CTAB-surface-functionalized magnetic MOF@MOF composite adsorbent for Cr(VI) efficient removal from aqueous solution

In this work, a surfactant-functionalized magnetic MOF@MOF adsorbent (Fe3O4@UiO-66@UiO-67/CTAB) was prepared by simple solvothermal method and applied to adsorb Cr(VI) from aqueous solution. It exhibited excellent adsorption performance and recyclability mainly due to the tunable pores and plenty surface active sites of the MOF@MOF structure, and electrostatic attraction and reduction of CTAB modifier. It had excellent adsorption capacity in a wide pH range of 1.0-11.0, and the maximum adsorption capacity was 932.1 mg g(-1) at pH 2.0. The adsorption reached equilibrium at contact time of 240 min. Adsorption capacity increased with the increase of initial Cr(VI) concentration. High valence coexisting ions had negative effects on adsorption for both anions and cations. The adsorption of Cr(VI) by Fe3O4@UiO-66@UiO-67/CTAB is mainly chemisorption and monolayer adsorption, and the adsorption process is a spontaneous endothermic process. This study provided a valuable strategy and path for designing and developing effective MOF-based multifunctional adsorbents.