Role of the similar molecular weight dyes on the adsorption by activated carbon

Abstract

In the current study, the effect on the adsorption of dyes (Basic red 2, Basic blue 3 and Ethyl orange) having almost similar molecular weight but belonging to different classes and functional groups on air activated carbon prepared from demineralised kraft lignin (DKLAAC) was investigated. The experimental and theoretical adsorption values for the dyes on DKLAAC were found to be 0.599, 0.550 and 0.395 mmol g-1 and 0.569, 0.520 and 0.387 mmol g-1 for Basic red 2, Basic blue 3 and Ethyl orange, respectively. Basic red 2 showed maximum adsorption (0.599 mmol g-1) on DKLAAC owing to more hydrophobicity and resonance in its structure. Contrarily, Ethyl orange showed minimum adsorption due to the hydrophilicity and less number of benzene rings. The presence of acid/basic site concentration of DKLAAC also affects the adsorption process. The obtained experimental data fitted best to the pseudo-second-order kinetic model. Thermodynamic parameters analysed confirms the feasibility, spontaneity and endothermic nature of the adsorption process.