玉米秸秆生物炭对水中戊唑醇和稻瘟酰胺的吸附特性研究

Adsorption Characteristics of Corn Straw Biochar on Tebuconazole and Fenoxanil from Aqueous Solution

以农业废弃物玉米秸秆为材料,在300、500、700℃下采用限氧碳化法制备生物炭,并测定了生物炭的元素组成,利用扫描电镜(SEM)和红外光谱(FTIR)表征了生物炭的形貌结构特征,考察了生物炭对水中戊唑醇和稻瘟酰胺的吸附动力学和热力学特征,并评价了pH对生物炭吸附的影响。结果表明:随着碳化温度的升高,玉米秸秆生物炭C元素含量增大,表面微孔形变程度及粗糙程度增大,芳香族化合物增加,芳香化程度提高,对两种农药的吸附性增强。准二级动力学方程能更好地描述玉米秸秆生物炭对两种农药的吸附动力学过程,颗粒内扩散表明膜扩散和颗粒内扩散共同控制着生物炭对两种农药的吸附过程;Langmuir和Freundlich方程均可以较好地描述玉米秸秆生物炭对两种农药的吸附热力学过程,说明生物炭对两种农药的吸附同时存在物理吸附和化学吸附两种形式,但以化学吸附为主。吸附过程中焓变(ΔHo)、熵变(ΔSo)和吉布斯自由能变(ΔGo)表明玉米秸秆生物炭对两种农药的吸附是自发的吸热过程。溶液pH值会对生物炭吸附两种农药产生较大影响,酸性条件下吸附率高,碱性条件下吸附率低。

Corn straw was used as raw material to prepare biochars under pyrolysis temperatures of 300,500 and 700°C in an oxygen-limited condition.The element contents of the biochars were determined,and the structure and properties were characterized using SEM and FTIR.The characteristics of adsorption kinetics and thermodynamics of pesticide tebuconazole and fenoxanil onto the biochars in aqueous solution were investigated,and the effects of pH on adsorption of two pesticides onto the biochars were also determined.The results showed the carbon content,pore deformation and stalk roughness,and aromaticity of the biochars,as well as its adsorption capacity to two pesticides increased with the increase of carbonization temperature.The pseudo-second order model provided the best adsorption kinetics of two pesticides onto the corn straw biochar.Intraparticle diffusion model suggested that adsorption process was controlled mainly by both liquid film and intraparticle diffusion.Langmuir and Freundlich models highly correlated with the sorption isotherm data,indicating the adsorption of the two pesticides onto the biochar was influenced by physical and chemical adsorption,especially chemical adsorption.The values ofΔH o,ΔS o,andΔG o indicated that the two pesticides onto biochar were spontaneous and endothermic process.The absorption ability of the two pesticides onto biochar could be influenced more by pH of aqueous solution,and it was higher in weak acid aqueous solution than in weak alkaline condition.