Enhanced adsorption of caprolactam on phenols-modified Amberlite XAD16
Phenol, catechol , and pyrogallol were employed as the hydrogen-bond donors to chemically modify the commercial adsorbent Amberlite XAD16 via Friedel-Crafts reaction, and three phenols-modified XAD16 were named as, XAD16-Ph(OH), XAD16-Ph(OH) 2 , and XAD16-Ph(OH) 3 respectively. The resulting polymers had porous parameters including Brunauer-Emmett-Teller (BET) surface area ( S BET ) and total pore volume ( V total ) similar to Amberlite XAD16, however the oxygen (O) content was remarkably increased after the Friedel-Crafts reaction in the presence of anhydrous FeCl 3 as catalyst. The synthesized polymers had larger equilibrium adsorption capacities toward ε-caprolactam ( q max = 69.2 mg/g) than Amberlite XAD16 due to the enhanced adsorption contributed by hydrogen bonding between the phenolic hydroxyl groups uploaded on the polymers and the carbonyl of ε-caprolactam (CPL). Experimental data indicated that the removal percentage of CPL reached 93.2% at a concentration of 0.2840 g/25 mL for XAD16-Ph(OH) 2 while the equilibrium data were fitted by the Freundlich and Langmuir models, and the kinetic data were described by the pseudo-second-order rate equation and characterized by the micropore diffusion model.
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