Zeolitic Imidazolate Framework‑8 for Fast Adsorption and Removal of Benzotriazoles from Aqueous Solution

Abstract

1<i>H</i>-benzotriazole (BTri) and 5-tolyltriazole (5-TTri) are\nemerging pollutants; the development of novel materials for their\nefficient adsorption and removal is thus of great significance in\nenvironmental sciences. Here, we report the application of zeolitic\nimidazolate framework-8 (ZIF-8) as a novel adsorbent for fast removal\nof BTri and 5-TTri in aqueous solution in view of adsorption isotherms,\nkinetics and thermodynamics, desorption, and adsorbent regeneration.\nThe adsorption of BTri and 5-TTri on ZIF-8 was very fast, and most\nof BTri and 5-TTri were adsorbed in the first 2 min. The adsorption\nfor BTri and 5-TTri follows a pseudo-second-order kinetics and fits\nthe Langmuir adsorption model with the adsorption capacity of 298.5\nand 396.8 mg g^–1 for BTri and 5-TTri at 30 °C,\nrespectively. The adsorption was a spontaneous and endothermic process\ncontrolled by positive entropy change. No remarkable effects of pH,\nionic strength, and dissolved organic matter on the adsorption of\nBTri and 5-TTri on ZIF-8 were observed. The used ZIF-8 could be regenerated\neffectively and recycled at least three times without significant\nloss of adsorption capacity. In addition, ZIF-8 provided much larger\nadsorption capacity and faster adsorption kinetics than activated\ncarbon and ZIF-7. The hydrophobic and π–π interaction\nbetween the aromatic rings of the BTri and 5-TTri and the aromatic\nimizole rings of the ZIF-8, and the coordination of the nitrogen atoms\nin BTri and 5-TTri molecules to the Zn²⁺ ions in the ZIF-8\nframework was responsible for the efficient adsorption. The fast adsorption\nkinetics, large adsorption capacity, excellent reusability as well\nas the pH, ionic strength, and dissolved organic matter insensitive\nadsorption create potential for ZIF-8 to be effective at removing\nbenzotriazoles from aqueous solution.