Adsorption properties of macroporous exchangers functionalized with various weak-base groups for aromatic acids: Coupling DFT simulation with batch experiments

Anion exchange resin has an excellent effect on the removal of aromatic acids in wastewater, while the adsorption affinities of the resins with different functional groups are various. In this work, six macroporous weak-base anion exchange resins were synthesized, and the adsorption characteristics of the resins for three typical aromatic acids including benzenesulfonic acid (BSA), benzoic acid (BA), phenol (PH) were investigated. The results showed that the adsorption performance for BSA and BA on these resins were more sensitive to pH than that for PH. The adsorption capacities of the secondary amine resins to aromatic acid in salt-rich environment were higher than that of the tertiary amine resins. In the binary system, when the adsorption mechanisms of the two adsorbates are overlapped to some extent, the competition between them on the resins was more significant. Density functional theory (DFT) simulations confirmed that the adsorption of BSA by the resins was mainly due to electrostatic interaction, and the adsorption of PH was attributed to hydrogen bond, while BA adsorption was the synergism of these two interactions. The functional resins with high binding energies and high natural bond orbital (NBO) charge transfer had good salt resistances. Furthermore, NaCl aqueous solution was suitable for desorption of BSA on the resins, while the proper desorbent for BA and PH was ethanol. These results indicated that DFT could guide the selection of the functional groups and provided an effective method for the design of selective separation materials for aromatic acids in wastewater.

Automated summary

The study found that different functional groups of macroporous weak-base anion exchange resins have varying adsorption characteristics for aromatic acids in wastewater, with secondary amine resins showing higher adsorption capacities for aromatic acids in salt-rich environments.