Highly efficient removal of Cr(vi) ions from wastewater by the pomegranate-like magnetic hybrid nano-adsorbent of polydopamine and Fe3O4 nanoparticles

Abstract

Fe₃O₄ nanoparticles have attracted extensive attention for solving Cr(VI) pollution because they can effectively reduce Cr(VI) to the less toxic and less soluble Cr(III)-containing species. However, these magnetic nano-adsorbents suffer from very low adsorption capacity and low stability. To solve these drawbacks, we developed a pomegranate-like hybrid nanosphere (PHN) with a polydopamine (PDA) peel and Fe₃O₄ nanocrystals as seeds, which were applied as the nano-adsorbent for removing Cr(VI) ions. The adsorption performance of the resultant PHN nano-adsorbent towards toxic Cr(VI) ions was evaluated systematically with respect to the solution pH, competing ions, and temperature. The adsorption of Cr(VI) ions onto the PHN nano-adsorbent was found to be highly pH dependent with the optimal pH ranging from 2 to 4 and the PHN nano-adsorbent exhibited a remarkable sorption selectivity in complex wastewater. The nano-adsorbent has a fast adsorption rate for Cr(VI) ions that can reach adsorption equilibrium in about 10 min and the maximum adsorption capacity of the PHN nano-adsorbent was as high as 454.55 mg g⁻¹ at 338 K. In addition, the developed PHN nano-adsorbent has good recyclability. After 5 cycles of regeneration and adsorption, it could still maintain a high removal efficiency of up to 92.5% for Cr(VI) ions.