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a b s t r a c tThe present investigation assesses the applicability of waste materials-bottom ash and deoiled soya-for the removal of the colorant Congo red from wastewaters. The adsorption characteristics and dye removal efficiency of adsorbents have been determined by investigating factors such as effect of pH, effect of concentration of the dye, amount of adsorbents, contact time, and temperature. Langmuir, Freundlich, Tempkin, and Dubinin-Radushkevich isotherm models have been used to evaluate the ongoing adsorption. With the help of adsorption isotherm data different thermodynamic parameters such as free energy; enthalpy, and entropy have been calculated. The estimated free energy has been obtained as À21.52 kJ mol À1 for bottom ash and À16.88 kJ mol À1 for deoiled soya. On the basis of pseudo-first-order and pseudo-second-order kinetic equations different kinetic parameters have been obtained. Column operations depicted good adsorptive tendencies for Congo red with 96.95% and 97.14% saturation of dye on bottom ash and deoiled soya, respectively. Regeneration of the saturated columns has been made by eluting NaOH solution and more than 90% dye has been recovered in both cases.

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a b s t r a c tBottom ash, a waste of thermal power plants, and deoiled soya, an agricultural waste material, were employed for successful removal and recovery of hazardous phenol red dye from wastewaters. The adsorption characteristics and operational parameters were determined by monitoring different parameters such as effect of pH, effect of concentration of the dye, amount of adsorbents, contact time, and temperature. The equilibrium data were analyzed on the basis of various adsorption isotherm models, namely Langmuir, Freundlich, Tempkin, and Dubinin-Radushkevich. The highest monolayer adsorption capacity has been obtained for the phenol red-bottom ash system (2.6 Â 10 À5 mol/g) at 50°C. Different thermodynamic parameters such as free energy, enthalpy, and entropy have been calculated and it was concluded that with the increase in temperature adsorption increases, indicating the endothermic nature of the process for both adsorbent materials. Kinetic parameters were derived from pseudo-firstorder and pseudo-second-order kinetics. Differentiation between particle and film diffusion mechanisms operative in the present study has been carried out. The column regeneration characteristic has been also investigated and recovery percentage greater than 90% was obtained for both adsorbents by utilizing acidic eluent.