Investigating innovative methods to re-use red mud emergent in the Bayer process for color removal

In this study, red mud as the by-product of aluminum industry was treated with ozone, and effect of ozone-treated red mud (OTRM) on the adsorption of Indigo Blue GLF dye in liquid solution was explored. To capture its effect on adsorption efficiency, the control group of raw red mud (RRM) was experimentally set. In determining the optimal adsorption conditions, the effects of adsorbent dose, and contact duration on the adsorption efficiency were tested holding 25 oC and pH 6.5 constant. Using the experimental data, the suitability of Langmuir and Freundlich isotherms to adsorption was studied. As a result of the experiments based on the synthetic solutions of 5 mg/L dye concentration, 4 g/100 mL adsorbent dose and 30 min contact duration led to 70.24 % and 80.99 % removal efficiencies by RRM and OTRM, respectively. For both materials, the increased adsorbent dose and contact duration enhanced the adsorption capacity. Overall, the ozone treatment enhanced the adsorption of raw red mud. Red mud, which is in abundant supply and easily and readily available, appears to be a promising alternative adsorbent for the color removal in wastewater.