Efficient removal of Cr (VI) and Cu (II) ions from aqueous media by use of polypyrrole/maghemite and polyaniline/maghemite magnetic nanocomposites

We examined the use of polypyrrole/maghemite (PPY/γ-Fe₂O₃) and polyaniline/maghemite (PANI/γ-Fe₂O₃) magnetic nanocomposites (MNCs) as active agents for removal of heavy metals ions from aqueous media. We have used chemical co-precipitation methods to prepare the maghemite nanoparticles. Subsequently, we synthesized the MNCs through emulsion polymerization of pyrrole or aniline. We estimated the efficiency of these MNCs for Cr (VI) and Cu (II) removal by using batch methods and inductively coupled plasma-optical emission spectroscopy (ICP-OES) to measure the metal content in the solutions before and after use of the MNCs. We evaluated the adsorption capacity (q_e) of each MNC as a function of the solution pH and of the time allowed for its interaction with the metallic ions in solution. In the Cr (VI) [Cu (II)] case, we determined the value of q_e as 209 [171] mg/g, for the PPY/γ-Fe₂O₃ MNC, and 196 [107] mg/g, for the PANI/γ-Fe₂O₃ MNC. In the PPY/γ-Fe₂O₃ [PANI/γ-Fe₂O₃] MNC case, the time necessary for attaining the q_e saturation limit was of the order of 15 [35] min for both Cr (VI) and Cu (II). These characteristics compare favorably to those of alternative agents for removal of dissolved metal ions reported in the literature.