Honeycomb-like macroporous crosslinked chitosan assisted EDTA-intercalated Ca-Mg-Al layered hydrotalcite composite...

The biosorption is considered to be highly efficient for the separation of radionuclide from radioactive wastewater. Herein, the crosslinked chitosan assisted EDTA intercalated Ca-Mg-Al layered double hydroxides composite foam (CS-EDTA-LDH) was synthesized by combining EDTA intercalation and freeze-drying methods. The macroporous and ultralight properties of CS-EDTA-LDH facilitates its rapid adsorption and facile recovery, and the inorganic/organic incorporation can avoid pore collapse and provide numerous adsorption sites, while the EDTA intercalation can enhance the complex capture of U(VI). The CS-EDTA-LDH presents various functional groups (carboxyl, hydroxyl and amino groups) for U(VI) adsorption, and the adsorption capacity for U(VI) reached 272.3 mg/g at pH 5.0 and 298 K. The adsorption kinetics of U(VI) conformed to PSO equation, whereas the isotherms conformed to the Freundlich model, indicating heterogeneous adsorption with diffusion process as a rate-controlling step. The thermodynamic parameters indicate that U(VI) adsorption by CS-EDTA-LDH is endothermic and spontaneous in nature. The adsorption mechanism is related to the synergic complexation by multi-functional groups, ion exchange, and possible isomeric substitution. Overall, CS-EDTA-LDH could be a promising biosorbent for the cleanup of radioactive pollution due to its high performance for U(VI) adsorption and facile recovery.