Amine-Modified Biochar for the Efficient Adsorption of Carbon Dioxide in Flue Gas

Abstract

Biochar-based carbonaceous adsorbents are gaining interest due to their high availability, ease of modification, and low cost; however, they show limited adsorption of CO2 in flue gas due to common textural properties. In this study, TEPA-modified biochar was used to prepare a solid amine adsorbent for the efficient capture of CO2 in flue gas. First, the porous biochar was prepared with FeCl3, Mg(NO3)2, and H2O (g) as activators and walnut shells as carbon sources. Next, the biochar was modified with TEPA to obtain a solid amine adsorbent. Porous texture properties and sample surface functional groups were characterized, and we measured the adsorption CO2 of the amine-modified biochar in a breakthrough adsorption device. Results showed that biochar has a large specific surface area (744.38 m2 g−1), a total pore volume of 1.41 cm3 g−1, and a high mesoporous volume ratio (82.7%). The high pore volume provided a more efficient support space for loading tetraethylenepentamine (TEPA). The adsorbent had an excellent CO2 adsorption capacity, corresponding to 2.82 mmol g−1, which increased to 3.31 mmol g−1 and kept water resistance at 10% H2O (g) simulated flue gas (SFG). The FTIR analysis showed that H2O (g) inhibited urea production after cyclic adsorption. Therefore, solid amine adsorbent created by amine-modified biochar has potential advantages in its application for capturing CO2 in SFG.

Effect of Pore Structure on CO2 Adsorption Performance for ZnCl2/FeCl3/H2O(g) Co-Activated Walnut Shell-Based Biochar

“…Biochar derived from sources such as agricultural waste [11], nut shells [12,13], and minerals [3] not only has the same advantages as activated carbon, but also has the benefits of rich surface functional groups, improved resource reuse, and relief of pressure on waste disposal. However, the conventional biochar obtained by direct high-temperature pyrolysis of biomass has many deficiencies, so it needs to be modified to optimize the structure of biochar.…”

“…H 2 O(g) is the green activator that can make biochar materials obtain new pore structures and expand pores. However, it is difficult to control the pore structure and activation efficiency of activated carbon when only steam is used for activation [13]. Metal salt activators (ZnCl 2 [14], FeCl 3 [15], MgCl 2 [13]), have the advantages of low corrosiveness, environmental friendliness and reusability compared to disposable activators (KOH [12], HNO 3 [16], H 3 PO 4 [17]).…”

“…However, it is difficult to control the pore structure and activation efficiency of activated carbon when only steam is used for activation [13]. Metal salt activators (ZnCl 2 [14], FeCl 3 [15], MgCl 2 [13]), have the advantages of low corrosiveness, environmental friendliness and reusability compared to disposable activators (KOH [12], HNO 3 [16], H 3 PO 4 [17]). Meanwhile, metal salts can enhance the graphitization and increase the porosity of biochar.…”