Microwave method, microwave method is not independent of the physical method and chemical method of the preparation of activated carbon, but on the basis of the physical method and chemical method instead of the traditional heating method, but it has a very significant effect.
Microwave refers to the electromagnetic radiation located between far-infrared and radio waves in the electromagnetic spectrum, with a frequency range of 300MHz to 300GHz and a wavelength of 1m to 1mmMicrowave generates "internal friction heat" through high frequency reciprocating motion of dipole molecules in the heated body, which raises the temperature of the material. It does not require any heat conduction process, and has the characteristics of high efficiency, selectivity, non-contact, integrity, uniformity, quick start and stop, and easy operation Studies have shown that activated carbon can effectively absorb microwave energy and make the temperature rise to 110o℃5' within a few minutes.
aluminum oxide blast mediaMicrowave heating can produce good effects in the preparation and modification of activated carbon (S2. Microwave modification, many backwater hole is opened, the distributed capacitance change obviously, promoting the improvement of the adsorption. The microwave power and irradiation time are key determinants of modified activated carbon adsorption performance. On the mechanism of microwave carbonization and activation, it is generally believed that
Plant waste is mostly made of plant fiber raw materials, in the plant body under the action of capillary, modified solution absorbed by material whole fully, between fiber is filled with the subtle space, make the dry material volume expansion after soaking wet, and reaction. Because of the water in the raw material, modified solution constitute a polar molecule, with a strong absorption of microwave dielectric properties,Therefore, polar molecules collide and rub violently with microwave frequency, generating a large amount of heat, which makes water and modified solution volatilize rapidly, and generate steam pressure, which explodes out from the inside of the raw material to the outside. This sharp action makes the fiber space of the raw material expand and produce sharp drying.In this way, the raw material has a more obvious pore structure and a larger internal specific surface area than before microwave irradiation. Compared with the traditional heating method, the mechanism of microwave in the preparation process of activated carbon is completely different.It shows its unique advantages: high efficiency, energy saving, uniformity, selectivity, low pollution, high thermal efficiency, low energy consumption, simple process and equipment and small footprint, conducive to automation, low carbon loss, and recovery of useful substances.
Many theoretical problems in this new field, especially the microwave heating mechanism, need to be further studied, and the mathematical model of the heating process needs to be establishedAdsorption at adsorption equilibrium was achieved after 14h, the adsorption capacityremained at 21.5 mg / g above. Grapefruit peei activated carbon Cr () in the adsorption processfollowed pseudo second order kinetic model; by the Langmuir equation and Freundlich equation of thecorrelation coefficient R' known,consistent with Langmuir isotherm model and the Freundlichisotherm model.Using Langmuir isotherm model to analyze the experimental data obtained in thesolution pH 4, the maximum adsorption capacity was 26.25mg / g;Freundlich isotherm model using
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