Microwave Heating Method Research Articles

ENHANCEMENT OF SOLUBILITY OF POORLY SOLUBLE DRUG LANSOPRAZOLE

Objective: To improve the solubility of lansoprazole with solid dispersion (SD) method by using hydrophilic polymer PEG 6000, PEG 15000 and amphiphilic polymer solupus. Methods: Solid dispersions of lansoprazole were prepared with polymers PEG 6000, PEG 15000 and amphiphilic polymer soluplus, using three methods of preparation–1) solvent melting 2) solvent evaporation and 3) microwave heating method along with different drug: carrier ratios. Performance of the prepared formulations were evaluated for solubility, fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC) parameters. Results: All SDs showed enhancement in solubility of lansoprazole. Solubility and also carrier concentration showed a positive effect on solubility. The lansoprazole-soluplus solid dispersion 1:3 in concentration showed enhanced aqueous solubility when formulated with a solvent melting procedure. Conclusion: The studies indicated that PEG 6000, PEG 15000 and Soluplus inhibite crystallization of lansoprazole, subsequently form amorphous state in solid dispersion, which is, confirmed via FTIR and DSC results of lansoprazole solid dispersion.

The Microwave Facile Synthesis of NiOx@graphene Nanocomposites for Application in Supercapacitors: Insights into the Formation and Storage Mechanisms

Recently, the strategy of combining carbon-based materials with metal oxides to enhance the electrochemical performance of electrodes has been a topic of great interest, but research focusing on the growth and charge storage mechanisms of such hybrid electrodes has rarely been conducted. In this work, a simple, reproducible, low-cost, and fast microwave heating method was used to synthesize NiOx@graphene nanocomposites. NiOx@graphene nanocomposites were used as a model system for exploring the growth and charge storage mechanisms of the hybrid electrode materials due to their simple preparation process, good stability, low cost, and high specific capacitance. The effects of reaction conditions (the type of metal precursor and feeding ratio between the nickel precursor and graphene) on the formation mechanism of the electrodes were examined, and it was demonstrated that the microstructure and morphology of the electrode materials were metal precursor-dependent, which was directly related to the electrochemical performance of the electrodes. Our work provides a new affordable approach to the synthesis of, and experimental support for designing, hybrid electrode architectures with a high electrochemical performance for next-generation energy storage devices.

Corn Starch-Based Sandstone Sustainable Materials: Sand Type and Water Content Effect on Their Structure and Mechanical Properties

A new biodegradable, sustainable and environmentally friendly building material is introduced and studied in this work, which can be applied to lightweight architectural structures, aiming for the reduction of the greenhouse gas emissions and mitigation of the climate change effects. The focus was to investigate the effect of water concentration and different types of sand on the mechanical properties of corn starch-based artificial sandstone. A series of cubic, cylindrical and disk specimens were prepared by varying the concentration of water and using different sources of commercial quartz sand. The quasi-static and cyclic compressive properties of starch-based artificial sandstone samples were measured as a function of water concentration and sand type, while the structure of the artificial sandstone specimens was examined by scanning electron microscopy (SEM) and optical microscopy. Moreover, the Brazilian Test was employed as the indirect method to determine the tensile strength of the samples based on the type of the commercial sand they contained. The experimental results showed that the homogeneous grading of sand grains and the latter’s chemical composition have a significant effect on the mechanical properties of the sandstone samples. The highest compression values were obtained using the microwave heating method at a water concentration of about 12 wt%, while the cyclic compression and Brazilian Tests have shown that the granulometric grading of the sand particles and the chemical composition of the sand influence the compressive and tensile strength of the material.

Post Synthetic Modification of NH2-(Zr-MOF) via Rapid Microwave-promoted Synthesis for Effective Adsorption of Pb(II) and Cd(II)

Excessive heavy metals in the water constitute a health hazard to humans, yet it may be efficiently purified using adsorbents. Herein, for the first time, UiO-66-NH2 was modified by Glycidyl methacrylate (GMA) via microwave heating method to investigate its potential for adsorption of Pb(II) and Cd(II) metal ions. Synthesized MOF was characterized by TGA, XRD, BET, FE-SEM-EDX, and FTIR. The MOF has a huge surface area of 1144 m2/g, a mean pore diameter of 2.84 nm, and a total pore volume of 0.37 cm3/g. The effect of UiO-66-GMA performance was evaluated by investigating the impact of pH (1–9), contact time (0–200 min), initial metal ions concentration (20–1000 mg/L), temperature (25–55 °C), adsorbent dosage (0.5–3 g/L), and co existences of other metals was investigated on Pb(II) and Cd(II) percentage removal. Following an analysis of the adsorption isotherms, kinetics, and thermodynamics, the Temkin isothermal model showed an excellent fit with the adsorption data (R2 = 0.99). The adsorption process was a spontaneous endothermic reaction and kinetically followed the pseudo-second-order kinetics model. Microwave heating method produced highly crystalline small Zr-MOF nanoparticles with a short reaction time. It promoted the simple yet highly efficient synthesis of Zr-based MOFs, as shown by the reaction mass space-time yield. The adsorption capability of Pb to the presence of several polar functional groups, including as primary and secondary amines, ester, alkene, and hydroxyl groups. This adsorbent is a potential candidate for wastewater treatment due to its outstanding structural stability in acidic and basic solutions, high removal efficiency, and recyclability.

Fuel gas production from microwave-induced biomass pyrolysis using char-supported metal composites as both catalysts and microwave absorbers

In this study, char-supported metal composites (0.2Ni-RHC, 0.2Fe-RHC and 0.2Co-RHC) were prepared via impregnation and subsequent microwave heating method, which were used as both microwave absorbers and catalysts for in-situ microwave-induced pyrolysis of pine sawdust, aiming to obtain high-quality fuel gas based on the interaction of microwave radiation and metal active sites in catalysts. The results showed that well-dispersed nanoparticles were generated in the three catalysts, which were firmly anchored on the matrix of the char support by several layers of graphitic carbon. The catalysts exhibited excellent microwave absorbing properties, a rapid heating rate was achieved which realized the temperature rise from room temperature to 800 °C within 110 s 0.2Fe-RHC exhibited the best catalytic performance among these three catalysts, with a high gas yield of 73.4% and low solid and bio-oil yield of only 4.1% and 13.6%, respectively. The yield of H2 and CO increased from 137.7 to 190.6 mL/g and from 241.2 mL/g to 393.9 mL/g compared with that of pure RHC. The microwave heating behavior and the catalytic activity of char-supported Fe catalyst were also influenced by the loading amount of Fe.

Heterogeneous catalytic carboxylation of terminal alkynes with CO2 over a copper(II)-based metal-organic framework catalyst

Developing efficient, inexpensive and robust heterogeneous catalysts for CO2 conversion is greatly important. In this study, a new stable copper(II)-based metal-organic framework [Cu(Fbtx)2Br2]n (denoted as CZU-7, CCDC-2165700, Fbtx = 1,4-bis(1,2,4-triazole-1-ylmethyl)-2,3,5,6-tetrafluorobenzene) was synthesized via a facile and fast microwave heating method. CZU-7 exhibits a two-dimensional layer structure with the 44-sql topology. This material was demonstrated to be an efficient heterogeneous catalyst for the direct carboxylation of 1-ethynylbenzene with CO2, and various propiolic acids were synthesized in moderate to good yields under optimized reaction conditions. Moreover, the catalyst could be easily recovered and reused five times without significant loss of catalytic activity.

Antimicrobial Properties of Lauric Acid and Monolaurin in Virgin Coconut Oil: A Review

AbstractVirgin coconut oil is obtained by wet processing of coconut milk using fermentation, centrifugation, enzymatic extraction, and the microwave heating method. Presently, VCO has several positive effects and benefits to human health, hence, it is regularly consumed and widely known as a unique functional food. VCO contains lauric acid (45 to 52 %). By lipase in the digestive system, VCO can undergo a breakdown into lauric acid, 1‐monolaurin, and 2‐monolaurin. These components have both hydrophilic and lipophilic groups and are also recognized as excellent antimicrobial lipids. Furthermore, lauric acid and monolaurin can be used as antibacterial, antifungal, and antiviral with broad‐spectrum inhibition. Lauric acid and monolaurin have a strong ability to destroy gram‐positive bacteria, especially S. aureus, fungi such as C. Albicans, and viruses including vesicular stomatitis virus (VSV), herpes simplex virus (HSV), and visna virus (VV). Lauric acid and monolaurin interact with certain functional groups located in the cell membrane and can cause damage to the cell. In general, the potential of VCO as healthy food is contributed by lauric acid and monolaurin which are antimicrobial agents.

Delignification of Cassava Peel as Bioethanol Raw Material using Combined Alkali and Microwave Heating Methods

Indonesia is ranked fourth as the largest cassava producing country with a total production of around 20 million tons per year. As much as 15-20% per kilogram of cassava is waste in the form of cassava peel which contains starch and allows it to be converted into alternative energy such as bioethanol. The bioethanol production process is carried out through the stages of pretreatment (delignification) to obtain cellulose used in the hydrolysis process, hydrolysis, fermentation, and purification. This paper discussed the use of combined alkali and microwave heating methods to increase the cellulose content and reduce the lignin content of cassava peel. Delignification was carried out by varying the NaOH concentration of 0.5, 0.75, and 1 M and microwave exposure of 5, 10, and 15 min. The data of the pretreatment variation were statistically tested using a completely randomized design. The results shows that combined alkali and microwave heating methods was able to increase cellulose content from 39.78 to 59.01 %, decrease hemicellulose content from 24.75 to 12.79 %, and decrease lignin content from 23.28 to 14.66 %. The combination of 1 M NaOH and 15 min microwave exposure showed the best results.

Oil Palm Empty Fruit Bunch Waste Pretreatment with Benzotriazolium-Based Ionic Liquids for Cellulose Conversion to Glucose: Experiments with Computational Bibliometric Analysis

This study aims to utilize benzotriazolium salt-ionic liquids (ILs) as solvents in the oil palm empty fruit bunch (EFB) waste pretreatment along with bibliometric analysis using VOSviewer. Three ILs have been synthesized and tested as EFB solvents by a microwave-heating method. Those are organic salts of 1,3-methyl-octyl-1,2,3-benzotriazolium ([MOBzt]+) cation with three kinds of anions such as bromide ([Br]-), acetate ([CH3COO]-), and thiocyanate ([SCN]-). The bibliometric analysis showed that new research needs to be conducted to improve the development of research relating to biomass pretreatment. The highest solubility of EFB is in [MOBzt]CH3COO is about 7,5% w/w. The effect of anions on the ability to dissolve EFB is CH3COO-SCN-Br-. When subject to ILs pretreatment, EFB exhibited increased cellulose crystallinity, changed in the structure of cellulose I to cellulose II, reduced particle size, and decreased lignin content compared to untreated one, improving the glucose yield from enzymatic hydrolysis. The highest glucose yield (1,237 mg/mL) was obtained when the EFB was pretreated by [MOBzt]CH3COO with enzymatic hydrolysis for 24 hours. This research is expected to contribute to the development of new biomass pretreatment methods.

Rational preparation of anti-water phosphorescent carbon-dots and flake C3N4 composites through microwave-heating method for multiple data encryption

The development of anti-water phosphorescent carbon dots (CDs) based materials is of great practical interest. Herein, we report a rational design of CDs based composite with anti-water phosphorescence by controlling a one-step microwave assisted heating of green fluorescent CDs and urea. Upon increasing the microwave-heating temperature, urea was gradually converted to C3N4, in which the CDs were uniformly embedded in the C3N4 matrix. The fluorescence/phosphorescence intensity of these CDs based composites are determined by the morphologies of the C3N4, which can be adjusted by controlling the microwave heating time. More importantly, the combining CDs in C3N4 not only promote the phosphorescence emission but also prevent the phosphorescence quenching by water, leading to stable phosphorescence emission in aqueous environment. Based on the anti-water phosphorescence properties of these CDs based composites, a concept of multiple data encryption was demonstrated.

Biodiesel production by single-step acid-catalysed transesterification of Jatropha oil under microwave heating with modelling and optimisation using response surface methodology

Biodiesel is known as one of the best alternative fuels for diesel engines. Low-cost Jatropha oil is considered a potential non-edible feedstock for biodiesel production in India and many other parts of the world. Jatropha oil contains a large amount of free fatty acids (FFA), and soap formation occurs during the alkali catalysed transesterification process, hence decreasing the biodiesel yield. The acid catalyst is less sensitive to FFA, but the reaction rate is extremely slow if the transesterification reaction occurs by conventional heating. In the present investigation, microwave heating was used for biodiesel production by the single-step transesterification reaction of Jatropha oil in the presence of an acidic catalyst (sulphuric acid). The central composite rotatable design (CCRD) matrix of response surface methodology (RSM) was employed to determine the optimum design conditions for the transesterification reaction under microwave irradiation. The effects of three selected variables, namely reaction time, catalyst concentration, and methanol, on the oil molar ratio, were assessed. The maximum yield of biodiesel produced in the selected design space by microwave heating was found to be 61.10% under the 11:7 M ratio of the methanol to oil, 2 wt% catalyst concentration, and 90 min reaction time, which was much higher than the biodiesel yield by conventional heating method (3.8%) for the same reaction time. The modified polynomial model for the microwave heating method was developed with the help of ANOVA, main effect plots, interaction plots, and surface plots. The experimental and predicted yield values for fatty acid methyl ester (FAME) showed a linear relationship. The validation of experiments confirmed the accuracy of the suggested model. The produced biodiesel was of good quality, as all the properties were within the prescribed limits of the ASTM D6751 standard. The results of this study showed that the microwave heating method can be used efficiently to obtain a high biodiesel yield from low-cost, high-FFA feedstock such as Jatropha oil in a sulphuric acid-catalysed single-step transesterification reaction.

Enhancing nonspecific enzymatic hydrolysis of chitin to oligosaccharides pretreated by acid and green solvents under simultaneous microwave-radiation

It is hard to degrade untreated highly crystalline chitin. In this study, two solvents pretreatment chitin (acid swollen chitin (AC), super fine chitin (FC)) and microwave-heating method were used to enhance nonspecific enzymatic hydrolysis (lysozyme and pepsin), which obviously improved the enzymolysis rates by at least 1.31 times. Characterizations of chitin substrates (Mv, SEM, XRD) showed that calcium solvent pretreatment (obtained FC) was milder but effective than phosphoric acid pretreatment (obtained AC). The highest yield of chitin oligosaccharides (37.58 mg/g) were obtained after hydrolyzing AC under five-hour simultaneous microwave radiation by pepsin, among them, the content of N-acetylglucosamine was 13.76 mg/g. While, more chitin oligosaccharides with DP (degree of polymerization) 3–4 and lower DA (degree of acetylation) were obtained when using lysozyme than pepsin. Significantly, the conversion rate of chitin to oligosaccharides went best only when microwave and enzymes acting together (simultaneous strategy), which were at least 35.59% higher than separately pretreatment enzymes and substrates by microwave. The damages of microwave radiation on lysozyme and chitin substrates were revealed, and the operating principle of the whole enzyme reaction system heated by microwave was preliminatively explored.

Direct microwave heating synthesis and characterization of highly efficient g-C3N4 photocatalyst

Graphitic carbon nitride (g-C3N4) material was rapidly synthesized by direct microwave heating method with different microwave powers and irradiation reaction periods of time. Phase, functional group, surface morphology and optical properties of as-prepared g-C3N4 samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible diffuse reflectance spectroscopy and photoluminescence (PL) spectroscopy. The samples synthesized by direct microwave heating at 600–800 W for 9–15 min were g-C3N4 single phase with typical CN stretching vibration and out-of-plane bending vibration of C–N heterocycle and good absorption in the visible light region. The photocatalytic activity of g-C3N4 was evaluated through the degradation of methylene blue (MB), methyl orange (MO) and rhodamine B (RhB) under visible light irradiation. In this research, the g-C3N4 sample synthesized at 800 W microwave power for 15 min has the best photocatalytic performance in degrading of 91.82 % MB, 81.86% MO and 97.48% RhB within 60 min.

Significant Reduction of Resonant Frequency by Multi-Layered Dielectric Material-Loaded Coaxial Cavity for Microwave Heating

This paper presents a microwave heating method using a cavity whose size is much smaller than the free-space wavelength. The resonant frequency was reduced by inserting multi-layer dielectrics into the cavity, and an appropriate mode was generated in the cavity to heat a specific area inside it. High-permittivity dielectrics were used to make the cavity resonate in the frequency range of a few gigahertz. A formula for the resonant frequency of the multi-layer dielectric material-loaded cylindrical cavity was analytically derived. The frequency reduction by using a dielectric-loaded cylindrical cavity geometry was predicted from the derived formula, from 12.2 GHz to 4.6 GHz, whereas the experiment results showed a reduction from 10.8 GHz to 4.5 GHz. The analytical and the experiment results were compared and analyzed with simulations, which showed good agreement. The heating efficiency at the target in the multi-layered dielectric geometry was analyzed. The electric field inside the target material was measured to prove the temperature response of the microwave heating and was compared with the simulation result. This paper confirms a technical possibility of microwave heating of a smaller-sized cavity with an insertion of low-loss dielectric material in the vicinity of a heating target.

Polyetherimide functionalized carbon dots with enhanced red emission in aqueous solution for bioimaging

Red emissive carbon dots (CDs) are highly desired for biological applications. However, serious luminescence quenching of red emissive CDs in aqueous solution greatly hinders their application in high performance biological imaging. Herein, we reported a facile strategy to realize enhanced red emission of CDs in aqueous solution by surface modification with polyetherimide (PEI) via microwave heating method. High photoluminescence quantum yield (PLQY) of 25% was realized from the PEI functionalized CDs (CDs@PEI) in aqueous solution. The proposed PEI functionalization strategy not only protects the red emission against water molecules quenching, but also reverses the surface charges from negativity to positivity to promote cellular uptake of CDs, leading to clear cell imaging in red fluorescence region. More important, CDs@PEI exhibits much better photostability than commercial red emissive dye (MitoTracker red) in cell fluorescent imaging. Potential application of CDs@PEI on fast staining of cells for clonogenic assay has also been demonstrated.

Experimental Study on Fe3O4 Nanoparticle-Assisted Microwave Enhancing Heavy Oil

Nanoparticle-assisted microwave heating of heavy oil has the advantages of fast temperature rise and high thermal efficiency. Compared with traditional heating methods, it can reduce viscosity in a shorter time. In addition, the heavy components in the heavy oil are cracked into light components at high temperatures (this high temperature cannot be reached by conventional heating methods). This process is irreversible and avoids the problem of viscosity recovery of heavy oil after the temperature is reduced. Through absorbing microwave heating experiments, study the effect of nanoparticles on the improvement of the ability of heavy oil to absorb waves and raise temperature; through the heavy oil upgrading experiment and the four-component analysis experiment, the effect of adding hydrogen donor to assist microwave on the viscosity reduction of heavy oil upgrading by nanoparticles was studied, and the problem of viscosity recovery was determined; Through the gravity drainage experiment, the mechanism of nanoparticle-assisted microwave to improve the recovery of heavy oil is studied, and the influence of water content, nanocatalyst, and microwave power on the production of drainage is analyzed. The results show that nanoparticles can improve the wave absorption and heating capacity of heavy oil, and adding 0.6 wt% of nanomagnetic iron oxide catalyst can increase the heating rate of heavy oil in microwave by 60.6%; nanoparticle-assisted microwave heating method can effectively upgrade heavy oil and reduce viscosity. The experimental conditions are 2 wt% tetralin mass concentration, 0.5 wt% nano-Fe3O4 particle mass concentration, microwave heating time 50-60 min, and microwave power 539 W. Under this experimental condition, the viscosity is reduced by 40%. This method has viscosity recovery problems, but final viscosity reduction effect is still very significant. Obtaining the mechanism of nanoparticle-assisted microwave to enhance oil recovery, one of which is that nanoparticles improve the wave absorption and heating capacity of heavy oil and increase the heating speed of heavy oil; the second is that the nanoparticles form local high temperature under the action of microwave, which catalyzes the hydrocracking reaction between the heavy components in the heavy oil and the hydrogen donor, upgrading and reducing the viscosity of the heavy oil, and accelerating the production of heavy oil.

Catalyst development for viability of electrochemical hydrogen purifier and compressor (EHPC) technology

Considering the disadvantages of conventional compressors, which are widely used in the world, it is thought that the electrochemical hydrogen purifier and compressor system (EHPC) to be developed will provide great advantages in hydrogen technologies. The electrocatalyst, which is one of the main components of the EHPC system, is critical for both the performance and applicability of the system. In this study, commercial carbon black supported Pt and Pd containing catalysts were prepared for the EHPC system by using microwave heating method. The synthesized catalysts were mono and bimetallic and were named as Pt/C, Pd/C and PtPd/C, respectively. By characterizing the prepared catalysts with ICP-MS, SEM-EDS, TEM, XRD and XPS, information about the distribution, amount, morphology and composition of metal nanoparticles on the support material was obtained. In addition, electrochemical properties of the catalysts were determined by CV analysis. The physical characterization results revealed that the catalysts were successfully synthesized by microwave method and that different ratios of metals and bimetallic could be loaded on the support material. It was also seen that the electrochemical activity of the PtPd/C bimetallic catalyst was better than the others.

Microwave heat treatment on kyanite for mullite formation and the preparation of zirconia toughened mullite

This article deals with the investigations on mullite ceramics formation from Kyanite sample- an alumino-silicate mineral with microwave heating. In the present investigation kyanite was heated in microwave sintering furnace with calcined alumina, silicon carbide, zirconium dioxide and binder for mullite formation as well as for the preparation of zirconia toughened mullite product. The results of these studies reveal that how a small amount of zirconium dioxide helps in toughening the mullite formation for refractory and ceramics applications. The results shows that microwave heating method is one of the most novel and eco-friendly process for such toughened mullite formation, well within very short period of time. The observations with mullite formation and zirconia toughened mullite formation were observed with the structural data using X-ray diffraction data, field effect scanning electron microscope and energy dispersive spectroscopy. Future studies are still in process.

Microwave Heating as an Innovative Road Maintenance Technology: Aging Effect on Binder and Feasibility Evaluation

The microwave heating/healing technique is regarded as a green maintenance approach for asphalt pavements thanks to its promising environmental and economic benefits. However, the main concern about this technology is represented by the possible aging effect generated on bituminous binders. Currently, there is a significant lack of studies dealing with this topic. Based on these premises, the main purpose of this study is to appraise the feasibility of implementing microwave-based maintenance operations considering the associated aging effect. The assessment of fatigue life after cyclic microwave heating (MH) based on a linear amplitude sweep (LAS) test and the changes in the chemical groups detected through Fourier transform infrared (FTIR) spectroscopy document the aging phenomenon. The results indicate that the microwave aging degree on bituminous binder is nonlinear with MH cycles. The microwave radiation causes a distinct aging impact on binders during the first 10 cycles, then the values become constant. Furthermore, a feasibility analysis of MH technology is developed, encompassing four main multidisciplinary aspects: evaluation of microwave aging degree, working mechanism of MH equipment, safety assessment, and economic and ecological considerations. Despite the associated aging issue, the MH method is an efficient technology, considering its various advantages (i.e., rapidity of execution, uniform and non-pollutant treatment, and deep penetration). Meanwhile, the use of steel slag as a microwave absorber bolsters the sustainability of MH technology. This study provides a new perspective to evaluate the microwave heating technique in road engineering comprising the generated aging effect. Practice-oriented recommendations are also formulated regarding the safe implementation of MH technical operations.

Effects of different soaking time and heating methods on the tenderness of mutton

In the process of heating the mutton, the length of the soaking time will affect the meat tenderness, and the proper change of the soaking time can improve the meat tenderness. The sample was treated by water bath and microwave heating method, and the cooking loss rate, collagen solubility, shear force and the like were used as indicators for measuring tenderness. The effect of different soaking time on the tenderness of mutton was studied under water bath and microwave heating. The prolonged incubation time, the total soluble protein, collagen solubility and cooking loss of the meat treated by water bath were significantly increased (P < 0.01); while the myofibrillar protein and shear force values showed a downward trend. The difference in soaking time has an effect on the meat tenderness. Extending the soaking time, the color of the 20 µ strip gradually deepened, and the 32 µ and 75 µ strips showed different degrees of weakening. This indicates that the protein is degraded and the myofiber structure of the meat is destroyed. This provides a theoretical basis for the production and processing of enterprises and the table culture of the people.