Microwave-assisted Degradation Research Articles

Photocatalytic performance of copper ferrite/polypyrrole nanohybrids: studies on visible light induced degradation of urea and microwave-assisted degradation of polyethylene films

Photocatalytic performance of copper ferrite/polypyrrole nanohybrids: studies on visible light induced degradation of urea and microwave-assisted degradation of polyethylene films

Microwave-assisted rapid degradation of Methyl red dye using Polyfuran/Polythiophene and its Co-oligomers as catalysts

The work reports for the first time microwave-assisted degradation of Methyl Red (MR) dye using polythiophene (PTh), polyfuran (PFu) and its co-oligomers. The co-oligomers were synthesized by sonication using varying mol ratios of PFu/PTh (80:20, 50:50 and 20:80). The polymers and its co-oligomers were analyzed for their spectral and morphological properties using FTIR, UV–visible and scanning electron microscopy (SEM) coupled with elemental mapping. The oligomers as well as pristine polymers were used as microwave active catalysts to degraded Methyl Red (MR) dye. The degradation was found to follow the pseudo-first-order model. Maximum degradation of 99% was achieved using PFu/PTh-50/50 as catalyst. Scavenging tests were also carried out to confirm the generation of radicals responsible for the effective degradation of the dye. The LCMS studies were used to explore the degraded fragments and a plausible mechanism was proposed to reveal the degradation pathway.

Microwave-assisted degradation of β-D-glucan from Ganoderma lucidum and the structural and immunoregulatory properties of oligosaccharide fractions

Microwave-assisted degradation of β-(1 → 3,1 → 6)-D-glucan from Ganoderma lucidum and correlated immunoregulatory activities were investigated in this study. The optimal temperature and degradation time for microwave hydrothermal hydrolysis were 140 °C and 40 min, respectively. Under these conditions, a high yield of degradation rate (98.4 %) and abundant β-oligosaccharide products (GLOS) with different degrees of polymerization (DP 2–24) were obtained. Four fractions including F1 (DP 2–8), F2 (DP 6–19), F3 (DP 8–24) and F4 (high DPs) with different average ratios of β-(1 → 3) to β-(1 → 6)-linked glucose units were isolated from GLOS. The structures of oligosaccharides with DP (2–6) in F1 were identified as linear β-(1 → 3)-linked glucooligosaccharides without or with β-(1 → 6)-linked glucose residues based on MS/MS analysis. The immunoregulation activity of β-glucooligosaccharides was correlated with their DPs and the average ratios of β-(1 → 3) to β-(1 → 6)-linked glucose units. F4 fraction with high DPs and ratio of 3.29:1 exhibited higher immunoenhancing activity on inducing NF-κB activation through binding to dectin-1. Surface plasmon resonance (SPR) analysis indicated that β-glucooligosaccharides could bind to Dectin-1 directly and the binding affinity increased with the increase of DPs and the ratios of β-(1 → 3)-linked glucose.

Highly Efficient Microwave-Assisted Fenton Degradation of Toluene Nitrification Wastewater Over Microwave-Responsive Catalyst of Fe3o4-Biocl

Highly Efficient Microwave-Assisted Fenton Degradation of Toluene Nitrification Wastewater Over Microwave-Responsive Catalyst of Fe3o4-Biocl

Microwave-assisted Degradation of Poultry Feather to Synthesize Protein-based Surfactant

Poultry feather is hydrolyzed into peptides and amino acids in sub-critical water without any acid or alkali as catalyst under microwave-assisted heating to produce protein-based surfactant. The optimal hydrolysis condition is as follows: temperature 200 °C, time 60 min, and the yield of peptides and amino acids 84.31%. The critical micelle concentration (CMC) and surface tension of the product of peptides and amino acids are 2.6 g/L and 48.2 mN/m. In order to increase lipophilicity, subsequently anionic protein-based surfactant was synthesized by acylation reaction between the hydrolysis product of peptides and amino acidsand oleoyl chloride. The CMC and surface tension decreased greatly with linkage with oleoyl. The synthesized anionic surfactant with weight ratios of 10% (wt.%) hydrolysis liquid/oleoyl chloride of 3:1, 4.5:1 and 6:1 are 0.5, 0.7 and 0.8 g/L and corresponding surface tension are 30.1, 34.0 and 35.7mN/m.

Preparation and characterization of catalysts and its application in microwave-assisted degradation of Acid Orange-8

Preparation and characterization of catalysts and its application in microwave-assisted degradation of Acid Orange-8

Energy analysis of the effectiveness of microwave-assisted fragmentation

Enhancing the energy-effectiveness of microwave-assisted fragmentation is one of the overlooked areas in the published literature. A novel calorimetric technique is proposed to quantify the effect of inductive heating within a microwave cavity on subsequent rock/ore fragmentation. Two new parameters are introduced to identify, differentiate, and quantifiably evaluate the effects of microwave-induced energy and thermally induced fracturing on mechanical strength degradation. Additionally, the influences of sample geometry and position and orientation with respect to the microwave waveguide are experimentally investigated to determine optimum conditions for microwave treatment. Comparisons with published literature show that establishing optimum electromagnetic heating conditions significantly improves microwave-induced weakening. Microwave-assisted degradation has significant potential application to in-situ mining, tunnelling, rock breakage, and comminution.

Microwave-Assisted Degradation of Paracetamol Drug Using Polythiophene-Sensitized Ag-Ag2O Heterogeneous Photocatalyst Derived from Plant Extract.

Ag–Ag2O nanoparticles were synthesized using Osmium sanctum plant extract. The nanoparticles were sensitized with polythiophene (PTh) and were characterized via scanning electron microscopy with energy dispersive X-ray and elemental mapping, transmission electron microscopy, X-ray diffraction (XRD), Fourier-transform infrared, and UV–vis spectroscopy analyses. The elemental mapping results revealed that the samples were composed of C, S, Ag, and O elements which were uniformly distributed in the nanohybrid. XRD analysis confirmed the crystalline nature of Ag–Ag2O nanoparticles, and the average particle size was found to be ranging between 36 and 40 nm. The optical band gap of Ag–Ag2O, PTh, and Ag–Ag2O/PTh was found to be 2.49, 1.1, 1.5, and 0.68 eV. The catalytic activity of Ag–Ag2O, PTh, and Ag–Ag2O/PTh was investigated by degrading paracetamol drug under microwave irradiation. Around 80% of degradation was achieved during 20 min irradiation. All degradation kinetics were fitted to the pseudo-first-order model. A probable degradation pathway for paracetamol degradation was proposed based on liquid chromatography mass spectrometry analysis of degraded fragments.

Microwave-Assisted Degradation of Biomass with the Use of Acid Catalysis

The aim of the study was to assess the effectiveness of microwave pretreatment combined with acid catalysis in the decomposition of various types of biomass (pine and beech chips and hemp stems). It was clearly demonstrated that sulfuric acid was a catalyst enabling the most effective decomposition of the tested plant biomass, guaranteeing the highest concentrations of simple sugars released. Acid catalysis with 1% v/v sulfuric acid combined with microwave radiation provided high glucose concentrations of 89.8 ± 3.4, 170.4 ± 2.4 and 164.6 ± 4.6 mg/g for pine chips, beech chips and hemp stems, respectively. In turn, the use of nitric acid promoted the degradation of hemicellulose, which resulted in high concentrations of galactose and xylose, i.e., 147.6 ± 0.6, 163.6 ± 0.4 and 134.9 ± 0.8 mg/g of pine chips, beech chips and hemp stems, respectively, while glucose levels remained relatively low. It was also demonstrated that the undesirable dehydration of sugars such as glucose and xylose is more pronounced in sulfuric acid than nitric acid processes. The use of H2SO4 and increased pressure generated 5-hydroxymethylfurfural (5-HMF) and furfural at a concentration of ca. 12 and 6 mg/g, 10 and 45 mg/g and 14 and 30 mg/g, of pine chips, beech chips and hemp shoots, respectively. Our studies confirmed the usefulness of the combined use of microwaves and acid catalysis in the degradation of softwood, hardwood and non-wood plant biomass. It should be emphasized that obtaining high concentrations of released simple sugars (as potential substrates in biosynthesis), while maintaining low levels of toxic by-products (inhibitors), requires precise selection of process parameters such as pressure, exposition time and type of acid catalyst.

Selection of Water-Soluble Chitosan by Microwave-Assisted Degradation and pH-Controlled Precipitation.

In the field of gene therapy, chitosan (CS) gained interest for its promise as a non-viral DNA vector. However, commercial sources of CS lack precise characterization and do not generally reach sufficient solubility in aqueous media for in vitro and in vivo evaluation. As low molecular weight CS showed improved solubility, we investigated the process of CS depolymerization by acidic hydrolysis, using either long time heating at 80 °C or short time microwave-enhanced heating. The resulting depolymerized chitosan (dCS) were analyzed by gel permeation chromatography (GPC) and 1H nuclear magnetic resonance (NMR) to determine their average molecular weight (Mn, Mp and Mw), polydispersity index (PD) and degree of deacetylation (DD). We emphasized the production of water-soluble CS (solubility > 5 mg/mL), obtained in reproducible yield and characteristics, and suitable for downstream functionalization. Optimal microwave-assisted conditions provided dCS with a molecular weight (MW) = 12.6 ± 0.6 kDa, PD = 1.41 ± 0.05 and DD = 85%. While almost never discussed in the literature, we observed the partial post-production aggregation of dCS when exposed to phase changes (from liquid to solid). Repeated cycles of freezing/thawing allowed the selection of dCS fractions which were exempt of crystalline particles formation upon solubilization from frozen samples.

Optimization of extraction technology of poly-mannuronic acid to a green delivery system for the water-insoluble pesticide, λ-Cyhalothrin

Poly-mannuronic acids (PMs) have been considered as great biodegradable polymers as a green carrier for the potential pesticide deliver. In this work, the response surface design and microwave-assisted degradation were employed to obtain the optimum extraction conditions (i.e., 81 °C, 4.1 h, acid concentration 17.65 g/L). Meanwhile, the Ugi multi-component reaction makes the PM to be amphiphilic, called Ugi-PM, which induces the aggregation in aqueous solution at the concentration of 0.0895 g/L. The corresponding chemical structure and thermal stability of PM and Ugi-PM were determined by the FTIR, 1H NMR and thermogravimetric analysis (TG). Furthermore, the construction of novel emulsion-based delivery system using synthetic Ugi-PM was explored to prepare the pesticide of λ-Cyhalothrin. Interestingly, with the Ugi-PM concentration at 0.5 wt%, the stability of the Ugi-PM emulsion and the sustainable release of λ-Cyhalothrin are better than other concentrations and our previous system without degradation (Ugi-Alg emulsion). It is possible that electrostatic repulsion and steric hindrance derived from the hydrophobic Ugi-PM can promote the stability and flexible structure may be the reason for excellent sustained release of Ugi-PM emulsions in the pesticide deliver. The above-mentioned preparation progress is an efficient way to provide a valuable pesticide formulation.

Super-fast degradation of high concentration methyl orange over bifunctional catalyst Fe/Fe3C@C with microwave irradiation

Bifunctional catalyst Fe/Fe3C@C with magnetism was successfully prepared by sol-gel method and proved to degrade methyl orange with high efficiency under microwave irradiation. The Fe/Fe3C@C catalysts calcined at 500 °C, 600 °C, 700 °C were intensively characterized and compared in their crystalline structure, porosity, morphology and dielectric property. The results imply a phase and structure transformation in the materials as the calcination temperature increased. Fe/Fe3C@C-700 exhibited a core-shell structure and an apparent Fe3C phase. In addition, Fe/Fe3C@C-700 demonstrated excellent dielectric property as a microwave absorber than Fe/Fe3C@C-500 and Fe/Fe3C@C-600. At the same time, it gave a 100 % removal rate in 30 s for the degradation of methyl orange under microwave irradiation, outperformed the Fe/Fe3C@C-500 and Fe/Fe3C@C-600 and most other reported catalysts in similar studies. The possible mechanism of the methyl orange degradation should be ascribed to the in situ generation of •OH and O2•− active species over the Fe/Fe3C@C catalyst. The excellent microwave absorbing property of Fe/Fe3C@C-700 could also boost its catalytic activity and play a critical role during the super-fast microwave-assisted degradation process. The findings in this study could be informative for the development of a continuous process of dye wastewater treatment for industrial implementation.

Formation of Cu2O Solid Solution via High-Frequency Electromagnetic Field-Assisted Ball Milling: The Reaction Mechanism.

The contamination of environmental water with organic pollutants poses significant challenges for society, and much effort has been directed toward the development of catalysts and methods that can decompose these pollutants. While effort has been directed toward the fabrication of Cu2O catalysts by ball milling, this technique can involve long preparation times and provide low yields. In this study, we synthesized a solid solution of Cu2O in 22 h by high-frequency electric-field-assisted ball milling below 40 °C in only one step under aqueous conditions. We investigated the catalytic activities of the produced Cu2O solid solution in the microwave-assisted degradation of dyes, namely rhodamine B, phenol red and methyl orange. The prepared Cu2O solid solution was very catalytically active and completely degraded the above-mentioned dyes within 2 min. The one-dimensional diffusion model and the phase boundary (planar) model were found to describe the kinetics well. Synergism between ball milling and the high-frequency electromagnetic field plays a key role in the preparation of Cu2O solid solution nanoparticles. Ball milling facilitates the relaxation of the Cu2O lattice and high-frequency electromagnetic radiation accelerates the diffusion of Fe atoms into the Cu2O crystal along the (111) crystal plane, quickly leading to the formation of a Cu2O solid solution.

Microwave-Assisted Degradation of Polysaccharide from Polygonatum sibiricum and Antioxidant Activity.

Four polysaccharide fractions (P-1: 71.40%, P-2: 1.95%, P-3: 1.14%, P-4: 1.64%) were isolated from crude Polygonatum sibiricum polysaccharide (PSP), processed by water extraction, ethanol precipitation, and further separated with diethylaminoethyl cellulose-52 anion-exchange chromatography. Their molecular weights and monosaccharide compositions were characterized by high performance gel chromatography with evaporative light scattering detector and ultraviolet-visible detector. The antioxidant activity of four polysaccharides fractions were assessed by the electron transfer menchanism (DPPH, ferric reducing power, and ABST assays) and chelation of transition metals (Fe2+ and Cu2+ chelation ability). The highest content fraction P-1 exhibited the lowest antioxidant activity, and the ranking of antioxidant capacity was P-4 > P-3 > P-2 > PSP > P-1. After processed by microwave-assisted degradation, the molecular weight of P-1 was decreased from 2.99 × 105 to 2.33 × 103 Da, while the antioxidant activity of degraded P-1 was about eightfold higher than natural P-1. These results indicated that the proposed microwave-assisted degradation approach was an efficacious methodology to improve their bioactivity by lower the molecular weight of polysaccharides. PRACTICAL APPLICATION: This study provided an environmentally friendly, convenient and efficient microwave-assisted degradation technology to process the neutral polysaccharides from Polygonatum sibiricum. The results could be used for the development and utilization of various plant polysaccharides as a kind of food supplement in our daily life.

Immunostimulatory Effects of Chitooligosaccharides on RAW 264.7 Mouse Macrophages via Regulation of the MAPK and PI3K/Akt Signaling Pathways.

Chitooligosaccharides (COS), the hydrolyzed products of chitin and chitosan, can be obtained by various methods. In this study, water-soluble COS were prepared from α- and β-chitosan by microwave-assisted degradation and their immunostimulatory effects were investigated in RAW 264.7 macrophages. The results indicated that α-COS were more active than β-COS in promoting the production of nitric oxide (NO) and cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6). Quantitative real-time reverse transcription polymerase chain reaction and Western blotting indicated that COS also enhanced the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and TNF-α. Further analyses demonstrated that COS induced the phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), p38, p85 and Akt, and the nuclear translocation of p65, indicating that they are able to activate the mitogen-activated protein kinases (MAPKs) and phosphoinositide 3-kinases (PI3K)/Akt signaling pathways dependent on nuclear factor (NF)-κB activation. In conclusion, COS activate RAW 264.7 cells via the MAPK and PI3K/Akt signaling pathways and are potential novel immune potentiators.

A fast and mild closed-loop recycling of anhydride-cured epoxy through microwave-assisted catalytic degradation by trifunctional amine and subsequent reuse without separation

Efficient recycling of anhydride-cured epoxy resin via microwave-assisted degradation by trifunctional amine without any waste discharge.

Microwave-assisted efficient depolymerization of alkaline lignin in methanol/formic acid media

Microwave-assisted degradation of alkaline lignin in methanol/formic acid media was investigated, concerning the effect of formic acid (FA) amount, reaction temperature, and reaction time on lignin depolymerization. The highest bio-oil yield of 72.0 wt% including 6.7 wt% monomers was achieved at 160 °C and a FA-to-lignin mass ratio of 4 after a reaction time of 30 min. Among the monomers, the yield of 2,3-dihydrobenzofuran was the highest (3.00 wt%), followed by p-coumaric acid (1.59 wt%). Formic acid acted mainly through acid-catalyzed cleavage of the linkages in lignin. Oligomers in bio-oil were mainly composed of dimers (molecular weight: 253–378) and trimers (molecular weight: 379–510) according to the Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) analysis. A possible mechanism about microwave-assisted depolymerization of lignin in methanol/formic acid media was proposed. This study will provide an efficient approach for lignin depolymerization.

Microwave-assisted heating: innovative use in hydrolytic forced degradation of selected drugs

ABSTRACTStress testing has been executed to illuminate the inherent stability characteristics of drug substances and drug products. As an alternative to the conventional hydrolytic forced degradation, which is carried out at the elevated temperature for an elongated time period, microwave-assisted heating is believed to be more promising. The later technique offers many advantages over conventional heating technique like fast, efficient heat source, a more reproducible result due to the control of parameters, eco-friendly, unlike conventional heating source, it heats up only the molecules which absorb microwave energy and not the apparatus first. Present work reports microwave-assisted hydrolytic degradation studies of selected drugs, namely Lurasidone, Risperidone, Paliperidone, Alprazolam, Escitalopram, Atomoxetine, Repaglinide, Furosemide, Hydrochlorothiazide and Olmesartan. The degradation samples were analysed by using high-performance liquid chromatography techniques. The degradation products generated by conventional and microwave heating methods were compared with respect to relative retention time. Though selected drugs have different chemical structures, the unaltered degradation profile was observed when conventional heating was replaced by microwave heating. With the proposed microwave heating technique, degradation products were generated in drastically lesser time from many hours to minutes without generation of secondary degradation products.

Microwave-assisted degradation of guaifenesin (GGE) to produce novel compounds in the presence of imidazolium-based ionic liquids

Thermal stabilities and degradation behaviors of guaifenesin (guaiacol glycerol ether = GGE) were studied by means of the differential scanning calorimetry and thermogravimetric (TG/DTG, in nitrogen atmosphere) analyses. To investigate the microwave-assisted pathways of guaiacol production from lignin, guaiacol glycerol ether (GGE) as a nonphenolic lignin model compound was exposed to microwave irradiation in the presence of three 1-butyl-3-methylimidazolium-based ionic liquids ([BMIm]-based ILs). GGE was subjected to microwave irradiation of 300 W in a batch reactor at a temperature of 200 °C, residence times of 5 min and air atmosphere. Based on the distribution of GGE conversion products identified by gas chromatography/mass spectrometry, the most degradation pathways of GGE were discussed. The highest yields of 2-methoxyphenol (guaiacol), 1-(2-methoxy-phenoxy)-propan-2-one, and 2-hydroxymethyl-1,4-benzodioxan were obtained using [BMIm][HSO4]. [BMIm][HSO4] was recovered and reused for three times without any loss of catalytic activity. It was found that it is possible to increase the yield of guaiacol from GGE by controlling of the different parameters such as temperature, molar ratio of water to GGE, acidity and anion effect of [BMIm]-based IL, amount of [BMIm]-based IL, microwave power and irradiation time.

Starch Derived Nanosized Graphene Oxide Functionalized Bioactive Porous Starch Scaffolds.

A fully starch-derived bioactive 3D porous scaffold is developed. The bioactivity is introduced through nanosized graphene oxide (nGO) derived from starch by microwave-assisted degradation to carbon spheres and further oxidation to GO nanodots. nGO is covalently attached to starch to prepare functionalized starch (SNGO) via an esterification reaction. nGO and SNGO exhibit no cytotoxicity to MG63 at least up to 1000 µg mL-1 under (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Porous scaffolds consisting of starch and SNGO (S/SNGO) or nGO (S/nGO) are prepared by freeze drying. The porosity and water uptake ability of the scaffolds depend on the concentration of nGO. Moreover, nGO, as a bioactive nanofiller, functions as an effective anchoring site for inducing CaP recrystallization in simulated body fluid. Among all modified starch-based scaffolds, the S/SNGO scaffold containing the highest concentration of covalently attached SNGO (50%) induces the largest amount of hydroxyapatite, a type of CaP crystal that is closest to bone. The prepared 3D porous nGO functionalized scaffold, thus, exhibits potential promise for bone/cartilage tissue engineering.