Removal characteristics of two anionic dyes by a polyethylenimine/poly(N,N-dimethylaminoethyl methacrylate) gel

The highly efficient gel obtained via the copolymerization of polyethylenimine (PEI) and poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) was successfully applied for the removal of two anionic dyes (amaranth and sunset yellow) from their aqueous solutions. Moreover, the results of the adsorption experiments for sunset yellow and amaranth on the PEI/PDMAEMA gel demonstrate that the adsorption equilibrium both could be achieved within 1 h, and the maximum adsorption capacities were 757 mg g^-1 and 744 mg g^-1 under unoptimized conditions, respectively. Moreover, the PEI/PDMAEMA composite gel was found to be pH-sensitive and the addition of salts together with ionic strength were also explored for understanding the adsorption performance. In addition, it can be found from the studies of adsorption mechanism that it is mainly electrostatic adsorption; moreover, the separation process conforms to the Langmuir adsorption isotherm model and the pseudo second-order kinetic model, which is a spontaneous endothermic process. When the PEI/PDMAEMA gel was used in continuous flow column, it could handle large volumes of dye solution with very low concentrations due to its strong enrichment capacity. Finally, the desorption experiments show that the PEI/PDMAEMA gel is easier to regenerate and has a longer lifetime. Therefore, the high adsorption capacity and easy operation of adsorption for amaranth and sunset yellow on the PEI/PDMAEMA gel make it a potential application prospect for the practical removal of other kinds of similar pollutants.