Effect of pore structure on adsorption behavior of ibuprofen by magnetic anion exchange resins

Abstract

A series of magnetic anion exchange resins (ND-1, ND-2 and ND-3) with different pore structure were prepared for ibuprofen (IBU) adsorption by using different amount of cyclohexanol as porogen in this work. For adsorption kinetics, resins with larger pore structure showed faster adsorption rates and higher equilibrium adsorption capacities because the internal diffusion process was facilitated by the increase of pore diameter and pore volume. As for adsorption isotherms, the experimental data was better fitted by Freundlich model especially for the resins with broader pores, suggesting that heterogeneous interactions took place in pores. The counter ion released by resin was measured, and ratios of equilibrium adsorption capacity to the counter ion were between 1.22 and 1.56, which confirmed that adsorption process was predominantly attributed to ion exchange while other interactions also existed. Hence, the co-existent anion reduced the adsorption amount of IBU onto resin by competing adsorption in ion exchange process, and the optimal pH ranged from 6 to 8. Resins with more open structure showed better regeneration abilities, of which the adsorption amounts witnessed no significant decrease during 7 circles of use, indicating the advantages of larger pore canal in the adsorption and regeneration behavior.