Microwave Hydrothermal Treatment Research Articles

Regulating the Pore Structure and Heteroatom Doping of Soybean Straw Carbon Based on a Bifunctional Template Method for the High-Performance Carbon Supercapacitor.

The previous research addressed the waste problem of agriculture and forestry residues by exploring the efficient utilization of liquefied soybean straw in supercapacitor. The structures of the liquefied soybean straw were controlled by coupling microwave hydrothermal treatment with carbonization under the influence of a C3N4 bifunctional template. What's more, C3N4 could effectively regulate the pore structures and provide an effective N active site of carbon materials C3N4. The obtained N-SLR Carbon-700 possess a specific surface area of up to 1593.7 m2 g -1, and the pore size is mainly concentrated in the range of 1.8-2.5 nm, providing efficient ions transmission channels and storage space. Its specific capacitance is up to 261.5 F g-1 (current density of 0.5 A g-1), and the capacity retention is 74.04 % when the current density is expanded by 20 times. In the two-electrode system, the energy density of N-SLR Carbon-700 could reach to 31.3 W h kg-1 at a power density of 360 W kg-1, as well as the energy surface density is maintained at 69 % when the power density is increased by a factor of 20. This work enhances effectively the charging and discharging stability and capacitance value of carbon-based supercapacitor.

In situ, fast constructing interface/doping-engineered NiCo bimetal-based composites boosting electrocatalytic oxygen reduction for zinc-air battery

Investigating cost-effective, high-performance, stable and durable oxygen reduction reaction (ORR) catalysts is imperative, yet it’s still a formidable obstacle in the advancement of metal-air batteries. In this research, NiCo-bimetallic oxides in situ combined with NiCo-bimetal alloy upon the surface of carbon-based matrix (reduced graphene oxide) (NiCo/Co-NiO/rGO) were synthesized by microwave hydrothermal treatment coupled with an ultrafast Joule heating shock process. The interfacial charge transfer between the bimetal alloy and metal oxide in NiCo/Co-NiO/rGO resulted in electron redistribution at the heterointerface, where *O species migrated to the NiCo alloy surface through Mn+-O-M0 (M=Ni, Co and n=2, 3) bonds, facilitating continuous electron transport between the two phases and unveiling added active sites. Introducing abundant oxygen vacancies by Ni3+ and Co3+ facilitated charge transfer between different valence states and led to forming more active sites, thus significantly enhancing ORR performance. More importantly, solid solution strengthening within the NiCo-bimetallic alloy mitigated the oxidation and corrosion of the catalyst. Therefore, the as-synthesized NiCo/Co-NiO/rGO(5 % Co) exhibited excellent ORR performance under an alkaline medium. It achieved a half-wave potential(E1/2) of 0.85 V(vs. RHE) and maintained 89.10 % of its current density after a 12-h long-term reaction. The assembled zinc-air battery (ZAB) employing this catalyst proved remarkable specific capacity (807.04 mAh·gZn−1), power density (95.54 mW cm−2) and cycling stability (over 240 h), outperforming that of commercial Pt/C+RuO2-based ZAB device. This study presents a viable approach for fabricating low-cost dual transition metal-based catalysts, thereby boosting their electrocatalytic performance and enhancing the efficiency and longevity of metal-air batteries.

Pressurized microwave-assisted hydrothermal treatment with various salts for efficient production of monosaccharides from rice straw

This study proposed a two-stage pressurized microwave hydrothermal treatment with a catalyst, followed by enzymatic saccharification, as a pretreatment method for efficiently converting cellulose and hemicellulose from rice straw into glucose and xylose. The use of various inorganic salts and dilute sulfuric acid as catalysts enhances sugar production. Using 1 wt% sulfuric acid as a catalyst at 150 °C for 5 min for the first-stage and then 180 °C for 5 min for the second-stage yielded the highest sugar production from rice straw compared with other inorganic salts tested. The filtrate and enzymatic saccharification solution contained a total sugar of 0.434 g/g-untreated rice straw (i.e. 0.302 g-glucose/g-untreated rice straw and 0.132 g-xylose/g-untreated rice straw). When inorganic salts such as NaCl, MgCl2, CaCl2, and FeCl3 were used as catalysts, the highest sugar yield of 0.414 g/g-untreated rice straw (i.e. 0.310 g-glucose/g-untreated rice straw and 0.104 g-xylose/g-untreated rice straw) was obtained when using 1 wt% FeCl3 at 170 °C for 5 min in the first-stage and 190 °C for 5 min in the second-stage, with a value close to that of 1 wt% sulfuric acid. These findings suggest that two-stage treatment with a catalyst is a suitable pretreatment method for the production of glucose and xylose from rice straw owing to the different hydrolysis temperatures of cellulose and hemicellulose.

Effects of hydrothermal–microwave treatment on bending properties of teak in plantation

In order to study the bending properties of tropical tree species rich in organic extracts, the effects of temperature and time on the bending performance of hydrothermal treatment were investigated. The effects of power and time on bending performance under microwave heating conditions were investigated. It is found that the chemical composition does not undergo obvious degradation at 80°C–100°C, and the bending performance gradually becomes better with the increase in heating time; when the hydrothermal time exceeds 4 h, the bending performance varies with heating time. The growth is better than the difference, reaching the maximum at 4 h. When the water temperature is 140°C, the bending performance is negatively correlated with the heating time. When the hydrothermal treatment time is the same, the bending property becomes better as the temperature increases. The most reasonable process for microwave softening heating is with a power of 480 W and a heating time of 4 min. A softening treatment method combining water heat and microwave can achieve a better softening effect. When the final moisture content is controlled to 8%, the bending setting effect is the best. The optimum drying time is 6 h, and the optimum drying temperature is 50°C.

Microwave treatment enhances the physical and sensory quality of quinoa-enriched gluten-free bread

The suitability of microwave-assisted hydrothermally treated (MWT) quinoa flour was investigated as an ingredient for enhancing the quality of gluten-free (GF) bread fortified with quinoa. Different levels (0%, 25%, 37.5%, 50%, and 75%) of native/untreated (N) or MWT quinoa flour (30% moisture content, 9 W/g, total 8 min of microwave exposure) were evaluated to replace maize starch in a starch-based GF recipe. The hydration of the dough was adjusted to obtain similar consistency in terms of complex modulus, G1*, to compensate its increase due to quinoa addition and treatment (up to +737%). The incorporation of increasing amounts of native quinoa flour reduced dough viscosimetric profiles, delayed its gelatinization peak in DSC scans (up to +3.4 °C), and decreased the dough's development and stability during the fermentation test (the final height decreased from 88 mm for 0% quinoa to 4 mm for 75%). When substituting native by MWT quinoa flour at a certain substitution level, a reduction in the breakdown viscosity, an increase in pasting temperature, and an increase in dough development and stability during the fermentation test were noted. As a result, the MWT quinoa flour-fortified breads exhibited a higher specific volume, lower hardness, and retarded staling. In addition, sensory evaluation of the breads showed a reduction in the herbaceous off-flavour associated with the quinoa (untreated) flour, and no effect on bitterness. The experimental findings indicate the feasibility of using microwave hydrothermal treatment to improve the physical properties and sensory quality of quinoa-enriched GF bread.

Mechanism of the effect of temperature on the characteristics of microwave hydrothermal products of dead pig model compounds

Microwave hydrothermal treatment is a promising technology for the environmentally friendly disposal and resource utilization of dead pigs. However, the hydrothermal transformation mechanism of animal-based biomass is unclear, impeding the regulated conversion of target products. To address this, bovine serum albumin, glycerol-oleic acid, and glucose were selected as model compounds for protein (P), lipid (L), and carbohydrate (C), respectively. In this paper, the product distribution and related properties of single, binary, and ternary model compounds at different microwave hydrothermal temperatures (120–240 °C) were investigated, and the essential reaction pathway of the dead pig model compounds during microwave hydrothermal treatment was proposed. The results showed that lipids dominated the formation of bio-oil. L&C and L&P showed a slight synergistic effect on bio-oil yield at 240 ℃, while exhibited antagonistic effects at other temperatures. L&P&C showed antagonistic effects on bio-oil yield at all temperatures. The participation of glucose was more conducive to the formation of carbonized solid products. The model compounds of dead pigs underwent a series of reactions such as dehydration, decarboxylation, deamination and condensation during microwave hydrothermal treatment. To a certain extent, lipids promoted the Maillard reaction of protein and carbohydrate, while glucose promoted the esterification reaction of fatty acids.

Nanoflower hydroxyapatite's effect on the properties of resin‐based dental composite

AbstractTo investigate the reinforcing effect of nanoflower‐like hydroxyapatite (NFHA) in resin‐based dental composites, we synthesized a novel NFHA using microwave irradiation (MW), hydrothermal treatment (HT), and sonochemical synthesis (SS). Silanized NFHA was then used as the reinforcing filler in dental resin composites. We characterized the structure and morphology of various HA nanostructures using x‐ray diffraction, scanning electron microscope, and TEM. The mechanical performance of dental resin composites reinforced with silanized NFHA was measured using a universal testing machine. Spherical HA, synthesized through chemical precipitation (CP), served as the control group. One‐way analysis of variance was employed for the statistical analysis of the acquired data. The results demonstrate that the nanoflower morphology significantly was improved mechanical and physical properties. After conducting trials, the NFHA synthesized using MW and HT showed a substantial enhancement in mechanical and physical properties compared to the other structures. Therefore, it can be concluded that NFHA can serve as a novel reinforcing HA filler, providing regenerative properties to resin composites with sufficient mechanical strength.

Evernia prunastri lichen as a source of bioactive glucans with potential for topical applications

Microwave hydrothermal treatment was selected to extract valuable fractions with bioactive and gelling properties from Evernia prunastri lichen with potential for topical applications. The impact of the extraction processing conditions on the soluble extracts, mucilage fraction and residual solid phase was analyzed within a lichen global valorization approach. A particular stress was made on the thermo-rheological and structural characteristics of the extracted glucan and galactomannan polymers, the corresponding gelled matrices, and their cosmetic feasibility. Results revealed that the proposed microwave-assisted treatment showed a relevant influence on the phytochemical features of the aqueous soluble extracts, accounting the major protein content at 120 °C and the enhanced antioxidant and anti-tyrosinase properties at 140 °C. Extracts at 200 °C showed the highest anti-inflammatory (COX-1 and COX-2 inhibition) efficacies. The biopolymer analyses indicated that those recovered after lichen hydrothermal treatment at 160 °C featured a good extraction performance, the highest molecular weight, apparent viscosity, and antiproliferative potential. The thermo-rheological properties of the corresponding matrices formulated at 10 % and 60 or 80 °C exhibited the strongest and most thermo-reversible characteristics, as well as antifreezing feasibility. Another advantage of the selected fractions was the absence of skin irritation according to the in vitro skin irritation assay.

Promising valorisation method of chitin biomass by producing 5-hydroxymethylfurfural using microwave hydrothermal treatment

ABSTRACT Chitin biomass is the second largest biomass resource on Earth but under-utilized. In this study, pretreated shrimp shells were converted into value-added platform chemical 5-hydroxymethylfurfural (HMF) using microwave hydrothermal treatment. Under the combined pretreatment of acid decalcification at room temperature and microwave-assisted alkali deacetylation, the HMF yield could reach 1.8 wt%. The key process parameters, including the holding temperature, holding time, and pH value, were evaluated and optimised. The highest HMF yield of 6.5 wt% was obtained at 202.6°C at a holding time of 5.8 min and a pH value of 1.5. This result demonstrates the potential of synchronously treating waste and recycling it, thereby offering a highly promising valorisation strategy for chitin-biomass utilisation.

Chromium removal from chromium gypsum through microwave hydrothermal crystal phase regulation.

Chromium gypsum (CG) is a common hazardous waste formed in chromium salt or electroplating industries. The trapped or lattice-doped CrO42- in gypsum crystals are difficult to be reduced or removed by traditional methods, which will be re-oxidized or slowly released during long-term hypaethral storage. In this study, microwave hydrothermal treatment was applied to remove chromium in CG. Under optimal conditions (solid-liquid ratio of 1:5, 0.1M sulfuric acid as liquid media, and 110°C), over 99% of the chromium in CG can be removed within 10min. XRD spectra indicated that 59.8% gypsum was transformed to from dihydrate gypsum to hemihydrate gypsum. The toxicity leaching test shows that chromium in CG is 377.0mg/L before detoxification and 0.55mg/L after detoxification, which proves that chromium in CG lattice can be efficiently removed. This work enables to significantly advance the dehydration phase transformation process of gypsum and release the heavy metal impurities within it more quickly and provides new possibilities to treat similar solid waste containing gypsum or minerals with hydration water.

Microstructure and surface performance of hydroxyapatite-modified multilayer amorphous coating on Ti-rich TiNbZrSn medium entropy alloy: A comparative study

The present study focuses on the formation of a hydroxyapatite-modified amorphous micro-arc oxidized (MAO) coating on the TiNbZrSn medium entropy alloy (TNZS MEA) through micro-arc oxidation and microwave hydrothermal treatment (MHT). The TNZS MEA primarily consists of a body-centered cubic (bcc) and hexagonal closed-packed (hcp) structure, exhibiting a low elastic modulus and high yield strength. A porous coating with an amorphous structure was obtained after MAO treatment, displaying superior corrosion resistance to MAOed Ti. After MHT, the MAOed TNZS MEA exhibited a multilayered structure consisting of three layers: an external growth layer (hydroxyapatite nanorods), an inner layer (amorphous and crystalline structures), and a substrate layer. This composite structure demonstrated enhanced superior apatite-inducing ability and corrosion resistance compared to MHTed Ti. The improvement in bioactivity and a slight decrease in corrosion resistance can be attributed to the incomplete structure of hydroxyapatite nanorods when compared to MHTed Ti. Consequently, this work successfully achieved a hydroxyapatite-modified multilayered oxidized coating with gradient performance in term of bioactivity and corrosion resistance, establishing it as a promising candidate material for hard tissue repair.

Controllable and complete conversion of agarose into oligosaccharides and monosaccharides by microwave-assisted hydrothermal and enzymatic hydrolysis and antibacterial activity of agaro-oligosaccharides

Hydrolysis of agar or agarose can yield two types of oligosaccharides: agaro-oligosaccharides (AOS) and neoagaro-oligosaccharides (NAOS). These oligosaccharides have various biological activities and promising applications in the future food industry and pharmaceuticals. In this study, we prepared AOS from agarose by microwave-assisted hydrothermal hydrolysis and then used a commercial β-galactosidase to treat AOS for producing NAOS. A complete conversion from agarose to AOS or NAOS can be achieved by microwave hydrothermal treatment and one-step enzyme reaction, and the production process was completely green. In addition, we combined β-galactosidase and α-neoagarobiose hydrolase from Saccharophagus degradans 2–40 (SdNABH) to treat AOS, and AOS was completely converted into monosaccharides. Then the results of the inhibitory activity of AOS on the growth of Streptococcus mutans showed that AOS might be a good potential sugar substitute for dental caries prevention. This study provides an efficient approach for the production of multiple mixed degrees of polymerization (DP) of pure AOS and NAOS without requiring acid catalyst and agarases while simplifying the production processes and reducing costs.

Rapid immobilization of Cs+ using Cs-containing ceramics obtained by hydrothermal-microwave treatment

Rapid immobilization of Cs+ using Cs-containing ceramics obtained by hydrothermal-microwave treatment

Two Types of Europium-Based Photoconversion Covers for Greenhouse Farming with Different Effects on Plants

In the present work, we investigated the effect of light conversion using europium (Eu(III))-based photoconversion covers on the cultivation of agricultural plants and their resistance to stress conditions. Two types of europium nanoparticles were used. The first one was obtained from europium oxide (Eu2O3) by laser fragmentation. The second one was Eu3+:LaF3 nanocrystals obtained by hydrothermal-microwave treatment, the content of europium ions in which was 50% of the total amount of cations. Tomatoes (Solanum lycopersicum) and cucumbers (Cucumis sativus) were used as model plants. It was shown that plants grown under cover with Eu2O3 (PCC-Eu2O3) were 30–40% larger, gave a higher yield, and the activation of gas exchange processes and the light phase of photosynthesis in the leaves in response to the lighting was faster. On the contrary, plants grown under cover with Eu3+:LaF3 (PCC-Eu3+:LaF3) tended to slow down the rate of biomass accumulation and decrease the rate of gas exchange activation. It was shown that photoconversion covers change the resistance of plants to stress conditions: if plants grown under PCC-Eu2O3 became more sensitive to heat (+40 °C) and cold (+4 °C) treatment, then plants grown under PCC-Eu3+:LaF3 became more resistant to high and low temperatures. It was found that PCC-Eu2O3 inhibited the development of the phytopathogen Phytophthora infestans on tomato plants. It was assumed that changes in the illumination spectrum by the photoconversion covers cause both the activation of plant growth in the case of Eu2O3 and an increase in plant resistance in the case of Eu3+:LaF3 applications.

A novel oleogel based on porous microgel from egg white

In this study, oleogel was prepared by oil absorption using egg white microgel (EWM), and the EWM was obtained through microwave hydrothermal treatment, freeze-thawing, ethanol solvent replacement, atmospheric drying and ball milling pulverization. Compared with water bath and hydrothermal method, microwave hydrothermal treatment had higher heating efficiency to form egg white hydrogel (EWH). Ethanol solvent exchange reduced the surface tension from water evaporation, allowing the porous structure of EWH to be maintained during atmospheric pressure drying, while EWH structure collapsed without solvent exchange. Ball milling made EWM present smaller particle size and higher specific surface area than common pulverization, owing excellent oil holding ability (1.24 ± 0.04 g/g) and great ability to form networks in oil. Compared to control oleogel based on microgel without solvent exchange or by common pulverization, EWM oleogel showed higher viscosity and gelatinability, which was beneficial to the improvement of oxidation stability. This oleogel can be further used as the solid fat alternative or bioactive substance delivery carriers in food industry.

Microwave-assisted hydrothermal fabrication of hierarchical-stacked mesoporous decavanadate-intercalated ZnAl nanolayered double hydroxide to exterminate different developmental stages of Trichinella spiralis and Schistosoma mansoniin-vitro

Hierarchically stacked mesoporous zinc-aluminium nanolayered-double-hydroxide intercalated with decavanadate (ZnAl-LDH-V10O28) is constructed using anion-exchange process via microwave-hydrothermal treatment. Physicochemical properties of ZnAl-LDH-V10O28 are characterized in detail. Decavanadate anions are intimately interacted with ZnAl-LDH nanosheets, generating highly ordered architecture of well-dimensioned stacking blocks of brucite-like nanolayers (∼8 nm). Such hierarchy improves surface-porosity and electrical-impedivity of ZnAl-LDH-V10O28 with declining its zeta-potential (ζav = 8.8 mV). In-vitro treatment of various developmental-stages of Trichinella spiralis and Schistosoma mansoni by ZnAl-LDH-V10O28 is recognized using parasitological and morphological (SEM/TEM) analyses. ZnAl-LDH-V10O28 exterminates muscle-larvae and adult-worms of Trichinella spiralis, and juvenile and adult Schistosoma mansoni, yielding near 100% mortality with rates achieving 5%/h within about 17 h of incubation. This parasiticidal behavior results from the symphony of biological activity gathering decavanadate and LDH-nanosheets. Indeed, ZnAl-LDH-V10O28 nanohybrid sample, as a promissory biocide for killing food-borne/waterborne parasites, becomes a futuristic research hotspot for studying its in-vivo bioactivity and impact-effectiveness on parasite molecular biology.

Boosting hydrogen evolution under simulated sunlight via constructing close electron transfer interface between 1D CdxZn1-xS nanorod and 2D MoS2@MoOy nanosheet

Designing an efficient non-noble metal photocatalyst, which utilizes solar energy, has great potential to produce clean energy hydrogen. The microstructural refinement of 1D Cd0.2Zn0.8S nanorod was induced by doping with 2D MoS2@MoOy layer during microwave hydrothermal treatment. The maximum H2 production rate of the composite prepared at optimum conditions was 186 mmol g−1 h−1, which increased by 34.8% compared with that of Cd0.2Zn0.8S (138 mmol g−1 h−1). The apparent quantum yields of the optimized composite were 10.3% and 15.6% at 365 and 420 nm, respectively. The tight S-scheme heterojunction contributed to the separation of photogenerated electron-hole pairs effectively, as confirmed by the characterization analysis of ·OH and ·O−2 radicals, surface potential under illumination and darkness and in situ XPS spectra. Moreover, the active species of sulfur coordinated-Mo5+ as low-coordinate center promoted the dissociation of water and decreased the over potential of H2 production. Furthermore, the optimal composite showed excellent stable catalytic activity for hydrogen evolution, and the H2 production rate was 176.7 mmol g−1 h−1 after five cycles (95% of the first cycle). Overall, this work provides a promising strategy for improving the effectiveness of H2 production by preparing non-noble metal composite photocatalysts.

Photodegradation and oxidizing action of peroxotitanium complex film

Photodegradation and accompanying oxidizing action of peroxotitanium complex (PTC) film were investigated, which made from PTC aqueous solution containing 61.3 mol % peroxo groups (O-O) to total Ti. The apparent activation energy (Ea) of the PTC degradation was revealed to be 132 kJ·mol−1 (λ = 905 nm), according to Arrhenius plot of the degradation rate constant of PTC aqueous solution with microwave hydrothermal treatment at 100–180 °C. The PTC films were slowly decomposed by light irradiation of UV lamp, visible light LED or light bulb, and simultaneously oxidatively decomposed methylene blue dissolved in water. The oxidation reaction occurred even under the light of long wavelength around 900 nm closed to the Ea. Furthermore, the utilization efficiency of active oxygen generated by the photodegradation to the oxidation reaction of acetaldehyde gas was estimated to be 66 and 80 % under UV light (2.00 mW·cm−2) and LED visible light (1.50 mW·cm−2), respectively.

Facile treatment of municipal solid waste incineration fly ash by one-step microwave hydrothermal method: Hazards detoxification and tobermorite synthesis

A one-step microwave hydrothermal method is proposed here for the harmless treatment and resource recycling of water-washed municipal solid waste incineration fly ash (WMSWI-FA). Dioxins and heavy metals in WMSWI-FA can be detoxified, tobermorite can be synthesized by adjusting the parameters of NaOH dosage, reaction temperature and time. We conclude that NaOH is essential to synthesize tobermorite from WMSWI-FA, and higher temperatures and longer times are beneficial for degrading dioxins. However, excessive NaOH has a negative effect on the degradation of dioxins. Experiments showed that adding 20 wt% NaOH to WMSWI-FA and reacting at 260 °C for 3 h, the tobermorite was successfully synthesized, the residual dioxins (42.80 ng-TEQ/kg) and the leaching concentrations of heavy metals were lower than the limited value of the HJ 1134–2020 standard. The hydrothermal treated WMSWI-FA contains tobermorite, which supports it to be recycled as construction material and adsorbent. The one-step microwave hydrothermal treatment demonstrates favorable industrialization prospects, as it performs well in harmless treatment and resource utilization of WMSWI-FA.

Microwave treatment effect on the enhanced basicity of porous clay heterostructured composites derived from Laponite

Porous clay heterostructured composites (PCH) derived from layered hydrous magnesium silicate, Laponite, were functionalized by Fe(NO3)3x9H2O with the use of mechano-chemical impregnation followed by microwave irradiation or hydrothermal treatment to evoke new base properties, active in CO2 sorption. It resulted in the progressive leaching of the Mg2+ from the octahedral sheets of the Laponite structure and their capture on the surface of PCH composites increasing the Mg/Si ratio. The increase of Mg/Si ratio was accompanied by the decline of the (Mg3OH) absorption bands intensity attributed to Laponite and discussed regarding the formation of dispersed nanostructured MgO moieties capable of adsorbing CO2. CO2-TPD temperature-programmed desorption technique revealed that sorption and stabilization of CO2 molecules are related to the coordination of oxygen sites in the formed MgO lattice and that edge and corner sites facilitate the interaction of CO2 molecules with O2− sites on MgO. Doping of PCH resulted also in the nucleation of nanocrystalline α-Fe2O3 able to capture CO2 with strength and stability higher than MgO. Microwave irradiation resulted in significant development of the surface basicity as part of the transformation of clay structure. This study confirms the importance of clay minerals in the uptake and retention of CO2.