Removal of perchlorate from aqueous solution using quaternary ammonium modified magnetic Mg/Al-layered double hydroxide

The magnetic and non-magnetic layered double hydroxide (LDH@Fe3O4 and LDH) were developed via simple co-precipitation method. After modified by methyltrioctylammonium chloride (N8881Cl), the absorption capability of the materials for inorganic pollutant perchlorate (ClO4-) improved obviously through ion exchange. Then the characteristics of studied materials were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectronic spectroscopy (XPS) and Zeta potential measurements. The removal performance of ClO4- from water was investigated, and the effects of adsorption parameters on the efficiency were studied, such as contact time, initial concentration, pH and co-existing anions. The adsorption process was quite rapid and the removal rate could reach over 90% on N8881Cl-LDH@Fe3O4 within just 1 min. Maximum adsorption capacities were observed as 50.58 and 60.68 mg g(-1) for N8881Cl-LDH and N8881Cl-LDH@Fe3O4 at 303 K. Moreover, the pH and common coexisting anions had little effects on adsorption capacity of ClO4-. It was found that the equilibrium adsorption process could be well described by pseudo-second-order kinetic model and Langmuir adsorption isotherm model. In brief, the N8881Cl-LDH@Fe3O4 synthesized in this study has the characters of low cost, mild conditions and easy operation, showing satisfactory absorption performance such as fast adsorption and low pH-dependence, which is potential on ClO4- removal from aqueous solution.