生物炭的制备及其镁改性对污染物的吸附行为研究

The preparation of biochar and adsorption behavior of Mg-modified biochar to pollutants

以小麦和玉米秸秆为原料,于不同温度下制备了生物炭样品,并采用氯化镁(MgCl_2)、乙酸镁(Mg(CH_3COO)_2)和硝酸镁(Mg(NO_3)_2)对秸秆及其生物炭进行改性.通过分析各生物炭产率、pH、元素分析、比表面积、CEC、XRD及FT-IR,探究了生物炭理化性质的变化规律.各样品对氨氮、Pb(Ⅱ)及乙草胺的吸附试验结果表明:小麦秸秆经Mg(CH_3COO)_2改性后得到的生物炭的饱和吸附量最大;对3种吸附质的吸附过程均符合准二级吸附动力学方程;低浓度下吸附过程均可自发进行,对氨氮的吸附符合Langmuir模型且以离子交换作用为主,对Pb(Ⅱ)的吸附符合Freundlich模型且以离子交换作用为主,对乙草胺的吸附符合Langmuir模型且以分配、氢键和π-π电子受体供体作用为主.

In this paper,wheat and corn straw were used to prepare biochar via slow anaerobic pyrolysis method under different temperatures. The biochar and the straw samples were further modified with magnesium chloride（ MgCl2）,magnesium acetate（ Mg（ CH3COO）2）,and magnesium nitrate（Mg（NO3）2）. The physicochemical properties of the biochar were investigated via yield,PH,elemental analysis,surface area analysis,cation exchange capacity（ CEC）,X-ray diffraction（ XRD）,and Fourier transform infrared spectroscopy（ FT-IR） spectra. The results of the adsorption experiments indicate that biochar prepared from wheat straw and modified with Mg（ CH3COO）2 exhibits excellent adsorption capability to NH4＋,Pb2＋,and acetochlor.The kinetics of the biochar samples fitted the pseudo-second-order kinetic model. The adsorption process was spontaneous and endothermic. The NH4 and Pb2＋ adsorption processes were well described by the Langmuir model and Freundlich model. And NH4＋ and Pb2＋ were adsorbed to the biochar by cation exchange. The acetochlor adsorption process fitted the Langmuir model. The adsorption process involved to distributional effect,hydrogen bonding,and π-π electron-donor-acceptor（ EDA） interactions.