Microwave-assisted Preparation Research Articles

Ternary SnO2/Fe2O3/RGO composite: Microwave-assisted preparation and its high H2S-sensing performance

A SnO2/α-Fe2O3 nanoparticle modified reduced graphene oxide nanosheets (SnO2/Fe2O3/RGO) composite was synthesized via a two-step microwave-assisted method based on graphene oxide. SnO2/α-Fe2O3 nanoparticles with particle sizes of 11-43 nm were formed on the surfaces of the RGO. SnO2 nanoparticles are uniformly dispersed on α-Fe2O3 surfaces with a mean particle size of approximately 5 nm. By adjusting the molar ratio of SnO2 to α-Fe2O3, the gas-sensing properties of the obtained SnO2/Fe2O3/RGO composite were studied, focusing on its response and selectivity to H2S gas at low temperatures. The results indicate that the 3-SnO2/Fe2O3/RGO sensor has the highest sensitivity, ultrafast response, and excellent selectivity to 1-25 ppm H2S gas at 180°C, achieving a response of up to 31 to 25 ppm H2S with a response time of only 4 seconds. Moreover, the sensor shows good selectivity and long-term stability. To other 100 ppm gases, the responses of the 3-SnO2/Fe2O3/RGO sensor are no more than 5 at 180°C. The enhanced H2S sensing performance of the SnO2/Fe2O3/RGO sensor should be attributed to the abundant oxygen vacancies, n-n heterojunctions, and p-n heterojunctions in the SnO2/Fe2O3/RGO composite with a unique hierarchical structure.

Diatomite supported highly-dispersed ZnO/Zn-co-embedded ZIF-8 derived porous carbon composites for adsorption desulfurization

The metal organic framework (MOFs)-derived porous carbon materials with highly dispersed metal active sites were of the exclusive application foreground in many field, such as catalyst, electrochemistry, adsorption desulfurization and so on. However, the loss issue of metal active sites in MOFs frame was indispensable during the high temperature carbonization because of the lower boiling point of many metals, thus fundamentally affecting the atom-scale uniform distribution merit of MOFs-derived porous carbon materials. This work was to provide a novel strategy to address the loss issue of the active metal volatilization in the fabrication of MOFs-derived porous carbon materials. The ZnO nanosheets were pre-grown on the surface of diatomite by using in-situ microwave-assisted preparation, and thereafter the Zn-containing ZIF-8 particles covered the surface of ZnO nanosheets by virtue of the ZnO-induced growth. The results affirmed that the high content Zn-doped porous carbon materials were achieved and the Zn volatilization in MOFs was restrained on account of the occurrence of ZnO on diatomite (DE) surface during the carbonization. The adsorption desulfurization performance of the ZnO/Zn-embedded porous carbon materials/DE (ZnO/Zn/C@DE) was examined by the sulfur-containing compounds in simulated oil. The adsorption desulfurization performance investigation indicated that the ZnO/Zn/C@DE had the optimum adsorption capacities of 45.3 mg/g for benzothiophene and 37.4 mg/g for thiophene. Nonetheless, the competitive adsorption desulfurization finding of toluene in simulated oil showed that the adsorption capacities of ZnO/Zn/C@DE for TH and BT were dramatically descended, suggesting the presence of S-M interaction, wherein S stood for the S atom in a thiophene molecule and their analogs, and M for Zn atoms in porous carbon materials.

Facile microwave-assisted preparation of Fe3O4 nanoparticles supported on carbonized cellulose nanocrystals derived from sugarcane bagasse

Microwave energy is an efficient form of energy used to speed up the synthesis of nanoparticles. Herein, we report the use of an unmodified domestic microwave oven to prepare magnetic spherical Fe3O4 (magnetite) nanoparticles (IONPs) supported on carbonized cellulose nanocrystals, forming a nanocomposite, in an expeditious and facile one-step reaction. This was achieved using the readily available precursors of FeCl3 as an iron source, and sugarcane bagasse, using activated charcoal as a microwave absorber. The nanocomposite was characterized using Raman spectroscopy which suggested a degree of crystallinity based on a G/D ratio of 1.25. The morphology of the Fe3O4/carbonized cellulose nanocrystal nanocomposite was characterized as spherical metallic nanoparticles supported on carbonized cellulose nanocrystals using Transmission electron microscopy (TEM), SEM, and EDX, while the identity of the Fe3O4 nanoparticles was confirmed with powder XRD.Graphical

A simple method for microwave-assisted preparation of tire samples

Heavy metals content in tires affects the safety of soil and agricultural products. The digestion method is a pretreatment for determining heavy metals in tire samples, and will affect the efficiency and accuracy of the heavy metal determination. The microwave digestion process and reagents for tire samples are not currently standardized. Therefore, this study attempts to provide an appropriate method of resolution for scholars. All digestion processes were performed in Mars One. We tested 15 different acid mixtures to determine the best reagent type and dose and then investigated the effect of maximum temperature, holding time, and sample grams on the degree of digestion. In summary, the best condition to digest the tire sample was a mixture of 3 ml HNO3 and 7 ml H2SO4, taking 0.1 (± 0.0005) g tire sample, at the maximum digestion temperature of 220 °C for 25 min. The experimental conclusion will provide a reliable experimental method for scientists using MARS One to study heavy metals in tires. At the same time, researchers using the MARS series can also find valuable references in this paper.

Machine Learning Study on Microwave-Assisted Batch Preparation and Oxygen Reduction Performance of Fe-N-C Catalysts.

The Fe-N-C catalyst represents one of the most promising candidates for replacing platinum-based catalysts toward the oxygen reduction reaction. The pivotal factor in the successful integration of Fe-N-C catalysts within applications is the attainment of a large-scale production capability. Microwave-assisted pyrolysis offers various advantages, including enhanced energy and time efficiency, uniform heating, and high yield in single-batch processes. These characteristics render it exceptionally suitable for the mass production of catalysts. Through a synergistic approach involving machine learning techniques and microscopic characterization, we discerned performance trends and underlying mechanisms within batch-synthesized Fe-N-C catalysts under microwave-assisted preparation conditions. Machine learning analysis revealed that the precursor mass exerts the most substantial influence on product performance. Furthermore, microscopic characterization unveiled that these influencing factors impact catalyst performance by modulating the degree of agglomeration. Our research introduces an efficacious machine learning model for prognosticating performance and dissecting the influencing factors pertinent to Fe-N-C catalyst synthesis within a microwave system.

In situ microwave-assisted preparation of NS-codoped carbon dots stabilized silver nanoparticles as an off-on fluorescent probe for trace Hg2+ detection

An off-on fluorescent probe (NS-CDs-AgNPs) was synthesized based on a one-pot microwave process by utilizing N, S co-doping carbon dots (NS-CDs) and silver nitrate as precursors. The significant peak of NS-CDs-AgNPs at 393 nm in ultraviolet spectrum indicated silver nanoparticle (AgNPs) were successfully synthesized. A faint blue fluorescence emission (442 nm) was displayed when excited NS-CDs-AgNPs at 371 nm. A remarkable fluorescence recovery was observed upon adding of trance Hg2+, whereas the other heavy metal ions did not elicit this response. The reason for this phenomenon was revealed in this work that a spontaneous redox reaction occurred between NS-CDs-AgNPs and Hg2+, which leaded to the formation of NS-CDs-Agn-2NPsHg complexes. On the basis of this mechanism, a new off-on fluorescent analytical method was constructed for Hg2+ detection with linear range of 10–400 nM (R2 = 0.9941), and the detection limit (LOD) of 5.16 nM. Additionally, satisfactory recovery (90.28%–106.13%) and the relative standard deviation (RSD) (RSD＜5.21%) were obtained in water sample detection. More importantly, the NS-CDs-AgNPs exhibited lower cytotoxicity and better biocompatibility, indicating a huge potential in cell imaging and clinical medicine.

Progress on the Microwave-Assisted Recycling of Spent Lithium Battery Graphite

The robust development of electric vehicles has driven a surging decommission stream of lithium-ion batteries (LIBs) owing to their limited service life. The recycling of spent LIBs has become an urgent and essential task for the sustainable development of the LIB industry. However, the prevailing recycling methods focus only on recycling valuable metal, whilst the graphite anode materials are usually discarded or burned as fuels, leading to great waste of valuable carbon material. A facile strategy to obtain value-added products in an efficient manner is of great significance for the recycling of spent graphite. As graphite has excellent microwave absorption capability and electrical conductivity, microwave radiation on spent graphite can induce a Joule heat–discharge–plasma coupled effect, leading to a rapid heating process, especially when discharge occurs, exhibiting a thermal shock effect with the generation of a large number of high-energy electrons and active materials. This special feature facilitates microwave heating that is tailored for assisting the removal of impurities, structure repair, and graphite intercalation and exfoliation in an efficient manner. Therefore, different from the conventional graphite recycling route that is associated with energy/solution-intensive processes, this paper reviews the progress on microwave-assisted removal of impurities, repair of damaged graphite structure, and innovatively discusses the breakthroughs in microwave-assisted preparation of graphite intercalation compounds, expanded graphite, graphene and graphene-based materials, and porous graphene, with an aim to provide a scientific reference for the value-added resource utilization of spent graphite and preparation of new energy storage materials.

Microwave-assisted preparation of polysubstituted imidazoles using Zingiber extract synthesized green Cr2O3 nanoparticles

Cr2O3 nanoparticles were prepared using Zingiber officinal extract which were used as an efficient and reusable catalyst in the practical synthesis of polysubstituted imidazoles by means of a convenient reaction of aromatic aldehydes with ammonium acetate and benzil under microwave irradiation and H2O as solvent. The structure of the compounds was studied by IR and 1H-NMR spectrum. The most important benefits of this process are operational simplicity, reasonable reaction times, and excellent yield of products. The results show that the optimal conditions for the formation of imidazole derivatives are as follow: power of 400 W, reaction time of 4–9 min, H2O as a solvent, and 15 mmol of catalyst amount.

Microwave-assisted preparation of novel graphene-like carbon material from waste bamboo for high-performance supercapacitors

Microwave-assisted preparation of novel graphene-like carbon material from waste bamboo for high-performance supercapacitors

Microwave-Assisted Preparation of the Cubic RuSe2/C Catalyst for Fuel Cell Applications

Microwave-Assisted Preparation of the Cubic RuSe₂/C Catalyst for Fuel Cell Applications

Microwave-induced fabrication of fiber-reinforced adsorbent from waste cardboard and chitosan for effective dye removal

An adsorption process is a familiar approach to the dye decontamination of polluted wastewater. Ecological and low-cost fabrication of a highly efficient adsorbent has been a typical predicament. Herein, we reported a microwave-assisted preparation of a waste-based three-dimensional fibrous material with reliable mechanical stability, efficient adsorbing characteristics, and excellent dye decontamination performance. The material was prepared by reinforcing the milled waste cardboard fibers using chitosan to establish dual-pore scaffolds composed of interconnected lamellar channels and random pores. The adsorbent demonstrated exceptional removal capacity for the dye solution which fitted well with the isotherm model of Langmuir and the thermodynamic analysis of the adsorption process verified the prominent physisorption process. The maximum removal efficiency of the obtained samples for 25 ppm dye solution was up to 99% at a maximum adsorption capacity of 53.87 mg g−1. It is also worth mentioning that m(CF/Ch-2)7 has consistent removal performance over multiple cycles of regeneration. These results featured to be a promising material for utilizing solid waste materials to address one major type of water pollution.

Rare transition metal doped hydroxyapatite coating prepared via microwave irradiation improved corrosion resistance, biocompatibility and anti-biofilm property of titanium alloy

Here, we synthesized niobium doped hydroxyapatite (Nb-HAP) coatings on grade-5 titanium (Ti6Al4V) alloy sheets via microwave irradiation for the improvement of its biocompatibility and corrosion resistance with excellent antibiofilm function. The functionalized coated sample confirmed the presence of calcium deficient hydroxyapatite (HAP) containing niobium (Nb). The coating was observed to be denser, thicker and crystalline after doping. The average roughness of the surface was enhanced and became more hydrophilic with the functionalization of Nb. Moreover, the doping was found to have greatly improved the corrosion resistance of the substrates. The apatite layer on the Ti alloy surface revealed to adsorb more protein and enhanced the cell survival by more than 30 %. The presence of Nb in the coating ensured anti-biofilm property against both gram -ve and gram +ve bacteria strains. An improved hemocompatibility towards goat erythrocytes and cytocompatibility towards human keratinocyte cells were also evident in the post coating state. Hence, the microwave-assisted preparation of Nb doped HAP coating not only could improve the physical traits of the substrate, but could enhance the biocompatibility of bone implant as well. Furthermore, the microwave irradiation techniques used here might make the process faster and economical for efficient bioactive HAP coating deposition on Ti alloy. • Microwave assisted niobium doped HAP coating was deposited on Ti alloy sheet. • The doping improved crystallinity and hydrophilicity of the coated surface. • Reinforcement of niobium improved the corrosion resistance of the metal alloy. • The coatings were noncytotoxic, hemocompatible and resistant to bacterial growth.

Microwave-assisted preparation of Mn3O4@sepiolite nanocomposite for highly efficient removal of uranium

Nuclear energy is an important alternative energy source to non-renewable fossil fuels. Nevertheless, the nuclear contamination associated with nuclear activities and wastes is a formidable concern worldwide. Uranium is one of the most commonly used and discharged radionuclides, and hexavalent uranium [U(VI)] has significant mobility owing to its good solubility in water, leading to serious environmental and health risks. However, facile and economical solutions to effectively treating U(VI)-contaminated water are still limited. Herein, Mn3O4 nanoparticles were dispersedly anchored on sepiolite nanofibers via a facile microwave-assisted method for adsorbing U(VI) from aqueous solutions. Batch adsorption experiments showed that the nanocomposite possessed faster removal kinetics and greater removal capacity than the individual sepiolite and Mn3O4, as well as better removal performance than many reported inorganic and organic adsorbents. The nanocomposite can also reduce the U(VI) concentrations to far less than the standard of drinking water. Furthermore, a systematic investigation of the adsorption mechanism revealed that the nanocomponents Mn3O4 and sepiolite were responsible for the high-affinity U(VI) capture through the bonding of ≡Mn–O–U(VI) and ≡Si/Mg–O–U(VI), respectively, but the loaded Mn3O4 nanoparticles dominated the adsorption. Given that the simple synthesis and excellent U(VI) removal performance, the Mn3O4@sepiolite nanocomposite holds great promise for practical applications in radioactive uranium treatment.

Moderate microwave-assisted preparation of phthalocyanine-based carbon quantum dots for improved photo-inactivation of bacteria

A pacific synthetic tactic has been used to provide the phthalocyanine-based carbon quantum dots (ZnPc-CQDs) via microwave thermolysis of zinc(II) tetra-amino-phthalocyanine (ZnPc) and citric acid (CA) at 2 min. The ZnPc-CQDs with a granule size of around 5 nm diameter exhibited the prominent stability and water dispersion distinction of carbon quantum dots, as well as the picturesque properties of spectrum. ZnPc-CQDs proved synergistic photothermal outcomes and ROS generation capability, and exhibited potent photoinactivtion for bacteria. ZnPc-CQDs can be anchored to the cell membrane and accumulate in bacterial cells while destroying their integrity. Therefore, ZnPc-CQDs have the potential for PDT/PTT application and provides a new paradigm for antibacterial therapy, which has broad prospects for future biomedical applications.

Microwave-assisted preparation of Ag/Fe magnetic biochar from clivia leaves for adsorbing daptomycin antibiotics

Abstract Novel clivia biochar adsorbing daptomycin (DAP) was prepared by microwave digestion–anaerobic carbonization in this work. Fe/Ag submicron particles were introduced to the biochar surface based on the reducibility of biochar to enhance its adsorption capacity. Characterization confirmed that modified biochar (AF-biochar) had a higher particle size (126 μm), larger specific surface area (521.692 m2 g−1), richer pore structure, and higher thermal stability. The effects of the main variables (e.g., the solution pH, contact time, initial DAP concentration, and temperature) were investigated during adsorption. The results showed that AF-biochar could reach the adsorption equilibrium at pH 4.8 for 85 min. Besides, the adsorption capacity was 48.25 mg g−1, and the adsorption efficiency was 96.50% when the concentration of DAP was 25 mg L−1. The pseudo-second-order kinetics (R 2 = 0.9997), Langmuir equation (R 2 = 0.9999), and thermodynamics (R 2 = 0.9631) of AF-biochar fit well, indicating that the main adsorption process of AF-biochar was spontaneous, exothermic, and monolayer. Their adsorption was analyzed by physical and chemical adsorption. The main adsorption mechanisms included the electron donor–acceptor interaction, electrostatic force interaction, Lewis acid–base interaction, and H-bond interaction.

Microwave-assisted hydrodistillation extraction based on microwave-assisted preparation of deep eutectic solvents coupled with GC-MS for analysis of essential oils from clove buds

In recent years, deep eutectic solvents (DESs) as green and sustainable solvents have been widely used in the effective extraction of natural products. Usually, DESs are synthesized by heating and stirring method which takes a long time and energy. In this case, a microwave assisted preparation technique was used to form DESs for saving time and energy. And the DESs as pretreatment solvents were combined with microwave-assisted hydrodistillation (MAHD) for the extraction of essential oils (EOs) from the clove buds in this work. The maximum essential oils yield of 4.60% was obtained with the microwave power of 600 W, the pretreatment time of 5 min and the hydrodistillation time of 40 min using a deep eutectic solvent composed of choline chloride and lactic acid (molar ratio with 1:2). In addition, the essential oil was analyzed by gas chromatography-mass spectrometry (GC-MS), a total of 40 compounds were identified. Compared with MAHD, water-based MAHD and traditional hydrodistillation (HD), the content and composition of essential oil extracted by DES-based MAHD were higher. Thus, the combination of deep eutectic solvents with a microwave-assisted technique in this study provided an eco-friendly way of extracting essential oils.

Enhanced catalytic oxidation of bisphenol A via persulfate oxidation by microwave-assisted preparation of ZnCoxFe2-xO4-loaded rice-husk-carbon

Cobalt-doped ZnFe2O4 supported on rice husk carbon (RHC) has been prepared by a microwave-assisted method as a catalyst for the degradation of bisphenol A (BPA) by persulfate (PS) oxidation. Ferrite is a good absorbing material, RHC contains abundant channels, which provide channels for microwaves(MW) reflecting and scattering, and accelerate the synthesis of ZC1.3FO. In addition, the polarization and synergistic effect of the contact interface between the two phases is enhanced, which not only improves the dispersity of the magnetic material, but also enhances electron delocalization in the mixed material, promoting electron transfer between Co3+/Co2+ and Fe3+/Fe2+, and improving the catalytic activity. Our results have shown the degradation rate of BPA by ZnCo1.3Fe0.7O4-50 wt%RHC (ZC1.3FO-5C) (0.0697 L/mg min) to be 28 times higher than that by ZC1.3FO (0.00251 L/mg min), and the extents of leaching of cobalt and iron were lower than 45 μg/L. Particle video microscopy (PVM) have been used to confirm improved dispersion of composite particles compared to that of a single catalyst during degradation. Free radical quenching experiments, electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS) have confirmed that BPA degradation was caused by the synergistic action of non-free radical and free radical pathways. Intermediates have been identified by electrospray ionization mass spectrometry (ESI-MS), on the basis of which a degradation pathway of BPA by activated PS oxidation in the presence of ZC1.3FO-5C is proposed. In brief, a ZC1.3FO-5C composite has been prepared by a microwave method to activate PS for the degradation of BPA, realizing the resource utilization of waste ferrous sulfate derived from titanium dioxide production, providing a new concept for the degradation of organic pollutants.

Microwave-assisted preparation of carboxylic graphene oxide-chitosan composite for adsorption of uranium and heavy toxic metals in water samples

ABSTRACT In this study, the microwave-assisted novel composite of carboxylic graphene oxide-chitosan (COOH-GO-CTS) was prepared by using carboxylic functionalized graphene oxide (COOH-GO). The prepared composite was characterized by FTIR, SEM, XRD, XPS and Raman spectroscopy successfully. The composite was used as an adsorbent material for the removal of heavy metals such as uranium (U), lead (Pb), chromium (Cr), and cadmium (Cd). Batch adsorption was carried out to study the effects of pH of the medium, initial concentration of heavy metals, amount of adsorbent dosage, contact time, and temperature. The removal percentages for U, Pb, Cr, and Cd were observed to be 92.4, 94.6, 90.2, and 90.6% at 5, 5.5, 3, and 5 pH, respectively. Adsorption isotherms were performed for Langmuir and Freundlich adsorption, and it was observed that the Langmuir adsorption isotherm well fitted (R2 > 0.99) the present adsorption study. The maximum adsorption capacities of the composite for U, Pb, Cr, and Cd were found to be 64.93, 384.61, 68.49, and 49.50 mg g−1, respectively. The heavy metal adsorption kinetics were also performed, and it was observed that the pseudo-second order was well fitted (R2 > 0.99) the present study. Further, the themodynamic studies confirmed the adsorption of the heavy metals to be endothermic and spontaneous in nature.

Microwave-assisted preparation of cotton stem-derived activated carbon for dye removal from synthetic wastewater.

Cotton stem is used to produce the high-efficient adsorbent (CSA) for Rhodamine B (RB) dye removal from wastewater, and hydrogen rich fuel gas via on-pot method using microwave heating. The adsorption data indicate that RB adsorption behavior follows the Langmuir model with the maximum adsorption capacity of 265.96mg/g, whereas the adsorption kinetics follows the pseudo-second-order model. Thermodynamic calculations indicate that RB adsorption on CSA is spontaneous and endothermic process. The adsorption data are fitted to the Thomas and Yoon-Nelson model to predict the breakthrough curve in the column experiment. The RB removal could still be maintained at 71.22% of the original value after five cycles, demonstrating the reusability of CSA. The chemical functional groups, electrostatic interaction, and pore filling of CSA are found to be responsible for high RB adsorption capability. CSA exhibits excellent RB removal efficiency in treating actual water. The major components of byproduct gases collected from activation process are H2 and CO.

Microwave-assisted fabrication of high-performance supercapacitors based on electrodes composed of cobalt oxide decorated with reduced graphene oxide and carbon dots

This study presents microwave-assisted preparation of cobalt oxide (Co3O4) based nanocomposite electrodes doped with carbon dots and reduced graphene oxide. The calcination of the precursors at 400 °C for 2 h results in nanocomposites. A three-electrode cell in 2M KOH solution is used for the electrochemical measurements. The carbon dot containing electrodes enables the highest specific capacitance of 936 Fg−1 at 0.5 Ag−1 current density. Specific capacitances of pure Co3O4, and Co3O4@RGO electrodes are 448 Fg−1 and 482 Fg−1 at 0.5 Ag−1, with good rate capability even at 10 Ag−1, respectively. The cyclic stability of the electrodes is reasonably high and the electrodes retain 93%, 87%, and 88% of their initial capacitance after 10,000 cycles for Co3O4, Co3O4@RGO, and Co3O4@RGO@CDs, respectively. The optimized Co3O4@RGO@CDs electrodes were used to fabricate a symmetric supercapacitor that exhibits high specific capacitance (126 Fg−1 0.25 Ag−1) and long cycle life (%81 retention after 10,000 cycles). The fabricated supercapacitor has energy density of 17.5 Wh kg−1 and power density of 2522 W kg−1. The outstanding results demonstrate the promise of carbon dots doped transition metal oxides-based nanoparticles as promising electrodes for supercapacitor applications.