Polyamidoamine-Based Hydrogel for Removal of Blue and Red Dyes from Wastewater

One of the major problems related to the use of dyes in industrial applications is their elimination from the water or soil and eventually their recovery and reutilization. In this context, a new biocompatible material, previously considered suitable for biomedical applications, is presented for the first time, as an innovative adsorbent material for wastewater treatment. A polyamidoamine-based hydrogel, prepared by Michael-type polyaddition in water, is used for efficiently adsorbing two anionic toxic textile dyes from aqueous solutions. Several parameters affecting the adsorption process, such as the pH of solutions containing dyes, the amount of hydrogel and dyes, and the effect of temperature, are investigated. Moreover, the hydrogel dehydration and swollen conditions by using dye water solution are studied by Thermo-Gravimetry (TG) and Differential Scanning Calorimetry (DSC) analyses, finding that the dehydration temperature plays a relevant role in determining the subsequent adsorbing behavior. The material characterization shows that the adsorption process can be attributed to a combination of electrostatic attraction and intermolecular interactions between hydrogel functional groups and the dye molecules. Visible absorption spectroscopy and Fourier Transform InfraRed-Attenuated Total Reflectance (FTIR-ATR) support the findings. The kinetics of the dye adsorption process are also evaluated, together with the adsorption isotherms.