Adsorption-enrichment characterization of CO2 and dynamic retention of free NH3 in functionalized biochar with H2O/NH3•H2O activation for promotion of new ammonia-based carbon capture

CO2 emission reduction has become a global consensus, and the most potential carbon emission reduction technology-Carbon Capture and Storage (CCS) is still in the development stage. In order to make up for the shortcomings of CCS technology, the idea of functionalized biochar-ammonia carbon capture system is proposed. Corn straw was used as raw materials, and activated biochar were prepared by one-step/two-step H2O/NH3 center dot H2O activation, to construct a hierarchical-functionalized structure of biochar, and explore its adsorption characteristics of CO2 and NH3. Various methods such as solid characterization, temperature programmed desorption, molecular dynamics and quantum chemical simulation were used to explore the structure-effect relationship between the physicochemical properties of biochar and the adsorption of CO2 and NH3. The results show that the pore structure of gas-physical activated biochar is dominated by micropores. The one-step method is beneficial to the construction of functional groups on biochar surface, while the two-step one is conducive to the improvement of pore formation and its aromatization. During NH3 center dot H2O activation, NH3 would inhibit the formation of O-containing functional groups on the surface of biochar by H2O. Compared with O-containing groups, the N-containing functional groups on biochar surface have greater adsorption energy for CO2 and NH3 adsorption. The adsorption sites of CO2 and NH3 are mainly in the micropores (d < 0.7 nm), and the contribution of functional groups in the micropores to the adsorption of CO2 and NH3 is greater than the pore structure. This study provided theoretical basis for the development of new biochar-ammonia CO2 capture system.

Automated summary

This research explored the adsorption characteristics of CO2 and NH3 by using one-step/two-step activated functionalized biochar. The results showed that the microstructure and surface functional groups of biochar play a crucial role in the adsorption process.