Adsorption of indole on KOH-activated mesoporous carbon

Ordered mesoporous carbons with a 3D wormhole-like structure were synthesized by a soft-templating method. The resorcinol-formaldehyde (RF) was used as a carbon source and a triblock copolymer Pluronic F127 was used as a soft templating agent. The molar ratios of Pluronic F127/Resorcinol were changed 0.0027 (RF-F127(1)), 0.0040 (RF-F127(2)) and 0.0053 (RF-F127(3)). The mesoporous carbons were activated using KOH to improve their porosity. After the KOH activation, the micropore volume and surface area of ultramicropore were largely increased for all the mesoporous carbons. The adsorption of indole from a buffer solution and an artificial intestinal juice solution was measured. The KOH-activated carbons showed high adsorption rate for indole in the buffer solution. This result suggests that the existence of mesopores and 3D-interconnected pore structures reduced the diffusion resistance. On the other hand, in the case of the adsorption of indole from the artificial intestinal juice solution, after a certain period, the desorption of indole was observed for K-RF-F127(2) and K-RF-F127(3). Other bulky compounds would diffuse slowly and be adsorbed in place of indole due to a strong interaction. However, the desorption of indole was not observed for K-RF-F127(1), whose mesopore is smaller than the other KOH-activated carbons. These results suggest that both an appropriate mesopore size tuning and an increase in the micropore surface area are essential for developing a high-performance adsorbent for indole.