Influence of NH3/CO2 Modification on the Characteristic of Biochar and the CO2 Capture

This paper was aimed to study the influence of modification of biochar on the performance of CO2 adsorption. Biochar, obtained from cotton stalk pyrolysis in a fixed bed reactor, was modified with ammonia and CO2. The physicochemical properties of biochars were characterized by the Fourier transform infrared spectroscopy and automatic adsorption equipment (Micromeritics, ASAP 2020, USA). CO2 adsorption of biochar was performed in thermogravimetric analyzer. The results showed that the surface area of char was increased significantly by CO2 modification, while N-contained compound on char surface was enriched obviously by NH3 modification. CO2 adsorption of biochar increased greatly with CO2 and NH3 modification. CO2 adsorption was mainly attributed to physical adsorption at 20 A degrees C, and the adsorption quantity (maximum = 99 mg/g) was proportional to the micropore volume of the char. However, at 120 A degrees C, molecular thermal motion increase, chemical adsorption start to play a dominated role, and the adsorption was directly proportional to the N content of this char.