Experimental Study On The Preparation Of Activated Carbon From Fruit Twigs By Physical-chemical Combined Activation

In this paper,the high-performance activated carbon was prepared from branches of fruit trees by the method of physical-chemical activation,that is,the combination of low-temperature phosphoric acid activation and high-temperature steam activation.Firstly,the effects of the kinds of raw materials,the particle size of raw materials,the treatment methods of raw materials,the concentration of impregnating solution and the temperature and time of impregnation on the properties of activated carbon were investigated.The results showed that the kinds of activated carbon absorbed The adsorption capacity increases first and then decreases with the increase of the particle size of raw materials,and the best particle size is 2-4mm.The micropores of the activated carbon prepared by this activation method are developed and concentrated.The physical method of raw material treatment has an important influence on the adsorption performance of activated carbon.The loose structure promotes the impregnation and activation effect.When the impregnation time or temperature is fixed,the increase of the impregnation temperature or the prolongation of the impregnation time is conducive to the improvement of the adsorption performance of the activated carbon;when the impregnation temperature is different,the effect of the increase of the loss on the adsorption change of the activated carbon is different;when the same raw material reaches the saturation time of the impregnation effect at different impregnation temperatures,the increase of the temperature can improve the impregnation effect.When the concentration of the impregnating solution is 2.0-4.0mol/l and the impregnating time is long enough,the influence of the concentration of the impregnating solution on the adsorption performance of activated carbon is small.In the study of physical-chemical activation process parameters,it is found that to a certain extent,increase of activation temperature in low temperature section,activation time in low temperature section,activation temperature in high temperature section and activation time in high temperature section are conducive to the improvement of activated carbon adsorption performance,and different factors have different effects.When the activation temperature is 500?,the maximum values of iodine adsorption and methylene blue adsorption are 1143mg/g and 296mg/g,respectively.The activation time in the low temperature range of 20-60min has a great influence on the iodine adsorption value.When the activation temperature is in the range of 700-750?,the adsorption value of methylene blue is greatly affected;when the temperature is higher than 750?,the effect of increasing the adsorption value of methylene blue is reduced.The activation time at high temperature has a great influence on the adsorption properties of activated carbon.Taking the activation temperature in low temperature,activation time in low temperature,activation temperature in high temperature and activation time in high temperature as the influencing factors,iodine adsorption value and methyl blue adsorption value as the response values,the Box-Behnken model was used to optimize the technological conditions for the preparation of activated carbon from fruit tree branches by the physical-chemical activation method.Through regression equation analysis,the order of influence of four factors on iodine adsorption value was high temperature activation time>high temperature activation temperature>low temperature activation time>low temperature activation temperature;the order of influence on methylene blue adsorption value is high temperature activation temperature>low temperature activation time>high temperature activation time>low temperature activation temperature;the main factors are high temperature activation time and high temperature activation temperature.The results show that the optimal conditions are 514?,66min,818?and 57 min.It is predicted that the iodine adsorption value can reach 1158mg/g and methylene blue adsorption value 321 mg/g;the mean values of the verification experiments were 1157 mg/g and 320 mg/g.The validation results are basically consistent with the prediction results of the model.The prepared activated carbon has a rich microporous system with a specific surface area of1630m~2/g,a total pore volume of 0.8097cm~3/g,and a microporosity of 81.98%.There are 50 figures,28 tables and 76 references in this thesis.