Numerical simulation of enhanced sludge drying via granulation and optimized dynamic transport

Hot air (HA) drying of banana has low drying efficiency and results in undesirable product quality. The objectives of this research were to investigate the feasibility of infrared (IR) heating to improve banana drying rate, evaluate quality of the dried product, and establish models for predicting drying characteristics. Banana slices of 5 mm and 8 mm thickness were dried with IR and HA at product temperatures of 60C, 70C and 80C. Banana drying characteristics and changes in residual polyphenol oxidase (PPO), Hydroxymethylfurfural (HMF), color, moisture content (MC) and water activity during the treatments were investigated. Results showed that significant moisture reduction and higher drying rates were achieved with IR drying compared to HA drying in the early stage. The drying data could be fitted to the Page model for accurate prediction of MC change for IR and HA drying with mean R2 of 0.983. It was noted that enzyme inactivation occurred more quickly with IR than with HA drying. A unique response of PPO under IR and HA drying was revealed. IR heating of banana inactivated PPO within the first 20 min of drying at 60C, 70C and 80C, while PPO was first activated before inactivation at 60C and 70C drying with HA. The highest HMF content occurred in banana slices with 5 mm thickness dried with IR at a product temperature of 80C. It is therefore recommendable to dry banana with IR at product temperature of 70C or below to preserve the product quality. These findings are new and provide more insight in the application of IR heating for drying banana for improved drying rate and product quality.

Effects of reduction conditions on the formation of porous MoOx from MoO3

CeO2 is an outstanding support commonly used for the CuO-based CO oxidation catalysts due to its excellent redox property and oxygen storage-release property. However, the inherently small specific surface area of CeO2 support restricts the further enhancement of its catalytic performance. In this work, the novel mesoporous CeO2 nanosphere with a large specific surface area (~190.4 m2/g) was facilely synthesized by the improved hydrothermal method. The large specific surface area of mesoporous CeO2 nanosphere could be successfully maintained even at high temperatures up to 500 °C, exhibiting excellent thermal stability. Then, a series of CuO-based CO oxidation catalysts were prepared with the mesoporous CeO2 nanosphere as the support. The large surface area of the mesoporous CeO2 nanosphere support could greatly promote the dispersion of CuO active sites. The effects of the CuO loading amount, the calcination temperature, mesostructure, and redox property on the performances of CO oxidation were systematically investigated. It was found that high Cu+ concentration and lattice oxygen content in mesoporous CuO/CeO2 nanosphere catalysts greatly contributed to enhancing the performances of CO oxidation. Therefore, the present mesoporous CeO2 nanosphere with its large specific surface area was considered a promising support for advanced CO oxidation and even other industrial catalysts.

Importance of mineral surface areas in Rotliegend sandstones for modeling CO2–water–rock interactions

Plasmonic metal nanostructures have shown great potential in sensing, photovoltaics, imaging and biomedicine, principally due to enhancement of the local electric field by light-excited surface plasmons, the collective oscillation of conduction band electrons. Thin films of nanoporous gold have received a great deal of interest due to the unique 3- dimensional bicontinuous nanostructures with high specific surface area. However, in the form of semi-infinite thin films, nanoporous gold exhibits weak plasmonic extinction and little tunability in the plasmon resonance, because the pore size is much smaller than the wavelength of light. Here we show that by making nanoporous gold in the form of disks of sub-wavelength diameter and sub-100 nm thickness, these limitations can be overcome. Nanoporous gold disks (NPGDs) not only possess large specific surface area but also high-density, internal plasmonic "hot-spots" with impressive electric field enhancement, which greatly promotes plasmon-matter interaction as evidenced by spectral shifts in the surface plasmon resonance. In addition, the plasmonic resonance of NPGD can be easily tuned from 900 to 1850 nm by changing the disk diameter from 300 to 700 nm. The coupling between external and internal nanoarchitecture provides a potential design dimension for plasmonic engineering. The synergy of large specific surface area, high-density hot spots, and tunable plasmonics would profoundly impact applications where plasmonic nanoparticles and non-plasmonic mesoporous nanoparticles are currently employed, e.g., in in-vitro and in-vivo biosensing, molecular imaging, photothermal contrast agents, and molecular cargos.

Increasing specific surface area and electrical conductivity are two crucial ways to improve the capacitive performance of electrode materials. Nanostructure usually enlarges the former but reduces the later; thus, it is still a great challenge to overcome such contradiction. Here, we report hydrogenated NiCo2O4 double-shell hollow spheres, combining large specific surface area and high conductivity to improve the capacitive performance of supercapacitors. The specific surface area of NiCo2O4 hollow spheres, fabricated via programmed coating of carbon spheres, was enlarged 50% (from 76.6 to 115.2 m2 g−1) when their structure was transformed from single-shell to double-shell. Furthermore, activated carbon impedance measurements demonstrated that the low-temperature hydrogenation greatly decreased both the internal resistance and the Warburg impedance. Consequently, a specific capacitance increase of >62%, from 445 to 718 F g−1, was achieved at a current density of 1 A g−1. Underlying such great improvement, the evolution of chemical valence and defect states with co-increase of these two factors was explored through X-ray photoelectron spectroscopy. Moreover, a full cell combined with NiCo2O4 and AC was assembled, and an energy density of 34.8 Wh kg−1 was obtained at a power density of 464 W kg−1. Hydrogenated hollow spheres with two shells rather than one are more suitable for use in supercapacitors, show scientists in China. Hollow microspheres are attractive electrodes for supercapacitors, which are promising power sources for hybrid electric vehicles. However, increasing the specific surface area of hollow microspheres tends to reduce their conductivity, whereas it is desirable to maximize both parameters for supercapacitors. Now, researchers have devised a two-pronged strategy to achieve this goal — using double-shell hollow spheres to increase the specific surface area and employing low-temperature hydrogenation to enhance the conductivity. By making both single-shell and double-shell NiCo2O4 hollow spheres, they showed that this strategy increased the specific surface area by 50% and greatly improved the conductivity, resulting in a 62% increase in the specific capacitance of the spheres. Hydrogenated NiCo2O4 double-shell hollow spheres, combining large specific surface area and high conductivity, are prepared. A specific capacitance increase of >62%, from 445 to 718 F g−1, is achieved at a current density of 1 A g−1. A full cell combined with NiCo2O4 and activated carbon is assembled, and an energy density of 34.8 Wh kg−1 is obtained at a power density of 464 W kg−1.

Ceramic foams with multi‐scale pores and large specific surface area have received extensive attention due to their unique structure and superior properties. Considering that there are still challenges to synthesize porous ceramics with large specific surface area, a novel ceramic foam material with ultra‐large specific surface area has been prepared using hollow silica mesoporous spheres (HMSSs) as building block in this work. These building blocks were made weakly hydrophobic in order to produce HMSS particle stabilized foams. The foams exhibit a uniform primary macropore structure, which is composed of a three dimensional HMSS‐assembled network, via HMSS‐stabilized foams. The influence of sintering temperature on the microstructure and properties of HMSS foams is investigated. The HMSS foams exhibit highest specific surface area of 1733 m2/g, attributed to the radial mesopores in HMSS shell, when sintered at between 500°C and 800°C. This specific surface area is much higher than that of existing ceramic materials. The uniform pore structure and ultra‐large specific surface area make it a promising lightweight material in potential application fields, including catalyst, adsorption, fire‐resistant thermal insulation, and load and control release system.

Minerals and organic matter comprise the solid phase of the soil. The geological origin of the soil minerals, and the input of organic matter from plants and ani­mals, are briefly discussed in section 1.2.1. A basic knowledge of the composition and properties of these materials is fundamental to understanding how a soil in­fluences the growth of grapevines. A striking feature of soil is the size range of the mineral matter, which varies from boulders (>600 mm diameter), to stones and gravel (600 to >2 mm diameter), to particles (<2 mm diameter)—the fine earth fraction. The fine earth fraction is the most important because of the type of miner­als present and their large surface areas. The ratio of surface area to volume de­fines the specific surface area of a particle. The smaller the size of an object, the larger is the ratio of its surface area to volume. This can be demonstrated by con­sidering spherical particles of radius 0.1 mm, 0.01 mm, and 0.001 mm (1 mi­crometer or micron, μm). The specific surface areas of these particles are 30, 300, and 3000 mm2/mm3, respectively. In practice, the specific surface area is mea­sured as the surface area per unit mass, which implies a constant particle density (usually taken as 2.65 Mg/m3). A large specific surface area means that more mol­ecules can be adsorbed on the surface. Representative values for the specific sur­face areas of sand, silt, and clay-size minerals are given in table 2.1. Note the large range in specific surface area, even for the clay minerals, from as little as 5 m2/g for kaolinite to 750 m2/g for Na-montmorillonite. Because specific surface areas are important, we need to know the size distri­bution of particles in the fine earth fraction. This is expressed as the soil’s texture. The types of minerals that make up the individual size fractions are also impor­tant because they too influence the reactivity of the surfaces. Both these topics are discussed here. All soils show a continuous distribution of particle sizes, called a frequency dis­tribution. This distribution relates the number (or mass) of particles of a given size to their actual size, measured by the diameter of an equivalent sphere.

2D TiO2 nanosheets for ultrasensitive humidity sensing application benefited by abundant surface oxygen vacancy defects

Nanostructured carbon materials possessing good mechanical properties, adsorption characteristics and electrochemical performances, are the most promising candidate for electrode materials of supercapacitors. Among all synthesis methods, hydrothermal synthesis of porous carbon nanosphere (PCNS) is mostly used. Structure-directing agent F108 (PEO132-PPO50-PEO132) has a similar function to popular agent F127(PEO106-PPO70-PEO106) and P123 (PEO20-PPO70-PEO20) used in hydrothermal synthesis, but has greater relative molecular mass and higher hydrophilic/hydrophobic volume ratio, so using block copolymer F108 as soft template will obtain PCNS with special physicochemical properties. In this paper, PCNS is prepared by post-processing, including carbonization and subsequent KOH activation, of phenolic resin nanoparticles obtained by hydrothermal synthesis through using phenolic resin as a carbon source and block copolymer F108 as a soft template. The as-prepared PCNS sample is characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction, nitrogen adsorption and FTIR, etc. The images of SEM, TEM and results of nitrogen adsorption show that the obtained PCNS has the advantages, such as uniform particle size about 120 nm, high spherical degree and large specific surface area of 1403 m2/g and also wide pore size distribution. The results show that post-processing has an important influence on the physicochemical property of PCNS sample such as specific surface area, pore size distribution, crystallinity and surface chemistry. The activation temperature plays an important role in forming pore structure as the specific area of PCNS sample increases from 519 m2g-1 to 1008 m2g-1 after activation at 700℃ (PCNS700), while the activation temperature changes to 900℃ (PCNS900), the specific area rises up to 1403 m2g-1. The pore size distributions show that the peaks are at the same position, which suggests that KOH activation at high temperature makes the primary pore of PCNS deeper. PCNS900 contains more mesopores than PCNS700, so it can be concluded that at the higher activation temperature, the deeper pores inside PCNS are formed, and it is worth noting that pores near 2 nm are largely produced when the temperature arrives at 900℃. KOH processing and high temperature processing contribute greatly to structural ordering, which means that PCNS samples are greatly graphitized. Last but not least, both KOH processing and high temperature processing reduce the number of functional groups on the surface of PCNS samples. Using PCNS samples as activated material to make electrodes, we study how the different physicochemical properties of PCNS samples affect the performance of PCNS electrode. As a result, PCNS700 and PCNS900 show notably larger specific capacitance than PCNS due to their great larger surface specific areas and more structural orderings in graphitic layer stacking. However, PCNS700 shows a lager specific capacitance of 146.75 F/g than PCNS900 (132 F/g) due to its higher number of surface functional groups than PCNS900, though its lower specific surface area. The pore size distribution has a huge influence on the supercapacitor rate capability as the PCNS900 which has more mesopores and the most structural orderings in graphitic layer stacking shows excellent rate capability as well as superior long-term cycling stability (97.5% capacitance retention over 10000 cycles). In summary, PCNS obtained by hydrothermal synthesis through using block copolymer F108 as soft template shows the special physicochemical properties which make it an ideal candidate for the electrode materials of supercapacitor. Moreover, the larger the specific area, more structural orderings in graphitic layer stacking, more appropriate content of mesopores and surface functional groups, the superior performance the electrode materials of surpercapacitor exhibit.

Introduction Quartz Crystal Microbalance (QCM) sensors are characterized by many potential applications. They are being widely used as biosensors, in pharmacological applications, for combustion control, environmental pollution monitoring, etc. [1]. Regardless the specific application, the recognition resolution of quartz chips is usually determined and restrained according to the Sauerbray equation (For example for 10 MHz QCM, the change of resonance frequency in 1 Hz corresponds to 4.4 ng/cm2 of adsorbed mass per surface). This fact is crucial mainly for gas sensor application where we need to detect concentration down to ppm or even ppb levels. However, there are some possibilities on how to enhance the QCM sensor properties and amplify their sensitivity, for instance by increasing the specific surface area of QCM electrodes, and thus providing more bonding sites for the analyte [2]. In this contribution, we propose a novel method that uses nanostructured materials called metal-blacks as a sublayer for the increase of active sensor surface, in combination with self-assembled monolayers (SAMs) that serves as a receptor layer. Metal-Blacks Metal-blacks – MBs are highly nanoporous and nanostructured materials with a large surface area. Their name originates in black colour, caused by the absorption of incident light on their surface. The incident light penetrates into the pores and channels where it undergoes multiple reflections in cavities and where it is almost completely absorbed. Due to the very large surface area, MBs are ideal materials for enhancement of QCM gas sensors properties [3]. Experimental The nanostructured layers of black gold (BAu) and black palladium (BPd) were prepared by evaporation from a tungsten boat at an elevated pressure of 200 Pa. Prepared layers of MBs were then characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SAMs of zinc octacarboxylphthalocyanine ZnPc(COOH)8 were prepared by two-step grafting method, where ZnPc(COOH)8 is covalently bonded to the molecule of aminothiophenol, which serves as an surface anchor via its gold/palladium-sulfur bond. The preparation procedure was as follows. At first, the QCM electrodes with MB layers were degreased in a sonicated ethanol bath during a few minutes and then dried under a nitrogen flow. Second, the QCM samples were cleaned by UV-ozone treatment and immediately immersed into 10-4 M solution of aminothiophenol in ethanol/DMF solvent for 24h. Third, after the 24h incubation time, the samples were moved into 10-4 M solution of the macrocycles and left there for another 24h. In the end, the samples were carefully rinsed with the solvent to eliminate adsorbed molecular overlayers and subsequently washed with ethanol in order to remove solvent residues and dried under nitrogen flux.Once prepared, QCM sensor impedance spectra were obtained by impedance analyzer Agilent 4294A. Responses towards different analytes (EtOH, CH4, H2O, NO2, toluene, acetaldehyde) were measured in a glass chamber that enables the measurement of up to 6 sensors at the same time. Sensors were measured at a constant gas flow and room temperature. The sensor resonant frequencies were measured by oscillattor circuits in connection with an NI PCI-6602 card used as a precise counter Results and Conclusions In this contribution, we have proved that highly nanoporous and nanostructured materials (such as metal-blacks), which have a large specific surface area, provide more binding sites for analytes and, hence, increase the response of the QCM sensors. As an example measurement, we present the response of QCMs with BAu towards ethanol vapours (Fig. 1). The curves illustrate that the response of the sensor with the BAu electrode is 10-times bigger than the one of the standard QCM (152Hz/15Hz). For the combined layer (BAu + ZnPc(COOH)8), the response amplification is not so large but it is still significant. In this case, the response is 3-times bigger than the one from the QCM with ZnPc(COOH)8 only (without BAu). However, in contrast with QCM with just bare BAu, the surface modification with SAMs layers influences the sensor selectivity. The combined layers of MBs and SAMs then result in a selective sensor with increased sensitivity. According to the presented results metal-blacks are promising materials that can significantly boost the sensitivity of QCM sensors and still preserve the selectivity of its active layers.

The effective conversion of carbon dioxide (CO2) into cyclic carbonates requires porous materials with high ionic content and large specific surface area. Herein, we developed a new systematic post-synthetic modification strategy for synthesizing imidazolium-based hypercrosslinked ionic polymers (HIPs) with high ionic content (up to 2.1 mmol g−1) and large specific surface area (385 m2 g−1) from porous hypercrosslinked polymers (HCPs) through addition reaction and quaternization. The obtained HIPs were efficient in CO2 capture and conversion. Under the synergistic effect of high ionic content, large specific surface area, and plentiful micro/mesoporosity, the metal-free catalyst [HCP-CH2-Im][Cl]-1 exhibited quantitative selectivities, high catalytic yields, and good substrate compatibility for the conversion of CO2 into cyclic carbonates at atmospheric pressure (0.1 MPa) in a shorter reaction time in the absence of cocatalysts, solvents, and additives. High catalytic yields (styrene oxide, 120 °C, 8 h, 94% yield; 100 °C, 20 h, 93% yield) can be achieved by appropriately extending the reaction times at low temperature, and the reaction times are shorter than other porous materials under the same conditions. This work provides a new strategy for synthesizing an efficient metal-free heterogeneous catalyst with high ionic content and a large specific surface area from HCPs for the conversion of CO2 into cyclic carbonates. It also demonstrates that the ionic content and specific surface area must be coordinated to obtain high catalytic activity for CO2 cycloaddition reaction.

CFD design and testing of an air flow distribution device for microwave infrared hot-air rolling-bed dryer

Supercapacitors is an electrochemical energy storage device typically used as sustainable power supply (such as electric vehicles and mobile electronic devices) due to their higher power density than batteries, higher energy density than conventional dielectric capacitors, and long life cycles. [1,2] Graphene, a two-dimensional (2D) one-atom-thick single layer of sp2-bonded carbon, is considered as an ideal electrode material in supercapacitors because of its superior electrical conductivity and exceptionally large specific surface area. Graphene sheets, unless well separated from each other, tend to form irreversible agglomerates through strong π-π stacking and van der Waals interaction.[3] Meanwhile, the electrochemical binders and additives are normally required to make graphene-based electrodes, which would have an adverse effect on the specific capacitance of the resulting electrodes. To tackle these challenges, three dimensional (3D) graphene networks with highly electrical conductivity and large specific surface area, short diffusion pathways for electrolyte ions and fast transport channels for electrons are very promising supercapacitor materials. To these aims, we have developed ways to synthesize a novel macroporous/nanoporous graphene sponge with tunable pore sizes. This 3D porous graphene sponge has i) an interconnected electrolyte-filled macroporous network that enables increase of contact surface between 3D network and electrolytic solution, and rapid ion transport, ii) short ion and electron transport lengths due to nanoporous structures, iii) a large electrode specific surface area and (iv) high electron conductivity in the electrode assembly. The structure characterization and capacitive properties of the 3D macroporous/nanoporous graphene sponge was investigated and discussed, indicating 3D porous graphene sponge as an ideal electrode materials for supercapacitors. Keywords：Graphene, 3D porous materials, supercapacitors, electrochemical energy

The quality and safety of agricultural products are strongly related to human livelihood. Thus, the government and consumers have recently paid increased attention to the quality and safety of agricultural products. The development of efficient, rapid, and sensitive analytical methods for detecting pesticides, veterinary drugs, heavy metals, mycotoxins, and environmental pollutants in agricultural products is of great significance. Owing to the complexity of many sample matrices and the low concentration of pollutants in a typical sample, appropriate sample pretreatment steps are necessary to enrich pollutants in agricultural products. Solid-phase extraction (SPE) is the most widely used sample pretreatment technology; in this technique, the adsorbent generally determines the selectivity and efficiency of the extraction process. An increasing number of novel materials have been used as SPE adsorbents. The extraction efficiency, extraction selectivity, and analytical throughput of SPE could be greatly improved by combining these novel materials with various extraction modes (e. g., solid-phase microextraction, dispersed SPE, and magnetic SPE (MSPE)) during sample preparation. Because of their large specific surface area and high affinity toward target analytes, nanomaterials are often used as SPE adsorbents, thereby greatly improving the selectivity and sensitivity of the analytical technology. More importantly, these materials have become a priority area of research on preconcentration technologies for trace compounds in agricultural products. This paper summarizes the adsorption characteristics of several new nanomaterials, including magnetic materials, carbon-based materials, metal nanomaterials (MNs), metal oxide nanomaterials (MONs), metal organic frameworks (MOFs), and covalent organic frameworks (COFs). These nanomaterials present numerous advantages, such as large specific surface areas, high adsorption capacities, and tailorable structural designs. MSPE employs magnetic materials as sorbents to afford fast dispersion and efficient recycling when applied to complex sample matrices under an external magnetic field. The use of MSPE can avoid several typical problems associated with SPE such as poor adsorbent packing and high pressure, thereby greatly simplifying the pretreatment process and providing a high flux for sample analysis. Carbon-based materials are powdered or bulk nonmetallic solid materials with carbon as the main component; carbon and nitrogen materials, mesoporous carbon, carbon nanotubes, and graphene are some examples of these materials. These materials provide large specific surface areas, abundant pore structures, good thermal stability, high mechanical strength and adsorption capacity, and controllable morphology. Pure and modified carbon nanomaterials have been successfully used to purify target analytes from agricultural products. Given their unique physical and chemical properties, MNs and MONs have attracted significant interest for use in sample preparation. MNs and MONs with excellent thermal and mechanical stabilities show good resistance to a wide pH range and diverse organic solvents, which is crucial in adsorbent-based extraction methods. The surface of these materials can be easily modified with various ligands to improve their selectivity. MOFs and COFs present many advantages such as large specific surface areas, high porosity, adjustable pore performance, and good thermal stability. Several methods that employ novel adsorbent materials to analyze pollutants in a variety of agricultural products, such as chromatography, spectroscopy, mass spectrometry, and other detection technologies, have been established. This paper also reviews the application of adsorbent materials in the analysis of agricultural product quality and safety, and discusses the future development trends of these sorbents in sample preparation for the safety analysis of agricultural products.