Fabrication of three functionalized silica adsorbents: Impact of co-immobilization of imidazole, phenyl and long-chain alkyl groups on bisphenol A adsorption from high salt aqueous solutions

Based on the physicochemical properties of bisphenol A (BPA), chemical co-immobilizations of imidazole, phenyl and hexadecyl were done onto silica to obtain three functionalized silica adsorbents. Accordingly, the combinations of hexadecyl and imidazole, hexadecyl and phenyl, and phenyl and imidazole were named as Sil-(HDTMS-MPS)-VIm, Sil-(HDTMS-MPS)-S and Sil-MPS-(S-VIm), respectively. The composites were characterized by FTIR, TGA and SEM. The aim of this work was to explore how these typical functional groups affect the adsorption behavior of BPA. Experiments demonstrated that alkaline imidazole would play a key role for the BPA adsorption, and the synergy of imidazole and hexadecyl exhibited the highest adsorption affinities for BPA in the pH range of 4.0–9.0 due to the high K ow value of BPA. The maximum adsorption capacity of Sil-(HDTMS-MPS)-VIm for BPA obtained from Langmuir model was 89.6 mg/g at 293 K. Furthermore, the prepared three functionalized silicas retained their good adsorption capacities of BPA in high salt solutions, and the adsorption behaviors of BPA for these adsorbents were well described by the pseudo-second-order kinetic model and the Freundlich model. This work suggests that the synergy of hydrogen bond-forming alkaline functional group and hydrophobic long-chain alkyl group benefits BPA removal from aqueous solutions.