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Study of Lignin Extracted from Rubberwood Using Microwave Assisted Technology for Fuel Additive
(2022-02-01)
Yimtrakarn, Trakarn
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Kaveevivitchai, Watchareeya
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Lee, Wen Chien
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Lerkkasemsan, Nuttapol
Lignin is the most abundant natural aromatic polymer, especially in plant biomass. Lignin-derived phenolic compounds can be processed into high-value liquid fuel. This study aimed to determine the yield of lignin by the microwave-assisted solvent extraction method and to characterize some essential properties of the extracted lignin. Rubberwood sawdust (Hevea brasiliensis) was extracted for lignin with an organic-based solvent, either ethanol or isopropanol, in a microwave oven operating at 2450 MHz. Two levels of power of microwave, 100 W and 200 W, were tested as well as five extraction times (5, 10, 15, 20, 25, and 30 min). The extracted lignin was characterized by Klason lignin, Fourier transform infrared spectroscopy (FT-IR), 2D HSQC NMR, Ultraviolet-visible spectrophotometry (UV-vis), and Bomb calorimeter. The results showed that the yield of extracted lignin increased with the extraction time and power of the microwave. In addition, the extraction yield with ethanol was higher than the yield with isopropanol. The highest yield was 6.26 wt.%, with ethanol, 30 min extraction time, and 200 W microwave power.
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Production of empty palm bunch biochar using microwave-assisted pyrolysis at low temperature
(2021-09-15)
Paikamnam, Atipong
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Clowutimon, Weerawat
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Chanpee, Sirayu
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Sriprom, Pongsert
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Assawasaengrat, Pornsawan
In this study, the production of palm empty fruit bunch biochar using microwave-assisted pyrolysis at low temperature was investigated. The empty palm bunch composition was analyzed by proximate analysis. The parameters relating to the production, i.e. type of microwave absorber, microwave power, heating time and ratio of palm empty fruit bunch to initial amount of microwave absorber, were studied to determine the optimum condition. The results found that the amount of fixed carbon in the empty palm bunch was approximately 10%. The optimum condition was microwave power 300-watt, heating 450 sec and ratio of empty palm bunch to concentrated sulfuric acid (the most suitable microwave absorber) 1:2.5. At this condition, the production yield was 50.78%. The iodine number of the biochar was 318.5 mg/g. The BET surface area of the biochar was 101.54 m2/g. The total pore volumes and pore diameter of the biochar were 0.144 cm3/g and 4.29 nm. respectively. The elemental analysis of biochar at the optimum condition was mainly composed of carbon and oxygen. The ratio of O/C is 0.73 indicating that the biochar is quite stable product against oxidation.
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Development of sensor module for detecting the magnetron power based on microwave oven frequency
(2018-12-10)
Satthamsakul, Sutham
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Sriratana, Witsarut
This study presents the design of sensor module to be used in analyzing the electromagnetic power created from magnetron by using microwave as the case study on basis of Rectenna (Rectifying antenna) consisting of 2 main parts including sensing part and transduction part. On part of sensing part, the design would be made on the basic principle of monopole antenna; on part of transduction part, the design would be made on the basis of rectifier circuit, to function in converting the electromagnetic power received from magnetron to be in form of DC current, here the Hall Effect Sensor that was installed inside the current sensor module was used as the measuring equipment, with Arduino UNO R3 as the controller for recording electrical current including temperature. The experimental results would be used to analyze the appropriate form of sensor module. This research compared sensor module for 3 forms including Type A, Type B, and Type C, with different sizes of diameter of wires consisting, by comparing the efficiency in preventing the leak of measured power. According to the test of sensor modules in 3 forms on the same condition, it was found that the means of electrical current from converting the electromagnetic power of microwave.
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Antibacterial activity and nanocomposite properties of monodispersed silver nanoparticles synthesized by the microwave method
(2016-01-01)
Lothongkum, Anchaleeporn W.
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Wongparb, Kornwika
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Sethapokin, Pinthep
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Chaisitsak, Sutichai
Monodispersed colloidal silver nanoparticles (Ag-NPs) were synthesized by a simple and rapid microwave method. A precursor, AgNO<inf>3</inf>, was reduced by ethylene glycol (EG) and N,N-dimethylformamide (DMF) in the presence of polyvinylpyrrolidone (PVP) as a stabilizer or capping agent. It was found that the concentration of AgNO<inf>3</inf> significantly affected Ag-NPs particle sizes. The particle sizes decreased when the concentration decreased from 0.1 to 0.05 and 0.01 M, which corresponded to narrow size distribution of the particle diameters of approximately 60 to 80, 30 to 40 and 10 to 20 nm. The spherical-shaped monodispersed Ag-NPs were obtained by using a volume ratio of EG to DMF of 2.75:2.25, microwave power of 400 W and heating time of 2 min. The volume ratio of EG to DMF and the microwave power influenced the uniformity of the Ag-NPs shape and size, while the heating time had no effect. For antibacterial application, 60-80 and 10-20 nm Ag-NPs showed good disinfection ability against Escherichia coli (ATCC 25922) at the minimum inhibitory concentrations (MIC) of 32 and 16 (μg × ml-1, respectively. In addition, the electrical resistance of the nanocomposites of DMF-loaded Ag-NPs (20-50 nm) without PVP on single-walled carbon nanotubes and polyethylene terephthalate (PET) was measured. As a result, it is obvious that the Ag-NPs help to increase the electrical conductivity of the nanocomposites as the electrical resistance of the Ag-NPs nanocomposites was 4.68 kΩ × cm-2 compared to that of the nanocomposites without Ag-NPs of 8.76 kΩ × cm-2.
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Modification of electrochemical working electrode using NiO/MWCNT nanocomposites synthesized by microwave-assisted route
(2011-09-26)
Woointranont, Papitchaya
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Pratontep, Sirapat
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Pecharapa, Wisanu
The modification of electrochemical working electrode using NiO/CNT nanocomposites was reported in this study. Nickel oxide/carbon nanotubes composites were prepared by chemically depositing nickel hydroxide onto carbon nanotubes under microwave irradiation and thermal annealing process. The as-prepared composites were characterized by Scanning Electron Microscopy and X-ray Diffractometer and the results indicated that NiO nanoparticles are well distributed on the surface of CNT. Current responses of the modified electrode using NiO/CNT nanocomposites demonstrated that the modified electrode with the composite prepared at 450 watt show the superiority in electrocatalytic activity. © 2011 IEEE.
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Effects of salt, moisture content and microwave power on puffing qualities of puffed rice
(2010-03-01)
Maisont, Suchada
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Narkrugsa, Woatthichai
In this study, the effects of salt, moisture content and microwave power on the puffing qualities of puffed rice were investigated. Paddy rice was adjusted with water and 2% salt solution at four moisture levels 10, 13, 16 and 19% (wb) and puffed with microwave power at 600, 700 and 800 watts. The results showed that all the main factors and their interactions significantly (p<0.05) affected the puffing qualities of total puffed yield, fully puffed yield, small puffed yield, expansion volume, texture, color and microstructure. Paddy rice soaked in 2% salt solution produced a higher puffed yield than paddy rice soaked in water. Higher moisture content and microwave power produced puffed rice with higher puffed yield and expansion volume, but lower hardness. Puffing paddy rice at low moisture content (10%) with low microwave power (600 watts) produced the hardest puffed rice texture. Puffing at low moisture content and high wattage decreased the lightness of the puffed rice. Puffing paddy rice at 19% moisture content with 600-700 watts produced the highest fully puffed yield, but the lowest total puffed yield. The results suggested that high puffed yield and expansion volume with moderate hardness was produced using soaked paddy rice at 2% salt solution, 13% moisture content and puffed with 700 or 800 watts microwave power.
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Effects of some physicochemical properties of paddy rice varieties on puffing qualities by microwave "original"
(2009-07-01)
Maisont, Suchada
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Narkrugsa, Woatthichai
Ten paddy rice varieties, both waxy and non-waxy paddy rice, which are cultivated in the northern and northeastern region of Thailand, were selected to study the effects of some physicochemical properties on the qualities of puffing rice (puffed yield, expansion volume, expansion ratio and bulk density) using microwaves at a frequency of 2450MHz and power at 800 watts. It was found that the amylose content (range 5.58-21.24%) was strongly negatively correlated with all qualities of puffed rice: puffed yield (r=-0.95**), expansion volume (r=-0.82**), expansion ratio (r=-0.79 **) and bulk density (r=-0.78**). The starting time of puffing negatively correlated with puffed yield (r=-0.67*), while tightness of husk (lemma-palea) interlocking, thickness of ventral region layer, husk content, width and length of brown rice were unrelated to puffed rice quality. Amylose content could explain the puffing qualities of puffing rice. The coefficient of determination (R2), for the linear correlation with amylose content with regard to the quality of rice puffing for puffed yield, expansion volume, expansion ratio and bulk density was 0.91,0.67,0.62 and 0.61, respectively. Paddy rice with suitable physicochemical properties for puffing by microwave heating has low amylose, a thin ventral region and a puffing time that starts quickly and continues, as exhibited in rice varieties RD 6, RD 10 and NSPT.
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Design of multimode-circular microwave cavity for agri-food processing
(2007-12-01)
Varith, J.
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Noochuay, C.
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Netsawang, P.
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Hirunstitporn, B.
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Janin, S.
This article presents a design for multimode-circular microwave cavity at 2.45 GHz as a section of vertical-typed microwave oven for agri-food processing. Microwave cavity with a diameter of 100 cm and a height of 25 cm was modeled using CST2006® commercial software. Finite integral method was performed to solve the model for design criteria including waveguide arrangement to obtain low coupling and uniform distribution, and choke design to minimize microwave leakage. Simulation results show that perpendicular arrangement of two waveguides with 30° angle apart from each other yielded the minimal mutual coupling. With this waveguide arrangement, microwave power density was linearly loss into the grape model in radial direction from wall toward the center of cavity. Simulated electric field (E-field) distribution agreed with experimental E'-field distribution on fresh grape as it was converted into heat captured by thermal imaging camera. The cavity design with three square choke of 31×31 mm2 (λ/4) placing with space of 20 mm (λ/6) exponentially attenuated the E-field. Attenuation trend of simulation agreed with experimental that of measurement which was below safely limit of 5 mW/cm2. Findings from this work are useful for the scale-up of multisection/multi-mode microwave oven suitable for agri-food drying process.
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Microwaves in the Asia-Pacific region
(2002-01-01)
Yamashita, Eikichi
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Bird, Trevor S.
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Feng, Zhenghe
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Bhat, Bharathi
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Akaike, Masami

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