Search Results (322)

5-Hydroxymethylfurfural (HMF) is a versatile platform molecule with the potential to replace many fossil fuel derivatives. It can be obtained through the dehydration of carbohydrates. In this study, we present a simple and cost-effective microwave-assisted method for producing HMF. This method involves the use of readily available sucrose as a substrate and glucose-derived bifunctional hydrochars as carbocatalysts. These catalysts were produced via hydrothermal carbonisation using thiourea and urea as nitrogen and sulphur sources, respectively, to introduce Brønsted acidic and basic sites into the materials. Using a microwave reactor, we found that the S, N-doped hydrochars were active in sucrose dehydration in water. Catalytic results showed that HMF yield depended on the balance between acidic and basic sites as well as the types of S and N species present on the surfaces of these hydrochars. The best-performing catalyst achieved an encouraging HMF yield of 37%. The potential of N, S-co-doped biochar as a green solid catalyst for various biorefinery processes was demonstrated. A simple kinetic model was developed to elucidate the kinetics of the main reaction pathways of this cascade process, showing a very good fit with the experimental results. The calculated rate constants revealed that reactions with a 5% sucrose loading exhibited significantly higher fructose dehydration rates and produced fewer side products than reactions using a more diluted substrate. No isomerisation of glucose into fructose was observed in an air atmosphere. On the contrary, a limited rate of isomerisation of glucose into fructose was recorded in an oxygen atmosphere. Therefore, efforts should focus on achieving a high glucose-to-fructose isomerisation rate (an intermediate reaction step) to improve HMF selectivity by reducing humin formation. Full article

The pore structure of a hydrotreating catalyst plays a pivotal role in hydrodemetallization (HDM) reactions. To effectively construct a meso-macroporous catalyst, we employed a CTAB-guided in situ TEOS hydrolysis approach to prepare silica-coated γ-Al₂O₃@SiO₂ composite supports. The silica shell incorporation significantly enhances specific surface area and reduces the metal–support interactions, thereby improving the dispersion of NiMo active components and boosting the deposition of metal impurity. Hence, the NiMo/Al₂O₃@SiO₂ catalyst (2.8 wt.% NiO, 4.3 wt.% MoO₃) exhibits much higher HDM activity than that of NiMo/Al₂O₃. This is evidenced by markedly higher demetallization rate constant (1.38 h⁻¹) and turnover frequency (0.56 h⁻¹) of the NiMo/Al₂O₃@SiO₂. The NiMo/Al₂O₃@SiO₂ catalyst further demonstrates excellent recyclability during sequential HDM reactions. This superior catalytic behavior stems from the hierarchical meso-macroporous structure, which simultaneously facilitates the deposition of metal impurities and mitigates deactivation by pore blockage. Full article

The sludge pyrolysis technology for biochar production delivers dual environmental benefits, addressing both sludge disposal challenges and enabling environmental remediation through the utilization of the resultant biochar. However, the complex multi-step procedures and low catalyst output in previous studies constrain the practical implementation of this technology. A facile sludge pyrolysis method was constructed to achieve the batch production of municipal sludge biochar (MSB) in this study. Compared to municipal sludge (MS), the resultant MSB showed a higher BET surface area, more well-developed pore channel architecture, and plentiful active sites for activating peroxymonosulfate (PMS). Under the optimized conditions (C_MSB = C_PMS = 0.2 g/L), 93.34% of Acid Red G (ARG, 20 mg/L) was degraded after 10 min, posing an excellent rate constant of 0.278 min⁻¹. Additionally, MSB demonstrated excellent broad pH adaptability, ion interference resistance, reusability, and recyclability for ARG elimination. It was primary Fe sites that excited PMS to generate ${\mathrm{O}}_2^{•-}$ and Fe-oxo species (Fe^IV=O) for ARG degradation. The reaction process exhibited minimal heavy metal leaching, indicating limited environmental risk. Therefore, the practical applicability of the sludge biochar production, coupled with its scalable manufacturing capacity and exceptional catalytic activity, collectively demonstrated that this study established a viable pyrolysis methodology for municipal sludge, offering critical insights for sludge disposal and resource reutilization. Full article

Antibiotic resistance has been recognized as a global threat to human health. Therefore, it is urgent to develop effective strategies to address the contamination of water environments caused by antibiotics. In this study, Fe/Mn bimetallic-modified biochar (FMBC) was synthesized through a one-pot oxidation/reduction-hydrothermal co-precipitation method, demonstrating an exceptional photocatalytic-Fenton degradation performance for oxytetracycline (OTC). Characterization techniques including FTIR, SEM, XRD, VSM, and N₂ adsorption–desorption analysis confirmed that the Fe/Mn bimetals were successfully loaded onto the surface of biochar in the form of Fe₃O₄ and MnFe₂O₄ mixed crystals and exhibited favorable paramagnetic properties that facilitate magnetic recovery. A key innovation is the utilization of biochar’s inherent phenol/quinone structures as reactive sites and electron transfer mediators, which synergistically interact with the loaded bimetallic oxides to significantly enhance the generation of highly reactive ·OH radicals, thereby boosting catalytic activity. Even after five recycling cycles, the material exhibited minimal changes in degradation efficiency and bimetallic crystal structure, indicating its notable stability and reusability. The photocatalytic degradation experiment conducted in a Fenton-like reaction system demonstrates that, under the conditions of pH 4.0, a H₂O₂ concentration of 5.16 mmol/L, a catalyst dosage of 0.20 g/L, and an OTC concentration of 100 mg/L, the optimal degradation efficiency of 98.3% can be achieved. Additionally, the pseudo-first-order kinetic rate constant was determined to be 4.88 min⁻¹. Furthermore, this study elucidated the detailed degradation mechanisms, pathways, and the influence of various ions, providing valuable theoretical insights and technical support for the degradation of antibiotics in real wastewater. Full article

The widespread contamination of aquatic environments by tetracycline antibiotics (TCs) poses a substantial threat to public health and ecosystem stability. Although photo-Fenton processes have demonstrated remarkable efficacy in degrading TCs, their practical application is limited by challenges associated with catalyst recyclability. This study reports the development of a novel magnetic recoverable SrFe₁₂O₁₉/g-C₃N₄ heterostructure photocatalyst synthesized via a facile one-step co-calcination method using industrial-grade precursors. Comprehensive characterization revealed that nitrogen defects and the formation of heterojunction structures significantly suppress electron (e⁻)–hole (h⁺) pair recombination, thereby markedly enhancing catalytic activity. The optimized 7-SFO/CN composite removes over 90% of oxytetracycline (OTC) within 60 min, achieving degradation rate constants of 0.0393 min⁻¹, which are 9.1 times higher than those of SrFe₁₂O₁₉ (0.0043 min⁻¹) and 4.2 times higher than those of g-C₃N₄ (0.0094 min⁻¹). The effectively separated e⁻ play three critical roles: (i) directly activating H₂O₂ to generate ·OH radicals, (ii) promoting the redox cycling of Fe²⁺/Fe³⁺ ions, and (iii) reducing dissolved oxygen to form ·O₂⁻ species. Concurrently, h⁺ directly oxidize OTC molecules through surface-mediated reactions. Furthermore, the 7-SFO/CN composite exhibits exceptional operational stability and applicability, offering a transformative approach for scalable photocatalytic water treatment systems. This work provides an effective strategy for designing efficient and recoverable photocatalysts for environmental remediation. Full article

This work aims to characterize flow-accelerated corrosion of carbon steel A36 coupons exposed to simulated treated reverse-osmosis seawater under ambient conditions and a Reynolds number range of 6000 to 25,000 using a standard corrosion testing method. The flow behavior in the corrosion compartment and the turbulent parameters were determined by computational fluid dynamics simulation. Using selected flow parameters, complemented with experimental corrosion rate measurements, the oxygen mass transfer coefficients (m_c) and the rate constant for the cathodic reaction (k_c) at the coupon surface were determined. As expected, m_c depends only on the fluid conditions, while k_c is highly influenced by interface resistance, leading to significantly different runs with and without a corrosion inhibitor. The dissimilar fluid flow distribution on intrados and extrados generates irregular corrosion patterns, depending on the angular position of the coupon inside the corrosion compartment. Morphological studies using scanning electron microscopy and atomic force microscopy support simulation results. Full article

Polydopamine (PDA) is an emerging biomimetic material that stimulates the distinctive physicochemical properties of the blue mussel byssus. In this study, we report a rapid and facile method for the decoration of gold nanoparticles (AuNPs) onto the mussel-inspired polydopamine nanospheres (PDA NSs) via cold atmospheric plasma treatment. After 10 min of plasma treatment, AuNPs with a size of 10.3 ± 2.0 nm were formed on the surface of PDA NSs. This reaction was performed without the need for any additional reducing agents, thereby eliminating the use of harsh chemicals during the process. The synthesized AuNP-decorated PDA nanohybrids (PDA-Au) exhibit effective catalytic activity for the decoloration of Rhodamine B, with a pseudo-first-order rate constant of 1.405 min⁻¹. The green synthesis approach in this work highlights the potential of plasma-assisted methods for decorating biomimetic materials with metallic nanoparticles for catalytic and environmental applications. Full article

Microcystins (MCs) are produced by cyanobacteria blooms in eutrophic water and can cause acute and chronic toxicity and even mortality to animals and humans. Previous MC removal strategies concernedonly highly contaminated water, in which the concentration of the pollutant was considerably larger than that in the natural world. In this study, we developed a composite of TiO₂-coated magnetic carbon microtube (C-TiO₂-Fe₃O₄) and used it as a photocatalyst to efficiently remove microcystin-LR (MC-LR) from water under visible light from water. And the huge surface of the carbon microtube dramatically boosted the adsorbability and charge mobility, which lowered the recombination rate of electron–hole pairs, and hence systematically enhanced photocatalytic activity. The combination of adsorption and photodegradation endowed the composite with a better performance in the removal of trace amounts of MC-LR than the C-TiO₂. It was found that increasing the contact time and catalyst dosage, acidic environment, and lower initial MC-LR concentration had positive effects on MC-LR removal. The optimum reaction conditions of C-TiO₂-Fe₃O₄ was a reaction time of 12.68 min, a catalyst dosage of 0.39 g·L⁻¹, and a pH of 7.72. The C-TiO₂-Fe₃O₄ (surface area normalized apparent reaction rate constants K/S_BET = 1.2 × 10⁻⁴) presented a higher reaction rate than C-TiO₂ (K/S_BET = 8.4 × 10⁻⁵). Moreover, the stable removal capability of C-TiO₂-Fe₃O₄ was confirmed over multiple cycles. Finally, the ecological safety performance was also evaluated after visible light illumination. This work paves the way for the development of more efficient and easily separable purifiers for the removal of pollutants and toxins from contaminated water. Full article

Gold nanoparticles (AuNPs) have surface plasmon resonance (SPR) and catalytic activity that are not found in bulk gold and have been studied in various fields. Among these, immobilization of AuNPs on various solid-phase substrates is known to produce stable catalytic activity and specific SPRs and research on the immobilization of AuNPs has been conducted actively. However, the conventional method requires the preparation and immobilization of AuNPs in separate processes, making it difficult to prepare immobilized AuNPs in a one-pot process. In this study, we attempted to synthesize and immobilize AuNPs using peptidyl beads, which are microbeads having immobilized a peptide capable of reducing gold ions. We successfully reduced Au ions from 0.5 to 1000 µM of HAuCl₄ and immobilized them on peptidyl beads in the form of AuNPs. The immobilized AuNPs have a constant particle size independent of the HAuCl₄ concentration. Furthermore, the peptidyl beads with AuNPs have catalytic activity. The quantity of the AuNPs on the peptidyl beads and, subsequently, the catalytic reaction rate of the sample, could be controlled. This study would also be expected to be applied to the immobilization of metallic nanomaterials other than AuNPs by modifying the peptide sequence. Full article

With the advancement of new synthetic techniques, 5-Methyl-2-ethylfuran (5-MEF) has emerged as a promising renewable biofuel. In this study, the potential energy surfaces for the unimolecular dissociation reaction, H-addition reaction, and H-abstraction reaction of 5-MEF were mapped at the CBS-QB3 level. The temperature- and pressure-dependent rate constants for these reactions on the potential energy surfaces were determined by solving the master equation, using both transition state theory and Rice–Ramsperger–Kassel–Marcus theory. The results showed that the dissociation reaction of the C(6) site on the branched chain of 5-MEF has the largest rate constant and is the main decomposition pathway, while the dissociation reaction of the H atom on the furan ring has a lower rate constant and is not the main reaction pathway. In addition, the dissociation of H atoms on the branched chain and intramolecular H-transfer reactions also have high-rate constants and play an important role in the decomposition of 5-MEF. H-addition reactions mainly occur at the C(2) and C(5) sites, and the generation of the corresponding products through β-breakage becomes the main reaction pathway. With the increase in temperature, the H-addition reaction at the C(2) site gradually changes to a substitution reaction, dominating the formation of C₂H₅ and 2-methylfuran. Full article

LaFeO₃/TiO₂ composites were prepared in the range 0–12.2 wt% of LaFeO₃, characterized, and tested for both benzoic acid (BA) and 4-methoxycinnamic acid (MCA) degradation in aqueous solution, and hydrogen evolution. The preparation method was via ball-milling without thermal treatment. The composite materials presented agglomerates of LaFeO₃ with an average size from 1 to 5 μm, and the TiO₂ powder was well dispersed onto the surface of each sample. They showed varying activities for BA degradation depending on composition and light wavelength. The 6.2 wt% and 12.2 wt%-LaFeO₃/TiO₂ composites exhibited the highest activity under 380–800 nm light and could degrade BA in 300 min at BA concentration 13.4 mg L⁻¹ and catalyst 0.12 g L⁻¹. Using a 450 nm LED light source, all composites degraded less than 10% of BA, but in the presence of H₂O₂ (1 mM) the photocatalytic activity was as high as 96% in <120 min, 6.2 wt%-LaFeO₃/TiO₂ composite being the most efficient sample. It was found that in the presence of H₂O₂, BA degradation followed first order kinetic with a reaction rate constant of 4.8 × 10⁻⁴ s⁻¹. The hydrogen production rate followed a classical volcano-like behavior, with the highest reactivity (1600 μmol h⁻¹g⁻¹ at 60 °C) in the presence of 3.86%wt- LaFeO₃/TiO₂. It was also found that LaFeO₃/TiO₂ exhibited high stability in four recycled tests without losing activity for hydrogen production. Furthermore, a discussion on photogenerated charge-carrier transfer mechanism is briefly provided, focusing on lacking significant photocatalytic activity under 450 nm light, so p-n heterojunction formation is unlikely. Full article

A Ppy/Ag-ZnO catalyst was successfully synthesized at room temperature using a novel, green methodology. It involves a mechanically assisted metathesis reaction. The Ppy/Ag-ZnO catalyst was analyzed via X-ray diffraction Technique (XRD), Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC), Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), UV–visible spectroscopy, Brunauer–Emmett–Teller (BET), and zeta potential. Debye Scherrer’s calculation suggested a crystallite size of 2.30 nm for Ppy/Ag-ZnO nanocomposite. SEM confirmed the production of aggregated particles with an average size of 2.65 μm, endorsing the -ve zeta potential value (−6.78 mV) due to the presence of Van der Waals forces among the particles of Ppy/Ag-ZnO. DSC confirms that the strong interfacial interaction between Ag-ZnO and the polar segments of Ppy is responsible for the higher Tg (107 °C) and Tm (270 °C) in Ppy/Ag-ZnO. The surface area and average pore size of Ppy/Ag-ZnO catalyst were determined to be 47.08 cm³/g and 21.72 Å, respectively. Methyl orange (MO) was used as a probe in a photocatalytic reaction of fabricated material, which demonstrated exceptional efficiency, exhibiting a removal rate of 91.11% with a rate constant of 0.028 min⁻¹. Photocatalytic degradation of MO was shown to follow pseudo-first-order kinetics. Full article

Magnesium sulfate leaching of ionic rare earth ores is generally characterized by a smooth outflow curve, a long leaching time, and a high impurity content in the leach liquor. To reveal the leaching law of rare earth cations and impurity aluminum ions in the leaching process of ionic rare earth ores in magnesium sulfate, equilibrium leaching and leaching kinetics experiments were carried out using ore samples of five particle sizes (<0.10, 0.10–0.25, 0.25–0.50, 0.50–1.00, and >1.00 mm). Furthermore, prediction models of equilibrium constants and rate constants were constructed based on ion-exchange theory. The results show that the equilibrium constants of the rare earth and aluminum ion-exchange reactions decrease gradually with the increase in the magnesium ion concentration, the decrease in the temperature, and the increase in the surface area of the particles. Moreover, the equilibrium constant prediction models of rare earth and aluminum with magnesium sulfate were constructed using data fitting. From the leaching kinetics experiment, there is a significant relationship between the reaction rate constant of ion exchange and the surface area of the particles: the larger the particle size, the smaller the reaction rate constant. Based on the kinetic test data and the Arrhenius equation, the frequency factors and activation energies of the ion-exchange reactions were inversely analyzed through the Chemistry Reaction Module of COMSOL. The reaction activation energy for rare earth and aluminum leaching is 10,743 J/mol and 10,987 J/mol, respectively. The rate constant prediction model was obtained by fitting the analyzed rate constant data. The rare earth and aluminum leaching results for the full-grade ores are in high agreement with the predictions of the constructed model, which verifies the validity of the proposed model. This study can provide theoretical support for the improvement of the leaching efficiency of rare earths and the optimization of the magnesium sulfate leaching process. Full article

The excessive utilization and emission of waste plastics have caused serious damage to the environment, and it is of great significance to explore high-value utilization methods for these waste plastics. To address this challenge, functional nano cobalt-loaded porous carbon materials (CoPC) with excellent antibiotic wastewater removal properties were prepared by one-step pyrolysis using waste PET plastics as a carbon source, a process described in this paper. Characterization revealed that the obtained CoPC-2 catalysts had a high degree of defects, a large specific surface area (343.41 m²/g), and an abundant pore structure. Degradation results displayed that CoPC-2 removed 87.93% of 20 mg/L tetracycline with a reaction rate constant of 0.0668 min⁻¹. Moreover, CoPC-2 exhibited excellent degradation performance for tetracycline over a wide range of pH levels (4–10) and in coexistence with multiple inorganic anions. Electron paramagnetic resonance and radical quenching experiments revealed that radicals (·OH, and SO₄·⁻) and non-radicals (¹O₂) pathway participated in tetracycline degradation, with the non-radical pathway being dominant. This study not only offers promising prospects for resource utilization of waste plastics, but also provides novel approaches for the design of functional nanomaterials for antibiotic wastewater treatment. Full article

The growing amount of carbon dioxide (CO₂) in the atmosphere significantly contributes to global warming and climate change. This study focuses on the use of aqueous potassium carbonate (K₂CO₃) solutions as a solvent for CO₂ absorption, emphasizing the role of titanium dioxide (TiO₂) nanoparticles in enhancing performance. A detailed understanding of reaction kinetics and the dynamic behavior of the absorber is crucial for optimizing the process. However, critical parameters such as the rate constant k_OH of the reaction between CO₂ and OH^- in K₂CO₃ solutions are rarely found in existing studies. This work investigates the kinetics of CO₂ absorption in 25 wt% K₂CO₃ solutions at three temperatures (40, 55, and 70 °C), varying concentrations of TiO₂ nanoparticles to identify optimal conditions. Reaction rates were measured in a stirred cell reactor, and the data were interpreted using Danckwerts theory. The results revealed a notable improvement in absorption efficiency with the addition of nanoparticles, and the study also pinpointed optimal operational parameters to prevent sedimentation issues. The presence of TiO₂ nanoparticles was found to enhance the solution’s physical properties, such as diffusivity and surface tension, which facilitated an improved mass transfer. The best performance was achieved with a TiO₂ concentration of 0.06 wt% at 70 °C, leading to an increase of diffusivity value equal to 1.5 times and, as a consequence, the same increase has been observed for the overall reaction rate. In contrast, higher or lower concentrations negatively impacted efficiency due to poor dispersion or nanoparticle agglomeration. These results provide practical insights for developing more efficient and sustainable CO₂ capture methods, contributing to solutions for the climate crisis. Full article