Nitrogen-rich magnetic hyper-cross-linked polymer as an efficient adsorbent for tetracycline

Antibiotic contamination remains a challenge for wastewater treatment. In this work, a hyper-cross-linked polymer (DHCP-TP3) with a dual nitrogen-rich structure was synthesized by a one-step facile Friedel-Crafts reaction, and a Fe3O4@DHCP-TP3 composite was prepared by postmodification with the introduction of magnetic iron oxide nanoparticles (Fe3O4 NPs), which were applied to the adsorption of tetracycline (TC) from aqueous solution. The TC adsorption capacities of the DHCP-TP3 and Fe3O4@DHCP-TP3 composites reached 519.65 and 893.85 mg·g−1, respectively, and the adsorption processes for both followed the pseudo-second-order kinetic model and the Freundlich isothermal model. Fe3O4@DHCP-TP3 can achieve adsorption equilibrium for TC within 200 min, and also exhibits excellent regeneration and magnetic separation capabilities. Complexation, hydrogen bonding, cation exchange and π-π interactions were the main adsorption mechanisms. Moreover, Fe3O4@DHCP-TP3 could also adsorb other pollutants, including sulfadiazine (SD), sulfamethoxazole (SMZ), methyl orange (MO), methylene blue (MB), 2,4-dichlorophenol (2,4-DCP), and iodine (I2). The brief synthesis, high adsorption capacity and easy regeneration certified that HCPs were ideal adsorbents for removing pollutants from wastewater.