Magnetic responsive Fe3O4-ZIF-8 core-shell composites for efficient removal of As(III) from water

Water stable Fe3O4@ZIF-8 composites were successfully fabricated by a facile modification. The composites were characterized by powder XRD, SEM, TEM and BET surface areas measurement. The results showed that as-obtained Fe3O4@ZIF-8 composites possess core-shell structures (Fe3O4 as core and ZIF-8 as shell) with a high surface area (1133 m2 g−1). The composites were also evaluated for adsorption of As(III) from solution. Langmuir model could be suitable to express the adsorption isotherm, indicating that the uptake of As(III) on Fe3O4@ZIF-8 is monolayer adsorption with maximum capacity being 100 m2 g−1. Thermodynamics data revealed that the adsorption followed a spontaneous, endothermic and entropy increase process. Batch adsorption experiments demonstrated that the adsorption kinetics fit pseudo-second-order better with correlation coefficient R2 of 0.9881. The effects of anions such as chloride, nitrate, carbonate, phosphate and sulfate on the removal of As(III) were also examined. The results indicated that ordinary anions would not hinder adsorption of As(III) except that the carbonate and phosphate anions could compete with As(III) for adsorptive sites on the adsorbent. This research showed Fe3O4@ZIF-8 is a promising composite in practical application as it can be easily separated by magnetism after used in the water treatment with efficient removal of As(III) from aqueous solution.