Mahmoud Ehteshami - Materials Research Center, SAPCO, Tehran, P.O. Box: ۱۳۱۸۵/۷۴۳, Iran
Shahram Raygan - Associate Professor, School of Metallurgy and Materials Engineering, University College of Engineering, University of Tehran
Hossein Abdizadeh - Associate Professor, School of Metallurgy and Materials Engineering, University College of Engineering, University of Tehran

Red mud is the waste material of alumina production industries. Hematite (Fe2O3) constituent of this material is an active component for adsorption of anion pollutants. In this study, removal of hexavalent chromium ions from aqueous solution using raw red mud (RRM) and chemically activated red mud (CARM) by nitric acid was investigated as an alternative to the conventional methods of Cr (VI) ions removal from industrial effluents. Raw and activated red muds were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Results showed that activation of red mud by nitric acid resulted in an increase on the removal percentage of Cr (VI) ions from 55% to 97% for the following condition: initial pH of solution 2.5, activated red mud dosage of 10 g/L, contact time of one minute and initial Cr (VI) concentration of 10 mg/L at the temperature of 30 oC and mixing velocity of 500 rpm. The percentage of Cr (VI) ions removal increased with higher amounts of adsorbent and decreased with higher concentration of Cr (VI) ions. The results suggested that activated red mud could be used as effective and economical adsorbent for Cr (VI) ions removal from aqueous solutions.

Red mud, Chemical activation, Hexavalent chromium, Industrial effluents