Synthesis, adsorption and theoretical calculation study of the two polar-modified hyper-cross-linked resins for efficient removal of o-toluidine from aqueous solution

Background In addition to their good structural designability, hyper-cross-linked resins (HCLPs) have a vast adsorption capacity. They are also easy to regenerate. It is an efficient adsorbent for o-toluidine (OT) removal and has broad application prospects. Method Two polar-modified hyper-cross-linked resins (PBJSG and BLWT) were synthesized by copolymerization of the monomers (trimellitic anhydride and 2-pyrrolidone) with the non-porous gel-type chloromethylated poly(styrene-divinylbenzene). The static adsorption method was used to study the influence of different factors on the adsorption. The adsorption mechanism of o-toluidine on the two resins was clarified by related theoretical calculations. The dynamic adsorption-desorption process of o-toluidine was finally studied. Significant findings The above resins had the best adsorption effect on o-toluidine. The adsorption of o-toluidine on the PBJSG and BLWT resins was feasible, exothermic, and spontaneous. The adsorption rate was controlled by the intraparticle diffusion and film diffusion steps. The affinity between OT and resins was higher than that between resins and OT+ ions. The relatively strong affinity of OT accounted for the high adsorption amount of OT in the pH range of 6–14. The affinity of PBJSG for o-toluidine was higher than that of BLWT. According to theoretical calculation studies, the mechanism of hydrogen-bonding and π-π stacking interaction was clearly revealed. The mixture of 75% ethanol (V/V) and 10% H2SO4 (V/V) was an effective desorption agent. In summary, this work provides a new convenient strategy for the preparation of novel o-toluidine removal adsorbents.