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Replacing cadmium ions in cadmium-containing solutions with aluminum powder is beneficial for cadmium resource recycling and environmental protection. However, the conventional aluminum powder replacement method requires harsh temperatures and prolonged conditions. In this study, the effect and mechanism of ultrasound on the replacement of cadmium with aluminum powder were investigated at low temperatures. Ultrasound has been proven to promote the etching of alumina films through the use of TEM and XPS, providing mechanistic support for the superiority of the new process. A degree of Cd replacement as high as 95.08 % is achieved at a low temperature (60 ℃) and in a short time (20 min) when using ultrasonicated aluminum powder replacement, which is 42.17 % higher than that of conventional aluminum powder. Compared with conventional aluminum powder replacement conditions with the same effect, the introduction of ultrasound can reduce the temperature by 30℃ and shorten the replacement time by 2/3, which has significant advantages in reaction efficiency and safety. The strengthening mechanism of ultrasound on the replacement effect of aluminum powder at low temperatures is revealed through detailed discussions on the corrosion of alumina films, agglomeration of aluminum powder, and adhesion of replacement products to the surface of aluminum powder, dissolved oxygen in the solution, and redissolution of cadmium. Therefore, a new approach for replacing aluminum powder in solutions with high Cd2+ concentrations at low temperatures is proposed in this work, which is expected to solve the existing harsh and dangerous problems of industrial aluminum powder replacement.

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Doped carbon dots have attracted great attention from researchers across disciplines because of their unique characteristics, such as their low toxicity, physiochemical stability, photostability, and outstanding biocompatibility. Nitrogen is one of the most commonly used elements for doping because of its sizeable atomic radius, strong electronegativity, abundance, and availability of electrons. This distinguishes them from other atoms and allows them to perform distinctive roles in various applications. Here, we have reviewed the most current breakthroughs in nitrogen-doped CDs (N-CDs) for fluorescent sensor applications in the last five years. The first section of the article addresses several synthetic and sustainable ways of making N-CDs. Next, we briefly reviewed the fluorescent features of N-CDs and their sensing mechanism. Furthermore, we have thoroughly reviewed their fluorescent sensor applications as sensors for cations, anions, small molecules, enzymes, antibiotics, pathogens, explosives, and pesticides. Finally, we have discussed the N-CDs' potential future as primary research and how that may be used. We hope that this study will contribute to a better understanding of the principles of N-CDs and the sensory applications that they can serve.

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The current investigation deals with the simple and ecological synthesis of CaO, MgO, CaTiO3, and MgTiO3 for the photocatalytic dilapidation of rhodamine B dye. CaO was procured from chicken eggshell waste by calcination process, while MgO was produced by solution combustion method using urea as a fuel source. Furthermore, CaTiO3 and MgTiO3 were synthesized through an easy and simple solid-state method by mixing thoroughly the synthesized CaO or MgO with TiO2 before calcination at 900 °C. XRD and EDX investigations confirmed the phase formation of the materials. Moreover, FTIR spectra revealed the existence of Ca-Ti-O, Mg-Ti-O, and Ti-O which resembles the chemical composition of the proposed materials. SEM micrographs revealed that the surface of CaTiO3 is rougher with relatively dispersed particles compared to MgTiO3, reflecting a higher surface area of CaTiO3. Diffuse reflectance spectroscopy investigations indicated that the synthesized materials can act as photocatalysts under UV illumination. Accordingly, CaO and CaTiO3 effectively degraded rhodamine B dye within 120 min with a photodegradation activity of 63% and 72%, respectively. In contrast, the photocatalytic degradation activity of MgO and MgTiO3 was much lower, since only 21.39 and 29.44% of the dye were degraded, respectively after 120 min of irradiation. Furtheremore, the photocatalytic activity of the mixture from both Ca and Mg titanates was 64.63%. These findings might be valuable for designing potential and affordable photocatalysts for wastewater purification.

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In this work, a novel co-precipitation coupled solvothermal procedure is proposed to prepare a SmMnOx catalyst (SmMnOx-CP + ST) with a reed flower-like structure for the selective catalytic reduction of NOx by NH3 (NH3-SCR). Over 90% NOx conversion and N2 selectivity was achieved at a low temperature range (25-200 °C), and 96% NOx conversion was achieved in the presence of 100 ppm SO2 at 75 °C. While the NH3-SCR of the SmMnOx catalysts prepared by co-precipitation (SmMnOx-CP) and solvothermal (SmMnOx-ST) methods performed much poorer than the SmMnOx-CP + ST catalyst. All catalysts were characterized by XRD, BET, SEM, XPS, H2-TPR, NH3-TPD, NOx-TPD, and FT-IR. The results revealed that the superior performance of the SmMnOx-CP + ST is due to the unique reed flower-like structure morphology, which endows the SmMnOx-CP + ST with the largest surface area, the strongest synergistic reaction of Sm and Mn, abundant surface oxygen species and surface active sites, and significantly enhances the redox ability. Furthermore, the amorphous reed flower-like structure showed strong short-range ordered interaction between the active components and weaken the formation of sulfates species. In addition, the highest content of Mn4+ and Mn3++Mn4+ greatly promotes the redox cycles of Sm2+↔Mn4+ and Sm2+↔Mn3+, and suppresses the production of sulfate species in the presence of SO2.

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In the present study, the n-SnO2/p-CuFe2O4 (p-CFO) complex was prepared by a two-step process. p-CFO synthesized by the molten salt method was coated with SnO2 synthesized by a facile in situ chemical precipitation method. The formation of n-SnO2/p-CFO was confirmed by powder X-ray diffraction (PXRD). Scanning electron microscopy (SEM) images showed that the sharp edges of uncoated pyramid-like p-CFO particles were covered by a thick layer of n-SnO2 on coated p-CFO particles. The complete absence of Cu and only 3 wt% Fe on the surface of the n-p complex observed in the elemental analysis using energy-dispersive X-ray spectroscopy (EDX) on the n-p complex confirmed the presence of a thick layer of SnO2 on the p-CFO surface. Diffuse reflectance spectroscopy (DRS) was employed to elucidate the bandgap engineering. The n-SnO2/p-CFO complex and p-CFO showed 87% and 58.7% methylene blue (MB) degradation in 120 min under sunlight, respectively. The efficiency of the n-p complex recovered after 5 cycles (73.5%) and was found to be higher than that of the uncoated p-CFO (58.7%). The magnetically separable property of the n-p complex was evaluated by using vibration sample magnetometry (VSM) measurements and it was confirmed that the prepared photocatalyst can be easily recovered using an external magnet. The study reveals that the prepared complex could be a potential candidate for efficient photodegradation of organic dyes under sunlight due to its efficient recovery and reusability owing to its magnetic properties.

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Combining biomass pyrolysis with microwave heating technologies provides a novel and efficient approach for low-grade pyrolusite reduction. The microwave reduction behavior and pyrolysis kinetic characteristics of walnut shell-pyrolusite blends were explored. Results indicated the optimal reduction parameters were: reduction temperature of 650 °C, holding time of 30 min, Mbio/More of 1.8:10, and microwave power of 1200 W. The co-pyrolysis characteristics of the blends included four stages: dehydration, pre-pyrolysis, intense pyrolysis and reduction, and slow pyrolysis and reduction. Fitting analysis based on Coats-Redfern method revealed that chemical reaction was the control step of the process of reducing pyrolusite by biomass, which the finding matched to the isothermal kinetic analysis results determined through unreacted shrinking nuclear model. The activation energies and pre-exponential factors were determined at 5.62 kJ·mol-1-16.69 kJ·mol-1 and 0.0426 min-1-0.515 min-1. The work provides sound references for promoting the industrial application of the combined method on minerals reduction.

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Micron-sized praseodymium oxide powders are prepared successfully from the praseodymium oxalate in a microwave field at 750 °C for 2 h in the present study. X-ray diffraction (XRD) analysis demonstrates that the presence of cubic structured crystalline Pr6O11 and complete decomposition of the precursor are confirmed by Fourier transform infrared (FT-IR) analysis. The scanning electron microscopy (SEM) results show yield powders with the desired particle size and uniform morphologies. Particle size analysis demonstrates that the median diameter (D 50) becomes stable at 750 °C. The D 50, average surface area, pore diameter, and pore volume calculated by Brunauer -Emmett-Teller (BET) are 4.32 µm, 6.628 m2/g, 1.86 nm, and 0.026 cm3/g at 750 °C for 2 h, respectively. Moreover, loss on ignition (L.O.I.) analysis indicates that the L.O.I. is as low as 0.39%, meeting the enterprise requirement (<1%). In comparison, conventional calcination experiments are carried out in the electric furnace. Both XRD and FT-IR analyses are in consistence with thermogravimetry-differential scanning calorimetry, which indicates that the temperature required for the decomposition of praseodymium oxalate hydrate is higher than that of microwave heating. Furthermore, SEM, particle size distribution, and BET analysis indicate that agglomeration generates, particle size enlarges, and average surface area increases. In all, it is confirmed that preparing rare-earth oxides from rare-earth oxalates is feasible using microwave heating to replace conventional heating.

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Vanadium slag contains high contents of vanadium and chromium with complex and dense structures, hence microwave heating instead of conventional methods is expected to destroy the dense structure and further to improve the extraction rate of vanadium and chromium, and exploring its dielectric properties is the prerequisite work. Microwave absorption properties and thermal behavior of vanadium slag were investigated. Results indicated that vanadium slag endowed excellent microwave absorption properties, with minimum εr' value of 34.447 (F/M). Dielectric properties of vanadium slag varied with temperature, which changing trend was matched to the three stages of microwave heating characteristics identified by heating rates. Meanwhile, the changing process of dielectric properties also corresponded to the three processes of thermogravimetric characteristics: dehydration stage (30 °C-280 °C), oxidation decomposition of olivine phase and normal spinel phase (280 °C-650 °C), and oxidation decomposition of vanadium chromium spinel (650 °C-950 °C). Moreover, the maximum dielectric constant and highest microwave heating rate of vanadium slag both appeared at the temperature regime of 500 °C-550 °C, which was also the main temperature regime for oxidation decomposition of olivine phase and normal spinel phase in vanadium slag, demonstrating the appropriate process temperature for microwave heating technology to recycle vanadium slag.

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High photoluminescent quantum yield carbon nanomaterials doped with heteroatoms are of profound attention in various fields like bio-imaging, chemical sensors and electronics. Among all heteroatoms, zinc is one of the low toxic significant elements and also involves in various electron-transfer processes. These properties are added advantages to utilize zinc as a dopant in CDs synthesis. In this investigation, our group reports a one-step microwave digestion method to synthesize nitrogen and Zinc doped carbon dots (N, Zn-CDs). The optical properties of N, Zn-CDs were investigated using UV-Vis and fluorescence spectrophotometry and also the N, Zn-CDs structural features were studied with other characterization tools like XPS, TEM, EDX, FTIR and XRD. N, Zn-CDs inherent the appreciable photoluminescent quantum yields about 63.28%. And the synthesized N, Zn-CDs utilized for detection of Fe3+ and temperature. The observed results are promising and exhibited the detection limit of 0.027 µM. Also, the proposed sensing system was successfully adopted for the detection of Fe3+ in the river and circulating water samples for the practical applications and satisfactory results are observed. The current synthesis methodology and sensing potential might open up a new prospect to develop potential applications in environmental monitoring.

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In recent times, fluorescent carbon quantum dots (CQDs) as an optical sensor have attained massive attention owing to their excellent optical properties. In current investigation, our group presented an easy and economical methodology to synthesize the nitrogen and phosphorous doped carbon quantum dots (N, P doped CQDs) for sensing dopamine (DA) and temperature in aqueous medium. The synthesized CQDs were characterized by using XRD, XPS, TEM, UV-Vis, FT-IR and fluorescence techniques. The N, P doped CQDs were synthesized via one-step microwave digestion method by using citric acid, ethylenediamine and urea phosphate as precursors. This method established the noble water solubility, good optical performances and fluorescence thermosensitivity of N, P doped CQDs. Also, N, P doped CQDs demonstrated a wide linear range of 10-500 µM (R2 = 0.994) and offered an electrifying detection limit of 0.021 µM for quantifying the dopamine. Moreover, this sensor possessed a good sensitivity, reversibility and linearity in the range of 10-70 °C. In addition, the CQDs sensing system repel the interference from probable foreign substances in real sample analysis, and attained good recoveries, which revealed the tremendous selectivity and adequate accuracy of the carbon quantum dots for sensing dopamine. The proposed N, P doped CQDs are simple as well as effective optical nanosensor and clasps venerable potential to widen the applications in analysis of biomolecules and other areas.

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The process of preparing metallic matrix diamond tool bits by microwave pressureless sintering (MPS) was exclusively studied in this paper. The effects of the sintering temperature, the cold pressure, and the holding time on the mechanical properties of the bit were determined by using the response surface methodology (RSM) with Box-Behnken Design (BBD). In addition, with RSM, the second-order polynomial equation of mechanical properties was obtained. The solutions were well matched with the experimental values. This indicates that major variations in mechanical properties of the sintered sample could be predicted by the models, which shows that the applied model is accurate. Conventional pressureless sintering (CPS) experiments were also conducted to make a comparison. The experimental results showed that the MPS can enhance the mechanical properties of sintered samples. A possible MPS mechanism is proposed in this work after analyzing all the experimental results.

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Microwave pressureless sintering (MPS) method is successfully applied in the fabrication of Cu based metallic matrix for diamond tools. The main purpose of this work is to obtain better mechanical properties when the metal binder of the diamond tools was prepared by the MPS method. The orthogonal experimental method is adopted to design the sintering process parameters. The optimized experimental conditions are suggested as 880 °C of sintering temperature, 375 MPa of cold pressure, and 35 min of withholding time. The contrastive investigation of the MPS and conventional pressureless sintering (CPS) are performed under optimized conditions. The microstructures information are obtained by scanning electron microscopy (SEM), X-ray diffraction (XRD), electron probe microanalysis (EPMA), and the necessary mechanical properties, such as relative density, hardness, and flexural strength are tested. Experimental results show that the MPS method, compared with CPS, can significantly improve the mechanical properties of the metallic matrix. The factors of relative density, hardness, and flexural strength increase 1.25%, 3.86%, and 6.28%, respectively. The possible sintering mechanism of the MPS method is also discussed. This work may provide a reference for the fabrication of metal-based diamond tools by microwave heating method.

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In the current work, forsterite samples with different surface area were investigated for its antibacterial activity. Dissolution studies show that the lower degradation of forsterite compared to other silicate bioceramics, which is a desirable property for repairing bone defects. Forsterite scaffold shows superior compressive strength than the cortical bone after immersion in simulated body fluid. Bactericidal tests indicate that the forsterite had inhibition effect on the growth of clinical bacterial isolates. Forsterite may be a suitable candidate material for load bearing applications with enhanced mechanical properties and lower degradation rate.

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The use of Pb/Sn/Al composite anode materials has been limited due to the thermodynamic immiscibility between Pb and Al sheets during the welding process. Thus, herein, Sn has been added between Pb and Al sheets to fabricate a Pb/Sn/Al laminated composite via vacuum hot-pressing welding (at a temperature of 230 °C for 12 h under 0.5 MPa). Furthermore, the interfacial microstructure and mechanical and electrical properties are investigated. Good metallurgical bonding has been realized due to the addition of Sn, and block α-Pb and a small amount of ß-Sn solid solutions are also formed at the interface. In comparison with the Pb-Ag alloy anode, the Pb/Sn/Al laminated composite presents superior mechanical strength (73.9 MPa), and good electrical conductivity of the Pb/Sn/Al composite has been obtained due to its sandwich laminated structure. Moreover, the Pb/Sn/Al composite reduces the electrode reaction energy and improves the electrocatalytic activity of the electrode to reduce the bath voltage.