Efficient removal of dyes from aqueous solutions using a novel hemoglobin/iron oxide composite

Magnetic particles entrapped in different matrices that display high thermal stability, low toxicity, interactive functions at the surface, and high saturation magnetization are of great interest. The objective of this work was to synthesize a novel hemoglobin/iron oxide composite (Hb/Fe₃O₄) for the removal of different dyes (indigo carmine, naphthol blue black, tartrazine, erythrosine, eriochrome black T and bromophenol blue) from aqueous solutions. The Hb/Fe₃O₄ composite was characterized using scanning electron microscopy (SEM), laser diffraction particle size analysis, FT-IR spectroscopy, isoelectric point determination and thermogravimetric analysis (TGA). The Hb/Fe₃O₄ composite showed high removal efficiency toward all the different classes of dyes studied and the mechanism of adsorption was dominated by electrostatic interaction. Adsorption was found to follow pseudo-second order kinetic model and Langmuir isotherm. The Langmuir monolayer adsorption capacities for all the dyes range from 80 to 178 mg/g. The Hb/Fe₃O₄ composite possesses extra advantage of being easily isolated from aqueous suspension using an external magnet. The stability of the prepared Hb/Fe₃O₄ composite was also demonstrated.