Effect of polyelectrolyte structure on perchlorate adsorption performance by functionalized montmorillonite

Polyelectrolyte (with different unit structure or molecular weight) modified montmorillonite (PMt) was synthesized for perchlorate (ClO 4 - ) removal. It was found polyelectrolytes were successfully loaded on montmorillonite (Mt), and the surface potential of most PMt changed from negative to positive. Polyelectrolyte desorption on Mt was < 10 % after 48 h. Poly(diallyldimethylammonium chloride) species modified montmorillonite (PDDA x -Mt) showed excellent adsorption performance for ClO 4 - with maximum adsorption amount over 2.78 mmol/g and equilibrium time within 10 min. The adsorption performance of PMt toward ClO 4 - followed this order: PDDA x -Mt > CH-Mt > PAM-Mt > PQ28-Mt. Moreover, PDDA x -Mt and CH-Mt showed a superior adsorption selectivity to ClO 4 - among competitive oxyanions in the quaternary-adsorbate system (ClO 4 -  > PO 4 3-  > SO 4 2-  > NO 3 – ). The enhanced ClO 4 - adsorption could be mainly attributed to the presence of anion exchange sites (−R 4 N + -Cl − or –NH 3 + -Cl − ) provided by PDDA or CH, followed by electrostatic gravitation and weak hydrogen bonding interaction. Density functional theory (DFT) calculation revealed that ClO 4 - adsorbed on PMt is a process of electrons transferring from O atoms in ClO 4 - to H atoms on C in PDDA + or N in CH + , PAM + and PQ28 + . The preparation method of PMt is simple with excellent adsorption performance and selectivity toward ClO 4 - , suggesting promising applications in anion wastewater treatment.