以农业废弃物玉米芯为原料,在双氰胺和碳酸氢钠的共同作用下经热解、活化得到氮掺杂玉米芯生物炭(N-CBC).利用扫描电子显微镜(SEM)、X射线衍射(XRD)、比表面积分析(BET)和红外光谱(FTIR)等手段对生物炭掺杂前后的形貌、组成和结构进行了表征,并系统分析了N-CBC对水中四环素的吸附性能、吸附动力学和吸附热力学.结果表明,在玉米芯、碳酸氢钠和双氰胺的质量比为1∶2∶0.7,700℃热解3h的条件下制备的N-CBC对四环素的吸附性能最优,N-CBC呈多孔纹理结构,比表面积高达 1 670 m2/g,为有机污染物的吸附提供了大量的活性位点,同时,氮的掺杂利于形成π-π共轭结构,促进吸附过程的进行.吸附动力学、吸附等温线和吸附热力学研究表明,N-CBC对四环素的吸附符合准二级动力学模型,且为自发的多分子层物理吸附.
Nitrogen-doped corn cob biochar(N-CBC)was prepared from agricultural waste corn cob by pyrolysis and activation in the presence of dicyandiamide and sodium bicarbonate.The morphology,composition and structure of biochar before and after nitrogen doping were characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),specific surface area analysis(BET)and X-ray photoelectron spectroscopy(XPS),and the adsorption performance,adsorption kinetics and thermodynamics of N-CBC on tetracycline were systematically analyzed.The results showed that N-CBC had the best adsorption performance for tetracycline,when it was prepared in the condition of mass ratio of corn cob,sodium bicarbonate and dicyandiamide of 1∶2∶0.7,temperature of 973 K and time of 3 h.N-CBC had a porous texture structure and the specific surface area of it reached up to 1670 m2/g,which provided a large number of active sites for the adsorption of tetracycline.Nitrogen doping was conducive to the formation of π-π conjugated structure,promoting the process of adsorption.The adsorption kinetics,adsorption isotherm and adsorption thermodynamics showed that the adsorption of tetracycline on N-CBC was in accordance with the quasi-second-order kinetic model and it was a spontaneous,multi-layer adsorption by physical interaction.