicate an enthalpy–entropy compensation. Moreover, a quality factor analysis demonstrated that the present relationship between entropy and enthalpy is not of a statistical origin at the 99% confidence level. Full article