Search Results (10,585)

Pyridine is a recalcitrant organic compound present in industrial wastewater that causes severe effects on the environment and the health of living beings, as it is considered a toxic, mutagenic, teratogenic, and carcinogenic agent. Therefore, this research explored the efficacy of a zinc oxide catalyst, doped with platinum nanoparticles and supported alumina through the precipitation method, for the photocatalytic degradation of pyridine using a fluidized bed reactor. A Box–Behnken experimental design was used to analyze the effect of the pH (4–10), the pyridine concentration (20–300 ppm), and the amount of catalyst (20–100 g). The X-ray diffraction (XRD) characterization results confirmed the hexagonal structure of the zinc oxide and the successful incorporation of platinum. Scanning electron microscopy (SEM) revealed a nano-bar morphology upon catalyst doping, favoring the photocatalytic activity. Pyridine removal of 57.7% was achieved under the following conditions: a pH of 4, 160 ppm of pyridine, and 100 g of catalyst. The process followed a pseudo-first-order model, obtaining the reaction constant k₁ = 1.943 × 10⁻³ min⁻¹ and the adsorption constant k₂ = 1.527 × 10⁻³ L/mg. The results showed high efficiency and stability of the catalyst in the fluidized bed reactor for pyridine degradation, especially under acidic conditions, representing a promising technological alternative for treating industrial wastewater contaminated with N-heterocycles such as pyridine. Full article

Photocatalysis offers a cost-effective and eco-friendly approach for environmental remediation, yet traditional powdered photocatalysts suffer from poor recyclability and separation challenges. To address these limitations, we developed a recyclable carbon fiber-supported composite photocatalyst (CC/TiO₂ NRs@MoS₂ NPs) featuring a three-dimensional hierarchical core–shell architecture. This structure comprises a TiO₂ seed layer, vertically aligned TiO₂ nanorod arrays as the core, and a MoS₂ nanoparticle shell, fabricated via sequential deposition. Under simulated solar irradiation, the TiO₂@MoS₂ heterojunction exhibited significantly enhanced uranium adsorption capacity, achieving a remarkable 97.3% photocatalytic removal efficiency within 2 h. At an initial uranium concentration of 200 ppm, the material demonstrated an exceptional extraction capacity of 976.7 mg g⁻¹, outperforming most reported photocatalysts. These findings highlight the potential of this 3D core–shell design for efficient uranium recovery and environmental purification applications. Full article

As a common semiconductor material, BiOBr has a unique layered structure and a suitable bandgap. However, the slow electron–hole separation efficiency leads to poor photocatalytic performance. To solve this problem, BiOBr/BNQDs heterojunctions were constructed. BiOBr/BNQDs composite photocatalysts were prepared by the solvothermal method, and the cocatalyst BNQDs were loaded onto BiOBr via electrostatic adsorption to enhance the photocatalytic degradation activity towards Rhodamine B (RhB). The photocatalysts were characterized by FT-IR, XRD, XPS, SEM-EDS, UV-Vis, PL, EIS, etc. Compared with pure BiOBr, the construction of heterojunctions BiOBr/BNQDs realized the rapid elimination of weak carriers and the effective separation and enrichment of high-energy carriers, which improved the efficiency of photocatalytic degradation of RhB. Among them, BiOBr/BNQDs-8.3% demonstrated the highest photocatalytic activity. The degradation rate of RhB under visible light irradiation for 60 min was up to 98.56%, and the reaction rate constant was 0.0696 min⁻¹, which was 2.80 times that of pure BiOBr. Moreover, after five photocatalytic cycles, the degradation rate was still 87.58%, demonstrating good cycling stability. Full article

Improving the catalytic performance of the oxygen evolution reaction (OER) for water splitting in acidic media is crucial for the production of clean and renewable hydrogen energy. Herein, we study the OER electrocatalytic properties of various active sites on four exposed (110) and ($\overline{1}$10) surfaces of Sn-doped RuO₂ (Sn/RuO₂) with antiferromagnetic arrangements in acidic environments. The Sn/RuO₂ bulk structure with the Cm space group exhibits favorable thermodynamic stability. The coordinatively unsaturated metal (M_cus) sites distributed on the right branch of the volcano plot are generally more active than the bridge-bonded lattice oxygen (O_br) sites located on the left. Different from the conventional knowledge that the most active site is located in the nearest neighbor of the doped atom, it has a lower OER overpotential when the active site is 3.6 Å away from the doped Sn atom. Among the sites studied, the 46-Ru_cus site exhibits the optimal OER catalytic performance. The inherent factors affecting the OER activity of each site on the Sn/RuO₂ surface are further analyzed, including the center of the d/p band at the active sites, the average electrostatic potential of the ions, and the number of transferred electrons. This work provides a reminder for the selection of active sites used to evaluate catalytic performance, which will benefit the development of efficient OER electrocatalysts. Full article

Commercial alumina and silica–alumina catalysts were investigated for propylene (PEN) production via an isopropanol (IPA) dehydration reaction between 200 and 300 °C at an atmospheric pressure and IPA partial pressure of 5136 Pa. The reaction conditions were chosen to fit with the further conversion of PEN into value-added compounds with minimal capital cost, and the conceptual process design was discussed. The textural properties, structure and chemical composition of as-received and hydrothermally treated catalysts were characterised by the adsorption–desorption of N₂, X-ray fluorescence, X-ray diffraction and Nuclear Magnetic Resonance spectroscopy. The adsorption microcalorimetry of NH₃ and SO₂ was used to determine the amount, strength and strength distribution of acid–base sites, while the nature of the acid sites was investigated by Fourier Transform Infraed spectroscopy. Surface area, pore-size distribution and pore volume were not determining factors for the catalytic performances of studied solids in the conditions used here. The best-performing catalyst combined stable textural properties and a high number of high-strength acid sites (Q_diff > 150 kJ/mol NH₃) under hydrothermal conditions. The importance of determining the number and strength of acid sites of water-aged catalysts, when considering reactions where water is present as reactive or product, is underlined. Full article

Because the interfacial Cu⁰/Cu⁺ in Cu-based electrocatalyst promotes CO₂ electroreduction activity, it would be highly desirable to physically separate Cu-based nanoparticles through coating shells and load them onto porous carriers. Herein, multilayered graphene-coated Cu (Cu@G) nanoparticles with tailorable core diameters (28.2–24.2 nm) and shell thicknesses (7.8–3.0 layers) were fabricated via lased ablation in liquid. A thin Cu₂O layer was confirmed between the interface of the Cu core and the graphene shell, providing an interfacial Cu⁰/Cu⁺. Cu@G cross-linked biochars (Cu@G/Bs) with developed porosity (31.8–155.9 m²/g) were synthesized. Morphology, crystalline structure, porosity, and elemental chemical states of Cu@G and Cu@G/Bs were characterized. Cu@G/Bs captured CO₂ with a maximum sorption capacity of 107.03 mg/g at 0 °C. Furthermore, 95.3–97.1% capture capacity remained after 10 cycles. Cu@G/Bs exhibited the most superior performance with 40.7% of FE_C2H4 and 21.7 mA/cm² of current density at −1.08 V vs. RHE, which was 1.7 and 2.7 times higher than Cu@G. Synergistic integration of developed porosity for efficient CO₂ capture and the fast charge transfer rate of interfacial Cu₂O/Cu enabled this improvement. Favorable long-term stability of the phase/structure and CO₂ electroreduction activity were present. This work provides new insight for integrating Cu@G and a biochar platform to efficiently capture and electro-reduce CO₂. Full article

Bilirubin is a key component in the preparation of two traditional Chinese medicines: Calculus bovis sativus and Calculus bovis artifactus. Currently, industrial-scale production of bilirubin is limited to extraction from pig bile in a very low yield and its market price is very high, so it is important to develop an alternative method for producing bilirubin. This study developed a potential process for bilirubin production through biotransformation of biliverdin. The codon-optimized gene for biliverdin reductase (BVR) from Synechocystis PCC6803 was recombinantly expressed in Komagataella phaffii GS115, resulting in the genetically modified strain GS115-bvdR, which successfully expressed BVR with intracellular activity. Whole cells of GS115-bvdR were capable of transforming biliverdin to bilirubin in vitro. The overexpression conditions were optimized to enhance BVR production by GS115-bvdR, and the optimal conditions for the biotransformation of biliverdin into bilirubin using resting GS115-bvdR cells were established (pH 5.0 buffer, at 30 °C for 24 h, with 200 mg/L biliverdin). Under these conditions, a bilirubin concentration of 153 mg/L was achieved, with a conversion of 76.2% from biliverdin. These findings provide valuable insights for future studies on the biosynthesis of bilirubin through metabolic engineering. Full article

Wastewater treatment has become a priority in the global attempt to address environmental pollution. Conventional wastewater treatment processes are often limited by their high energy consumption, so it is necessary to develop new technologies. This work shows the results obtained using a passive aerated membraneless microbial fuel cell (PAML-MFC) system consisting of 10 individual units, designed to treat 1000 L/day of real wastewater, using granular activated carbon anodes and cathodes. The pilot-scale water treatment system under study combines design and materials to result in low-cost operation. After 300 days of treating real wastewater originally characterized by a chemical oxygen demand (COD) value of 500 mg/L on average, it was found that the PAML-MFC under study removed 60 to 80% of the COD contained in real wastewater. Under these conditions, the individual MFCs reached an average power density below 1 mW/m³. Full article

Pyrolysis of oily sludge (OS) faces two significant challenges, dehydration in emulsion and coke formation, which cause extra energy consumption. Targeting energy saving, this paper first reported on solar photothermal dehydration and confined catalytic pyrolysis of OS using a single material. A wood sponge loaded with carbon dots (CM-CDs) can generate heat by absorbing solar energy and promote rapid phase separation and water transport via capillary action of oil–water emulsion in OS under sunlight. Almost all free water in OS with varied content can be removed after 3 h. Hydrocarbons entered the internal space of CM-CDs instead of contacting with soil minerals, contributed to the subsequent confined catalytic pyrolysis, led to a reduction in Ea (35.61 kJ/mol), inhibited coking and caking, and yielded higher oil recovery efficiency. In addition, CDs can form hotspots to enhance pyrolytic behaviors in local regions. When the ratio of OS to CM-CDs reached 10:0.6, the recovery rate of the oil fraction through combined pyrolysis was as high as 89%, which was 17% higher than that of OS pyrolysis alone. This discovery provides a new way to solve the bottleneck problems of OS pyrolysis in the industry. Full article

The development of low-cost and high-efficiency oxygen evolution reaction (OER) catalysts is essential to enhance the practicality of electrochemical water splitting for green hydrogen production. Layered double hydroxides (LDHs), especially those based on nickel and cobalt, have attracted attention due to their tunable composition, abundant redox-active sites, and earth-abundant constituents. However, their application is hindered by their limited conductivity and sluggish reaction kinetics. In this study, rare-earth-element-doped NiCo LDHs were synthesized directly on nickel foam through a one-step hydrothermal approach to improve the OER activity by modulating the electronic structure and optimizing the surface morphology. Among the representative catalysts, the incorporation of Sm significantly influenced the microstructure and electronic configuration of the catalyst, as confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Electrochemical tests showed that the optimized Sm-NiCo LDH achieved a low overpotential of 172 mV at 10 mA cm⁻² and a small Tafel slope of 84 mV dec⁻¹ in 1 M KOH, indicating an expanded electrochemically active surface and improved charge transport. Long-term stability tests further showed its durability. These findings suggest that Sm doping enhances the OER performance by increasing active site exposure and promoting efficient charge transfer, offering a promising strategy for designing rare-earth-modified, non-precious-metal-based OER catalysts. Full article

In this study, a novel strategy to enhance the performance of palladium (Pd)-based catalysts by doping with metal oxides (Mn₃O₄, MoO₃, and SnO) has been developed in order to overcome the limitations of its low activity and high cost in the catalytic oxidation of formaldehyde (HCHO). The novelty of this strategy lies in the fact that by precisely controlling the types and doping ratios of the metal oxides, a significant enhancement of the electrochemical performance and catalytic activity of the Pd-based catalysts was achieved, while the dependence on precious metals was reduced and the cost-effectiveness of the catalysts was improved. The effects of different metal oxide doping on the catalytic performance were systematically investigated by electrochemical characterization and catalytic activity tests. Among the prepared catalysts, Pd-Mn₃O₄ showed the most excellent performance, with an electrochemically active surface area of 20.6 m²/g and a formaldehyde oxidation reaction (FOR) current density of 3.5 mA/cm², which were 31.6% and 169.2% higher than pure Pd, respectively. In a 1000 s timed current method stability test, the limiting current density of Pd-Mn₃O₄ reached 0.48 mA/cm², which is 4.4 times higher than that of pure Pd. The excellent catalytic performance is attributed to the abundant surface hydroxyl (-OH) groups provided by Mn₃O₄, which contribute to the oxidation of formaldehyde intermediates, as well as the electronic synergistic effect between Pd and Mn₃O₄, which is manifested as a 0.4 eV downshift of the Pd 3d binding energy. In addition, the sensor evaluation showed that the Pd-Mn₃O₄-based formaldehyde sensor exhibited a high sensitivity (1.5 μA/ppm), excellent linearity (R² = 0.995), minimal long-term degradation (<7% in 30 days), and ~20-fold selectivity for formaldehyde over interfering gases (e.g., ethanol). This study provides a theoretical basis and practical material reference for the development of efficient and low-cost catalysts for formaldehyde oxidation. Full article

With the increasing severity of global water pollution, traditional wastewater treatment methods have gradually revealed limitations in dealing with complex and refractory pollutants. Advanced oxidation processes (AOPs) have emerged as a promising alternative due to their ability to generate highly reactive radicals (such as hydroxyl and sulfate radicals) that can effectively degrade a wide range of pollutants. This review provides a detailed overview of various AOP technologies, including Fenton processes, ozone-based AOPs, persulfate-based AOPs, photocatalytic AOPs, electrochemical AOPs, and sonochemical AOPs, focusing on their fundamental principles, reaction mechanisms, catalyst design, and application performance in treating different types of wastewater. The research results show that the improved Fenton process can achieve a chemical oxygen demand (COD) removal rate of up to 85% when treating pharmaceutical wastewater. Photocatalytic AOP technology demonstrates higher degradation efficiency when treating industrial wastewater containing refractory pollutants. In addition to effectively degrading refractory pollutants and reducing dependence on traditional biological treatment methods, these advanced oxidation processes can also significantly reduce secondary pollution generated during the treatment process. Moreover, by optimizing AOP technologies, the deep mineralization of harmful substances in wastewater can be achieved, reducing the potential pollution risks to groundwater and soil while also lowering energy consumption during the treatment process. Additionally, this review discusses the challenges faced by AOPs in practical applications, such as high energy consumption, insufficient catalyst stability, and secondary pollution. This review summarizes the research progress and application trends of catalytically driven AOPs in the field of wastewater treatment over the past five years. It aims to provide a comprehensive reference for researchers and engineering professionals on the application of AOPs in wastewater treatment, promoting the further development and practical implementation of these technologies. Full article

CO₂ methanation offers a sustainable route to reduce greenhouse gas emissions by converting carbon dioxide into methane, a valuable renewable fuel. This exothermic reaction not only mitigates its environmental impact but also provides energy-efficient benefits, as the heat generated can be reused in industrial applications. In this study, CO₂ methanation was carried out in a continuous flow reactor with a CO₂:H₂ molar ratio of 1:4 and a gas hourly space velocity (GHSV) of 12,000 h⁻¹, using a Ni-Al-LDH catalyst with a molar ratio of 2.3. The research focused on how calcination and reduction conditions affect catalyst structure and activity. Characterization techniques such as BET, XRD, TPR, H₂-TPD, and CO₂-TPD revealed that these conditions significantly influence surface area, crystallinity, phase composition, and metal dispersion. A higher reduction temperature decreased the surface area and increased both the crystallite size and basicity. The findings highlight that thermal treatment play a crucial role in optimizing the catalytic properties of NiAl catalyst. The sample calcined at 600 °C showed greater activity at lower reaction temperatures, while the catalyst calcined at 400 °C performed better above 300 °C. Additionally, the evaluation of the effect of the reduction atmosphere during catalyst activation showed that H₂ is a more effective reducing gas at lower reaction temperatures, whereas biogas showed a better performance at higher temperatures. Importantly, XRD results showed the catalysts maintained their structural integrity post-reaction, with no significant carbon deposition in the H₂ atmosphere, confirming their potential for long-term application in CO₂ methanation. Full article

Integrating photocatalysis with adsorption represents an efficient approach to improving the removal performance of organic contaminants from aqueous environments. To address the issues of severe charge recombination and poor adsorption activity in TiO₂ photocatalysts during the photocatalytic degradation of organic pollutants. In this study, we used macroporous resin as a carrier and prepared La/N-doped TiO₂/macroporous resin composite materials (La/N/TiO₂-MAR) via a hydrothermal-assisted sol–gel method. The results show that the composite material has a spherical morphology. N can be doped into the TiO₂ crystal, while La³⁺ remains on the surface of TiO₂ without entering the crystal lattice. La/N/TiO₂-MAR demonstrates a higher specific surface area and enhanced light absorption capacity, which facilitates both adsorption and photocatalytic degradation. At the La³⁺ doping concentration of 0.05 M, La_0.05/N/TiO₂-MAR demonstrates optimal photocatalytic degradation performance, achieving an 85.36% removal rate of Rhodamine B after 240 min of visible-light exposure. Full article