生物质炭对气态挥发性有机污染物的吸附性能及机理

Adsorption performance and mechanism of biochars for gaseous VOCs

为探究生物质炭对气态有机污染物的吸附能力及作用机理,以核桃壳和椰子壳为原料制备生物质炭.采用元素分析仪、傅里叶红外光谱仪、Boehm滴定和比表面积及孔隙率分析仪分析生物质炭理化特征,并利用吸附柱实验考察生物质炭对气态挥发性有机污染物(苯和甲苯)的吸附行为.结果表明:相同制备条件下,椰壳生物质炭吸附性能高于核桃壳生物质炭.在实验温度范围内(400~700℃),随着制备温度的升高,生物质炭吸附性能增大.低温下制备的生物质炭(400℃)吸附行为符合准二级动力学模型,高温下制备的生物质炭(700℃)的吸附过程符合准一级动力学模型.在吸附温度30℃时,生物质炭对苯和甲苯的等温吸附过程符合Toth模型,计算得到生物质炭最大的理论饱和吸附量为18.98 mg/g苯和61.73 mg/g甲苯.生物质炭的表面酸性官能团和孔道结构在吸附过程中起关键作用,影响吸附质在生物质炭的表面吸附和粒内扩散吸附过程.

Biochars converted from pyrolysis of walnut shell and coconut shell were used as an alternative adsorbent for adsorbing volatile organic compounds（ VOCs）. Biochars were characterized by Elemental analysis,Fourier transform infrared spectra,Boehm titration and specific surface area and porosity analyzer. And the adsorption behaviors of benzene and toluene on biochar were investigated by column experiments. The results suggested that the adsorption performance of coconut shell biochar was better than walnut shell biochar under the same preparation conditions. The adsorption capacity of biochar was increased with the increasing pyrolytic temperature within the temperature range（ 400 ℃ to 700 ℃）. The adsorption process of low pyrolytic temperature biochar（ 400 ℃） and high pyrolytic temperature biochar（ 700 ℃） were described with the pseudo-second-order model and the pseudofirst-order model,respectively. At the adsorption temperature of 30 ℃,the isothermal adsorption process could be fitted by Toth model,and the maximal adsorption amounts of benzene and toluene calculated by Toth were 18. 98 and 61.73 mg/g. The surface acidic groups and porous structure of biochar played an important role on adsorption capacity,affecting the surface adsorption and intraparticle diffusion process.