(Fernando F. Rivera, Berenice Miranda-Alcántara, Germán Orozco, Carlos Ponce de León, Luis F. Arenas, pp. 399‒409)
Redox flow batteries are being developed to contribute to the large-scale energy storage required for the full implementation of renewable energy sources. A grid incorporating energy storage is capable of managing the load-levelling needs set by wind and sol [Detail] ...
Zeolitic imidazolate framework-8 (ZIF-8), composed of Zn ions and imidazolate ligands, is a class of metal-organic frameworks, which possesses a similar structure as conventional aluminosilicate zeolites. This material exhibits inherent porous property, high loading capacity, and pH-sensitive degradation, as well as exceptional thermal and chemical stability. Extensive research effort has been devoted to relevant research aspects ranging from synthesis methods, property characterization to potential applications of ZIF-8. This review focuses on the recent development of ZIF-8 synthesis methods and its promising applications in drug delivery. The potential risks of using ZIF-8 for drug delivery are also summarized.
The emergence of electronic devices has brought earth-shaking changes to people’s life. However, an external power source may become indispensable to the electronic devices due to the limited capacity of batteries. As one of the possible solutions for the external power sources, the triboelectric nanogenerator (TENG) provides a novel idea to the increasing number of personal electronic devices. TENG is a new type of energy collector, which has become a hot spot in the field of nanotechnology. It is widely used at the acquisition and conversion of mechanical energy to electric energy through the principle of electrostatic induction. On this basis, the TENG could be integrated with the energy storage system into a self-powered system, which can supply power to the electronic devices and make them work continuously. In this review, TENG’s basic structure as well as its working process and working mode are firstly discussed. The integration method of TENGs with energy storage systems and the related research status are then introduced in detail. At the end of this paper, we put forward some problems and discuss the prospect in the future.
Nanosized NiO, CeO2 and NiO-CeO2 mixed oxides with different Ni/Ce molar ratios were prepared by the soft template method. All the samples were characterized by different techniques as to their chemical composition, structure, morphology and texture. On the catalysts submitted to the same reduction pretreatment adopted for the activity tests the surface basic properties and specific metal surface area were also determined. NiO and CeO2 nanocrystals of about 4 nm in size were obtained, regardless of the Ni/Ce molar ratio. The Raman and X-ray photoelectron spectroscopy results proved the formation of defective sites at the NiO-CeO2 interface, where Ni species are in strong interaction with the support. The microcalorimetric and Fourier transform infrared analyses of the reduced samples highlighted that, unlike metallic nickel, CeO2 is able to effectively adsorb CO2, forming carbonates and hydrogen carbonates. After reduction in H2 at 400 °C for 1 h, the catalytic performance was studied in the CO and CO2 co-methanation reaction. Catalytic tests were performed at atmospheric pressure and 300 °C, using CO/CO2/H2 molar compositions of 1/1/7 or 1/1/5, and space velocities equal to 72000 or 450000 cm3∙h–1∙gcat–1. Whereas CO was almost completely hydrogenated in any investigated experimental conditions, CO2 conversion was strongly affected by both the CO/CO2/H2 ratio and the space velocity. The faster and definitely preferred CO hydrogenation was explained in the light of the different mechanisms of CO and CO2 methanation. On a selected sample, the influence of the reaction temperature and of a higher number of space velocity values, as well as the stability, were also studied. Provided that the Ni content is optimized, the NiCe system investigated was very promising, being highly active for the COx co-methanation reaction in a wide range of operating conditions and stable (up to 50 h) also when submitted to thermal stress.
Hierarchical single-crystal ZSM-5 zeolites with different Si/Al ratios (Hier-ZSM-5-x, where x = 50, 100, 150 and 200) were synthesized using an ordered mesoporous carbon-silica composite as hard template. Hier-ZSM-5-x exhibits improved mass transport properties, excellent mechanical and hydrothermal stability, and higher catalytic activity than commercial bulk zeolites in the benzyl alcohol self-etherification reaction. Results show that a decrease in the Si/Al ratio in hierarchical single-crystal ZSM-5 zeolites leads to a significant increase in the acidity and the density of micropores, which increases the final catalytic conversion. The effect of porous hierarchy on the diffusion of active sites and the final catalytic activity was also studied by comparing the catalytic conversion after selectively designed poisoned acid sites. These poisoned Hier-ZSM-5-x shows much higher catalytic conversion than the poisoned commercial ZSM-5 zeolite, which indicates that the numerous intracrystalline mesopores significantly reduce the diffusion path of the reactant, leading to the faster diffusion inside the zeolite to contact with the acid sites in the micropores predominating in ZSM-5 zeolites. This study can be extended to develop a series of hierarchical single-crystal zeolites with expected catalytic performance.
Polymer-derived porous carbon was used as a support of iron and nickel species with an objective to obtain an efficient oxygen reduction reaction (OER) catalyst. The surface features were extensively characterized using X-ray diffraction, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. On FeNi-modified carbon the overpotential for OER was very low (280 mV) and comparable to that on noble metal catalyst IrO2. The electrochemical properties have been investigated to reveal the difference between the binary alloy- and single metal-doped carbons. This work demonstrates a significant step for the development of low-cost, environmentally-friendly and highly-efficient OER catalysts.
A series of Ni/HZSM-5 and Ni/HIM-5 bi-functional catalysts were synthesized and applied to the aqueous-phase hydrodeoxygenation (HDO) of phenol. The Ni dispersibility and particle sizes were shown to be directly related to the porosity and crystal sizes of the parent zeolites, which further influenced the catalytic performances. The large pores and small crystal sizes of the parent zeolites were beneficial for dispersing Ni and forming small Ni particles, and the corresponding Ni/zeolite catalyst exhibited a higher phenol conversion and selectivity towards hydrocarbons. Importantly, the Ni/HIM-5 bi-functional catalyst exhibited a high activity (98.3%) and high selectivity for hydrocarbons (98.8%) when heated at 220°C for 1 h and is thus a new potential catalyst for the HDO of phenolics to form hydrocarbons in the aqueous phase.
In this paper, a series of cobalt catalysts supported on reduced graphene oxide (rGO) nanosheets with the loading of 5, 15 and 30 wt-% were provided by the impregnation method. The activity of the prepared catalysts is evaluated in the Fischer-Tropsch synthesis (FTS). The prepared catalysts were carefully characterized by nitrogen adsorption-desorption, hydrogen chemisorption, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, temperature programmed reduction, transmission electron microscopy, and field emission scanning electron microscopy techniques to confirm that cobalt particles were greatly dispersed on the rGO nanosheets. The results showed that with increasing the cobalt loading on the rGO support, the carbon defects are increased and as a consequence, the reduction of cobalt is decreased. The FTS activity results showed that the cobalt-time yield and turnover frequency passed from a maximum for catalyst with the Co0 average particle size of 15 nm due to the synergetic effect of cobalt reducibility and particle size. The products selectivity results indicated that the methane selectivity decreases, whereas the C5+ selectivity raises with the increasing of the cobalt particle size, which can be explained by chain propagation in the primary chain growth reactions.
Recently, many efforts have been dedicated to creating enzyme-mimicking catalysts to replace natural enzymes in practical fields. Inspired by the pathological biomineralization behaviour of L-cystine, in this study, we constructed a laccase-like catalyst through the co-assembly of L-cystine with Cu ions. Structural analysis revealed that the formed catalytic Cu-cystine nanoleaves (Cu-Cys NLs) possess a Cu(I)-Cu(II) electron transfer system similar to that in natural laccase. Reaction kinetic studies demonstrated that the catalyst follows the typical Michaelis-Menten model. Compared with natural laccase, the Cu-Cys NLs exhibit superior stability during long-term incubation under extreme pH, high-temperature or high-salt conditions. Remarkably, the Cu-Cys NLs could be easily recovered and still maintained 76% of their activity after 8 cycles. Finally, this laccase mimic was employed to develop a colorimetric method for epinephrine detection, which achieved a wider linear range (9–455 μmol·L−1) and lower limit of detection (2.7 μmol·L−1). The Cu-Cys NLs also displayed excellent specificity and sensitivity towards epinephrine in a test based on urine samples.
Dimethyl ether (DME) carbonylation is considered as a key step for a promising route to produce ethanol from syngas. Heteropolyacids (HPAs) are proved to be efficient catalysts for DME carbonylation. In this work, the reaction mechanism of DME carbonylation was studied theoretically by using density functional theory calculations on two typical HPA models (HPW, HSiW). The whole process consists of three stages: DME dissociative adsorption, insertion of CO into methoxyl group and formation of product methyl acetate. The activation barriers of all possible elementary steps, especially two possible paths for CO insertion were calculated to obtain the most favorable reaction mechanism and rate-limiting step. Furthermore, the effect of the acid strength of Brønsted acid sites on reactivity was studied by comparing the activation barriers over HPW and HSiW with different acid strength, which was determined by calculating the deprotonation energy, Mulliken population analyses and adsorption energies of pyridine.
This study focuses on the synthesis of new liquid aromatic bismaleimide monomers in order to improve self-curing on demand (SCOD) systems previously based on aliphatic bismaleimides. These SCOD systems are based on Diels-Alder (DA)/retro-DA reactions. The syntheses of new different aromatic bismaleimides with ester and amide bonds are presented. These maleimides have been protected using DA reaction and characterized by 1H NMR analysis to determine protection rate and diastereomer ratios. The retro-DA reactions of both aromatic and aliphatic DA adducts in presence of thiol molecules were studied. Kinetic analysis was monitored by 1H NMR and compared to model study. Finally, both aromatic and aliphatic bismaleimides-based polymers were synthesized with 2-mercaptoethyl ether and thermal properties of polymers were compared. The glass transition temperature values ranged from –20 °C to 14 °C and very good thermal stabilities were observed (up to 300 °C).
In this study, a facile and environmentally friendly method with low energy consumption for preparing nanoscale AgCl and BaSO4 co-precipitates (AgCl@BaSO4 co-precipitates) was developed based on the metathetical reaction. Then, the dried co-precipitates were melt-compounded with polyamide 6 (PA6) resins at a specified mass ratio in a twin-screw extruder. The results demonstrated that in the absence of any coating agent or carrier, the nanoparticles of AgCl@BaSO4 co-precipitates were homogeneously dispersed in the PA6 matrix. Further analysis showed that after the addition of AgCl@BaSO4 co-precipitates, the antibacterial performance, along with the flame-retardance and anti-dripping characteristics of PA6, was enhanced significantly. In addition, the PA6 composites possessed high spinnability in producing pre-oriented yarn.
Polyamide (PA) hollow fibre composite nanofiltration (NF) membranes with a coffee-ring structure and beneficial properties were prepared by adding graphene oxide (GO) into the interfacial polymerization process. The presentation of the coffee-ring structure was attributed to the heterogeneous, finely dispersed multiphase reaction system and the “coffee-stain” effect of the GO solution. When the piperazine concentration was 0.4 wt-%, the trimesoyl chloride concentration was 0.3 wt-%, and the GO concentration was 0.025 wt-%, the prepared NF membranes showed the best separation properties. The permeate flux was 76 L·m−2·h−1, and the rejection rate for MgSO4 was 98.6% at 0.4 MPa. Scanning electron microscopy, atomic force microscopy, and attenuated total reflectance-Fourier transform infrared spectroscopy were used to characterize the chemical structure and morphology of the PA/GO NF membrane. The results showed that GO was successfully entrapped into the PA functional layer. Under neutral operating conditions, the PA/GO membrane showed typical negatively charged NF membrane separation characteristics, and the rejection rate decreased in the order of Na2SO4>MgSO4>MgCl2>NaCl. The PA/GO NF membrane showed better antifouling performance than the PA membrane.
A mixture of Pingdingshan lean coal and acid-treated Huadian oil shale was co-pyrolyzed in a drop-tube fixed-bed reactor in the temperature range of 300 °C–450 °C. To reveal the formation mechanism of the solid co-pyrolysis product, changes in some physicochemical properties were investigated, using analysis by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, pore analysis, thermogravimetry, and electron spin resonance. X-ray diffraction showed that the lattice plane spacing for the co-pyrolyzed mixture decreased from 0.357 nm to 0.346 nm and the average stacking height increased from 1.509 nm to 1.980 nm in the temperature range of 300 °C–450 °C, suggesting that pyrolysis treatment increased its degree of metamorphism. The amount of oxygen-containing functional groups and pore volume decreased with increasing temperature. Thermogravimetry and electron spin resonance results showed that synergistic effects occurred during the co-pyrolysis process. A formation mechanism for the solid product was proposed. Hydrogen-rich radicals generated from the pyrolysis of the oil shale were trapped by hydrogen-poor macromolecular radicals of the intermediate metaplast produced from coal pyrolysis, thereby increasing the yield of solid product.
Mass transfer usually affects the rate of chemical reactions in coal. The effect of internal diffusion on char gasification with CO2 in the temperature range from 1123 K to 1273 K was investigated via thermo-gravimetric analysis and assessment of char morphology features. The results revealed that the effect of internal diffusion on the initial reaction rate was more significant with an increase of particle size, due to the concentration gradient of the gasification agent within the solid particles. In the early stage of gasification, the generation of new micropores and the opening of closed pores led to an increase in specific surface area. As the reaction proceeded, the openings were gradually expanded and the specific surface area continued to increase. However, with further reaction, disappearance of edge pores, melting and collapse of the pore structure led to a decrease in specific surface area. The intrinsic activation energy and reaction order based on the nth-order model were 157.67 kJ∙mol−1 and 0.36, respectively. Thus, temperature zones corresponding to chemical reaction and diffusion control were identified. Moreover, the calculated effectiveness factor provided a quantitative estimation of internal diffusion in the initial stage.
The jet-flow high shear mixer (JF-HSM) is a new type of intensified equipment with special configurations of the rotor and the stator. The mass transfer property and power consumption were studied in the solid-liquid system for a series of JF-HSMs involving different configuration parameters, such as rotor diameter, rotor blade inclination, rotor blade bending direction, stator diameter, and stator bottom opening diameter. The flow characteristics were examined by computational fluid dynamic simulations. Results indicate that the turbulent power consumption of the JF-HSM is affected by the change in rotor blade inclination and stator bottom opening. With the increase in the shear head size and the change in the rotor into a backward-curved blade, the solid-liquid mass transfer rate can be remarkably increased under the same input power. Dimensionless correlations for the mass transfer coefficient and power consumption were obtained to guide the scale-up design and selection of such a new type of equipment to intensify the overall mixing efficiency.
Description of electrolyte fluid dynamics in the electrode compartments by mathematical models can be a powerful tool in the development of redox flow batteries (RFBs) and other electrochemical reactors. In order to determine their predictive capability, turbulent Reynolds-averaged Navier-Stokes (RANS) and free flow plus porous media (Brinkman) models were applied to compute local fluid velocities taking place in a rectangular channel electrochemical flow cell used as the positive half-cell of a cerium-based RFB for laboratory studies. Two different platinized titanium electrodes were considered, a plate plus a turbulence promoter and an expanded metal mesh. Calculated pressure drop was validated against experimental data obtained with typical cerium electrolytes. It was found that the pressure drop values were better described by the RANS approach, whereas the validity of Brinkman equations was strongly dependent on porosity and permeability values of the porous media.
Graphene oxide (GO) has been increasingly utilized in the fields of food, biomedicine, environment and other fields because of its benign biocompatible. We encapsulated two kinds of GO with different sizes on yeast cells with the assistance of polyelectrolytes poly (styrene sulfonic acid) sodium salt (PSS) and polyglutamic acid (PGA) (termed as Y@GO). The result does not show a significant difference between the properties of the two types of Y@GO (namely Y@GO1 and Y@GO2). The encapsulation layers are optimized as Yeast/PGA/PSS/PGA/GO/PGA/PSS based on the morphology, dispersity, colony-forming unit, and zeta potential. The encapsulation of GO increases the roughness of the yeast. It is proved that the Y@GO increases the survival time and enhance the activity of yeast cells. The GO shell improves the resistance of yeast cells against pH and salt stresses and extends the storage time of yeast cells.
Fungi play an important role in dying wastewater treatment. In this work, the mycelia of Lactarius deliciosus exhibited an excellent capacity in decolorizing coomassie brilliant blue (CBB). The results demonstrated that the mycelia could treat CBB with high concentrations over a broad range of pH and temperature. The decolorization rate of 99.19% and the removal rate of 16.31 mg·L‒1·h were realized. The mycelia could be recycled from decolorizing process for 19 times, indicating a good re-usability. It verified that the lignin peroxidase (121.65 U·L‒1) and manganese peroxidase (36.77 U·L‒1) were involved in the degradation and decolorization process of CBB. Toxicity assessments indicated the seed germination rate was up to 82.22% while inhibition to Escherichia coli decreased dramatically and no significant effect on Caenorhabditis elegans growth was found. The removal of CBB was a synergistic process accomplished by adsorption and biodegradation. The mycelia could be used for eco-friendly CBB treatment.
Metal organic frameworks (MOFs) are promising adsorbents for CO2 capture. Functional groups on organic linkers of MOFs play important roles in improving the CO2 capture ability by enhancing the CO2 sorption affinity. In this work, the functionalization effects on CO2 adsorption were systematically investigated by rationally incorporating various functional groups including –SO3H, –COOH, –NH2, –OH, –CN, –CH3 and –F into a MOF-177 template using computational methods. Asymmetries of electron density on the functionalized linkers were intensified, introducing significant enhancements of the CO2 adsorption ability of the modified MOF-177. In addition, three kinds of molecular interactions between CO2 and functional groups were analyzed and summarized in this work. Especially, our results reveal that –SO3H is the best-performing functional group for CO2 capture in MOFs, better than the widely used –NH2 or –F groups. The current study provides a novel route for future MOF modification toward CO2 capture.
In this research, an eco-friendly magnetic adsorbent based on Fe3O4/salicylic acid nanocomposite was fabricated using a facile one-pot co-precipitation method. The crystalline and morphological characterization of the prepared nanocomposite was performed by field emission scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The nanocomposite was employed as a magnetic solid-phase extraction agent for separation of Cd(II) ions from synthetic solutions. Some experimental factors affecting the extraction efficiency were investigated and optimized. Following elution with acetic acid (pH 3.5), the pre-concentrated analyte was quantified by flame atomic absorption spectrometry. In optimal conditions, a linear calibration graph was achieved in the concentration range of 0.2–30 ng·mL−1 with a determination coefficient (R2) of 0.9953. The detection limit, the enhancement factor, inter- and intra-day relative standard deviations (for six consecutive extractions at the concentration level of 10 ng·mL−1) were 0.04 ng·mL−1, 100, 2.38% and 1.52%, respectively. To evaluate the accuracy of the method, a certified reference material (NIST SRM 1643e) was analyzed, and there was a good agreement between the certified and the measured values. It was successfully utilized to determine cadmium in industrial wastewater samples and the attained relative recovery values were between 96.8% and 103.2%.