Chemical activation of willow with co-presence of FeCl tailors pore structure of activated carbon for enhanced adsorption of phenol and tetracycline.

FeCl is a Lewis acid catalyzing condensation reaction, which might be beneficial for enhancing mass yield of activated carbon (AC) if used as a co-activator. Herein, this was verified by conducting activation of willow with various activators (ZnCl, KCO, HPO) in the presence/absence of FeCl. The results indicated that FeCl competed with acid-catalyzed reactions induced by ZnCl or HPO, interfering aromatization and diminishing AC yields (from 40.8 % to 37.0 % with ZnCl). In the activation with KCO + FeCl, In-situ IR measurement showed that FeCl catalyzed polymerization reactions, but polymeric products were not stable and were further cracked with KCO, reducing AC yield drastically from 27.6 % to 7.1 %. The co-presence of FeCl in the activation reduced overall specific surface area (1201.6 versus 1127.2 m g for KCO) by merging of micropores to form a higher percentage of mesopores (i.e. 2.0 % to 17.1 % for KCO, and 9.2 % to 41.4 % for HPO). This pore restructuring significantly enhanced tetracycline adsorption (99.9 % removal for AC- KCO + FeCl versus 61.1 % for AC-KCO alone), while compromising phenol adsorption (48.7 % versus 96.1 %) due to reduced micropore availability. The reduced specific surface area was also attributed to the retention of inorganics by solid phase reactions between FeCl and KCO or HPO. Additionally, the presence of FeCl resulted in more fragmented surface of ACs generated from all activators.