不同裂解温度稻壳生物炭对阿特拉津的吸附行为及机制

为探究不同裂解温度下稻壳生物炭的结构和性质差异及其对阿特拉津（AT）的吸附作用机制和构-效关系，以稻壳为原料在300、500和700℃下制备稻壳生物炭（分别记为RH300、RH500、RH700），通过电镜扫描、元素分析仪、比表面积分析仪和傅里叶变换红外光谱分析仪等对3种稻壳生物炭进行结构表征分析，并采用批量等温吸附法研究稻壳生物炭对AT的吸附特性.结果表明:裂解温度由300℃升至700℃时，稻壳生物炭中w（C）由48.81%升至64.67%，w（H）、w（N）和w（O）则由3.22%、1.45%和34.66%分别降至0.89%、0.92%和16.29%，原子比H/C、O/C和（O+N）/C值均降低.可见，随着裂解温度升高，稻壳生物炭的芳香性增强，亲水性和极性降低，且比表面积和孔体积增大，平均孔径减小.3种稻壳生物炭对AT的吸附均可用Freundlich和Langmuir两种等温吸附模型进行较好地拟合（R≥0.948，P < 0.01），吸附作用及非线性程度与生物炭的比表面积（SSA）、芳香性（H/C）、亲水性（O/C）和极性〔（O+N）/C〕呈良好的指数关系，大小表现为RH700 > RH500 > RH300.稻壳生物炭对AT的吸附机制主要包括分配作用和表面吸附，分配作用强度与生物炭的极性和炭化程度有关；而表面吸附作用与AT的分子大小有关，3种稻壳生物炭对AT的表面吸附除表面覆盖外，还存在多层平铺、毛细管现象和孔隙填充等.研究显示，裂解温度是影响生物炭吸附有机污染物的重要因素，在综合考虑成本和制备工艺的同时，适当提高裂解温度可增强生物炭对有机污染物的吸附作用. 

Adsorption of Atrazine by Biochar Obtained from Pyrolysis of Rice Husk at Different Temperatures

This study focused on the effect of pyrolysis temperature on the structure and properties of rice husk biochars, and the adsorption mechanism and structure-activity relationship of biochars towards atrzine (AT). The biochars were prepared by the pyrolysis of rice husk at 300, 500 and 700 ℃. The structure of the biochars were characterized by scanning electron microscopy (SEM), elemental analysis, specific surface area analysis (BET) and Fourier transform infrared spectroscopy (FTIR), while their adsorption property towards AT was investigated through batch experiment. With the increase of the pyrolysis temperature from 300 ℃ to 700 ℃, the content of carbon (C) increased from 48.81% to 64.67%, while the content of hydrogen (H), nitrogen (N) and oxygen (O) decreased from 3.22%, 1.45% and 34.66% to 0.89%, 0.92% and 16.29%, respectively. This resulted in the decrease in the ratio of H/C, O/C and (O+N)/C, indicating the enhancement of aromaticity, and the weakening of hydrophilicity and polarity. Moreover, the pyrolysis process also increased the specific surface area (SSA) and pore volume of biochars, but reduced the average pore size. The adsorption of AT on three biochars was well described by both Freundlich and Langmuir equations (R≥0.948, P < 0.01). The adsorption intensity and nonlinearity had a good exponential relationship with the SSA, aromaticity (H/C), hydrophilicity (O/C) and polarity ((O+N)/C) of the biochars, with the adsorption intensity and nonlinearity decrease in the following order: RH700 > RH500 > RH300. The adsorption mechanism of AT on biochars mainly included distribution and surface adsorption. The intensity of distribution was related to the polarity and carbonization of biochars, while surface adsorption was dependent on the molecular size of AT. In addition to surface coverage, the surface adsorption of AT on biochars was also through multi-layer tiling arrangement, capillary phenomenon and pore-filling. The above results illustrated that pyrolysis temperature is an important factor for the adsorption of biochars towards organic pollutants. Therefore, besides the cost and preparation technology, pyrolysis temperature should also be considered to improve the adsorption capacity of biochars towards organic pollutants.