Microwave synthesis of mesoporous WO_3 doping with bismuth and photocatalytic oxidation of water to H_2

Lixia Zou,Qingcheng Liu,Qiong Xu,Guanjie Mi 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.5

Mesostructured tungstic acid was prepared from Na_2WO_4 with protonated cation-exchange using a surfactant cetyltrimethyl ammonium bromine (CTAB) as the structure-directing agent under microwave radiation. The surfactant was removed by high-temperature calcination, microwave radiation extraction and Soxhlet extraction, respectively. The effects of these methods for removal of the surfactant were investigated in detail. XRD, TEM, FT-IR and UV-Vis were employed to characterize the mesostructured materials. The results showed that the microwave extraction and Soxhlet extraction were favorable to the synthesis of mesostructured tungstic oxide. Mesoporous structure was destroyed as the calcining temperature rising to 823 K. The mesoporous structure of WO_3 prepared by microwave radiation extraction had an average pore diameter of 3.4 nm and specific surface area of 120.46m^2·g^(−1). And also, the mesoporous materials WO_3 doping with Bi_2O_3 displayed much higher photocatalytic activity than commercial Degussa P25 TiO_2under visible light and UV irradiation.

High-performance expanded graphite from flake graphite by microwave-assisted chemical intercalation process

Qun Wei,Lei Xu,Zhimeng Tang,Zhangbiao Xu,Cheng Xie,Lirong Guo,Wei Li 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.122 No.-

Herein, a facile preparation method with characteristics of energy-saving, efficient and environmentallyfriendly is proposed. Firstly, GICs (Graphite Intercalation Compounds) were synthesized by microwaveassisted hydrothermal method using flake graphite (FG) as raw material, H2SO4, and K2S2O8 as oxidativeintercalations by microwave-assisted oxidation for 5 min, and then EG was prepared from obtained GICsby microwave irradiation for 40 s under the microwave power of 800 W, and the effect of different processconditions on EG expansion volume (EV) was studied. The results show that EG with a good expansioncan be rapidly prepared by microwave irradiation, and the EV value can reach 455 mL /g under theoptimal conditions. In particular, the prepared EG has a high graphitization degree with less structuraldamage, exihibiting good industrial application prospects. The mechanism of K2S2O8 oxidation and graphiteexpansion under microwave irradiation was analyzed. In adition, flexible graphite foil papers preparedwith the obtained EG exhibit good electrical conductivity and thermal properties. The as preparedEG material shows an efficient adsorption of hydraulic oil and vegetable oil and excellent flame retardantperformance. This preparation method is green, low cost, and safe, and can be used for the efficient batchpreparation of EG.

Production of activated carbon derived from agricultural by-products via microwave-induced chemical activation: a review

Ahmad Abdulbari A.,Al-Raggad Marwan,Shareef Noama 한국탄소학회 2021 Carbon Letters Vol.31 No.5

Biomass of agricultural waste is getting increasing attention all over the world as it is a kind of renewable, abundantly available, low cost, and environmentally friendly resource. Preparation of activated carbon from agricultural waste via microwave-assisted chemical agent activation. The porosity, surface area, and functional and surface chemistry were featured by means of low-temperature nitrogen adsorption, Scanning Electron Microscopy, (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The best conditions resulted in activated carbon with adsorption capacity of 517.5 mg/g and carbon yield of 80.99%. The activated carbons from carbonized tobacco stem with K2CO3 activation by microwave radiation is highest of surface area, and total pore volume corresponded to 2557 m2 /g, and 1.647 cm3 /g, respectively, with a high contribution of mesopores, microwave power of 700 W, and irradiation time of 30 min. The results of the review showed that chemical activation could develop both microporosity and mesoporosity. The fndings support the potential to prepare high surface area and micropore-activated carbon from agricultural waste by microwave-induced chemical activation.

Microwave-Assisted Heating of Electrospun SiC Fiber Mats

Khishigbayar, Khos-Erdene,Joo, Young Jun,Cho, Kwang Youn The Korean Ceramic Society 2017 한국세라믹학회지 Vol.54 No.6

Flexible silicon carbide fibrous mats were fabricated by a combination of electrospinning and a polymer-derived ceramics route. Polycarbosilane was used as a solute with various solvent mixtures, such as toluene and dimethylformamide. The electrospun PCS fibrous mats were cured under a halogen vapor atmosphere and heat treated at $1300^{\circ}C$. The structure, fiber morphology, thermal behavior, and crystallization of the fabricated SiC fibrous mats were analyzed via scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermal imaging. The prepared SiC fibrous mats were composed of randomly distributed fibers approximately $3{\mu}m$ in diameter. The heat radiation of the SiC fiber mats reached $1600^{\circ}C$ under microwave radiation at a frequency of 2.45 GHz.

The Microwave-Assisted Extraction of Fats from Irradiated Meat Products for the Detection of Radiation-Induced Hydrocarbons

Joong-Ho Kwon,Tusneem Kausar,Jeongeun Lee,Hyun-Ku Kim,Dong U Ahn 한국식품과학회 2007 Food Science and Biotechnology Vol.16 No.1

Microwave-Enhanced Reduction of Cr (vi) in Contaminated Soil

Li Lin,Xiaohua Lu,Qingyun Li 한국토양비료학회 2014 한국토양비료학회 학술발표회 초록집 Vol.2014 No.6

Ammonia Nitrogen Removal and Recovery from Swine Wastewater by Microwave Radiation

Joohee La,Tae Young Kim,Jae Kyung Jang,In Seop Chang 대한환경공학회 2014 Environmental Engineering Research Vol.19 No.4

Microwave (MW) radiation was developed to remove and recover ammonia nitrogen in the real swine wastewater. The effect of operating parameters of MW radiation such as initial pH, power, radiation time, aeration, and stirring for removal ammonia nitrogen in swine wastewater was determined. The pH, radiation time, and power were significantly influenced on the removal of ammonia nitrogen, and aeration and stirring showed relatively minor effect on the removal of ammonia nitrogen. Optimum condition was achieved to retrieve the nitrogen efficiently at pH 11, 700 W for 5 min in MW radiation process. Through this process, 83.1% of ammonia nitrogen concentration was reduced in swine wastewater and also 82.6% of ammonia nitrogen was recovered as ammonium sulfate at the optimized condition. The high ammonia removal and recovery efficiency of the MW radiation method indicated that MW radiation was an effective technique to remove and recover ammonia nitrogen in the swine wastewater.

Changes in the chemical properties and anti-oxidant activities of curcumin by microwave radiation

Jung, Yu Na,Kang, Smee,Lee, Bo Hyun,Kim, Joo Hyoun,Hong, Jungil Korean Society of Food Science and Technology 2016 Food Science and Biotechnology Vol.25 No.5

Curcumin is a dietary phenolic compound that has numerous beneficial health effects. In the present study, changes in the chemical properties and anti-oxidant activities of curcumin by microwave radiation were investigated. Degradation of curcumin dissolved in distilled water was accelerated according to the increase in radiation time or radiation intensity. Residual levels of curcumin after 5 min radiation at 500 W were 24-29%. Scavenging activities of curcumin against DPPH radical decreased by microwave radiation; those of curcumin against ABTS and AAPH radicals and nitrite were rather significantly enhanced. Conventional heating at $95^{\circ}C$ also increased scavenging activities of ABTS, AAPH, and nitrite of curcumin but to a lesser extent. Fluorescence intensity of curcumin increased by regular heating but decreased by microwave heating. Among curcuminoids, bisdemethoxycurcumin was most resistant under microwave radiation as compared to curcumin or demethoxycurcumin.

Changes in the chemical properties and anti-oxidant activities of curcumin by microwave radiation

정유나,Smee Kang,이보현,김주현,홍정일 한국식품과학회 2016 Food Science and Biotechnology Vol.25 No.5

Curcumin is a dietary phenolic compound that has numerous beneficial health effects. In the present study, changes in the chemical properties and anti-oxidant activities of curcumin by microwave radiation were investigated. Degradation of curcumin dissolved in distilled water was accelerated according to the increase in radiation time or radiation intensity. Residual levels of curcumin after 5 min radiation at 500 W were 24-29%. Scavenging activities of curcumin against DPPH radical decreased by microwave radiation; those of curcumin against ABTS and AAPH radicals and nitrite were rather significantly enhanced. Conventional heating at 95oC also increased scavenging activities of ABTS, AAPH, and nitrite of curcumin but to a lesser extent. Fluorescence intensity of curcumin increased by regular heating but decreased by microwave heating. Among curcuminoids, bisdemethoxycurcumin was most resistant under microwave radiation as compared to curcumin or demethoxycurcumin.

An Experimental Study on the Effectiveness of Microwave Hyperthermia Combined with Radiation on the Small and Large Intestine in rats

안경숙,이경자,이정식,Ahn, Kyung-Sook,Lee, Kyung-Ja,Rhee, Chung-Sik The Korean Society for Radiation Oncology 1987 Radiation Oncology Journal Vol.5 No.2

온열요법은 조직에 $40^{\circ}C-44^{\circ}C$의 열을 가함으로서 방사선에 저항성이 큰 DNA합성기의 세포 및 pH가 낮은 세포에 민감하게 작용하는 생물학적 효과를 암 치료에 이용하는 것이다. 그러나 온열요법은 방사선과의 병행요법에 의하여 발생되는 열증강율 및 치료 이득이 방사선량, 열량, 온도, 가열시간, 온도분포, 조사시간 등에 민감하고 변화가 많으므로 객관적인 치료효과와 통일된 치료방법을 결정하기가 어렵다. 저자는 2450MHz, 100watt의 마이크로파 온열기구와 조직등가인 팬톱을 직접제작하여 예비측정을 통해 방열 조사조건과 방법을 결정한 후 생물학적 반응을 관찰하기 위하여 102마리 흰쥐 소장 및 대장의 조직학적 면화를 관찰하고 열증강율에 따른 효과를 비교 평가하여 다음과 같은 결론을 얻었다. 1 온열요법 단독으로는 소장과 대장의 조직학적 면화는 볼 수 없었다. 2. 방사선 조사 단독군과 병행군에서 소장 및 대장의 점막상피 괴사는 방사선 조사 6Gy에서 관찰되었으며 방사선량의 증가와 관찰시간 경과에 따라 그 정도가 심하여졌다. 3. 방사선 조사 단독군과 병행군에서 소장 및 대장의 근육층의 괴사는 방사선 조사 10Gy에서 관찰되기 시작하였으며 관찰시간의 경과에 따라 그 정도가 심하여졌다. 4. 방사선 조사와 온열요법 병행군에서 소장과 대장의 조직학적 변화(점막상피와 근육층의 괴사)를 관찰하여 열증강율은 증가되지 않았다. The synergistic effect of combining radiation therapy and hyperthermia kills significantly more cells than using either modality alone. The reason for enhanced cell killing from the combined treatment is that the two modalities are complementary. For histopathological exmination, 102 rats were divided into 4 groups as hyperthermia, radiation, hyperthermia combined with radiation and normal control groups. The effect of prior irradiation (6-15 Gy of X-ray) on the response of small and large bowel of rats to $40^{\circ}C-44^{\circ}C$ (for 30 minutes) microwave (2450 MHz) hyperthermia was investigated. The musculature of the small and large intestine remained intact and the circumference of the histological sections were not significantly altered by the heated at $43^{\circ}C$ for 30 minutes. Thermal enhancement ratios of normal tissue is 1.0 Thermal enhancement ratio was not increased in combination therapy by evaluation of histopathologic changes in small and large intestine.