Removal of safranin-O dye from aqueous solution using modified red mud: kinetics and equilibrium studies

Abstract

The object of this study was to evaluate the efficiency of safranin-O dye removal from aqueous solutions with application of red mud waste as an adsorbent. For this propose, the surface of the red mud was modified by the addition of sodium dodecyl sulphate as an anionic surfactant. Different instrumental techniques were used to understand the physiochemical properties and the surface properties of the modified red mud for the adsorption of safranin-O dye. Batch adsorption experiments were carried out to understand the optimum conditions with respect to solution pH, contact time and initial dye concentration. Kinetics data were best fitted with a pseudo-second-order model. The adsorption isotherms data were a good fit to the Langmuir model with a maximum monolayer adsorption capacity of 89.4 mg g⁻¹ at 308 K. Desorption experiments were carried out by testing several solvents such as water, sulphuric acid, hydrochloric acid and acetic acid and the maximum (93.2%) desorption was found using hydrochloric acid.