Immobilization of chitosan grafted carboxylic Zr-MOF to porous starch for sulfanilamide adsorption.

A novel hierarchical porous starch-chitosan-UiO-66-COOH composite for the treatment of pharmaceutical-bearing sewage was developed. UiO-66-COOH-type carboxylic zirconium metal organic framework (Zr-MOF) was synthesized and immobilized within porous starch through a facile chitosan-adhesive strategy. The porous starch offered a stable macro-porous structural skeleton to accommodate the UiO-66-COOH nanoparticles, and chitosan played the role of an affinity agent to strengthen the decoration effect via electrostatic interaction and hydrogen bonding with carboxylic Zr-MOF particles and porous starch, respectively. The carboxylic Zr-MOF composite not only preserved the intrinsic accessibility of UiO-66-COOH but also maintained unique crystallization and thermal properties. The adsorption of sulfanilamide into the porous starch-chitosan-UiO-66-COOH composite conformed to pseudo-second-order kinetic and Langmuir isothermic models, demonstrating that adsorptions could be considered as homogeneous monolayer chemisorption. The Zr-O group within the carboxylic Zr-MOF composite displayed high affinity for sulfanilamide and possibly played a crucial role in sulfanilamide adsorption.