Adsorption of orange G dye on paper mill sludge: Equilibrium and kinetic modeling

In the present study, paper mill sludge (generated as a waste material from paper industries) was investigated as an adsorbent for the removal of orange G dye (an anionic dye) from aqueous solutions. The adsorption capacity of paper mill sludge adsorbent for orange G dye was found to be 62.3 mg/g at 25°C. The adsorption was studied as a function of contact time, concentration, and pH, by batch method. The adsorption data conform best to the Langmuir model. Three simplified kinetic models viz. pseudo-first-order, pseudo-second-order, and intra-particle diffusion models were tested to fit the experimental data. Kinetic parameters, rate constants, equilibrium sorption capacities and related correlation coefficients, for each kinetic model were determined. It was shown that the present system of orange G dye adsorption on paper mill sludge adsorbent could be well described by pseudo-second-order kinetic model. Based on the present investigations, it is reasonable to conclude that paper mill sludge can be utilized as low-cost adsorbent in treating colored dye effluents.