The adsorption of two phenolic compounds, namely phenol and o-cresol, on four activated carbon fibers (ACC-10, ACC-15, ACC-20, and ACC-25) with increasing micropore volumes and BET surface area and on one commonly used granular activated carbon (GAC) F400 was conducted in this study. Investigations were conducted to study the impact of pore size of activated carbon fiber (ACF) on adsorptive capacity and the potential for oglimerization of phenolic compounds on the surface of ACF in the presence of molecular oxygen. Adsorption isotherms were collected under anoxic (absence of molecular oxygen) and oxic (presence of molecular oxygen) conditions. There was obvious increase in adsorptive capacity for phenol on all the five adsorbents under oxic conditions when compared to the anoxic ones, but for o-cresol, this increase was not significant on ACC- 10 which has the least average pore width and pore volume compared to the other ACFs. The oglimerization of o-cresol on ACC-10 was hampered by the small pore size of ACC-10. For both phenol and o-cresol, GAC F400 showed the highest increase under oxic conditions as compared to the increase obtained for the different ACFs studied. Binary adsorption of phenol and o-cresol on ACC-10, which has the least pore size, had shown no obvious differences between oxic and anoxic isotherms. Phenol didn't show oglimerization on ACC-10 in the binary system because of the less available sites under competitive adsorption. This is further confirmed by the predictions obtained by the Ideal Adsorbed Solution Theory (IAST). On the other hand, F400 showed significant differences between oxic and anoxic isotherms for the binary system due to its wide range of pore size. The IAST accurately described the anoxic binary adsorption isotherms of phenol and o-cresol on F400, but failed predicting the oxic ones.
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