麻风树果壳活性炭表面分形维数的实验研究

Experimental research on the fractal dimensions of the activated carbons from Jatropha curcasl shell

在温度77K条件下对化学活化法制备的几种麻风树果壳活性炭进行N2吸附-脱附实验研究,得到了孔结构参数。并利用等温吸附数据分析了活性炭的分维,研究了不同碱炭比(R)条件下得到的活性炭的表面特征、孔结构和特征吸附能。结果表明,麻风树果壳活性炭含有分形特征,分形维数在2～3之间。在多层吸附早期阶段和高度覆盖期所得的分形维数不同,但变化趋势基本一致,随着R的增加而增大。R=4时,分形维数最大,分别为2.619和2.993。活性炭的分形维数与活性炭的比表面积、孔容、碘吸附值和微孔相对含量基本一致,可以用来表征微孔的发育程度。

The present paper is concerned about its authors＇ experimental study on the fractal dimensions of the activated carbon from Jatropha curcasl shell. As is known, Jatropha curcasl shell can be made to be an activating agent in the surroundings of nitrogen in activated carbon by chemistry activation with KOH. In our study, we have conducted experiments with a few kinds of activated carbon by different ratios of KOH to the shell （R） on their nitrogen adsorption- desorption （at 77 K）, so as analyze the features of the pore structure parameters. As a result, we have fotmd that such kinds of carbon tend to change along with the change of R and gain the best parameters. For example, in a specific surface area, the micropore volume, pore size distributions and iodine adsorption capacity of the carbon would increase to the biggest when R = 4, even getting to 1 890 m^2/g, 0.95 mL/g, 91.76% and 2 218.44 mg/g, respectively, but their pore average diameter would be the smallest, that is, only 1. 124 nm. Then, we have examined the fractal dimensions and the correlation coefficient of activated carbon by using the isotherm data and nitrogen adsorption-desorption isotherms. And, here, the fractal dimensions defined at early stages （ the fractal dimensions is D1 ） of the multilayer formation prove to be different from those estimated at higher coverage（the fractal dimensions is D2）. However, the trends turn to be consistent. That is to say, when R = 4, the fractal dimensions would be the biggest, they may increase to 2.619 or 2.993. And, the pore size distribution curve of activated carbon can be expected to be found by using the method of Horvath-Kawazoe （H-K）. The above facts also show that the fractal dimensions and the ultramicropore proportion are interactive by nature, in which, the latter would get improved as the former becomes bigger. And, finally, the ultramicropore proportion proves to be equal to 43.37 when the fractal dimension （D1） equals 2.619, so as for it to be rich in ultramicropore, Thus, the conclusion should be that the activated carbon made from Jatropha curcasl shell is good in adsorption on pore structure parameters and fractal dimensions, and the performance of the carbon would be the best when R = 4,