Effect of UV-C on pre-oxidation prior amination for preparation of a selective CO2 adsorbent

• Published in: Journal of analytical and applied pyrolysis 2014-01, Vol.105, p.191-198
• Main Authors: Adelodun, Adedeji Adebukola, Lim, Yun-Hui, Jo, Young-Min
• Format: Article
• Language: English
• Subjects: Amination; Carbon surface chemistry; CO2 selectivity; Pre-oxidation; UV-C
• ISSN: 0165-2370; 1873-250X
• DOI: 10.1016/j.jaap.2013.11.004

•O3 oxidation enhanced both the textural and chemical properties of AC and the amination efficiency compared to H2O2.•UV-C reduced the amount of refractory SOFs, thereby increasing the proportion of those available for amination.•Carbonyl, carboxyl and hydroxyl aid the formation of pyridine and pyrrole groups, which showed high affinity toward CO2.•Narrower micropores achieved by O3 treatment enhanced the CO2 physisorption. In order to enhance the selectivity of activated carbon (AC) toward CO2, surface modification was carried out in a two-step approach viz. pre-oxidation and amination. First, the most suitable oxidation was determined by using O3 and H2O2 with or without UV-C (λ≈253.7nm), to impregnate surface oxygen functionalities (SOFs) on the AC surface, followed by optimization of the most efficient technique. Chemical characterization showed that pre-oxidation increased the total amount of SOFs tethered on the AC surface. However, it was reduced when the oxidation was carried out under the influence of UV-C. Upon amination, less thermally refractory SOFs such as ether, carbonyl and carboxylic groups, tend to favor the formation of surface nitrogen functionalities such as pyridine and pyrrole-N types, which showed comparatively higher affinity toward CO2. Pre-oxidation and amination parameters of AC treatment with O3 in the presence of UV-C (ROUV), which exhibited most favorable condition for CO2 low-level selectivity, were optimized. The intrinsic capture affinity of AC for low and high levels CO2 was ultimately enhanced from 0.016 and 0.46 to 0.36 and 0.9mmol/g respectively. Conclusively, UV-C inhibits the formation of recalcitrant SOFs during oxidation, thereby reducing steric hindrance and promoting amination and eventual CO2 adsorption.