Adsorption of Reactive Blue and Direct Red Dyes on Powdered Activated Carbon (PAC) - Equilibrium, Kinetics and Thermodynamic Studies

The present study deals with the adsorptive removal of Reactive Blue 19 (RB19) and Direct Red 81(DR81) from their aqueous solutions. Powdered Activated Carbon (PAC) was used as an adsorbent. Batch studies were performed to analyse various experimental parameters like adsorbent dose, pH, contact time and initial dye concentration. Optimum PAC doses for RB19 and DR81 were found to be 0.2 g/L and 0.3 g/L, respectively. Effective pH for RB19 and DR81 removal was found to be 2 and 7, respectively. In addition, high percent removal with decrease in initial dye concentration was observed. Quasi-equilibrium was attained in 3h for both dyes. Pseudo-second-order rate equation satisfactorily represented the adsorption kinetics for both the dyes. Langmuir and Temkin isotherms were found to best represent the equilibrium data for DR 81-PAC system whereas for RB19-PAC system Langmuir isotherm was found to be best suited. Furthermore, thermodynamic studies showed that the adsorption of both the dyes onto PAC was exothermic in nature.