Efficient ion-enhanced adsorption of congo red on polyacrolein from aqueous solution: Experiments, characterization and mechanism studies

Polyacrolein (PA) was prepared by photoinduced free radical polymerization for adsorption of congo red (CR). The structural and physicochemical properties of PA were characterized using BET, zeta potential measure-ments, SEM, FT-IR and XPS. The adsorption process of CR accorded with the pseudo-second-order kinetics, while the adsorption isotherm conformed to be the Langmuir model and the adsorption was proved to be the spon-taneous and endothermic process (Delta G(0) < 0, Delta H-0 > 0). Electrostatic attraction, hydrogen bond and chemical reaction (formation of imine) were the critical driving forces of adsorption. The good removal efficiency ob-tained during the five executed cycles suggested a good reusability of PA. It was noteworthy that salts in CR solution could promote the adsorption capacity of PA, in which Ca (II) could obviously improve the adsorption capacity and shorten the time to reach adsorption equilibrium. These results have provided very useful in-formation for removing CR and enhanced our understanding of the adsorption mechanism of PA on CR.