Synthesis of orange-like Fe3O4/PPy composite microspheres and their excellent Cr(VI) ion removal properties

Uniform orange-like Fe3O4/polypyrrole (PPy) composite microspheres have been synthesized using Fe3O4 microspheres as a chemical template under sonication. In the orange-like Fe3O4/PPy composite microspheres, the Fe3O4 particles played the role of “seeds” while the PPy was the “pulp and peel”. A growth mechanism for the orange-like Fe3O4/PPy composite microspheres was proposed in which partial pyrrole monomers are immersed into the gaps of Fe3O4 microspheres under sonication, meanwhile Fe3+ ions released from Fe3O4 microspheres in an acidic environment initiated the polymerization of pyrrole monomers in the interior or around the Fe3O4 microspheres, finally forming an orange-like structure. When used as an absorbent of Cr(VI) ions, the as-obtained Fe3O4/PPy microspheres showed strong adsorption capability with an adsorption capacity of about 209.2 mg g−1, which is mainly attributed to the PPy “pulp and peel”. Furthermore, the magnetic Fe3O4 “seeds” in composite microspheres make them easy to separate from wastewater by magnetic separation.