Ammoniated and activated microporous biochar for enhancement of SO_2 adsorption

摘要

Multiporous and alkaline carbon-based adsorbents, which generally show abundant pore structures, high surface area and improved surface chemistry characteristics, have a potential to be used for SO2 adsorption. In this work, biochar, as a precursor, was used to prepare nitrogen-rich and microporous carbon-based adsorbents for SO2 adsorption by high temperature ammonification with ammonia and physical activation with CO2. The results show that physical activation with CO2 can improve the microporous structure of biochar, the micropore area (S-mic) increasing from 252.88-481.37 m(2)/g. However, the high temperature ammonification can not only improve the microporous structure of biochar, S-mic increasing from 252.88-488.10 m(2)/g, but also introduce alkaline nitrogen functional groups on the surface of biochar, nitrogen content increasing from 1.38 to 6.22 wt. %. In addition, the relationship between the SO2 adsorption and physicochemical properties indicates that the improvement of microporous structure on biochars can enhance the SO2 adsorption at 30 degrees C, and the introduction of alkaline nitrogen functional groups can enhance the SO2 adsorption at 120 degrees C. The ammonification at 800 degrees C can make the SO2 adsorption capacity of biochar increasing from 92.8-175.9 mg/g at 30 degrees C, and from 56.3-115.4 mg/g at 120 degrees C.