微波诱导热解法制备落叶吸附剂及其工艺优化

Research on the adsorbent from the fallen leaves by the microwave induced pyrolysis and its process-optimization

采用微波诱导热解法制备低成本落叶吸附剂,以实现落叶的资源化利用。以碘吸附值为响应值,采用响应面分析法研究了微波诱导热解法制备落叶吸附剂的工艺条件。结果表明,热解时间与微波功率之间存在交互作用,当热解功率增加时,可适当缩短热解时间。落叶吸附剂的最佳制备工艺条件为:热解时间4.04 min,微波功率488.72 W,氯化锌质量分数27%。落叶吸附剂以微孔吸附为主,BJH孔径分布较窄,孔容最高峰对应的孔径在1.9 nm左右,Langmuir比表面积为769.61 m2/g。

The present paper is aimed at searching for an effective disposal method for fallen leaves. For the research purpose,we have developed a microwave induced pyrolysis for preparing a low-cost adsorbent derived from such fallen leaves. Taking zinc chloride as a chemical activator and the iodine as the response agent,we have managed to be successful in optimizing the technological parameters by using the surface response methodology.The results of our experiment have shown that there has been going on with a significant interaction between the microwave power and the pyrolysis time. With the increase of the microwave power as the heating process is going,the pyrolysis time could be made shortened. Practically speaking,there is no virtual interaction existing between the pyrolysis time and the content of the zinc chloride. Or,to be exact,no remarkable interaction has happened between the microwave power and the content of zinc chloride.And,therefore,it is necessary for us to obtain the optimal technology parameters as follows： the optimal pyrolysis time as we have found is equal to 4. 04 min. whereas the microwave power of488. 72 W and the concentration of zinc chloride has been found to be 27%（ by mass）. The actual adsorption and desorption isotherms of the adsorbents have shown that the isotherm of the adsorbent from the fallen leaves tends to be of type Ⅰ adsorbent as is defined by IUPAC standard. In accordance with the Langmuir monolayer adsorption process,the process of adsorption turns to be reversible as it occurs mainly within the micropores,which indicates that the adsorption opacity of the adsorbent can be affected by the micropore volume. At higher pressures,the adsorption and desorption isotherms do not seem to be coincided with each other due to the capillary condensation. At the same time,it is supposed that the hysteresis can be observed in this region that its shape was similar to H4 type,which indicates that there exist some slit pores that can be produced by the layered structure of the leaves. The curve of BJH can help to display the distribution of the aforementioned narrow pore size,whose peak value can be about 1. 9 nm. What is more,the nitrogen adsorption results demonstrate that the total pore volume of the adsorbent stands for0. 352 5 cm3/ g whereas the micropore volume turns to be about0. 182 2 cm3/ g. Furthermore,the average pore size tends to be about 3. 12 nm,with the Langmuir specific surface area being769. 61 m2/ g.