Thermodynamics, kinetics, and isotherms for phenol removal from wastewater using red mud

The phenol removal through adsorption using industrial waste has been studied. The red mud generated as waste in the aluminum plants was used in this research. The surface characterizations of red mud were assessed. The batch experiment was investigated with pH (2–12), adsorption period (120–600 min), phenol content (40–200 mg/L), adsorbent dose (2–7 g/L), and temperature (30–50 °C). At the optimum operating condition, the percentage of phenol removal was 87.5%. The pseudo-second-order kinetic model (r2 = 0.98625–0.99994) fitted better than the pseudo-first-order kinetic model. The Freundlich isotherm model was best fitted (r2 = 0.99734–0.99955) among Langmuir, Dubinin–Radushkevich (D-R), and Temkin isotherms. The Langmuir monolayer adsorption capacity was 49.30966 mg/g at 30 °C. The adsorption mechanisms were supported by Reichenberg, Fick, Elovich, Furusawa, and Smith and Boyd models (r2 > 0.8). The thermodynamics suggested endothermic, random, and spontaneous adsorption above 50 °C. The scale-up design using the Langmuir isotherm, and the disposal of used adsorbent after incineration, was established in this study. The research concludes that the red mud generated from the aluminum plant can be used to remove the phenol from wastewater.