One-Pot Hydrothermal Synthesis of Polyethylenimine Functionalized Magnetic Clay for Efficient Removal of Noxious Cr(VI) from Aqueous Solutions

Abstract

In this work, the polyethylenimine functionalized magnetic montmorillonite clay (MMT-Fe3O4-PEI) was synthesized via a facile hydrothermal method. The formed nanocomposite was applied as a magnetically separable adsorbent for hexavalent chromium (Cr(VI)) removal from aqueous solution. The impact of several influential parameters including initial adsorbate concentration, pH, adsorbent mass and temperature were investigated to optimize the conditions for maximum Cr(VI) adsorption. The Langmuir, Freundlich, and Temkin models were employed to describe isotherm constants. The adsorption process was well interpreted with the Langmuir adsorption isotherm and the maximum adsorption capacity of Cr(VI) was achieved as 62.89 mg g−1. The pseudo-second-order kinetic model was fitted well suggested that the rate-controlling step of the adsorption could be controlled by chemical reactions. The main Cr(VI) uptake mechanism was confirmed to be electrostatic attractions between protonated amino groups with Cr(VI) anions, and followed by partial reduction of Cr(VI) to Cr(III). Moreover, reusability studies showed that the prepared magnetic adsorbent can be reused after successive Cr(VI) removal, which will be beneficial in water treatment.