Enhancement mechanism behind the different adsorptive behaviors of nitro/amine modified hypercrosslinked resins towards phenols

A hypercrosslinked resin, named St-DVB-Al, was prepared by optimizing the conditions of the Friedel-Crafts reaction. The nitro and amine groups were further introduced into the skeleton to prepare the composite functional resins St-DVB-nitro and St-DVB-amine. The adsorption capacity of the modified resins for phenolic compounds reached to 412.9 mg/g, which were 16.4-47.7% higher than the commercial resin H103 with similar physical structure. For the p-nitrophenol and p-hydroxybenzoic acid, the adsorption capacity trends were St-DVB-amine > St-DVB-Al > St-DVB-nitro, but for the hydroquinone was St-DVB-nitro > St-DVB-amine > St-DVB-Al. The reason St-DVB-nitro exhibited efficient adsorption for hydroquinone was that the electron-acceptor group enhanced the synergistic conjugation with the electron-donating compound. The introduction of the electron-donor group in St-DVB-amine enhanced the synergistic conjugation with electron-acceptor compounds as well as the hydrogen bonding and acid-base interaction, thus exhibiting highly efficient adsorption for p-nitrophenol and p-hydroxybenzoic acid. The DFT model was used to calculate the Delta E values of St-DVB-nitro, St-DVB-amine and St-DVB-Al with three adsorbates, and the results were consistent with the adsorption trends. Relationship between adsorption capacity and adsorption behavior was clarified by a quantitative perspective. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.