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Zeolitic Imidazolate Framework‑8 for Fast Adsorption and Removal of Benzotriazoles from Aqueous Solution
1<i>H</i>-benzotriazole (BTri) and 5-tolyltriazole (5-TTri) are
emerging pollutants; the development of novel materials for their
efficient adsorption and removal is thus of great significance in
environmental sciences. Here, we report the application of zeolitic
imidazolate framework-8 (ZIF-8) as a novel adsorbent for fast removal
of BTri and 5-TTri in aqueous solution in view of adsorption isotherms,
kinetics and thermodynamics, desorption, and adsorbent regeneration.
The adsorption of BTri and 5-TTri on ZIF-8 was very fast, and most
of BTri and 5-TTri were adsorbed in the first 2 min. The adsorption
for BTri and 5-TTri follows a pseudo-second-order kinetics and fits
the Langmuir adsorption model with the adsorption capacity of 298.5
and 396.8 mg g<sup>–1</sup> for BTri and 5-TTri at 30 °C,
respectively. The adsorption was a spontaneous and endothermic process
controlled by positive entropy change. No remarkable effects of pH,
ionic strength, and dissolved organic matter on the adsorption of
BTri and 5-TTri on ZIF-8 were observed. The used ZIF-8 could be regenerated
effectively and recycled at least three times without significant
loss of adsorption capacity. In addition, ZIF-8 provided much larger
adsorption capacity and faster adsorption kinetics than activated
carbon and ZIF-7. The hydrophobic and π–π interaction
between the aromatic rings of the BTri and 5-TTri and the aromatic
imizole rings of the ZIF-8, and the coordination of the nitrogen atoms
in BTri and 5-TTri molecules to the Zn<sup>2+</sup> ions in the ZIF-8
framework was responsible for the efficient adsorption. The fast adsorption
kinetics, large adsorption capacity, excellent reusability as well
as the pH, ionic strength, and dissolved organic matter insensitive
adsorption create potential for ZIF-8 to be effective at removing
benzotriazoles from aqueous solution