不同碳化温度下玉米秸秆生物炭的结构性质及其对氮磷的吸附特性

摘要

以玉米秸秆为生物质材料,分别在250,350,450℃碳化温度下制备3种玉米秸秆生物炭(分别命名为 B250,B350,B450),利用红外光谱和扫描电镜对其结构和表面形貌进行表征,并通过实验室模拟考察其对氮磷的吸附性能。结果表明：随着碳化温度的升高,玉米秸秆生物炭表面的微孔形变程度加剧,粗糙程度增大,芳构程度提高,稳定性增强；B250玉米秸秆生物炭稳定性相对较弱,在吸附过程中存在较强的磷释放作用,对磷呈现显著负吸附；B350和 B450对磷的吸附动力学过程均可用 Lagergren 准二级动力学模型描述；3种玉米秸秆生物炭对磷的吸附热力学过程均可用 Langmuir 方程描述,对磷的饱和吸附量为 B450>B350>B250；玉米秸秆生物炭对氮的吸附动力学过程符合 Lagergren 准二级动力学模型,吸附热力学过程符合 Langmuir 方程,对氮的吸附速率为 B450>B350>B250,饱和吸附量为 B450>B350>B250。%Corn straw biochar may be of an important role in improving soil fertility and controlling non-point source pollution of nitrogen and phosphate.Three biochars named B250,B350 and B450 were produced from corn straw biomass materials at temperatures 250,350 and 450 ℃,respectively. The characteristics of structure and surface of the biochars were measured by SEM (scanning electron microscopy)and FTIR (Fourier Transform infrared spectroscopy),and the adsorption characteristics of the biochars for nitrogen and phosphate were also investigated by laboratory simulation.The results from SEM and FTIR show that the pore deformation and the stalk roughness increased as the carbonization temperature rose,furthermore making the pore canal effect easier and the adsorption properties more excellent.Meanwhile,the biochars were of a higher degree of stability enhancement with temperature rising. The results from nitrogen and phosphate adsorption kinetics and thermodynamics on biochars show that B250 released some phosphate from itself during the adsorption process,so adsorption results of B250 is negative,while the adsorption kinetic processes of B350 and B450 were consistent with the Lagergren pseudo-second order kinetic model,and the adsorption isotherms of three biochars agreed well with the Langmuir formulae.The shortest time to reach the adsorption equilibrium is 5 h for B450,and the longest time to reach the adsorption equilibrium is 12h for B350,while adsorption capacity is in descending order of B450 >B350 >B250. In addition,the adsorption kinetic process for nitrogen is consistent with the Lagergren pseudo-second order kinetic model,the adsorption isotherms agree well with the model of Langmuir.Adsorption rate of nitrogen on the biochars is in descending order of B450 > B350 > B250,while adsorption capacity is in descending order of B450>B350>B250.