Facile preparation of polyethyleneimine functionalized MXene nanosheets for enhanced adsorption and reduction of Cr(VI) from aqueous solutions: behaviors and mechanisms

Abstract

A novel PEI/MXene adsorbent was synthesized via a facile grafting method to enhance the removal of Cr(VI) from wastewater. The PEI modification introduced abundant amino groups as active adsorption sites, achieving an excellent adsorption capacity of 557.79 mg/g, which is 4.8 times higher than that of pristine MXene. The synthesized adsorbents were comprehensively characterized to evaluate their structural and surface properties. The introduction of PEI effectively modulates the charge properties of MXene layers and enhance the electrostatic attraction between the adsorbent and Cr(VI). The adsorption process could be well fitted to the pseudo-second-order model and Freundlich isotherm model. After five adsorption-desorption cycles, the as prepared adsorbent still maintained an outstanding removal rate of 84.16% for Cr(VI). Furthermore, PEI/MXene also exhibited excellent selectivity for Cr(VI) over other competing cations or anions. Adsorption mechanism revealed that Cr(VI) undergoes redox-mediated reduction to less toxic Cr(III) during the adsorption process, which is subsequently immobilized on the adsorbent via Ti–O–Cr and N→Cr interactions. These findings demonstrate that PEI/MXene exhibits significant potential for the remediation of Cr(VI) contaminated wastewater.