Biomimetic Design of Glutamic Acid-Functionalized Polyacrylonitrile Fiber: Advanced Phosphate Capture via Intermolecular Weak Interactions.

Excessive phosphorus discharge is a primary driver of aquatic eutrophication, highlighting the need for efficient and sustainable phosphate removal technologies. In phosphate-binding protein PstS, amino acid residues construct multiple hydrogen-bonding networks with phosphate ions, facilitating high-affinity phosphate sequestration. Inspired by this mechanism, glutamic acid was employed as a functional monomer and introduced onto polyacrylonitrile fiber to mimic the intermolecular weak interaction environment of the active site of PstS, generating the glutamic acid-functionalized polyacrylonitrile fiber (PANF-Glu). It exhibits desirable adsorption performance (maximized at 123.69 mg P/g) over a wide pH range (3-11). It also showed outstanding regeneration performance. >91% adsorption capacity was retained after 5 adsorption-desorption cycles. Characterization and theoretical calculations indicate that abundant carboxyl and amine groups on the surface of PANF-Glu allowed the formation of a stable hydrogen-bonding network with phosphate ions. The enhanced hydrophilicity of the adsorption interface further facilitates the diffusion and mass transfer of phosphate ions towards the adsorbent surface. Electrostatic attractions from protonated amine groups and van der Waals forces rendered an enhanced phosphate capture. By establishing a synergy between hydrogen bonding and electrostatic attraction, this material achieves efficient phosphate adsorption and regeneration, offering a valuable practice for the development of phosphate adsorbents based on multiple intermolecular weak interactions. Furthermore, this biomimetic design involves no metal, avoiding the risk of secondary pollution caused by potential metal leaching. Consequently, PANF-Glu holds theoretical and practical promise for advanced phosphate removal from water and wastewater, which may have important implications for the development of advanced phosphate adsorption materials.