Search Results (3,205)

Abstract: The photocatalytic reduction of CO₂ to useful products is an area of active research because it shows a potential to be an efficient tool for mitigating climate change. This work investigated the modification of titania with copper(II) nitrate and its impact on improving the CO₂ reduction efficiency in a gas-phase batch photoreactor under UV–Vis irradiation. The investigated photocatalysts were prepared by treating P25-copper(II) nitrate suspensions (with various Cu²⁺ concentrations), alkalized with ammonia water, in a microwave-assisted solvothermal reactor. The titania-based photocatalysts were characterized by SEM, EDS, ICP-OES, XRD and UV-Vis/DR methods. Textural properties were measured by the low-temperature nitrogen adsorption/desorption studies at 77 K. P25 photocatalysts modified with copper(II) nitrate used in the process of carbon dioxide reduction allowed for a higher efficiency both for the photocatalytic reduction of CO₂ to CH₄ and for the photocatalytic water decomposition to hydrogen as compared to a reference. Similarly, modified samples showed significantly higher selectivity towards methane in the CO₂ conversion process than the unmodified sample (a change from 30% for a reference sample to 82% for the P25-R-Cu-0.1 sample after the 6 h process). It was found that smaller loadings of Cu are more beneficial for increasing the photocatalytic activity of a sample. Full article

The influence of the addition of ground buckwheat hulls on the properties of biocomposite on the basis of 3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) is presented here. The changes in the material after repeated reprocessing—up to five recycling cycles—are written in the paper. Analysis of the shrinkage, water adsorption, selected mechanical properties, tensile impact strength, hardness and the microstructure of the surface layer was performed. The results show that the application of the buckwheat hulls into the biopolymer decreases the material shrinkage. It improves the material dimensional stability, as well as increases the water adsorption in the wake of the hydrophobic properties of the filler. The addition of the natural filler also leads to an increase in composite stiffness. The decrease in the tensile impact strength and the elongation at break is also noted. The reprocessing of the biocomposite initially led to a decrease in its mechanical properties, but the results stabilized after further processing cycles. This indicates the improvement of the microstructure homogeneity. The microscopic analysis shows that buckwheat hull particles were better embedded in the matrix after recycling. The increase in hardness was also noted. The PHBV–ground buckwheat hull biocomposite is characterized by stable mechanical properties and by recycling resistance, which makes it a promising material in terms of the sustainable development. Full article

Developing highly efficient and cost-competitive electrocatalysts for the hydrogen evolution reaction (HER), which can be applied to hydrogen production by water splitting, is of great significance in the future of the zero-carbon economy. Here, by means of first-principles calculations, we have scrutinized the HER catalytic capacity of single-atom catalysts (SACs) by embedding transition-metal atoms in the C and Mo vacancies of a tetragonal Mo₃C₂ slab, where the transition-metal atoms refer to Ti, V, Cr, Mn, Fe, Co, Ni and Cu. All the Mo₃C₂-based SACs exhibit excellent electrical conductivity, which is favorable to charge transfer during HER. An effective descriptor, Gibbs free energy difference (ΔG_H*) of hydrogen adsorption, is adopted to evaluate catalytic ability. Apart from SACs with Cr, Mn and Fe located at C vacancies, all the other SACs can act as excellent catalysts for HER. Full article

Existing studies have demonstrated the positive effects of nano-sized iron oxide on compost maturity, yet the impact of nano-sized iron oxide on phosphorus speciation and bacterial communities during the composting process remains unclear. In this study, pig manure and straw were used as raw materials, with biochar-supported nano-sized iron oxide (BC-Fe₃O₄NPs) as an additive and calcium peroxide (CaO₂) as a co-agent, to conduct an aerobic composting experiment with pig manure. Four treatments were tested: CK (control), F1 (1% BC-Fe₃O₄NPs), F2 (5% BC-Fe₃O₄NPs), and F3 (5% BC-Fe₃O₄NPs + 5% CaO₂). Key findings include the following. (1) BC-Fe₃O₄NPs increased compost temperatures, with F3 reaching 61℃; F1 showed optimal maturity (C/N ratio: 12.90). (2) BC-Fe₃O₄NPs promoted stable phosphorus forms; Residual-P proportions were higher in F1, F2, and F3 (25.81%, 51.16%, 51.68%) than CK (19.32%). (3) Bacterial phyla Firmicutes, Actinobacteria, and Proteobacteria dominated. BC-Fe₃O₄NPs altered community composition, especially on day 7. Firmicutes dominated CK, F1, and F3; Proteobacteria dominated F2. At the genus level, day 7 showed Corynebacterium (CK), Clostridum (F1, F3), and Caldibacillus (F2) as predominant. (4) Pearson correlation analysis revealed shifted correlations between phosphorus forms and bacterial phyla after BC-Fe₃O₄NPs addition. Firmicutes positively correlated with NaOH-OP in F1 during the thermophilic phase, facilitating phosphate release and adsorption by BC-Fe₃O₄NPs. The significance of correlations diminished with increasing additive concentration; in F3, all phyla positively correlated with various phosphorus forms. Full article

In the process of oilfield development, the surfactant–polymer (SP) composite system has shown significant effects in enhancing oil recovery (EOR) due to its excellent interfacial activity and viscoelastic properties. However, with the continuous increase in the volume of composite flooding injection, a decline in injection–production capacity (I/P capacity) has been observed. Through the observation of frozen core slices, it was found that during the secondary composite flooding (SCF) process, a large amount of residual oil in the form of intergranular adsorption remained in the core pores. This phenomenon suggests that the displacement efficiency of the composite flooding may be affected. Research has shown that polymers undergo flocculation reactions with clay minerals (such as kaolinite, Kln) in the reservoir, leading to the formation of high-viscosity mixtures of migrating particles and crude oil (CO). These high-viscosity mixtures accumulate in local pores, making it difficult to further displace them, which causes oil trapping and negatively affects the overall displacement efficiency of secondary composite flooding (SCF). To explore this mechanism, this study used a microscopic visualization displacement model (MVDM) and microscopy techniques to observe the migration of particles during secondary composite flooding. By using kaolinite water suspension (Kln-WS) to simulate migrating particles in the reservoir, the displacement effects of the composite flooding system on the kaolinite water suspension, crude oil, and their mixtures were observed. Experimental results showed that the polymer, acting as a flocculant, promoted the flocculation of kaolinite during the displacement process, thereby increasing the viscosity of crude oil and affecting the displacement efficiency of secondary composite flooding. Full article

Phenothiazine-based photosensitizers bear the intrinsic potential to substitute various expensive organometallic dyes owing to the strong electron-donating nature of the former. If coupled with a strong acceptor unit and the length of N-alkyl chain is appropriately chosen, they can easily produce high efficiency levels in dye-sensitized solar cells. Here, three novel D-A dyes containing 1H-tetrazole-5-acrylic acid as an acceptor were synthesized by varying the N-alkyl chain length at its phenothiazine core and were exploited in dye-sensitized solar cells. Differential scanning calorimetry showed that the synthesized phenothiazine derivatives exhibited behavior characteristic of molecular glasses, with glass transition and melting temperatures in the range of 42–91 and 165–198 °C, respectively. Based on cyclic and differential pulse voltammetry measurements, it was evident that their lowest unoccupied molecular orbital (LUMO) (−3.01–−3.14 eV) and highest occupied molecular orbital (HOMO) (−5.28–−5.33 eV) values were fitted to the TiO₂ conduction band and the redox energy of I⁻/I₃⁻ in electrolyte, respectively. The experimental results were supported by density functional theory, which was also utilized for estimation of the adsorption energy of the dyes on the TiO₂ and its size. Finally, the compounds were tested in dye-sensitized solar cells, which were characterized based on current–voltage measurements. Additionally, for the compound giving the best photovoltaic response, the efficiency of the DSSCs was optimized by a photoanode modification involving the use of cosensitization and coadsorption approaches and the introduction of a blocking layer. Subsequently, two types of tandem dye-sensitized solar cells were constructed, which resulted in an increase in photovoltaic efficiency to 6.37%, as compared to DSSCs before modifications, with a power conversion value of 2.50%. Full article

The development of lanthanide–organic frameworks (Ln-MOFs) using for luminescence sensing and selective gas adsorption applications is of great significance from an energy and environmental perspective. This study reports the solvothermal synthesis of a fluorine-functionalized 3D microporous Tb-MOF with a face-centered cubic (fcu) topology constructed from hexanuclear clusters (Tb₆O₃₀) bridged by fdpdc ligands, formulated as {[Tb₆(fdpdc)₆(μ₃-OH)₈(H₂O)₆]·4DMF}_n (1), (fdpdc = 3-fluorobiphenyl-4,4′-dicarboxylate). Complex 1 displays a 3D framework with the channel of 7.2 × 7.2 Ų (measured between opposite atoms) perpendicular to the a-axis. With respect to Ba²⁺ cation, the framework of activated 1 (1a) exhibits high selectivity and reversibility in luminescence sensing function, with an LOD of 4.34665 mM. According to the results of simulations, compared to other small gas molecules (CO₂, N₂, H₂, CO, and CH₄), activated 1 (1a) shows a high adsorption selectivity for C₂H₂ at 298 K. Full article

Nitrogen oxides (NO_x) and chlorobenzene (CB) released during waste incineration and iron ore sintering pose significant threats to both the atmosphere and human health, necessitating effective control measures. Vanadium-based catalysts are commonly employed for the simultaneous control of NO_x and CB; however, their catalytic performance requires further enhancement. In this study, the NH₃-SCR activity and CB catalytic oxidation (CBCO) activity were significantly enhanced by doping the V10W/Ti catalyst with Ce. During the multi-pollutant control (MPC) reaction, the optimized 15CeV10W/Ti catalyst demonstrated NO_x conversion approaching 100% and N₂ selectivity exceeding 95% at temperatures between 210 and 450 °C. Additionally, it achieved CB conversion nearing 100% and CO₂ selectivity above 80% at temperatures above 350 °C. These results were markedly superior to those of the conventional commercial 1%V₂O₅–10%WO₃/TiO₂ catalyst. Characterization studies indicated that the 15CeV10W/Ti catalyst possessed improved redox performance and more acidic sites. In the MPC reaction, the declined CBCO activity, compared to the CB separate oxidation, can be attributed primarily to the competitive adsorption of NH₃ with CB. Conversely, the observed decrease in NO_x conversion at lower temperatures was primarily due to the suppression of the oxidation of NO to NO₂ by CB. Full article

Metal–organic frameworks (MOFs) represent a category of crystalline materials formed by the combination of metal ions or clusters with organic linkers, which have emerged as a prominent research focus in the field of photocatalysis. Owing to their distinctive characteristics, including structural diversity and configurations, significant porosity, and an extensive specific surface area, they provide a flexible foundation for various potential applications in photocatalysis. In recent years, researchers have tackled many issues in the MOF-based photocatalytic yield. However, limited light adsorption regions, lack of active sites and active species, and insufficient efficiency of photogenerated charge carrier separation substantially hinder the photocatalytic performance. In this review, we summarized the strategies to improve the photocatalytic performance and recent developments achieved in MOF and MOF-based photocatalysis, including water splitting, CO₂ conversion, photocatalytic degradation of pollutants, and photocatalytic nitrogen fixation into ammonia. In conclusion, the existing challenges and prospective advancements in MOF-based photocatalysis are also discussed. Full article

Triazine-based covalent organic framework CTF-1 was synthesized via polymerization of 1,4-dicyanobenzene in the presence of zinc chloride. Two different methods of the post-synthesis treatment of the obtained material were compared. It was demonstrated that ultrasonication effectively removes impurities from CTF-1. Adsorption of hydrocarbon gases (methane and ethane) and carbon dioxide was measured at 298 K in a wide pressure range for the first time. Ideal selectivity and IAST values for methane/ethane and methane/CO₂ pairs were calculated from the obtained isotherms. Full article

Methyl mercaptan is a sulfur-based chemical found as a co-product in produced natural gas and it causes corrosion in pipelines, storage tanks, catalysts, and solid adsorption beds. To improve the quality of methane produced, researchers have studied the use of metal oxides and aluminum silicates as catalysts for removing mercaptan. However, there are restrictive limitations on the efficiency of metal oxides or aluminum silicates as adsorbents for this application. Therefore, this study investigated the performance of these materials in a fixed-bed reactor with simulated natural gas streams under various operating conditions. The testing procedure includes a detailed assessment of the adsorbent/catalysts by several techniques, such as Braeuer–Emmett–Teller (BET), Scanning Electron Microscope (SEM), Energy-Dispersive X-ray Spectrometry (EDS), and X-ray Photoelectron Spectroscopy. The results revealed that metal oxides such as copper, manganese, and zinc performed well in methyl mercaptan elimination. The addition of manganese, copper, and zinc oxides to the aluminum silicate surface resulted in a sulfur capacity of 1226 mg S/g of catalyst. These findings provide critical insights for the development of catalysts that combine metal oxides to increase adsorption while reducing the production of byproducts like dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) during methyl mercaptan removal. Full article

Landfill leachate contains a range of organic and inorganic pollutants, including per-/polyfluoroalkyl substances (PFASs), which can infiltrate into surrounding soil and groundwater through leaching processes, and can pose a threat to human health via food chains and drinking water processes. Thus, the transport of PFASs in landfill leachate is a research hotspot in environmental science. This study investigates the complexation and adsorption mechanisms between humic substances and PFASs in landfill leachate at the molecular level. Experimental results demonstrate that the binding constant logK_sv of humic substances with PFASs correlates positively with specific ultraviolet absorbance (SUVA₂₅₄), absorbance ratio (A₂₅₀/A₃₆₅), humification index (HIX), and fluorescence index (FI), while it exhibits a negative correlation with the biological index (BIX). These findings indicate that high aromaticity is a prerequisite for molecular interactions between humic substances and PFASs, with polar functional groups further facilitating the interaction. Molecular-level analysis revealed that humic substances undergo complexation and adsorption with PFASs through hydrophobic interactions, van der Waals forces, hydrogen bonding, ionic bonding, and covalent bonding, by functional groups such as hydroxyl, aliphatic C-H bonds, aromatic C=C double bonds, amides, quinones, and ketones. Future efforts should focus on enhanced co-regulation and mitigation strategies addressing the combined pollution of PFASs and humic substances in landfill leachate. Full article

To investigate the micro-mechanism of the erosion of hydrated calcium silicate (C-S-H gel) in a sulfate environment, a solid–liquid molecular dynamics model of C-S-H gel/sodium sulfate was developed. This model employs molecular dynamics methods to simulate the transport processes between C-S-H gel and corrosive ions at concentrations of 5%, 8%, and 10% sodium sulfate (Na₂SO₄), aiming to elucidate the interaction mechanism between sulfate and C-S-H gel. The micro-morphology of the eroded samples was also investigated using scanning electron microscopy (SEM). The findings indicate that the adsorption capacity of C-S-H for ions significantly increases with higher concentrations of Na₂SO₄ solution. Notably, the presence of sulfate ions facilitates the decalcification reaction of C-S-H, leading to the formation of swollen gypsum and AFt (ettringite). This process results not only in the hydrolysis of the C-S-H gel but also in an increase in the diffusion coefficients of Na⁺ and Ca²⁺, thereby exacerbating the erosion. Additionally, the pore surfaces of the C-S-H structure exhibited strong adsorption of Na⁺, and as the concentration of Na₂SO₄ solution increased, Na+ was more stably adsorbed onto the C-S-H pore surfaces via Na-O_s bonds. The root-mean-square displacement curves of water molecules were significantly higher than those of ${\mathrm{SO}}_4^{2-}$, Na⁺ and Ca²⁺, which indicated that ${\mathrm{SO}}_4^{2-}$ could co-penetrate and migrate with water molecules faster compared with other ions in the solution containing ${\mathrm{SO}}_4^{2-}$, resulting in stronger corrosion and hydrolysis effects on the C-S-H structure. Full article

Biochar is a potential material for making slow-releasing phosphorus (P) fertilizers for the sake of increasing soil P-use efficiency. The adsorption of phosphorus by pineapple leaf biochar (PB) prepared at different pyrolysis temperatures and its mechanism remain unclear. In order to study the effect of preparation temperature on the structural characteristics of biochar from pineapple leaves and the adsorption of phosphorus by biochar, pineapple leaves were used as raw materials to prepare biochar by restricting oxygen supply at 300 °C, 500 °C, and 700 °C. The structural characteristics and adsorption of phosphorus by pineapple leaf biochar at different temperatures (PB300, PB500, and PB700) were analyzed. The results showed the following: (1) The pore structure of biochar pyrolysis at 300 °C (PB300) did not significantly change, while the surface structure of biochar pyrolysis at 700 °C (PB700) significantly changed, the specific surface area (S_BET) increased by 26.91~37.10 times that observed in PB300 and PB500, and the pore wall became thinner. (2) The number of functional groups (C=O) in PB700 decreased, and the relative content of C-H/-CHO in PB500 and PB700 increased by 4.38 times that observed in PB300. (3) The adsorption of phosphorus by biochar was a multi-molecular layer chemisorption, accompanied by single-molecular-layer physical adsorption and intramolecular diffusion. For PB300, both the physical and chemical processes of the adsorption of PO₄³⁻ by biochar were weakened, and the chemical process was dominated by cationic (Ca²⁺, Mg²⁺, Fe³⁺, and Al³⁺) adsorption at 500 °C. For PB700, the physical adsorption dominated by pore size structure was the main process, and the physicochemical adsorption at 700 °C was significantly stronger than that observed at 300 °C and 500 °C. These results indicate that biochar prepared at 500 °C can save energy in the preparation process and has excellent physical and chemical structure, which can be used as the basic material for further modification and preparation of biochar phosphate fertilizer. Full article

Accurate characterization of coal reservoir micro- and nanopores is crucial in evaluating coalbed methane storage and gas production capacity. In this work, 12 coal-bearing rock samples from the Jurassic Yan’an Formation, Longdong area, Ordos Basin were taken as research objects, and micro- and nanopore structures were characterized via scanning electron microscopy, high-pressure mercury pressure, low-temperature N₂ adsorption and low-pressure CO₂ adsorption experiments. The main factors controlling coal pore structure development and the influence of pore development on the gas content were studied by combining the reflectivity of specular samples from the research area, the pore microscopic composition and the pore gas content determined through industrial analyses and isothermal absorption experiments. The results show that the coal strata of the Yan’an coal mine are a very important gas source, and that the coal strata of the Yan’an Formation in the study area exhibit remarkable organic and clay mineral pore development accompanied by clear microfractures and clay mineral interlayer joints, which together optimize the coal gas storage conditions and form efficient microseepage pathways for gas. Coalstone, carbonaceous mudstone and mudstone show differential distributions in pore volume and specific surface area. The general trend is that coal rock is the best, carbonaceous mudstone is the second best, and mudstone is the weakest. The coal samples’ microporous properties are positively correlated with the coal sample composition for the specular group, whereas there is no clear correlation for the inert group. An increase in the moisture content of the air-dried matrix promotes adsorption pore development, leading to increases in the microporous volume and specific surface area. CH₄ adsorption in coal rock increases with increasing pressure, and the average maximum adsorption is approximately 8.13 m³/t. The limit of the amount of methane adsorbed by the coal samples, V_L, is positively correlated with the pore volume and specific surface area, indicating that the larger the pore volume is, the greater the amount of gas that can be adsorbed by the coal samples, and the larger the specific surface area is, the greater the amount of methane that can be adsorbed by the coal samples. The P_L value, pore volume and specific surface area are not correlated, indicating that there is no direct mathematical relationship between them. Full article