| Activated carbons (ACs) are amorphous carbon-based materials with large surface area, typicalmicroporous structure, and high adsorption capacities. ACs are widely used in the removal ofpollutants present in liquid and gaseous effluents. Once spent, these ACs become hazardous residueswhich are usually incinerated or disposed of in landfills, resulting in risks of pollution. For energeticand environmental purposes their regeneration is a more attractive alternative. Regeneration mayproceed through different pathways to shift the adsorption equilibrium toward desorption. Traditionalthermal regeneration is achieved by heating the exhausted carbons through the way of heat conduction.Under these conditions the carbonaceous structure may change and the mass may loss up to a highlevel. So, it makes researcher to develop new regeneration method. This thesis has studied a newregeneration method which called electrothermal regeneration. It uses the electrothermal regenerationmethod on the exhausted granular activated carbons, and the degradation of regenerated carbons isresearched by using thermalgravimetric-fourier transform infrared spectrum (TG-FTIR) andnitrogen gas adsorption. The contents are as following:(1) The background and significance of the regeneration of activated carbons were elaborated, theconcept of structure, property and application of ACs were introduced, and the main method and theprinciple of regeneration of ACs were summarized.(2) This paper provided detail information of the basic principle of electrothermal regeneration, andthe equipment of regeneration of ACs, including dryer, regeneration furnace, power and so on. Withthese equipment, the experiment of regeneration of exhausted ACs was conducted. The analysis ofTG-FTIR, and the specific experiment conduction of nitrogen gas adsorption were elaborated, the TGcurves of ACs, the spectrum of pyrolysis gas and the adsorption isothermal were obtained after theanalysis of ACs sample. The spent ACs were pre-processed in different operation conditions, and thevoltage-electricity character of ACs during flows in regeneration furnace was studied.(3) The regenerated carbons were analyzed by TG-FTIR. It shows that there are four steps of itsdesorption of its adsorbents. The main mass loss was found in the middle two stages, one is thedesorption of weak adsorption, another is the decomposition of chemisorption. And the mainpyrolysis gases included CO2, CO and H2O, of which CO only can be found at the stage ofdecomposition. And it also can be found that the mass loss decrease by increasing the regenerationtemperature. But it may need pay attention of that the higher temperature may change thecarbonaceous structure. Through the TG-FTIR analysis, it indicates that850℃is a betterregeneration temperature. (4) The characteristic of mass loss of regenerated carbons was tested by using non-isothermthermalgravimetric analysis at the heating rates of5K/min,10K/min,15K/min,20K/min,30K/min,50K/min. The thermaldynamics model was calculated by FWO method, which shows the activeenergy is255.57kJ/mol. And also the mechanism function was determined by Satava-Sestak Equation.(5) The adsorption isothermal of regenerated carbons, spent carbons and fresh carbons were gainedby using nitrogen gas adsorption. The specific surface area, pore volume and pore distribution werecalculated by the adsorption isothermal. By observing the result, the regenerated carbon at850℃hasthe best recovery, which specific surface area is838.743m2/g,93.7%of fresh carbon, and pore volumeis0.436cc/g,97.94%of fresh carbon, and its pore distribution is very good as well as fresh carbon. |
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