碱改性小麦秸秆生物炭对水中四环素的吸附性能

以小麦秸秆为原料，在873K温度下炭化6h制备了小麦秸秆生物炭（WBC），再用KOH浸渍法制备了3种碱炭比（质量比为1：1，2：1和3：1）的改性秸秆生物炭（WBCK1、WBCK2和WBCK3）.通过扫描电镜、比表面及孔径分析仪和傅里叶红外光谱对3种WBCK结构特征和表面性质进行表征.通过批量吸附实验，探讨了3种WBCK对溶液中四环素的吸附动力学和热力学特征.相比于WBC，WBCK有更丰富的孔径结构和更大的比表面积，且对四环素的吸附容量显著增加.3种WBCK对四环素的吸附动力学过程均符合准二级动力学模型，吸附速率常数大小顺序为k_2（WBCK2） > k_2（WBCK3）> k_{2（WBCK1）.}WBCK对四环素的吸附量随温度升高而增大，吸附过程同时存在物理吸附和化学吸附作用.Langmuir、Freundlich和Temkin模型均能较好地拟合吸附等温线，吸附机理较复杂.3种WBCK对四环素的吸附均为自发、吸热、熵增加过程.当溶液pH值范围为4.0~8.0时，3种WBCK对四环素的吸附性能较高.3种改性WBCK均可重复使用，其中WBCK2重复使用5次后吸附去除效率仅下降13.9%.

Adsorption performance of tetracycline in water by alkali-modified wheat straw biochars

The wheat straw biochar (WBC) was prepared through carbonization for 6 hours at pyrolyzing temperatures of 873K; and three alkali-modified WBCK (WBCK1, WBCK2, and WBCK3) with different KOH-char mass ratios (1:1, 2:1, and 3:1) were subsequently prepared with KOH impregnation modification. The structure characteristics and surface properties of WBCK were characterized with scanning electron microscopy (SEM), specific surface area and porosity analyzer (SSAP), and Fourier transform infrared spectrometer (FT-IR). Batch adsorption experiments were carried out to evaluate the adsorption performance of tetracycline (TC) onto WBCK. Compared to WBC, WBCK possessed a richer pore structure and a higher specific surface area. The adsorption capacities of TC by WBCK were significantly enhanced. The adsorption of TC by WBCK followed the pseudo-second-order kinetics model, and the adsorption rate constants were in the order of k_2(WBCK2) > k_2(WBCK3) > k_2(WBCK1). The adsorption capacities of TC by WBCK increased with an increase in temperature, and the physical adsorption and chemical adsorption coexisted in the adsorption process. Langmuir, Freundlich, and Temkin model could describe the adsorption isotherm perfectly, implying that the adsorption mechanism is complicated. The adsorption of TC by WBCK was a spontaneous endothermic process with entropy increment. WBCK had good adsorption performance for TC in the solution pH range of 4.0 to 8.0. WBCK1, WBCK2, and WBCK3 had good reusability, especially, the adsorption removal efficiency of WBCK2 decreased by only 13.9% after five cycles.