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

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 per-formance. 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 elec-trostatic 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.