Adsorption Investigations on the Removal of Azoic Dye by Untreated Wood Sawdust

Batch adsorption of the azoic dye Congo red (CR) was carried out successfully on untreated low-cost wood sawdust. The impact of several variables (contact time, amount of solid adsorbent, initial adsorbate concentration, temperature, and pH) on the sorption process was studied. A maximum removal efficiency was achieved after 50 minutes at pH = 5 and 25 °C. To characterize the adsorbent, FTIR, SEM, EDX, and BET analyses were performed. The equilibrium isotherms were described using four alternative models. The data were found to fit the Freundlich model the best. The kinetic analysis demonstrates that the process is best represented by a pseudo-second-order model. The thermodynamic studies revealed the spontaneity and the exothermic nature of the sorption process. The optimal isotherm model served as the foundation for the design of a one-stage batch adsorber for the sorption of CR onto wood sawdust.