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Dielectric properties are some of the main parameters of materials, determining their interaction with electromagnetic energy during microwave heating. The dielectric properties of spent automobile catalyst were measured by using the resonance cavity perturbation technique from room temperature to 800°C at 915 MHz and 2450 MHz. The effects of temperature and frequency on the dielectric constant, dielectric loss factor, loss tangent, and penetration depth were studied. The results indicate that spent automobile catalyst is weakly polar, making it difficult to transform electromagnetic energy into heat. The relaxation time and conductivity obtained by numerical calculations further explain from the microlevel that spent automobile catalyst cannot dissipate electromagnetic energy through dipole loss or conduction loss under microwave irradiation. This work describes an effective way to explore the dielectric heating mechanism and a basis for understanding the interactions between microwaves and spent automobile catalyst. [ABSTRACT FROM AUTHOR]

In traditional large-scale industrial applications of solvent extraction, there are some limitations such as low extraction efficiency, emulsification, co-extraction, and potential safety hazards. Recently, the application of microfluidic technology in solvent extraction has been dedicated to avoid the above problems effectively. However, manufacturing microchannels becomes a key problem before the application of such a new technology. In this article, the design and fabrication of a "Y"-shaped microreactor by using a three-dimensional (3D) printer, and its feasibility for extraction and separation, is illustrated. The extraction performance of a "Y"-shaped microreactor was investigated by carrying out the extraction of In3+ and Fe3+ from a sulfate solution under different experimental conditions. When the residence time was 210 s, the volume fraction of extractant (D2EHPA) was 30%, and the initial pH value of the aqueous solution was 0.7, the extraction rate of In3+ and the separation coefficient βIn/Fe were 98.07% and 1593, respectively. Remarkably, the handling capacity of the 3D-printed "Y" microreactor presented in this work with a channel length of 36 mm was superior, whereas the extraction rate of In3+ was very close to that of the previously reported microchip with a channel length of 120 mm. [ABSTRACT FROM AUTHOR]

CuCl residue is a hazardous waste from the hydrometallurgical zinc recovery plant. It is very difficult to recycle due to complicated composition, highly corrosive nature, and refractory characteristics. Recently, a new process of microwave drying and roasting was successfully developed to produce both CuO solid and HCl gas products from the CuCl residue. In this paper, the dielectric property of the CuCl residue was measured under different moisture contents. The microwave absorption characteristics of the CuCl residue improved considerably as its moisture content increased. Laboratory-scale drying tests were conducted to evaluate the kinetics of microwave drying and to optimize the operation parameters. The efficiency of microwave drying was further demonstrated in industrial-scale level by microwave dryer developed in in-house. Finally, the drying mechanism of microwave heating of the sticky material was discussed and several measurements were optimized/implemented to intensify the drying process. [ABSTRACT FROM AUTHOR]

A comparison study about the extraction and separation of Cu2+ and Ni2+ with Lix984N in a microchannel reactor and separating funnel has been conducted. The results showed that, in the microchannel reactor, the overall volumetric mass transfer coefficient of copper was 20 times that of nickel, whereas in the separating funnel, it was only 2 times that of nickel. In addition, the separation coefficient of copper and nickel in the microchannel reactor was 5 times that of the conventional one. Typically, at initial pH=2.5, contact time 1.95 s, volume fraction of extractant Lix984N 15% and within 1.9 g l−1 nickel ion concentration, the extraction rate of copper was higher than 95%, but the nickel was hardly extracted. In comparison, it needed almost 50 s to reach a Cu extraction of 95% in the separation funnel, with more than 5% Ni co-extraction rate. Although the microfluid extraction showed excellent extraction performance, there exists a need to further improve its processing capacity to apply it to industrial production. Furthermore, scaling up the microreactor has become increasingly promising under the fast developing 3D printing technology. [ABSTRACT FROM AUTHOR]

Water is a kind of strongly microwave absorbing material. However, water is generally believed that it cannot enhance the effect of heat transfer and mass transfer of reactions at high temperature in the microwave field, due to its performance of easy drying. In this work, the intensifying effect of water on the high temperature reactions in the microwave field is proved. Specifically, the effects of different mixing methods of bauxite and alkaline, including wet mix and dry mix, on phase constitution, microstructure and leaching effect of roasting products in microwave heating process are compared. The results show that compared with the dry mixing, the wet mixing method is more benefit for forming NaAlO2and Ca2SiO4. The roasted product of wet mix is looser and more homogeneous, which is more conducive to the subsequent leaching process. The leaching rate of Al2O3is calculated to be 96.68% with wet mix at 800 °C and 92.58% with dry mix at 1000 °C. In addition, the mechanism of intensifying action of water on the high temperature reactions in the microwave field is discussed. [ABSTRACT FROM AUTHOR]

This work focuses on the column absorption and regeneration behavior of a granular red mud (GRM) for absorbing methylene blue (MB) in wastewater. By investigating key parameters, such as packing column height of adsorbent, initial concentration of MB, and flow rate, on the adsorption effects of GRM, the results show that the GRM can effectively remove MB from wastewater. The breakthrough time of the absorption process can be as high as 330 min, when 20.5 cm GRM column was used, with initial concentration and flow rate of MB wastewater being 150 mg L−1and 4 mL min−1, respectively. The Thomas model is capable of describing the adsorption kinetics. Finally, for assessing the regeneration ability of the loaded GRM, a series of experiments of eluting the MB-loaded column with dilute nitric acid solution, whose pH value is about 3.0, were conducted. The results showed that the regeneration and re-adsorption effect of the GRM column is good. [ABSTRACT FROM PUBLISHER]

[Display omitted] In the process of nitric acid dissolving precious metals, a large amount of NOx exhaust gas will be produced. This research aims at the development of a new method for the removal of low-concentration nitrogen oxides from metallurgical flue gas. In this process, a printed three-dimensional large-flow microstructure reactor and urea solution are used for the removal of NOx, which facilitates the greater efficiency of denitrification(≥94%). Urea plays an important role in the redox of NO 2 , such as NO 2 is reduced to N 2 in solution. Both the gas and the liquid phase simultaneously react in the microchannels of the microfluidic reactor. The channels allow the proper mixing of urea and NaClO 2 during the flow which efficiently removes NO x at low concentrations. The optimum condition for high denitration efficiency is outlined: the urea solution with 3%,temperature of the mixed solution is 293.15 K, gas–liquid flow mass ratio is 1:1, pH value (8.0–10.0), C NaClO2 = 0.02 mol/L. This work successfully describes the use of a microfluidic reactor to enhance and maintain the denitration efficiency. This work describes how to successfully enhance and maintain the denitration efficiency while using a printed three-dimensional large-flow microstructure reactor. [ABSTRACT FROM AUTHOR]

• Microwave flash evaporation(MFE) process could be utilized to concentrate sulfuric acid. • Power consumption and heat transfer of concentration process were analyzed. • Clean production mode averts the corrosion and the pollution of products. The ameliorative microwave flash evaporation system (MFE) was utilized to concentrate and distillate waste sulfuric acid, the system may overcome the problems of equipment corrosion, product pollution, high energy consumption, long process flow, and low heat transfer rate during recovery process of waste sulfuric acid. The dilute sulfuric acid with mass fraction of 75 wt% was used as experimental medium, 5 experimental cases was generated to verify the effects of MFE with the conditions of different volume, microwave power and depressurization rate. Experimental results demonstrated that the sulfuric acid could be concentrated to mass fraction of 85–95%, and the heating efficiency was among 30% to 80%, heat transfer volume coefficient was among 100 J/K·L-1 to 500 J/K·L-1 with the combination of vacuum and microwave heating during flash evaporation process. Thermal process analysis indicated that the interaction among experimental factors affected concentration and distillation process. At last, we gave the modeling and process optimization method for concentrating sulfuric acid through MFE process based on analyzing those experimental cases. [ABSTRACT FROM AUTHOR]

• Polyphosphoric acid (PPA) preparation though microwave intensification flash evaporation. • Over 92% fluorine separation and recycling for reduced environmental impact. • PPA with 75 wt.% P 2 O 5 content has only 89.98% operation cost in contrast to traditional method. • The influencing mechanism of the PPA preparation and fluorine recycling was studied. Traditional evaporators for the concentration of wet process phosphoric acid (WPA) suffer from concentration, corrosion, and low fluorine yield (less than 40 wt.%). Based on the excellent heating and permittivity properties of phosphoric acid in microwave fields, a microwave intensification flash evaporation (MFE) system is proposed to concentrate highly corrosive WPA for preparing polyphosphoric acid (PPA) and efficiently recovering valuable fluoride resources. A polytetrafluoroethylene tank in a microwave resonant cavity coupled with a vacuum pump is used to facilitate boiling and evaporation. This study reports the evolution of the PPA preparation process by flash evaporation, defluorination, and the boiling phenomenon. In addition, the influencing mechanism of pressure and temperature on PPA preparation and fluorine recovery are investigated. The experimental results indicate the successful preparation of PPA with a P 2 O 5 content higher than 75 wt.% and the cost is considerably much lower than the traditional method. Meanwhile, the recovery yield of fluorine exceeds 90 wt.%, alleviating the depletion of strategic natural resources and potential risk of environmental pollution. This study provides a basis for the efficient preparation of PPA and recovery of fluorine resource from WPA. It is also potentially significant to industries such as metallurgy and sewage treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • After 20 h of irradiation, 11.3 % BDOM mineralized, forming CH 3 /CH 2 /CH aliphatics. • BDOM400 exhibited 44% and 52% max binding with PHE and PTR, strong affinity. • Max binding of BDOM and PHE rose 12 % after 20 h light exposure. • The main quenching mechanisms for PHE and PTR were static and dynamic quenching. This study explores the physicochemical attributes of dissolved organic matter from rice straw biochar (BDOM) at varying pyrolysis temperatures and photo-irradiation conditions, focusing on the binding mechanisms of phenanthrene (PHE) and 9-phenanthrol (PTR) using multiple spectroscopic techniques and fluorescence quenching. Following 20 h of photo-irradiation, only 11.3 % of BDOM underwent mineralization, forming new CH 3 /CH 2 /CH aliphatics structures. BDOM from biochar produced by pyrolysis at 400°C exhibited a stronger binding affinity with PHE and PTR, achieving 44 % and 52 % maximum binding, respectively. Static and dynamic quenching governed PHE and PTR binding, which was influenced by temperature. Photo-irradiated BDOM showed enhanced binding with PHE, attributed to increased aliphatic content. Hydrogen bond and π-π electron-donor–acceptor (EDA) interactions dominated PTR binding, while π-π interactions and hydrophobic interactions controlled PHE. This study provides valuable insights into BDOM photochemical behaviors and their impact on the environmental fate of polycyclic aromatic hydrocarbons (PAHs) after BDOM photo-irradiation. [ABSTRACT FROM AUTHOR]

Biodegradable potato starch-assisted nanoferrite and ferrite–semiconductor nanocomposites have been synthesized by the co-precipitation method for the degradation of MB dye under visible light irradiation. Ferrite and ferrite–semiconductor composites synthesized using biodegradable potato starch displayed remarkable dye degradation activity which can be further explored for photocatalysis application. XRD confirms the pure phases for Fe3O4 (FFO) and ZnO–Fe3O4 (ZFFO), but a secondary SITO phase for TiO2–Fe3O4 (TFFO) and microwave-annealed TiO2–Fe3O4 (TFFO-MWA) due to dynamics between Fe, Ti, and NaOH. FTIR and Raman spectra confirmed the characteristic peaks of the starch surfactant and ferrite and/or semiconducting phase. TEM micrographs demonstrated mixed morphology: spherical particles of size 5–10 nm and rod shape of size 14–67 nm in length and 4–21 nm in diameter. XPS showed different valence states along with satellite peaks besides confirming the elemental composition. BET studies showed type-IV isotherms with H3 adsorption hysteresis indicative of mesoporous structures with ZFFO having the highest surface area (85.9 m2 g−1), minimum pore size, and maximum pore volume, while TFFO-MWA having the lowest surface area (19.1 m2 g−1), maximum pore size, and minimum pore volume. The direct bandgap of FFO, ZFFO, TFFO, and TFFO-MWA samples is found to be 2.50, 2.47, 3.18, and 3.16 eV, respectively. The photocatalytic degradation of MB dye under visible light irradiation was achieved to be 93% in 285 min by FFO, 96% in 150 min by ZFFO, 99% in 180 min by TFFO, and 99% in 90 min by TFFO-MWA. The R2 values of adsorption kinetics studies validated that the kinetics can be best described by the first-order model for FFO, TFFO, TFFO-MWA, and second-order model for ZFFO considering the maximum R2 values being established. [ABSTRACT FROM AUTHOR]

Investigating the microwave-absorbing characteristics of secondary copper smelting fly ash (SCFA), which is both a hazardous waste and valuable secondary resource, can be expected to expedite the efficient application of microwave heating technology in the comprehensive treatment of fly ash. Here, we have examined SCFA and its pure components, namely PbCl 2 , ZnO, and ZnS phases, with regard to thermal behavior and microwave-absorbing characteristics. Our results indicate that SCFA has excellent microwave-absorbing performance in the temperature range 30–800 °C, with a dielectric loss coefficient ε ″ of 5.68 × 10−2 F m−1 at ambient temperature and a maximum value of 36.29 × 10−2 F m−1 at 550 °C. As a consequence, the SCFA could be heated to 700 °C within 12.6 min. The heating process of SCFA can be divided into three main stages: removal of adsorbed water and bound water (<260 °C), oxidation reactions of Pb, PbO, ZnS, and PbS (260–437 °C), and deoxygenation reactions of PbO 2 , Pb 3 O 2 , and Pb 3 O 4 (437–1000 °C). The dielectric properties and thermal characteristics of SCFA are closely related, with PbCl 2 exerting a significant influence. We propose herein a microwave-heating mechanism of SCFA based on analysis of its thermogravimetric characteristics, dielectric properties, and heating behavior in a microwave field. • The dielectric properties and thermal behavior of SCFA were systematically investigated. • SCFA endowed excellent microwave-absorbing ability with increasing temperature. • PbCl 2 dominated the dielectric properties of SCFA. • Dielectric and heating properties studies suggest the microwave heating mechanism. [ABSTRACT FROM AUTHOR]

Good photocatalysts is one of the best approaches to harvest the solar energy. The performance of two-dimensional photocatalytic materials depends on their distinctive geometric structure and optical absorbed efficiency. However, the tendency to recombine the photogenerated electron-hole pairs in many two-dimensional materials limits their photocatalytic performances. Here, we find a novel FeOCl-type InBrSe monolayer of superior photocatalysis through first-principle calculations. Its electron mobility is 42.53 times greater than that of hole along y -axis, indicating that anisotropic mobilities limit the recombination of photogenerated electron-hole pairs. Its solar to hydrogen efficiency (27 %) exceeds the critical value (10 %) of commercial application of photocatalytic water splitting. Moreover, its suitable band edges are advantageous for spanning water redox potentials to achieve photocatalytic processes. Under biaxial strains, it obtains large optical absorption coefficients within the visible light range. Additionally, it exhibits favorable thermal, mechanical and structural stability, indicating that it is feasible for real-life experimental synthesis. Thus, we predict that the InBrSe monolayer is a promising candidate for photocatalyst. [ABSTRACT FROM AUTHOR]

Submicron zeolite has become the focus of research because of its high thermal stability, high catalytic activity, and uniform size. A rapid method for synthesizing submicron zeolite Y by using microwave heating is introduced in this work. The effect of directing agent, synthesis temperature, crystallization time, and alkali ratio on the synthesis of submicron zeolite Y is systematically investigated. XRD, SEM, and particle size investigations are carried out to characterize the obtained product. The experimental results show that adding directing agent, increasing the alkali ratio, increasing the temperature or prolonging the microwave radiation time are advantageous to the formation and growth of zeolite Y. However, the high alkali ratio leads to the dissolution of the generated crystal, while excessively increasing the temperature or crystallization time easily generates uneven-sized particles or causes crystal transformation. Submicron zeolite Y of particle size 0.5–0.8 μm accounting for 80% is synthesized at 110°C in just 2 h using alkali ratio of 3 under microwave heating. [ABSTRACT FROM AUTHOR]

This review highlights the synthesis, structure modification, morphology, and properties of nano manganese dioxide (MnO2). Though MnO2 has been widely employed for electrode materials due to its superior electrochemica1 performance, abundant storage, low cost, and environmental friendly nature, the usage in bioapplications and dye mineralisation studies have started since few decades only. Currently, nano MnO2 plays an important role in solar cell devices and gas sensing as it can be easily tunable into desired polymerphic structure and morphology. Herein, the use of nano MnO2 as advanced material in energy, gas sensing, biological application and wastewater remediation are described. Based on the recent research, the available preparation procedures, surface modification and applications of nanostructured MnO2 are systematically presented. Also, structure stabilization and performance improvement of nano MnO2 by doping or composite formation with metals, carbon materials, and conductive polymers are summerised. According to the latest research progress, new trends and strategies of nano MnO2 towards specific applications besides energy storage application are focused in this review, as well as a brief overview of the challenges and future perspectives of MnO2, synthetic methodologies, and their state-of-the-art applications in different fields are presented. [ABSTRACT FROM AUTHOR]

• A Large Flow Microstructure Reactor is designed and fabricated by using 3D Printing. • Shorter time and better extraction efficiency are obtained in microflow. • The mixing process of fluid material in the reactor was studied by finite element simulation. • Large flow rate extraction was realized by superposition of microchannels. • Mass transfer performance are identified from experimental results. A large-flow microstructured reactor has been designed and fabricated using microfluidics and 3D printing technology. The finite element model is used in order to study the mixing processes of the species in the reactor. The flow is cut by convection and then mixed with chaos into several zigzag channels to induce recirculation mixing. The distribution of pressure, concentration and inlet velocity of each channel are obtained by solving successively the Navier-Stokes equation and the diffusion-convection equation in the steady state form. The results illustrate the effect of both flow rate and reactor geometry on hydrodynamics efficiency and the influence of flow rate and reactor geometry on fluid dynamics. The simulation reveals the combined contribution of chaotic mixing and laminar flow recirculation with Reynolds number (Re) 1 < Re < 400. In the experimental study, microfluidic solvent extraction of copper from sulfate solution containing Cu2+ and Fe3+ using DZ988N show the extraction efficiency of copper to be greater than 75% while the extraction efficiency of iron is less than 5% at high flow rates, with the characteristics of high extraction efficiency, large treatment capacity, and wide range of application. [ABSTRACT FROM AUTHOR]

A rapid microwave heating method is proposed for the liquid phase synthesis of Y-type zeolite under high-temperature conditions. The effect of microwave heating temperatures, crystallization time and silica to alumina ratio on the synthesis of Y-type zeolite is systematically investigated. The synthesized samples are characterized by XRD, SEM, FT-IR, N 2 sorption and particle size analysis. Microwave treatment was found to promote the high-temperature synthesis of Y-type zeolite with the advantages of shorter crystallization time and product properties of the produced Y-type zeolite. Specifically, under the optimized conditions, such as input ratio of Si/Al of 4, microwave heating temperature of 150 °C, crystallization time of 0.5 h, pure Y-type zeolite is synthesized with BET specific surface area of 645 m2/g and the total pore volume is 0.322 cm3/g. The evolution order of zeolites with crystallization temperature is as follows: amorphous phase, Y-type zeolite, and P2 zeolite. An extended crystallization time or increased ratio of Si/Al facilitated the formation of P2 zeolite and analcime-C. The synthesis process promoted by microwave is explained by the high-speed rotation of polar water molecules, the formation of isolated water molecules and the dispersion of initial aluminosilicate gel in the microwave field. Image 1 • Microwave is used for the synthesis of zeolite Y under high-temperature conditions. • The BET specific surface area of zeolite Y synthesized at 150 °C for 0.5 h is 645 m2/g. • The evolution order of zeolites with crystallization temperature is obtained. • The influence of microwave on the synthesis of zeolite is explained. [ABSTRACT FROM AUTHOR]

Zinc ferrite (ZnFe 2 O 4) nanoparticles and ZnFe 2 O 4 -TiO 2 nanocomposite have been synthesized by simple and effective co-precipitation method followed by annealing at 500 °C for 5 h. The x-ray diffraction patterns suggest ZnFe 2 O 4 and/or TiO 2 phases with no other impurities. TEM images demonstrate that ZnFe 2 O 4 nanoparticles are spherical in shape (9 ± 2 nm) and ZnFe 2 O 4 -TiO 2 nanocomposite exhibits spherical-like morphology (11 ± 3 nm). HRTEM and SAED studies further confirm the phase purity of the samples and reveal the formation of core-shell in case of the composite. The direct band gap of ZnFe 2 O 4 nanoparticles (2.11 eV) and ZnFe 2 O 4 -TiO 2 nanocomposite (2.30 eV) demonstrate their ability as visible light photocatalysts. The larger band gap of the composite may be due to the mixing effect of bandgap and the interfacial coupling effect between ZnFe 2 O 4 and TiO 2. The PL spectra with λ ex = 317 nm display peaks corresponding to the recombination of charge carriers in deep traps of surface localized states and lattice defects. The nature of PLE peaks for the ZnFe 2 O 4 -TiO 2 nanocomposite suggest its improved photocatalytic activity compared with ZnFe 2 O 4 nanoparticles. Such results provide new prospects for optimizing and improving the properties and performance of semiconductor nanocomposites in photocatalytic degradation of dyes and water splitting. • Synthesized nano ZnFe 2 O 4 and ZnFe 2 O 4 -TiO 2 composite by co-precipitation route. • E g values reveal the ability of both the samples as visible light photocatalysts. • Higher band gap (E g) of the composite indicate the mixing effect of bandgap. • ZnFe 2 O 4 -TiO 2 exhibits the luminescence quenching due to the trap levels. • PL suggests enhanced photocatalytic activity for the ZnFe 2 O 4 -TiO 2 nanocomposite. [ABSTRACT FROM AUTHOR]