KCl活化核桃壳热解制备的生物炭对亚甲基蓝的吸附性能

Preparation of Biochar by KCl-Activated Walnut Shell Pyrolysis and Its Adsorption Performance for Methylene Blue

采用KCl活化核桃壳热解制备生物炭,并测量其对亚甲基蓝的吸附性能。相比于直接热解的生物炭,KCl活化法制备的生物炭对亚甲基蓝的吸附量更大。为了分析吸附量增大的原因,对生物炭分别进行负载KCl和水洗处理,结合SEM、FT-IR、XRD、N2吸脱附表征结果,发现KCl对亚甲基蓝没有吸附作用,而且KCl会堵塞生物炭的孔道,降低其对亚甲基蓝的吸附量。吸附量增大的根本原因是KCl活化法可以促进生物炭孔结构的形成,尤其是小于3 nm的中微孔。对吸附等温线进行理论拟合和热力学计算,结果表明Langmuir方程对实验数据的拟合度高,该过程为自发的物理吸附过程。

A biochar from KCl activated walnut shell pyrolysis is prepared and used to adsorb methylene blue.The biochar prepared by KCl activation turns out to be superior to the biochar obtained by direct pyrolysis in adsorption capacity.In order to find out the reason,the biochars are treated by loading KCl and water wash,respectively.Combined with the results of SEM,FT-IR,XRD and N2 adsorption-desorption characterizations,it is found that KCl has no effect on methylene blue adsorption.Meanwhile,the KCl would block the pores of the biochar,reduc-ing the adsorption capacity of methylene blue.The KCl activation can promote the formation of the pore structure of biochar,especially the meso-micropore less than 3 nm.This is the reason for the increase of adsorption capacity.The theoretical fitting of adsorption isotherms suggests that Langmuir equation has a higher fitting degree to the ex-perimental data.The thermodynamic calculation proves that the adsorption of methylene blue on biochar is a spon-taneous physical adsorption process.