Adsorptive removal of Congo red, a carcinogenic textile dye, from aqueous solutions by maghemite nanoparticles

Abstract The adsorption of Congo red (CR) onto maghemite nanoparticles (γ-Fe 2 O 3 ) and its desorption was investigated. The adsorption capacity was evaluated using both the Langmuir and Freundlich adsorption isotherm models. Maghemite nanoparticles (γ-Fe 2 O 3 ) were prepared easily in a surfactant-less microemulsion by co-precipitation method. The size of the produced maghemite nanoparticles was determined by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Synthesized maghemite nanoparticles showed the highest adsorption capacities of CR compared to many other adsorbents and would be a good method to increase adsorption efficiency for the removal of CR in a wastewater treatment process. The maximum adsorption occurred at pH 5.9. The Langmuir adsorption capacity ( q max ) was found to be 208.33 mg g −1 of the adsorbent.