Adsorption of basic dye from wastewater using raw and activated red mud

Red mud, an industrial by-product generated during the processing of bauxite ore, was investigated as an inexpensive and effective adsorbent for the adsorption of methylene blue from aqueous solution. Chemical and heat treatments were applied to the raw red mud. The effects of contact time, adsorbent amount, pH, temperature and initial dye concentration were investigated. The adsorption isotherm and kinetics of the raw and activated red mud were studied. Freundlich, Temkin and Dubinin-Radushkevich isotherms were obtained using concentrations of methylene blue ranging from 10 to 70 mg/L. The results indicated that the Dubinin-Radushkevich model provides the best correlation of the experimental data. The adsorption rate data were analysed according to the pseudo-first order kinetic, pseudo-second order kinetic, intraparticle diffusion kinetic and Elovich kinetic models. The pseudo-second order kinetic was the best fit kinetic model for the experimental data.