氮掺杂生物炭的制备及其对亚甲基蓝的吸附性能研究

Study on preparation of nitrogen⁃doped biochar and its adsorption properties for methylene blue

采用生物质枸杞杆为原料、KHCO_(3)为活化剂、尿素为氮源,制备枸杞杆氮掺杂生物炭。利用氮气吸附-脱附仪、扫描电子显微镜(SEM)、X射线衍射仪(XRD)、拉曼光谱(Raman)、傅里叶变换红外光谱(FT-IR)和X射线光电子能谱(XPS)等分析所制生物炭的形貌、结构和表面官能团等特性,并探析其对水中亚甲基蓝(MB)的吸附行为。结果表明,KHCO_(3)活化枸杞杆的最佳条件:m(枸杞杆炭化料)∶m(KHCO_(3))=1∶2、活化温度为800℃、活化时间为1 h。在枸杞杆生物炭(LBC)表面掺杂尿素的最佳条件:LBC与尿素的负载比为1∶4(质量比),800℃下煅烧1 h,得到氮掺杂生物炭(LBC-N)。LBC和LBC-N的比表面积分别为940.29 m^(2)/g和1169.78 m^(2)/g,总孔体积分别为0.57 cm^(3)/g和0.72 cm^(3)/g,平均孔径分别为5.81 nm和3.20 nm,均是以介孔为主的生物质活性炭材料。在相应实验条件下,LBC和LBC-N对MB的吸附量分别为542.02 mg/g和639.20 mg/g。准二级动力学模型、颗粒内扩散模型和Langmuir等温模型能很好地描述LBC和LBC-N对MB的吸附过程。根据氮掺杂生物炭的理化性质和吸附实验,LBC-N对MB分子的吸附过程是以π-π相互作用、氢键作用、静电吸引作用等化学作用为主,孔隙填充物理吸附协同作用的结果。

Biomass lycium chinensis stalks were used as raw materials,KHCO_(3) as activator,and urea as nitrogen source to explore the preparation of nitrogendoped biochar.The morphology,structure,and surface functional groups of the produced biochar were characterized was performed using scanning electron microscopy(SEM),nitrogen adsorptiondesorption instrumentation(BET),X-ray powder diffraction(XRD),Raman spectroscopy(Raman),Fourier transform infrared spectroscopy(FT-IR),and X-ray photoelectron spectroscopy(XPS).And its adsorption behavior towards methylene blue(MB)in water was explored.The results showed that the optimal conditions for KHCO_(3) to activate Lycium chinensis stalks were as follows:mass ratio of 1∶2(Lycium chinensis stalks carbonized material and KHCO_(3)),activation temperature of 800℃,and activation time of 1 h.The optimal conditions for doping urea on the surface of lycium chinensis stalks biochar(LBC)were as follows:mass ratio of 1∶4(LBC and urea),and nitrogendoped biochar(LBC-N)was prepared by calcination at 800℃for 1 h.The specific surface area of LBC and LBC-N were 940.29 m^(2)/g and 1169.78 m^(2)/g,the total pore volumes were 0.57 cm^(3)/g and 0.72 cm^(3)/g,and the average pore sizes were 5.81 nm and 3.20 nm,respectively.All of them were mainly mesoporous biomass activated carbon materials.Under the corresponding experimental conditions,the adsorption capacities of LBC and LBC-N for MB were 542.02 mg/g and 639.20 mg/g,respectively.The Pseudosecondorder model,Intraparticle diffusion model and Langmuir isothermal model could well describe the adsorption process of MB by LBC and LBC-N.According to the physicochemical properties and adsorption experiments of nitrogenous biochar,the adsorption process of LBC-N on MB molecules was mainly a result ofπ-πinteraction,hydrogen bonding,electrostatic attraction and other chemical effects,and the synergistic effect of physical adsorption by pore filling.