Highly efficient removal of Cr(VI) ions from wastewater by the pomegranate-like magnetic hybrid nano-adsorbent of polydopamine and Fe3O4 nanoparticles
Fe3O4 nanoparticles have attracted extensive attention to solve the Cr(VI) pollution, because they can effectively reduce Cr(VI) to less toxic and less soluble Cr(III)-containing species. However, these magnetic nano-adsorbents suffer from a 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 nanocrystal as seeds and applied as the 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 PHN nano-adsorbent is highly pH dependent with the optimal pH ranging from 2 to 4 and the PHN nano-adsorbent exhibit a remarkable sorption selectivity in complex wastewater. The nano-adsorbent has a fast adsorption rate for Cr(VI) ions that can reach the adsorption equilibrium in about 10 min and have a maximum adsorption capacity of PHN nano-adsorbents as high as 454.55 mg/g at 338K. In addition, the developed PHN adsorbent has a good recyclability. After 5 cycles of regeneration and adsorption, it can still maintain a high removal efficiency of Cr(VI) ions up to 92.5%.