Nonthermal Microwave Effects Research Articles

Underlying mechanism of the microwave non-thermal effect as additional microbial inactivation on Clostridium sporogenes at pasteurization temperature level

Microwave processing can induce non-thermal effects that can inactivate additional levels of microorganisms at pasteurization temperature level (80–100 °C). The objective of this study was to investigate the mechanism behind the non-thermal effects of microwaves on vegetative cells of Clostridium sporogenes. Cell membrane damage were assessed through nuclear fluorescent dyes and by measuring nuclear acid and protein leakage. The results showed that microwave non-thermal effects and conventional water bath treatment resulted in similar nuclear acid leakage. However, microwave non-thermal effects inflicted more severe damage to the cell membranes of Clostridium sporogenes, resulting in increased protein leakage from both the inner of the cell and the cell membrane (A260 = 0.25 vs. 0.18). Consequently, it can be inferred that the inactivation of additional Clostridium sporogenes by microwave non-thermal effects is primarily attributed to the disruption of cell membranes induced by alternating electromagnetic fields, and this phenomenon is further potentiated at elevated temperatures.

Effect of non-thermal effects in microwave heating on the rheology and chemical properties of petroleum asphalt

This study systematically analyses the rheological properties of typical petroleum asphalt heated by microwaves at different temperatures through viscosity, penetration, dynamic shear, low-temperature bending, and other rheological tests. The results show that the non-thermal effect of microwaves enhances the fluidity of petroleum asphalt in the high-temperature viscous flow state, becomes softer in the medium-temperature viscoelastic state, and becomes hard and brittle in the low-temperature glassy state. The effect of microwaves also causes some specific changes in the properties of bitumen, including softening point and glass transition temperature in the opposite direction, as well as a large difference in the response of bitumen of different viscosities. The chemical changes in microwave-heated bitumen were analyzed using component tests and microscopic observation. It was found that microwave heating homogenized and dispersed the asphaltene aggregates into small particles, with the heavy components significantly reduced and the light components increased.

Heat transfer, crystallization and properties of Bayan Obo tailings-based nanocrystalline glass-ceramics processed with microwave radiation

Using Bayan Obo tailings containing rare earth element as raw material to prepare nanocrystalline glass-ceramics by microwave heating is a feasible scheme for the sustainable development of resources and low-carbon production. In this paper, the effects of conduction, infrared, microwave and plasma heating on nucleation were studied in order to obtain evidence for a thermal and non-thermal microwave effect. The differences in the mechanical properties, high-temperature softening properties and microstructures of the glass-ceramics prepared by conventional and microwave heating were analyzed. The results showed that microwave heating had a higher heating rate than conventional heating. The volumetric heating reduced the dependence of heat conduction within the sample, forming a uniform thermodynamic system for nucleation. The polymeric character of the silicon-oxygen network could be reduced by microwave radiation to promote nucleation, and fine nanocrystals with globular crystals and a uniform microstructure were produced after continuous nucleation-crystallization. In contrast to conventional heat treatment, the flexural strength of the samples increased from 169 MPa to 219.9 MPa under microwave radiation, and the thermal stability improved. The excellent mechanical properties were attributed to the increased Si–O stretching vibration frequency and bond force. In addition, the structure of the diopside cell tended to be dumpy with a decreased β angle, and the crystal orientation was affected. Tailings-based nanocrystalline glass-ceramics with excellent properties can be prepared in a short processing time by microwave heating.

Microwave pyrolysis of sewage sludge for bio-oil production: Effects of organic components and mechanisms

The microwave pyrolysis (MWP) of sewage sludge (SS) was conducted to investigate the impact of the organic composition of SS on the yield and composition of the derived bio-oil. The experiments were conducted in a microwave oven at 900 °C with a heating rate of 50 °C/min and achieved the product yield of 43.10 ± 2.23% bio-oil, 48.07 ± 1.26% bio-char, 8.83 ± 1.65% bio-gas. The chemical composition of bio-oil was investigated using gas chromatography–mass spectrometry and 145 species were identified. Protein and lipid contents in SS are the primary source of bio-oil yield, while bio-gas are predominantly derived from lignocellulosic materials. The unique non-thermal effects of microwaves can facilitate the ring-opening of small cycloalkanes to form straight olefins through hydrogen transfer reactions. Additionally, they can promote aldol condensation reactions, Pinacol rearrangements, and methoxy cleavage to form phenolic and aromatic structures with methyl groups. Furthermore, microwaves can aid in the dehydration, condensation, and cyclization reactions of amino acids to produce N-heterocycles while also facilitating lipid depolymerization into fragments for Diels–Alder cyclization. The results of this study will be beneficial for deeply understanding reactant characteristics and the reaction process during the MWP of SS.

Evaluation of the microwave-assisted enzymatic inactivation process of tomato pulp

In this study, the thermal and non-thermal effects of microwaves on the enzymatic inactivation of pectin methylesterase in the tomato pulp were validated. An amount of 30 kg of tomato pulp was subject to two different types of treatments: thermal effects and then non-thermal effects using microwaves, implementing a system that allowed simultaneous cooling of microwave heating. An experimental rotational central composite design was used to analyze the effect of the interactions of the variables involved in the process. The activity analysis of the PME enzyme, pH, titratable acidity, total soluble solid, and color was performed on both processed and non-processed tomato pulps, which showed that the heating process with thermal effect did not significantly change physical-chemical properties and were found to be more effective, reaching the enzymatic inactivation of 99% and the temperature of 80ºC after 425 s of processing. However, the non-thermal analysis with temperatures at a maximum of 40ºC attained 56.8% of enzymatic inactivation.

Effect of Induction Heating on Surface Properties of Hot-Pressed Ceramics Based on Nanopowders Si3N4 and TiN

The effect of induction heating on the surface properties of hot-pressed ceramics based on plasma chemical nanopowders Si3N4 and TiN (additives: Al2O3, AlN, and Y2O3) has been studied. The research demonstrates the formation of a modified layer on the surface of the hot-pressed material. The study examines the porosity, hardness, fracture toughness, brittleness, distribution of elements, and wear of hot-pressed ceramics on the surface before and after additional grinding. Removal of the surface porous layer results in increased density and hardness, leading to a higher number of acoustic emission signals during scratching with a Vickers indenter. A different response to scratching indicates a transgranular or intergranular fracture of the structure. The presence of porosity and carbon contamination on the surface layer of materials negatively impacts the properties of TiN-reinforced ceramics based on Si3N4-Al2O3-AlN (SIALON). However, the addition of Y2O3 effectively prevents carbon penetration and reduces the effect of grinding. Additionally, the dark-colored tone observed on the outer volume of the samples suggests a non-thermal microwave effect of the induction furnace.

An Exposimetric Electromagnetic Comparison of Mobile Phone Emissions: 5G versus 4G Signals Analyses by Means of Statistics and Convolutional Neural Networks Classification

To gain a deeper understanding of the hotly contested topic of the non-thermal biological effects of microwaves, new metrics and methodologies need to be adopted. The direction proposed in the current work, which includes peak exposure analysis and not just time-averaged analysis, aligns well with this objective. The proposed methodology is not intended to facilitate a comparison of the general characteristics between 4G and 5G mobile communication signals. Instead, its purpose is to provide a means for analyzing specific real-life exposure conditions that may vary based on multiple parameters. A differentiation based on amplitude-time features of the 4G versus 5G signals is followed, with the aim of describing the peculiarities of a user’s exposure when he runs four types of mobile applications on his mobile phone on either of the two mobile networks. To achieve the goals, we used signal and spectrum analyzers with adequate real-time analysis bandwidths and statistical descriptions provided by the amplitude probability density (APD) function, the complementary cumulative distribution function (CCDF), channel power measurements, and recorded spectrogram databases. We compared the exposimetric descriptors of emissions specific to file download, file upload, Internet video streaming, and video call usage in both 4G and 5G networks based on the specific modulation and coding schemes. The highest and lowest electric field strengths measured in the air at a 10 cm distance from the phone during emissions are indicated. The power distribution functions with the highest prevalence are highlighted and commented on. Afterwards, the capability of a convolutional neural network that belongs to the family of single-shot detectors is proven to recognize and classify the emissions with a very high degree of accuracy, enabling traceability of the dynamics of human exposure.

Studying the non-thermal effects of microwave on amino acids in sterilized rainbow trout (Oncorhynchus mykiss) fillets using a double side approximating method

The aim of this study was to investigate the impact of microwave non-thermal effects on thermal sensitive amino acids in rainbow trout (Oncorhynchus mykiss) fillets. To distinguish non-thermal effects from thermal effects occurring simultaneously, a Double Side Approximating Method (DSAM) derived from computational mathematics was developed. Two corresponding water bath treatments were designed for each microwave processing to approximate the time–temperature profiles at the hot and cold spots of the microwave processed samples while maintaining a comparable thermal intensity (F0). The microwave non-thermal effects on amino acids were determined by comparing the amount of each of 22 amino acids between the microwave processed and the two corresponding water bath treated rainbow trout fillets. The results indicated that the DSAM was successfully implemented, as the amino acid contents' order curve in the microwave processed samples was clearly exceeded the boundary formed by the two corresponding water bath treated samples. This finding confirmed the occurrence of microwave non-thermal effects on amino acids. The non-thermal effect resulted in a notable increase in the quantity of most amino acids, while it reduced the content of Lys and Hyp. Longer microwave processing times intensified these effects, while higher thermal processing intensities resulted in more damage to each amino acid.

Accumulative Effects of Multifrequency Microwave Exposure with 1.5 GHz and 2.8 GHz on the Structures and Functions of the Immune System

Microwave ablation can produce immune activation due to thermal effects. However, the nonthermal effects of microwaves on the immune system are still largely unexplored. In this study, we sequentially exposed rats to 1.5 GHz microwave for 6 min and 2.8 GHz microwave for 6 min at an average power density of 5, 10, and 30 mW/cm2. The structure of the thymus, spleen, and mesenteric lymph node were observed, and we showed that multifrequency microwave exposure caused tissue injuries, such as congestion and nuclear fragmentation in lymphocytes. Ultrastructural injuries, including mitochondrial swelling, mitochondrial cristae rupture, and mitochondrial cavitation, were observed, especially in the 30 mW/cm2 microwave-exposed group. Generally, multifrequency microwaves decreased white blood cells, as well as lymphocytes, monocytes, and neutrophils, in peripheral blood, from 7 d to 28 d after exposure. Microwaves with an average density of 30 mW/cm2 produced much more significant inhibitory effects on immune cells. Moreover, multifrequency microwaves at 10 and 30 mW/cm2, but not 5 mW/cm2, reduced the serum levels of several cytokines, such as interleukin-1 alpha (IL-1α), IL-1β, interferon γ (IFN-γ) and tumor necrosis factor α (TNF-α), at 7 d and 14 d after exposure. We also found similar alterations in immunoglobulins (Igs), IgG, and IgM in serum. However, no obvious changes in complement proteins were detected. In conclusion, multifrequency microwave exposure of 1.5 GHz and 2.8 GHz caused both structural injuries of immune tissues and functional impairment in immune cells. Therefore, it will be necessary to develop an effective strategy to protect people from multifrequency microwave-induced immune suppression.

Multifunctional Nanoplatform for Mild Microwave-Enhanced Thermal, Antioxidative, and Chemotherapeutic Treatment of Rheumatoid Arthritis.

Rheumatoid arthritis (RA) is usually associated with excessive proliferation of M1-type proinflammatory macrophages, resulting in severe hypoxia and excess reactive oxygen species (ROS) in the joint cavity. Inhibiting M1-type proinflammatory macrophages and/or repolarizing them into M2 phenotype anti-inflammatory cells by alleviating hypoxia and scavenging ROS could be a promising strategy for RA treatment. In this work, a microwave-sensitive metal-organic framework of UiO-66-NH2 is constructed for coating a nanoenzyme of cerium oxide (CeO2) and loading with the drug celastrol (Cel) to give UiO-66-NH2/CeO2/Cel, which is ultimately wrapped with hyaluronic acid (HA) to form a nanocomposite UiO-66-NH2/CeO2/Cel@HA (UCCH). With the microwave-susceptible properties of UiO-66-NH2, the thermal effect of microwaves can eliminate the excessive proliferation of inflammatory cells. In addition, superoxide-like and catalase-like activities originating from CeO2 in UCCH are boosted to scavenge ROS and accelerate the decomposition of H2O2 to produce O2 under microwave irradiation. The nonthermal effect of microwaves could synergistically promote the repolarization of M1-type macrophages into the M2 phenotype. Accompanied by the release of the anti-RA chemotherapeutic drug Cel, UCCH can efficiently ameliorate RA in vitro and in vivo through microwave-enhanced multisynergistic effects. This strategy could inspire the design of other multisynergistic platforms enhanced by microwaves to exploit new treatment modalities in RA therapies.

Alkali-activated fly ash cured with pulsed microwave and thermal oven: A comparison of reaction products, microstructure and compressive strength

The reaction products and microstructure of an 8 M NaOH-activated fly ash (AAFA) cured with microwave and thermal oven curing were comparatively investigated. The results show that the formation of an Al-rich N-A-S-H gel with a flaky morphology and crystalline chabazite-Na between fly ash particles were favoured under the microwave curing, whilst a Si-rich N-A-S-H gel with a fibrilllar morphology and crystalline hydroxysodalite on the surface of fly ash particles were dominant under the thermal oven curing. The formation of these unique reaction products and microstructure under the microwave curing is attributed not only to the thermal effect of microwaves which can increase the temperature of AAFA volumetrically, but also to the non-thermal effects of microwaves which can promote the dissolution and diffusion of silica and alumina during the AAFA reaction process. This explains why AAFA can achieve a high early strength within a short period of microwave curing.

Decoupling thermal effects and possible non-thermal effects of microwaves in vacuum evaporation of glucose solutions

Microwave vacuum evaporation (MVE) is a promising alternative to conventional methods. However, the mechanisms underlying its efficiency remain elusive. In this study, the effects of microwaves on glucose solutions were investigated via molecular dynamics (MD) simulations and experimental studies to elucidate possible microwave non-thermal and thermal effects, respectively. MD simulations on energy-related parameters, interfacial properties, and molecular migration indicated that a microwave electric field of 10 5 V/m could not influence water evaporation behavior at a constant temperature of 90 °C, validating the absence of non-thermal effects in the MVE of glucose solutions. Meanwhile, superheating was not observed in this study during microwave heating at atmospheric pressure or in vacuum. High-intensity microwaves enabled the solution to reach its boiling point rapidly and remarkably induced an intensified film boiling during MVE, thereby shortening the evaporation time. Therefore, the high efficiency of MVE may be attributed to the thermal effects of strong microwaves. • Thermal effects and possible non-thermal effects during MVE were studied. • Non-thermal effects were not observed during microwave evaporation at 10 5 V/m. • 10 9 V/m-z and 10 9 V/m-x microwaves accelerated and impeded evaporation, respectively. • Superheating did not occur during microwave heating with solution agitation.

Effect of microwave electric field on asphaltene aggregation in a heavy oil system: MD and DFT investigation

An in-depth understanding of asphaltene aggregation is vital for the viscosity reduction of heavy oils, and essential for fully utilizing heavy oil resources. Therefore, the influence of microwave electric field on the aggregation of asphaltene in the heavy oil system was investigated via Molecular Dynamic simulation and Density Functional Theory calculation. The aggregation forms, interaction types and rheological behavior of asphaltene and other components were calculated by processing the trajectories. The results reveal that microwave electric fields play a significant role in the packing morphology of asphaltenes and other components at the micro-molecular level, leading to changes in the apparent viscosity of heavy oil system. It can be clearly manifested that under 5 V/nm of microwave electric field, asphaltenes primarily stack in π - π, connecting intimately with resin, constructing a stable colloidal structure of the system with high viscosity. Whereas, by enhancing the electric field, π-π stacking will gradually be destroyed, resulting in viscosity reduction. The T-shaped stacking of asphaltenes is favorable to form at 20 V/nm, inducing a stable network among the components, which is detrimental to the viscosity reduction. The achievements further confirm that an appropriate microwave electric field is the key to reducing the viscosity. In addition, considering the thermal and non-thermal effects of microwave, it is explored that microwave is more effective at low temperature. Therefore, the efficient combination of microwave power and treatment temperature is the critical factor to achieve better viscosity reduction effect.

Polyvinyl chloride cooperates with biomass to assist in the directional conversion of N and Cl as NH3 and HCl to prepare clean fuel by low-temperature microwave heating

This work proposed an innovative integrated process to produce clean fuel. Waste polyvinyl chloride (PVC) was co-pyrolysis with biomass as a hydrogenation agent to enhance the conversion N of biomass to NH3 in the gaseous product by microwave heating. This work demonstrated the conditions suitable for the co-pyrolysis of PVC and the biomass (straw and rice husk, respectively) process based on the denitrification and dechlorination effects including indexes of N and Cl removal ratio and NH3 and HCl production ratio. The mass ratio of PVC to biomass (PVC: biomass), microwave heating power, active carbon (AC), and the pyrolysis temperature turned out to be significant factors for N and Cl removal and PVC: biomass and AC were also positive for converting N and Cl to NH3 and HCl. The optimum operating conditions were PVC: biomass 1:9, microwave heating power 500 W, active carbon 1.6 g, and heating temperature 300 °C. The mechanism could be primarily related to the volumetric and selective heating advantage of microwave heating, being attributed to producing abundant H radicals from PVC and promoting the hydrogenation reaction of biomass to remove N as NH3. Moreover, the denitrification and dechlorination effect differences between microwave heating and electric heating were studied to explore the microwave non-thermal heating effect. The amount of the N removal ratio and the NH3 production ratio by microwave heating was almost 5%–10% higher. The amount of the Cl removal ratio and the HCl production ratio was almost 10% and 7% higher than that by electric heating. The pyrolysis reaction enhancement and the better denitrification and dechlorination effect of microwave heating could be a result of specific microwave non-thermal effects in addition to the thermal effect, containing more uniform heat distribution and selective heating characteristics. The present work may provide a new viewpoint for the clean utilization of biomass and chlorinated plastic waste as a fuel and avoid HCl corrosion when treating the chlorinated plastic waste.

Non-thermal effect of microwave on organic sulfur removal from coal by microwave with peroxyacetic acid

This work investigated the non-thermal microwave effect during organic sulfur removal from coal by microwave irradiation combined with oxidation assistants. XANES was used to analyze the change of sulfur forms in the desulfurization process of high organic sulfur coal under microwave heating and conventional heating conditions. The effects of microwave fields on the molecular properties, bond strength and reaction kinetic of organic sulfur-containing groups were studied by quantum chemical calculation. Results showed that the desulfurization rate with microwave heating improved by 26% at the same temperature compared with conventional heating. The XANES analysis indicated that microwave radiation promoted the transformation of low-valence sulfur into high-valence sulfur, which resulted in the sulfur in the treated coal mainly existing as heterocyclic sulfur and oxidized sulfur. For the theoretical calculation, it is observed that the nucleophilic reaction activity of sulfur-containing groups could be improved and the strength of CS bands could be reduced under the extra electric fields due to the non-thermal microwave effect. Besides, the reaction activation energy was reduced and the reaction rate was increased under the same extra electric fields, promoting the formation of oxidized sulfur in coal. Therefore, there was a competitive relationship between sulfur-containing bond dissociation and group oxidation under the action of microwave non-thermal effect, which provided a reference for coal desulfurization research.

Using molecular dynamics simulations to study the non-thermal effects of microwave radiation on the mechanism of char gasification

Studying the chemical effects of alternating electric fields on char gasification is key to exploring the non-thermal effects of microwaves on the reaction mechanism. The gasification mechanism of char in the presence of an electric field was explored through molecular dynamics (MD) simulations and quantum chemical calculations. The results show that the promotion effect of 0.02 V/Å alternating electric field on the gasification reaction rate of char is about 8 times that of non-electric field, and the square wave electric field and static electric field are 6.79 times and 5.39 times respectively, this effect increases exponentially as the field intensity increases. Interestingly, the use of alternating electric fields showed, for the first time, that the changes in the electric field intensity and direction also have a significant effect. In terms of the adsorption process during gasification, the electric field promotes the formation of O and OH free radicals (about 5 times of no electric field) and increases the polarity of the char edge, both of which are conducive to adsorption. The electric field can weaken the curling of char macromolecules and expose more active carbon sites, thus increasing the overall reaction rate. For the desorption process during gasification, the presence of the electric field promotes the deformation and tear of char, which destroys its aromaticity, loosening the carbon-oxygen compounds at the carbon edge, which facilitates the desorption of CO, the desorption rate is about 10 times that of non-electric field system. Further, the change in direction of the electric field also promotes the desorption process. The results from this study suggest that the remarkable effects of alternating electric fields on char molecules can have an impact on the field of solid fuel gasification.

The Biological Effects of Compound Microwave Exposure with 2.8 GHz and 9.3 GHz on Immune System: Transcriptomic and Proteomic Analysis

It is well-known that microwaves produce both thermal and nonthermal effects. Microwave ablation can produce thermal effects to activate the body's immune system and has been widely used in cancer therapy. However, the nonthermal effects of microwaves on the immune system are still largely unexplored. In the present study, we exposed rats to multifrequency microwaves of 2.8 GHz and 9.3 GHz with an average power density of 10 mW/cm2, which are widely used in our daily life, to investigate the biological effects on the immune system and its potential mechanisms. Both single-frequency microwaves and multifrequency microwaves caused obvious pathological alterations in the thymus and spleen at seven days after exposure, while multifrequency microwaves produced more pronounced injuries. Unexpectedly, multifrequency microwave exposure increased the number of both leukocytes and lymphocytes in the peripheral blood and upregulated the proportion of B lymphocytes among the total lymphocytes, indicating activation of the immune response. Our data also showed that the cytokines associated with the proliferation and activation of B lymphocytes, including interleukin (IL)-1α, IL-1β and IL-4, were elevated at six hours after exposure, which might contribute to the increase in B lymphocytes at seven days after exposure. Moreover, multifrequency microwave exposure upregulated the mRNA and protein expression of B cell activation-associated genes in peripheral blood. In addition to immune-associated genes, multifrequency microwaves mainly affected the expression of genes related to DNA duplication, cellular metabolism and signal transduction in the peripheral blood and spleen. In conclusion, multifrequency microwaves with 2.8 GHz and 9.3 GHz caused reversible injuries of the thymus and spleen but activated immune cells in the peripheral blood by upregulating mRNA and protein expression, as well as cytokine release. These results not only uncovered the biological effects of multifrequency microwave on the immune system, but also provide critical clues to explore the potential mechanisms.

Kinetic study of multiphase reactions under microwave irradiation: A mini-review

Microwave (MW) heating is rapid, selective, and volumetric, and it is a compelling non-conventional heating approach for driving chemical reactions. The effect of MW irradiation on the kinetics of thermal/catalytic reactions is still under debate. A group of researchers reported that the effect of MW heating on reaction kinetics is highlighted through the non-thermal effects of MWs on kinetic parameters and reaction mechanisms in addition to the thermal effect. However, another group attributed the observations to the thermal effect only. In the present work, we summarized and critically synthesized available information in the literature on the subject. It can be concluded that MW heating has solely the thermal effect on gas-solid reactions, and the variations of kinetic parameters are related to the direct and indirect impacts of that. Temperature measurement limitations, physical structure variation, and non-uniform temperature distribution are the primary sources of the discrepancy in previous studies. In ionic liquid-solid reactions, the presence of electromagnetic fields can affect the movement of ions/polar molecules which can be considered a non-thermal effect of MWs. However, the effect of MW absorption by solid/catalyst, and the formation of hot spots must be taken into account to avoid potential discrepancy. Therefore, further theoretical/experimental studies are required to clarify the effect of MWs on liquid-solid reactions. In addition, developing reliable temperature measurement methods and isothermal reaction domain are required for an accurate kinetic study during MW irradiation.

Introduction of oxygen vacancy to manganese ferrite by Co substitution for enhanced peracetic acid activation and 1O2 dominated tetracycline hydrochloride degradation under microwave irradiation

High microwave-response cobalt-substituted manganese ferrite (CMFO-0.5) was successfully synthesized as a heterogeneous catalyst for efficient peracetic acid (PAA) activation and tetracycline hydrochloride (TCH) degradation with singlet oxygen (1O2) as the dominated reactive oxidized species (ROS). The removal efficiency of TCH could reach 98.16% within 6 min under microwave irradiation when the CMFO-0.5 was added at 20 mg/L. It's found that the Co substitution could produce the oxygen vacancies (OVs), improve the microwave (MW) absorbing performance and enhance the internal electron transfer efficiency of materials. The phenomenon why 1O2 as the dominated ROS rather than hydroxyl radical (•OH) and organic radicals (R-O•) would be explained by the following aspects: the oxygen adsorbed on the OVs can accept the electron transformed from PAA to form superoxide radical (•O2−), which will disproportionate to form 1O2; the energy generated by the non-thermal effect of MW can dissociate PAA to generate peroxy-group for 1O2 generation. Furthermore, the possible TCH degradation pathways were proposed based on DFT theory calculations and product identification, and the toxicity predictions of the degradation products were also performed by the Ecological Structure-Activity Relationship Model (ECOSAR) software. Additionally, the decrease of acute toxicity of treated TCH, excellent stability and strong resistance towards water matrix fully demonstrate the superiority of the proposed system for practical application in wastewater treatment.

Mechanistic study of the solid-liquid extraction of phenolics from walnut pellicle fibers enhanced by ultrasound, microwave and mechanical agitation forces

The molecular diffusion of phenolics inside walnut pellicle fiber particles under solid-liquid extraction enhanced by ultrasound (US), orbital agitation (OA), impeller agitation (IA), and the combined microwave and impeller agitation (MW-IA) were explored. Numerical modeling considering the temperature-dependent diffusivity revealed that the internal diffusivity of phenolics was the highest under MW-IA and the lowest under OA. At 35 °C, IA (126.246 mg/g, t = 10 min) was more effective to strengthen the phenolic diffusivity than the US-39W (95.538 mg/g, t = 10 min). Due to the simultaneous enhancement of internal diffusivity and external dissolution, the MW-IA extraction reached equilibrium within 16 min, reaching the highest yield among all the treatments (176.944 mg/g). The extraction was then divided into the increasing and falling driving force periods. The comparison of phenolic diffusivity among MW-IA and IA roughly indicated that the proportion of non-thermal effect of microwave at 315 W was 889% higher than 189 W at the extraction equilibrium. Moreover, some soluble polyphenols, i.e. quercitrin and syringic acid, could be adsorbed by the cell wall after equilibrium. The correlations between any two soluble phenolics varied with the phenolic type, deducing that soluble phenolics may interact with each other either positively or negatively. Besides, the mining of phenolic data also indicated that intensive impeller agitation is a good substitution for ultrasonication to extract phenolics effectively.