Adsorption of nitrate from water by quaternized chitosan wrinkled microspheres@MgFe-LDH core–shell composite

Abstract

In recent years, nitrate pollution in water has become a global ecological problem. In this study, a new core–shell composite (GCS@CTA@MgFe-LDHs) was prepared by in situ growth of MgFe–Cl-layered double hydroxides (LDHs) plates on 3-chloro-2-hydroxypropyl trimethylammonium chloride (CTA)-modified chitosan (CS) wrinkled microspheres (GCS@CTA), which were applied for removal of nitrate from water. CS wrinkled microspheres were crosslinked with glutaraldehyde (GCS). Afterwards, the positive charge of GCS was enhanced by CTA modification, which enabled GCS to effectively remove nitrate at a wider range of pH. The addition of MgFe–Cl⁻-LDHs provided a larger specific surface area, and the interlayer boundary of MgFe–Cl⁻-LDHs effectively fixed nitrate ion and enhanced the adsorption performance. In addition, the GCS@CTA core effectively prevented the aggregation of MgFe–Cl⁻-LDHs. The synthesis of GCS@CTA@MgFe-LDHs was successfully proved by various characterization analyses. The mechanisms of nitrate adsorption on GCS@CTA@MgFe-LDHs were investigated and confirmed by experiments and characterization analyses. The adsorption kinetics, isotherm model, and reusability of GCS@CTA@MgFe-LDHs were also investigated. Herein, we provide a new core–shell adsorbent for nitrate adsorption.