Adsorptive removal of diclofenac sodium from water with Zr-based metal-organic frameworks

The adsorptive removal of diclofenac sodium (DCF), one of the most frequently detected pharmaceuticals and personal care products (PPCPs), was studied for the first time with metal-organic frameworks (MOPS). Zr-based MOFs, UiO-66 and functionalized UiO-66s (with SO3H/NH2), were applied in the adsorption and the results were compared to that of activated carbon (AC). The pristine and functionalized UiO-66s showed much better performances than AC in terms of both the adsorption kinetics and capacities. The faster adsorption kinetics is significant as the pore size of UiO-66 is smaller than that of AC, which also suggests that certain interactions, such as electrostatic interaction or pi-pi stacking, might exist between DCF and UiO-66. In addition, the functionalization of UiO-66 with SO3H groups resulted in a remarkable enhancement of the adsorption kinetics and capacity. However, the opposite trend was found after the NH2 functionalization of UiO-66. These results suggest that some additional interactions might exist, such as base-base repulsion between the NH2 group of NH2-UiO-66 and the NH group of DCF, or acid-base attraction between the SO3H group of SO3H-UiO-66 and the NH group of DCF. Furthermore, at low concentrations, the adsorption capacity of the SO3H-functionalized UiO-66 was approximately 13-times higher than that of AC, which is very important from a practical point of view. (c) 2015 Elsevier B.V. All rights reserved.