Removal of reactive dye from aqueous solution using thermally treated red mud

Abstract

The removal of color from wastewater is a major problem for textile industries. The best option to remove color is to combine conventional treatments with additional processes, such as adsorption. Industrial waste has been studied for use as adsorbents, specifically red mud (RM), which is an insoluble residue that is generated in large quantities during the processing of bauxite. In this study, a typical reactive dye, reactive blue 19 dye (RB 19), used in the textile industry was selected, and its ability to adsorb RM that was thermally treated at 500°C (RM 500°C) was evaluated. The adsorption of RB 19 was highest when the pH values were lower than the pHPCZ (7.0). The experimental adsorption capacity data were analyzed using the Langmuir and Freundlich models. The Langmuir model was more appropriate for describing this phenomenon in acidic conditions, with a maximum adsorption capacity of 178.4 mg g−1 (R2 of 0.84). Kinetics studies indicate that a pseudo-second-order reaction mechanism is responsible for the adsorption of RB 19, indicating that adsorption occurs through electrostatic interactions. Thus, these results indicate that the RM 500°C has potential applications for treating effluents from textile industries.