玉米秸秆碱化处理制备的生物炭吸附锌的特性研究

Adsorption characteristics of biochar prepared by corn stalk alkalization on zinc

为研究玉米秸秆碱化处理制备的生物炭对模拟废水中Zn的吸附特性,以玉米秸秆为原料制备玉米秸秆生物炭(BC),同时对玉米秸秆进行碱化浸渍处理来获得碱化改性生物炭(K-BC),并在此基础上研究了BC和K-BC对Zn的吸附动力学、吸附热力学以及pH对其吸附的影响,结合元素分析、比表面积孔径测定、扫描电镜及红外光谱等表征来分析其对Zn的吸附差异。结果表明:当Zn浓度为60 mg·L^(-1),BC和K-BC对Zn的吸附过程由快速吸附和慢速吸附2个阶段组成,且符合准二级动力学吸附模型;BC和K-BC对Zn的吸附量随温度(288~318 K)和Zn浓度(10~120 mg·L^(-1))的增加而增加,其中K-BC对Zn的理论饱和吸附量大于BC,且由Freundlich模型对吸附过程进行描述较为合适;热力参数表明BC和K-BC对Zn的吸附为自发、吸热和无序度增加的过程;在pH_2.0~5.0范围内,当pH为5.0时K-BC对Zn的吸附量最大,吸附率接近50%。由BC和K-BC结构表征及理化特性差异可以推知,这2种生物炭对Zn吸附差异来源于其比表面积、孔隙结构和芳香结构之间的差异。

The adsorption characteristics of biochar prepared by corn stalk alkalization treatment to simulated wastewater were studied.Corn-stalk biochar（BC）and alkaline-modified biochar（K-BC）were prepared using corn stalks and alkalized impregnated corn stalks, respectively. The effects of BC and K-BC on the adsorption kinetics, Zn adsorption thermodynamics, and pH on Zn adsorption were investigated. Simultaneously, adsorption mechanisms and differences of Zn by BC and K-BC were characterized using elemental analysis, specific surface area pore size determination, scanning electron microscopy（SEM）, and fourier transform infrared spectrometer（FTIR）. The results indicated that adsorption process of Zn on BC and K-BC were consisted of the rapid and slow section at Zn concentration of 60 mg·L^-1, and the quasi-second-order kinetic adsorption model could describe the adsorption process effectively. The adsorption capacity of Zn on BC and K-BC increased with increasing temperature from 288 K to 318 K and Zn concentrations from 10 mg·g^-1 to 120 mg·g^-1, and the adsorption process was well fitted to the Freundlich equation. Thermodynamic parameters revealed that Zn adsorption by BC and K-BC was a feasible,spontaneous, and endothermic process with an increase in disorder. Over a pH range of 2.0~5.0, the adsorption capacity of K-BC to Zn was the highest, and the adsorption rate was close to 50% at pH =5.0. According to the structural characterization and physical and chemical properties of BC and K-BC, differences in Zn adsorption by BC and K-BC were derived from their specific surface area, pore structure, and fragrance structure.