Surface Oxidation Modification of Nitrogen Doping Biochar for Enhancing CO2 Adsorption

• Published in: Industrial crops and products 2023-12, Vol.206, p.117582, Article 117582
• Main Authors: Guo, Tianxiang, Zhang, Yonghe, Geng, Yuhan, Zhu, Zhihui, Chen, Jiahui, Bedane, Alemayehu Hailu, Du, Yarong
• Format: Article
• Language: English
• Subjects: adsorption kinetics; adsorption selectivity; biochar; CO2 adsorption; coconut shell; oxidation modification
• ISSN: 0926-6690; 1872-633X
• DOI: 10.1016/j.indcrop.2023.117582

The purpose of this paper is to demonstrate a surface oxidation modification strategy of nitrogen doping biochar for enhancing CO2 adsorption. The porous structure and surface group distribution of nitrogen doping biochars before and after modification (remarked as TF and OTFs) were characterized. Then the thermodynamic and kinetic characteristics of CO2 adsorption such as adsorption capacity, selectivity and activation energy were systematically investigated. The results indicated that the modified biochars OTFs exhibited high adsorption capacity of CO2 between 5 and 8mmol·g-1 at 100 kPa and 273K. The oxidation modification affected CO2 adsorption behaviors by the ways of adjusting surface pore size and surface group distributions. The former decreased the mass transfer diffusion resistance of CO2 from gas phase to biochar surface by transforming some micropores to the mesopores. And the later improved the adsorption selectivity of CO2 to the other gases such as N2 based on the interaction difference enhancement by those oxygen-containing (OFGs) and nitrogen-containing functional groups (NFGs). When the molar ratios of CO2/N2 in gas mixture were 1:1 and 15:85, the modified biochar OTF-10 exhibited the better selectivity, and the maximum selectivities of CO2 to N2 at 273K were 44.7 and 69.4, respectively. Furthermore, the behavior of CO2 adsorption on the biochars well conformed to the quasi-first-order dynamical model, accompanied by the higher adsorption rate of CO2 and activation energy. The obtained activation energies for TF and OTF-10 were 12.98 and 16.62kJ·mol-1, respectively. The higher activation energy for OTF-10 meant that the adsorption temperature had a stronger effect on adsorption rate of CO2. [Display omitted] •A promising absorbent of CO2 was prepared based on nitrogen doping, thermal activation by medium temperature ionic liquid and surface oxidation modification.•The porous structure and surface group distribution of nitrogen doping biochar before and after surface oxidation modification were systematically investigated.•The thermodynamic and kinetic characteristics of CO2 adsorption on the prepared biochar such as adsorption capacity, adsorption selectivity, adsorption heat, adsorption rate and adsorption activation energy were detailedly revealed.