Removal of congo red from wastewater by adsorption onto waste red mud

Waste red mud, an industrial byproduct, generated during the processing of bauxite ore, is recycled for the adsorption of congo red from aqueous solution. Adsorption kinetics were studied using the parameters such as dye concentration, adsorbent dose, agitation time and pH. Adsorption followed first rate expression. The equilibrium adsorption data obeyed both Langmuir and Freundlich isotherms. The adsorption capacity of the red mud for the dye was 4.05 mg/g. Adsorption was found to be nearly quantitative at pH 2.0. Effect of pH and desorption studies suggest that the mechanism of adsorption is mostly ion exchange.