木薯渣基生物质炭对阿维菌素吸附解吸行为研究

摘要

In the study,the adsorption kinetics,isotherm and thermodynamics of avermectin on biochars,which were prepared using cassava residue at 350,550 and 750 ℃ temperature (labeled as MS350,MS550 and MS750,respectively)were investigated.The approach of Fourier transform infrared spectroscopy(FTIR) analysis was used to elucidate the possible adsorption mechanism.The results showed that the biochar had lower yield and polarity with the increase of preparation temperature,but the pH value,ash,specific surface area and aromaticity increased accordingly.The results of adsorption kinetics demonstrated that the avermectin was rapidly absorbed by biochar in the right beginning of absorption process,and then increased slowly until achieving the plateau of adsorption equilibrium.The adsorption isotherms showed that the adsorption capacity:MS750＞MS550＞MS350 and all the adsorption isotherm of avermectin on biochar met the nonlinear L type.Desorption isotherm results showed that there was desorption hysteresis in the adsorption of avermectin by cassava residue based biochar.The adsorption thermodynamics showed that the adsorption capacity of biochar could be improved by increasing temperature.Besides,the results of Gibbs free energy indicated that the physical adsorption played a main role in the adsorption of abamectin on biochar,and it was an endothermic,entropy increasing spontaneous reaction.The pore-filling mechanism,π-π bonding interactions,electrostatic interaction and hydrogen bonding on biochar might be the main contributors to adsorption abamectin.%为了研究阿维菌素在生物质炭上的吸附动力学,吸附-解吸等温线和吸附热力学特征,通过FTIR分析进一步阐述阿维菌素在生物质炭上可能存在的吸附机制.以木薯渣为原料,在限氧条件下,分别于350、550、750 ℃制备生物质炭(分别记作MS350、MS550、MS750),并对其理化性质进行表征.结果表明:随着制备温度升高,生物质炭呈现产率降低,pH值、灰分及比表面积增加,芳香性增大、极性减弱等特征;生物质炭吸附阿维菌素呈现先快速后缓慢最后平衡的3个阶段;吸附能力表现为MS750＞MS550＞MS350,吸附等温线属于非线性L型等温吸附线;解吸等温线结果表明木薯渣基生物质炭吸附阿维菌素存在解吸滞后现象.吸附热力学结果表明随着环境温度的上升,生物质炭的吸附量会得到提升.同时根据吉布斯自由能方程计算,可知生物质炭吸附阿维菌素是物理吸附为主,且是一个吸热的、熵增大的自发反应.孔隙填充效应、π-π电子供受体作用、静电相互作用和氢键作用等可能是阿维菌素在生物质炭上的吸附机制.