Sorption of synthetic aromatic anions onto polymeric ion exchangers: Genesis of selectivity and effects of equilibrium process variables on sorption kinetics

Many environmentally significant synthetic aromatic compounds such as pentachlorophenol and naphthalene sulfonates exist as anions in water over a wide range of pH. Because the synthetic aromatic anions have both ionic charges and hydrophobic moieties, ion exchange can be employed as an efficient and selective process for their removal from contaminated water. In this study, the equilibrium behaviors and kinetics in the sorption of the synthetic aromatic anions on polymeric anion exchangers were investigated.; The study reports the very favorable sorption of the synthetic aromatic anions on polymeric anion exchangers. It is indicated that the electrostatic interaction is not the determinant of the ion-exchange selectivity. From experimental results, it is proved that the hydrophobic interaction plays an important role in determining ion-exchange selectivity for the synthetic aromatic anions. Experimental data show that the sorption of synthetic aromatic anions onto polymeric ion exchangers is an endothermic and entropy-driven process.; Experimental results show that the ion-exchange selectivity for the synthetic aromatic anions can be reduced, even reversed, in organic solvent/water cosolvents. The addition of organic solvents into water and the presence of competing inorganic ions have a synergistic effect in reversing the sorption process and attaining the efficient desorption or regeneration of ion exchangers loaded with the synthetic aromatic anions. Experimental results indicate that the sorption in cosolvents is an exothermic and enthalpy-driven process.; This study reports the results of the kinetics in the sorption of the synthetic aromatic anions on macroporous ion exchangers. In this study, it is verified that the intraparticle pore diffusion is a rate-limiting step for the sorption of the synthetic aromatic anion in ion-exchange fixed-beds. It is revealed that the effective intraparticle diffusivity of the synthetic aromatic anions decreases with increasing the sorption affinity toward ion exchangers. This study demonstrates the effects of equilibrium non-linearity on the effective intraparticle diffusivity.