As(V) removal from aqueous environments using quaternary ammonium modified ZIF-8/chitosan composite adsorbent

Abstract

This work report the as-synthesized a nanocomposite by -N+(CH3)3-modified ZIF-8/chitosan adsorbents, which has high adsorption performance for As(V). The structural characteristics of ZIF-8/CS-N were analyzed in detail by FTIR, XRD, TGA, Zeta, SEM, EDS, XPS, and N2 adsorption–desorption. The effects of pH, kinetics, initial As(V) concentration, and temperature were studied. The kinetics and isotherms of ZIF-8/CS-N for As(V) follow the pseudo-second-order kinetics and Langmuir isotherms, respectively. The maximal adsorption capability of ZIF-8/CS-N for As(V) achieve at 54.2 mg/g, and reach equilibrium within 60 min. The adsorption was spontaneous and endothermic reactions. ZIF-8/CS-N demonstrated good selectivity on the adsorption with coexisting ions. Consecutive adsorption recycling experiments demonstrate that ZIF-8/CS-N have remarkable reusability performance. Fixed-bed column adsorption was shown that the treatment volume of ZIF-8/CS-N was 882 BV at 6 BV/h. The analysis of the adsorption mechanism by the detailed spectroscopy and DFT calculation. The electrostatic interaction and surface complexation are the primary adsorption mechanism for As(V) removal. It confirms that surface hydroxyls of Zn sites and nitrogen-containing groups (-C=N and -N+(CH3)3) can capture As(V). This work provides a possibility of adsorbent structure design with high adsorption performance on As(V) in practical industrial applications.