Article

The Use of Microwave Radiation in Preparationof the Carbonaceous Adsorbents

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  • Institute of Non-Ferrous Metals Division in Poznań Central Laboratory of Batteries and Cells
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In microwave processing, energy is supplied by an electromagnetic field directly to the material. This results in rapid heating throughout the material thickness with reduced thermal gradients. Volumetric heating can also reduce processing times and save energy. The microwave field and the dielectric response of a material govern its ability to heat with microwave energy. A knowledge of electromagnetic theory and dielectric response is essential to optimize the processing of materials through microwave heating. The fundamentals of electromagnetic theory, dielectric response, and applications of microwave heating to materials processing, especially fiber composites, are reviewed in this article.
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In this study, the drying of wood by microwave energy using a continuous microwave belt drier was compared to that by conventional method. By using a continuous microwave belt drier, the microwave power was generated by means of 14 compressed air-cooled magnetrons of 800 W each that gives a maximum of 11.2 kW. The power setting could be adjusted individually in 800 W steps. Most importantly, this work focuses on the investigation of drying phenomena under microwave environment. In this analysis, the effects of the irradiation time and microwave power level on overall drying kinetics and mechanical properties were studied. The results showed that using the continuous microwave applicators technique has several advantages over the conventional method such as shorter processing times, volumetric dissipation of energy throughout a product, high energy efficiency as well as improvements in product quality. The results presented here provide a fundamental understanding of microwave-heating of various kinds of dielectric materials.
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The present study attempts to utilize coconut shell to prepare activated carbon using agents such as steam, CO(2) and a mixture of steam-CO(2) with microwave heating. Experimental results show that the BET surface area of activated carbons irrespective of the activation agent resulted in surface area in excess of 2000 m(2)/g. The activation time using microwave heating is very much shorter, while the yield of the activated carbon compares well with the conventional heating methods. The activated carbon prepared using CO(2) activation has the largest BET surface area, however the activation time is approximately 2.5 times higher than the activation using steam or mixture of steam-CO(2). The chemical structure of activated carbons examined using Fourier transformed infra-red spectra (FTIR) did not show any variation in the surface functional groups of the activated carbon prepared using different activation agents.
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Czepirski L., Łaciak B., Komorowska-Czepirska E., Wykorzystanie promieniowania mikrofalowego w technologii adsorbentów węglowych, [w:] Węgiel aktywny w ochronie środowiska i przemyśle, Wydawnictwo Politechniki Częstochowskiej, Częstochowa 2006.
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Rumian M., Czepirski L., Zastosowanie promieniowania mikrofalowego w technologii adsorpcyjnej, Przemysł Chemiczny 2005, 85, 329-332.