Easy separated 3D hierarchical coral-like magnetic polyaniline adsorbent with enhanced performance in adsorption and reduction of Cr(VI) and immobilization of Cr(III)

Abstract

A coral-like hierarchical micro/nano-structural polyaniline consisting of short nanowires (CL-PANI) was synthesized via a simple chemical oxidation method and firstly used as an adsorbent for removal toxic Cr(VI) ions. Two types of magnetic CL-PANI nanocomposites, i.e., CL-PANI shell coated by Fe3O4 nanoparticles (CL-PANI@Fe3O4) and Fe3O4 nanoparticles protected by CL-PANI (Fe3O4@CL-PANI), were further prepared for the easy separation purpose in the practical application. As-prepared adsorbents were well characterized and their performance for the removal of Cr(VI) were systemically investigated and compared. Adsorption results showed that the adsorption of Cr(VI) ions was dependent on solution pH and temperature for all three adsorbents. The fitted data revealed that the adsorption process followed the pseudo-second-order kinetic model and Langmuir isotherm model. CL-PANI exhibited an enhanced adsorption performance due to its well-defined and accessible mesoporous and plenty surface active sites compared with common synthesized irregular nanorod PANI. Moreover, modified with Fe3O4 nanoparticles endowed CL-PANI with a slight decreased adsorption capacity, but provided more active sites for immobilizing the reduced Cr(III) ions. Besides, compared with CL-PANI@Fe3O4, Fe3O4@CL-PANI was found to be more promising in the practical treatment of Cr(VI)-containing wastewater.