Investigation of Adsorption Isotherm Models for Interaction of P(AAm-ClAETA) and Carminic Acid, and Theoretical Approaches

In this study, the adsorption isotherm models for the sorption of carminic acid on P(AAm-ClAETA) hydrogels are explained by experimental and theoretical studies. The crosslinked hydrogels with ethylene glycol dimethacrylate were prepared by radical addition reaction of acrylamide (AAm) and 2-(acryloyloxy)ethyl trimethylammonium chloride (ClAETA) monomers in an aqueous solution. The spectral and morphological analyses of P(AAm-ClAETA) hydrogels were performed by FTIR/ATR and SEM, respectively. The adsorbed amounts of carminic acid on P(AAm-ClAETA) hydrogels were evaluated by Giles, Langmuir, and Freundlich adsorption isotherm models. Langmuir parameters were calculated for the adsorption of the dye on the hydrogels according to the L-type Giles isotherm. In addition, it was determined that its adsorption was appropriate from the RL values calculated for 500 mg L-1 carminic acid concentration. In addition, molecular electrostatic potential (MEP) mapping was performed to predict the reactive sites of P(AAm-ClAETA) hydrogels and carminic acid. The results showed that the theoretical and experimental data of the hydrogels were in agreement with each other. As a result, it can be said that P(AAm-ClAETA) hydrogels are suitable for the removal of anionic dyes such as carminic acid from aqueous solutions.