Zeolitic imidazolate framework dispersions for the fast and highly efficient extraction of organic micropollutants

Abstract

Development of advanced strategies for the extraction and preconcentration of trace levels of pollutants is essential for the quality control of water resources. A new procedure for the fast and highly efficient extraction of organic micropollutants from water using dispersions of zeolite imidazolate framework-8 (ZIF-8) crystals in a mixture of solvents is reported. The synergistic effect of using ZIF-8 dispersions in mixtures of water miscible and immiscible solvents enhances mass transfer and greatly improves extraction kinetics and capacity in comparison with the use of porous crystals or solvent microextraction separately. The effect of the ZIF-8 crystal size and surface composition has been evaluated using four different ZIF-8 samples spanning the micro- to nanometer range. The relevant parameters involved in the extraction such as the composition of the dispersion medium, the amount of ZIF-8 crystals, the extraction time, or the volume of dispersion required to ensure the maximum extraction efficiency, has also been studied using diethyl phthalate as a model compound. The use of 26 nm ZIF-8 crystals obtained using n-butylamine modulated synthesis has shown very fast extraction kinetics and excellent enrichment factors ranging from 150 to 380 for a mixture of six phthalate esters listed as priority pollutants by the United States EPA, allowing detection limits below the ng L⁻¹ to be reached.