Microwave Power Research Articles

Analysis of a plasma reactor performance for direct nitrogen fixation by use of three-dimensional simulations and experiments

This study utilizes state-of-the-art in-situ measurements and advanced three-dimensional simulations to investigate the operation of a microwave plasma reactor for nitrogen fixation at a high subatmospheric pressure under various power inputs. It is shown that the system should be treated as a warm plasma due to negligible differences in vibrational and rotational temperatures and that it is required to account for chemical non-equilibrium. Complex flow field and significant temperature and concentration gradients are observed, emphasizing the need for three-dimensional simulations to accurately describe the interactions between mass, heat, and momentum transport and chemical reactions in non-equilibrium conditions. The innermost plasma regions reach temperatures close to 6000 K, while wall temperatures remain low due to presence of a low-temperature swirling flow field around the hot core. Analysis reveals that the swirling flow field around the hot core provides intrinsic partial quenching in regions with large temperature gradients which counteract the return to chemical equilibrium and enrich the flow surrounding the hot core. The inner flow exhibits a recirculation zone, stagnation point, and a transition into an increasingly parabolic flow profile closer to the reactor outlet. The agreement between the numerical modeling and the measurements is strong. In-situ Raman spectroscopy measurements confirm the calculated temperature field inside the reactor. Thermocouple measurements on the reactor wall are also in good agreement with the simulation. Additionally, Fourier-transform infrared spectroscopy measurements agree very well with the simulated amount of nitrogen oxide exiting the reactor at different microwave power inputs. The understanding and modeling capabilities are expected to support the development of future reactor designs that can facilitate higher yields.

Adaptive Neuro-Fuzzy Inference System and Artificial Neural Network Models for Predicting Time-Dependent Moisture Levels in Hazelnut Shells (Corylus avellana L.) and Prina (Oleae europaeae L.)

Nowadays, in parallel with the rapid increase in industrialization and human population, a significant increase in all types of waste, especially domestic, industrial, and agricultural waste, can be observed. In this study, microwave drying, one of the disposal methods for agricultural waste, such as prina and hazelnut shell, was performed. To reduce the time, energy, and cost spent on drying processes, two recently prominent machine learning prediction methods (Artificial Neural Network (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS)) were applied. In this study, our aim is to model the disposal of waste using artificial intelligence techniques, especially considering the importance of environmental pollution in today’s context. Microwave power values of 120, 350, and 460 W were used for 100 g of hazelnut shell, and 90 W, 360 W, and 600 W were used for 7 mm thickness of prina. Both ANN and ANFIS approaches were applied to a dataset obtained from the calculation of moisture content and drying rate values. It was observed that the ANFIS and ANN models were applicable for predicting moisture levels, but not applicable for predicting drying rates. When the coefficient of determination (R2), Root Mean Square Error (RMSE) and Mean Absolute Percentage Error (MAPE) values for moisture level are examined both for ANN and ANFIS models’ predictions, it is seen that the R2 value is between 0.981340 and 0.999999, the RMSE value is between 0.000012 and 0.015010 and the MAPE value is between 0.034268 and 23.833481.

Drying Process of Senna alata Medicinal Leave: Comparative Empirical and Artificial Neural Networks Modelling of Mass Transfer Kinetics with Energy Analysis

This study investigated the microwave drying of Senna alata leaves (SAL) for sustainable utilization. The effect of SAL form (un-chopped and chopped) and microwave power (200, 400 and 600 W) on the drying characteristics and energy utilization with comparative semi-empirical and artificial neural network (ANN) modelling was investigated. SAL was dried at the selected drying factors (leaf form and microwave power); and moisture transport characteristics including moisture content, moisture ratio, effective moisture diffusivity, activation energy, energy consumption, specific energy consumption and energy efficiency were determined gravimetrically and empirically. In addition, models were utilized to represent the experimental observations and compared statistically. Results showed that un-chopped SAL had a drying time of 10, 8.87, 7.34 s while chopped SAL had a drying time of 8.34, 5.45, 3.5 s at 200, 400 and 600 W, respectively. The effective moisture diffusivity of un-chopped and chopped SAL ranged between 1.40e-6 - 1.94e-6 m2/s and 1.99e-6 – 3.79e-6 m2/s at 200, 400 and 600 W, respectively; while activation energy was 1.79 and 3.64 W/g, respectively. The un-chopped SAL has energy efficiency of 47.38, 26.71 and 21.52% while chopped SAL has energy efficiency of 56.47, 43.49 and 45.14 KJ/kWs at 200, 400 and 600 W. The range of coefficient of determination (R2) of empirical models was 0.9963 – 0.9994 while R2 value of ANN model was 0.9996. It was generally observed that the form of SAL and selected microwave power affected the drying and energy indicators, where size alteration (chopping) and increment in microwave power reduced the drying time and improved the energy indicators. The semi-empirical and ANN models performed well in representing the drying process with ANN having a marginal edge. These results are useful in conservation of SAL, control and commercialization of the microwave drying process.

Tungsten-needle intensifies microwave-sustained plasma accelerating direct H2S conversion to H2

Direct sustainable conversion of hydrogen sulfide (H2S) enables collaborative recovery of H and S resources via a metal-enhanced microwave plasma strategy, avoiding the hydrogen waste in the traditional Claus process. However, the metal size effect on microwave plasma property, the optimal process parameters, and the enhancement mechanism remain unclear in H2S conversion. Herein, the optimal tungsten needle (diameter: 1 mm, length: 60 mm, and tip angle: 10°) is experimentally proven for intensifying microwave discharge in multi-mode cavities. Theoretical calculations and plasma distribution reveal that the optimized tungsten needle achieves the ideal coupling with the microwave field, exhibiting extreme electric field augmentation around the needle tip. Tungsten-needle intensifies microwave-sustained plasma, realizing 40.2 % (90.1 %) conversion of 100 % (10 %) concentration H2S to H2 at a low microwave power of 300 W with a good stability of 30 hrs. Low power, large flow rate, and high H2S concentration are beneficial for improving energy efficiency. The excitation of microwave plasma is accompanied by a massive generation of highly energetic electrons. The direct high-energy electron-H2S collision contributes a lot to H2S splitting, especially for high-concentration H2S. In-situ optical emission spectroscopy confirms the vital S and H radicals in the plasma. The free radical reactions triggered by electron collisions are responsible for the production of H2 and S. This work opens an avenue to sustainable and low-carbon hydrogen production from the direct conversion and utilization of H2S.

Microwave-assisted co-pyrolysis of rice straw pellets and plastic packaging wastes for value-added products and energy recovery

The sustainable utilization of agricultural residues and waste plastics to mitigate environmental pollution, while generating renewable energy through pyrolysis has achieved significant attention through the years. In this study, microwave-assisted pyrolysis and co-pyrolysis of plastic packaging wastes (PPW) and rice straw pellets (RSP) of different mixture compositions (10 % PPW, 20 % PPW, and 30 % PPW) have been carried out to evaluate the synergistic effect of the two different feedstocks on product yields, composition, energy recovery, energy and exergy efficiency. With an intention to avoid pulverization of the feedstocks to fine particle sizes, a unique configuration resembling a chocolate is adopted to mix the biomass pellet with sheets of PPW, while using activated carbon as a susceptor. The calorific value of the co-pyrolysis oil was higher (30–35 MJ kg−1) than the pyrolysis oil obtained from RSP (22–28 MJ kg−1). The maximum oil yield from co-pyrolysis was 40 wt% for a feed-to-susceptor ratio of 2.5:1 w/w, 10 % PPW at 600 °C, and 800 W microwave power. Compared to the pyrolysis of RSP, co-pyrolysis resulted in significant deoxygenation in the oil fraction (50–60 %). The oil composition data revealed an increase in aliphatic hydrocarbons from 37 % to 42 % along with increased aromatics from 13 % to 19 % when PPW content was increased from 10 % to 30 % in the feedstock. High energy recovery (∼91 %) and feed conversion efficiency (∼99 %) were recorded for 20 % PPW at 800 W and 600 °C. The net energy balance for co-pyrolysis was positive (9–16 MJ kg−1) at different reaction conditions, which proves the energetic feasibility of the process. At 800 W and 600 °C, the total exergy efficiency was maximum (57.7 %) for 10 % PPW feedstock, and the exergy efficiencies were lower than the energy efficiency values.

Comparative evaluation of α-Bi2O3/CoFe2O4 and ZnO/CoFe2O4 heterojunction nanocomposites for microwave induced catalytic degradation of tetracycline

Two microwave (MW) responsive heterojunction nanocomposite catalysts, i.e., α-Bi2O3/CoFe2O4 (BO/CFO) and ZnO/CoFe2O4 (ZO/CFO), with weight% ratio of 70/30, 50/50, 30/70 were synthesized by sequential thermal decomposition and co-precipitation methods, and used for the degradation of tetracycline (TC) under MW irradiation. The formation of desired catalysts was confirmed through the characterization results of XRD, FT-IR, SEM, VSM, UV-DRS, XPS, BET, etc. Using batch MW experiments, the catalyst dose, pH, initial TC concentration, reaction temperature, and MW power were optimized for TC removal. Under the following reaction conditions: catalyst dose ∼1 g/L, initial TC concentration ∼1 mg/L, temperature ∼90 °C, MW ∼450 W, BO/CFO, and ZO/CFO showed ∼97.55% and 88.23% TC degradation, respectively, after 5 min. The difference in the catalytic response against TC degradation indicated the difference in reflective loss (RL) between these two catalysts. The presence of other competitive anions has affected the removal efficiency of TC due to the scavenging effect. The radical trapping study revealed the significant contribution of TC degradation by hydroxyl radicals in the case of ZO/CFO, whereas for BO/CFO, superoxide (●O2−) and hydroxyl radicals (●OH) both played influential roles. The Z-scheme heterojunction of BO/CFO allowed the formation of ●O2− but the same was inhibited in type-II heterojunction of ZO/CFO due to the valance band position. The dielectric loss, magnetic loss, interfacial polarization, and high electrical conductivity, ‘hotspots’ were produced over the catalyst surface alongside electron-hole separation at heterojunctions, which were responsible for the generation of reactive oxygen species. In addition, Co3+/Co2+ and Fe3+/Fe2+ redox cycles have promoted ●O2− and sulfate radical production during persulfate application. Among the two MW responsive catalysts, BO/CFO could be a potential material for rapidly destroying emerging organic pollutants from wastewater without applying other oxidative chemicals under MW irradiation.

Design and Microwave Absorption Performance Study of SiC-Fe3O4 Emulsified Asphalt Mixture.

To address the challenges of slow curing speed and suboptimal microwave absorption during the paving of cold-mixed and cold-laid asphalt mixtures, this study introduces SiC-Fe3O4 composite material (SF) into emulsified asphalt mixtures to enhance microwave absorption and accelerate curing via microwave heating. Initially, based on the maximum density curve theory, an appropriate mineral aggregate gradation was designed, and the optimal ratio of emulsified asphalt mixture was determined through mixing tests, cohesion tests, wet wheel wear tests, and load wheel sand adhesion tests. Subsequently, the influence of SF content on the mixing performance of emulsified asphalt mixtures was analyzed through mixing and consistency tests. Finally, the microwave absorption performance of the mixture was evaluated by designing microwave heating tests under different conditions, using temperature indicators and quality indicators. The experimental results indicate that when SF content ranges from 0% to 4%, the mixing performance of the emulsified asphalt mixture meets specification requirements. The dosage of SF, SF composite ratio, and microwave power significantly impact microwave absorption performance, whereas environmental temperature has a relatively minor effect. The optimal mix ratio for the emulsified asphalt mixture is mineral aggregate:modified emulsified asphalt:water:cement = 100:12.8:6:1. The ideal SF dosage is 4%, with an optimal SiC to Fe3O4 composite ratio of 1:1, and a suitable microwave power range of 600-1000 W.

Demonstration of high-efficiency microwave heating producing record highly charged xenon ion beams with superconducting electron cyclotron resonance ion sources

Intense highly charged ion beam production is essential for high-power heavy ion accelerators. A novel movable Vlasov launcher for superconducting high charge state electron cyclotron resonance ion source has been devised that can affect the microwave power effectiveness by a factor of about 4 in terms of highly charged ion beam production. This approach based on a dedicated microwave launching system instead of the traditional coupling scheme has led to new insight on microwave-plasma interaction. With this new understanding, the world record highly charged xenon ion beam currents have been enhanced by up to a factor of 2, which could directly and significantly enhance the performance of heavy ion accelerators and provide many new research opportunities in nuclear physics, atomic physics, and other disciplines. Published by the American Physical Society 2024

Integrated choline chloride/citric acid-microwave pretreatment for efficient nanolignin extraction and bioethanol production from cocoa pod husk waste

The necessity to address environmental issues has driven efforts toward exploring sustainable bio-based materials as a viable alternative to conventional energy sources. The current study explores the utilization of cocoa pod husk (CPH) biomass for lignin extraction and cellulose production, aiming to contribute to the eco-friendly production of lignin nanoparticles and bioethanol. A synergistic green deep eutectic solvent (DES) (choline chloride/citric acid)-microwave method was employed to effectively fractionate CPH biomass, resulting in an impressive 77.58% lignin removal at 600 W microwave power. The extracted lignin (211.56 mg/g biomass) was utilized to synthesize lignin nanoparticles that were subsequently characterized. Enzyme-driven hydrolysis of the residual cellulose yielded a reducing sugar content of 198.34 mg/g biomass, demonstrating a saccharification efficiency of 70.78%. Fermentation of monomeric sugars by Saccharomyces cerevisiae and Scheffersomyces stipitis, respectively, gave a maximum ethanol yield of 130 mg/g biomass with a high fermentation efficiency (67.17%). The alterations in the CPH's surface structure and morphology following sequential pretreatment were assessed through FT-IR, BET, and SEM analyses, facilitating effective enzymatic hydrolysis. The current investigation adds to the increasing recognition of sustainable approaches in leveraging waste biomass resources toward a more environmentally conscious future.

Experimental Study on Combined Microwave-Magnetic Separation-Flotation Coal Desulfurization.

In order to reduce the content of sulfur and ash in coal, improve the desulfurization and deashing rates, a combined experiment method of microwave magnetic separation-flotation was proposed for raw coal. The desulfurization and deashing rates of three experiment methods, namely, single magnetic separation, microwave magnetic separation, and microwave magnetic separation-flotation, were compared. Taking the microwave magnetic separation-flotation experiment method as the main line, the effects of the microwave irradiation time, microwave power, grinding time, magnetic field intensity, plate seam width, foaming agent dosage, collector dosage, and inhibitor dosage on desulfurization and deashing were discussed, and the mechanism of microwave irradiation on magnetic separation and flotation was revealed. The results show that under the conditions of a microwave irradiation time of 60 s, a microwave power of 80% of the rated power (800 W), a grinding time of 8 min, a plate seam width (the plate seam width of a magnetic separator sorting box) of 1 mm, a magnetic field intensity of 2.32 T, a foaming agent dosage of 90 g/t, a collector dosage of 2125 g/t, and an inhibitor dosage of 1500 g/t, the desulfurization and deashing effect is the best. The desulphurization rate is 76.51%, the sulfur removal rate of pyrite is 96.50%, and the deashing rate is 61.91%. Microwaves have the characteristic of selective heating, and the thermal conductivity of organic matter in coal is greater than that of mineral. Microwave irradiation can improve the reactivity of pyrite in coal, pyrolyze pyrite into high-magnetic pyrite, improve the magnetic properties, and improve the magnetic separation effect. Therefore, microwave irradiation plays a role in promoting magnetic separation. Through microwave irradiation, the positive and negative charges in coal molecules constantly vibrate and create friction under the action of an electric field force, and the thermal action generated by this vibration and friction process affects the structural changes in oxygen-containing functional groups in coal. With the increase in the irradiation time and power, the hydrophilic functional groups of -OH and -COOH decrease and the hydrophilicity decreases. Microwave heating evaporates the water in the pores of coal samples and weakens surface hydration. At the same time, microwave irradiation destroys the structure of coal and impurity minerals, produces cracks at the junction, increases the surface area of coal to a certain extent, enhances the hydrophobicity, and then improves the effect of flotation desulfurization and deashing. Therefore, after the microwave irradiation of raw coal, the magnetic separation effect is enhanced, and the flotation desulfurization effect is also enhanced.

Resonance-driven microwave heating for improved methane conversion to hydrogen

Efficient hydrogen production through methane pyrolysis is hindered by high temperature required and frequent catalyst deactivation due to carbon deposition. This study proposes a novel use of variable-frequency microwave heating to enhance the efficiency and stability of methane pyrolysis by leveraging the resonance effects between microwave frequencies and dielectric properties of activated charcoal (AC). A solid-state variable-frequency microwave reactor was employed to modulate microwave frequencies to match the dielectric properties of AC, with a peak tanδ of 0.19 at 4600 MHz. Experimental results showed that at a resonance frequency of 4650 MHz and a microwave power of 100 W, the reaction temperature of AC reached 960 °C within 2 min, achieving a 100% methane conversion rate. However, carbon deposition reduced the conversion rate to 35.1% after 150 min. By cyclically adjusting the microwave frequencies between 4650 MHz and 4640 MHz, the catalyst was successfully reactivated, restoring the conversion rate to 100%. This frequency modulation method enabled continuous methane pyrolysis for 1300 min, highlighting the potential of variable-frequency microwave heating as a novel and efficient approach for a sustainable production of green hydrogen.

Designing Heterogeneous Catalysts for Microwave Assisted Selective Oxygenation

AbstractMicrowave dielectric heating is an emerging technology in heterogeneous catalysis. However, catalyst design in this field is not as well developed as when conventional heating is used. In this study the selective oxidation of propene to acrolein has been used as a model reaction to understand the how the properties of bismuth mixed metal oxide catalysts can be tuned for use in microwave assisted catalysis. The role of the dielectric properties, that are crucial to enable the catalyst to be heated in the microwave electric field, were determined using cavity perturbation methods. Catalysts with a very high loss tangent reached high temperatures leading to combustion products, whereas materials with a low loss tangent could not be heated and were inactive. Bi2MoO6 and BiVO4 both showed promising performance during an initial screening and were investigated further. For Bi2MoO6, a partial substitution of molybdenum with vanadium resulted in the formation of Bi1−X/3V1−xMoxO4, with a decrease in particle size and dielectric loss tangent, and the highest rate of acrolein production was found when x=0.6 at 15 W microwave power. Higher microwave power resulted in thermal runaway which decreased the activity of the catalyst.

Effect of linear antenna chemical vapor deposition process parameters on the growth of nanocrystalline diamond-on-GaN films

The present work will systematically study the effect of different linear antenna microwave plasma enhanced chemical vapor deposition (LACVD) processing parameters on the optimal deposition of the diamond films. The low pressure and low temperatures of LACVD growth conditions is expected to deposit diamond films on otherwise reactive gallium nitride (GaN) surfaces, without any intermediate nitride buffer layer. First, the distances between the quartz tube and the samples put on the stage are varied (3–15 cm), which has a direct impact on the substrate temperature (415°–300 °C). Thereafter, the microwave input power was also altered (1.5–2.8 kW) to attain low substrate temperatures. It was found that 300 °C is the temperature limit, which can be attained by heating only with microwave plasma when the substrates are kept farthest (15 cm) away from the liner antenna quartz tube. An additional heater was used under the stage for rapidly achieving such minimum substrate temperature of 300 °C. Substrate heater was used for efficient growth of the diamond phase while using pulse mode frequency of microwave power input for optimization of the diamond films. The microstructure (plate-like and cauliflower-like) of the deposited nanocrystalline diamond (NCD) films and the cross-sectional images for thickness measurements was observed under the scanning electron microscope and the elemental analysis of the film surfaces was done by electron diffraction spectroscopy. Moreover, the diamond film quality and crystallinity were evaluated by Raman spectroscopy with 488 nm laser light. Diamond-on-GaN film results were compared with conventional Si substrate. Different LACVD reactor parameters like, antenna to stage distances, microwave input power in continuous wave mode, and growth temperatures have significant impacts on the grown films, both in terms of their quality and microstructure. It was found that the optimum deposition of nanocrystalline diamond film on GaN substrates without its surface etching was possible, under pulse mode (20 kHz, 45 % duty cycle) with 2 kW average input microwave power.

Microwave-assisted synthesis of electrode materials for LIBs: MoS2/rGO heterostructures

The incomplete reduction of graphene oxide (GO) yields reduced graphene oxide (rGO), characterized by a zero band gap and intrinsic layer stacking, thus constraining its practical utility across diverse domains. Fortunately, this challenge can be effectively addressed by employing a suitable substrate for the fabrication of MoS2/rGO heterostructures. Nanocomposites of MoS2/reduced graphene oxide (MoS2/rGO-700W and MoS2/rGO-560W) were synthesized using MoS2 and GO solutions as starting materials through microwave-assisted synthesis with microwave power treatments of 700W and 560W, respectively. Structural characterization results reveal that the particle size of MoS2 within the composites is notably smaller compared to that of pure MoS2. The MoS2/rGO-700W composite demonstrates a more homogeneous dispersion of MoS2 and features a well-developed hierarchical porous structure with increased pore volume and specific surface area. The MoS2/rGO-700W composite demonstrates elevated ID/IG ratio, C/O ratio and C = C peak area, suggesting that increased microwave power enhances the removal of oxygen-containing groups from rGO. This process significantly restores the extended conjugated structure of graphene, thereby offering enhanced conductivity at the MoS2 interface. Furthermore, the proposed strategy holds considerable theoretical value and provides significant insights for the development process of novel MoS2-based composite electrode materials.

Drying kinetics and energy efficiency of Y2O3–CeO2 co-doped ZrO2 powder under microwave heating

Zirconia has important application prospects in the field of ceramics. However, during a high-temperature heating process, pure zirconia will undergo martensite transformation, which seriously affects its service performance. Metal oxides, such as Y2O3–CeO2 doping ZrO2, effectively improve the toughness and fire resistance of the material. Thus, the drying of Y2O3–CeO2 co-doped ZrO2 powder is an essential step before practical application. The study employs contemporary microwave drying techniques. The results of the experiment show that the average microwave drying rate increases with an increase in mass, water content, and microwave heating power. When the initial mass was 30 g, the initial moisture content was 12 %, microwave power was 720 W, and the drying rate was the fastest. We used four dynamic models: Modified Page, Quadratic, Wang and Singh, and Page to fit the experiment data. The best model was Modified Page, which describes the kinetic process most accurately. Fick's second law describes how, in the drying process, when microwave power is 720 W, initial mass is 15 g and initial water content is 8 %, the effective diffusion coefficient is 5.25 × 10−16 m2/s. Fourier Transforms of the infrared spectrum of the samples before and after drying were analyzed, the intensity of the O–H absorption peak located at 3442.03 cm/s, and O–H–O absorption peak located at 1594.48 cm/s. Both decreased significantly after drying. To discuss the relationship between the microwave power and the diffusion coefficient, the activating energy of microwave heating was 32.01 W/g. The experimental results show high heating efficiency and selective heating of the microwave method. This study provides a theoretical basis and research data for microwave drying of Y2O3/CeO2 co-doped ZrO2 powder in industry.

Prediction of product properties and identification of key influencing parameters in microwave pyrolysis of microalgae using machine learning

Exploring the effects of operating parameters and microalgae composition on product distribution and properties using machine learning is an effective and economical approach. However, there is currently a lack of research utilizing machine learning to comprehensively describe the microwave pyrolysis of microalgae. In this study, machine learning was employed to accurately model microalgae microwave pyrolysis based on microalgae composition, operating parameters, and the yields and properties of three-phase products. Using the collected data set, machine learning models, including Support Vector Regressor, Random Forest Regressor, Gradient Boosting Regressor, and eXtreme Gradient Boosting, were employed to model microalgae microwave pyrolysis. Results showed that the Gradient Boosting Regressor model outperformed the other three models, with average coefficients of determination (R2) of 0.998 and 0.762 in the training and testing phases, respectively. SHapley Additive exPlanations analysis revealed that reaction temperature, reaction time, and microwave power significantly influenced the predictions of the yields and properties of three-phase products. The findings of this study can effectively save costs and time in the future study on microwave pyrolysis of microalgae, and serve as an important tool for guiding subsequent experiments and process optimization.

Metasurface Antenna Designed for Quasi-Nondiffraction Beam Size Adjustment and Microwave Power Transmission

Metasurface Antenna Designed for Quasi-Nondiffraction Beam Size Adjustment and Microwave Power Transmission

Study on the Load Model of Microwave Power Detection Chip Based on MEMS Fixed Beams

Study on the Load Model of Microwave Power Detection Chip Based on MEMS Fixed Beams

An environmentally friendly production method: The pectin and essential oil from the waste peel of juvenile pomelo (Citrus maxima ‘Shatian Yu’) were extracted simultaneously in one step with an acid-based deep eutectic solvent

In agricultural production, the juvenile pomelo (Citrus maxima ‘shatian Yu’) is sometimes disregarded, yet its peel is rich in pectin and essential oils. The following parameters were found to be ideal for the extraction of pectin and essential oil: pH of 5.75, a liquid-solid ratio of 4 mL/g, a microwave power of 560 W, and a 30-min irradiation period. The maximum production of pectin was 26.70% ± 1.35% and the greatest output of essential oil was 2.09% ± 0.11% under these circumstances, both exceeding the yields of traditional steam distillation. Utilizing gas chromatography-mass spectrometry, the constituents of the essential oil were identified. There were 62 chemicals were found in the oil that was prepared by combining eutectic solvent extraction with microwave assistance, which better conserved the biological activity of juvenile pomelo peel essential oil. Overall, this technique shows how effective and eco-friendly acid-based deep eutectic solvent microwave-assisted extraction can be as a solution for treating agricultural waste.

Simultaneous extraction and derivatization of biogenic amines during in-situ deep eutectic solvent-based liquid phase extraction from Doogh samples prior to HPLC analysis

A simple and efficient microwave-assisted extraction method using deep eutectic solvent was developed for the simultaneous analysis of four biogenic amines (putrescine, tyramine, cadaverine and histamine) in Doogh (yogurt-based beverage) samples. Important parameters like precipitating agent volume, vortexing time, microwave power, and exposure time were optimized. Zinc sulfate was utilized for proteins precipitation prior to extraction of analytes with the deep eutectic solvent choline chloride/p-anisidine. The analytes were derivatized with dansyl chloride and analyzed by HPLC-DAD. The method showed good linearity (r2 ≥ 0.994) over wide ranges with low limits of detection (0.52–0.78 ng mL−1) and quantification (1.7–2.5 ng mL−1). Extraction recoveries ranged from 68–72 % and relative standard ≤8.1 %. Negligible matrix effects were observed. When the method was applied to real Doogh samples and several biogenic amines were detected. The developed method provided reliable results in terms of sensitivity and selectivity.