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Eco-friendly synthesis of TiO2/ZIF-8 composites: Characterisation and application for the removal of imidacloprid from wastewater

The aim of this work was to develop hybrid TiO2/ZIF-8 photocatalysts and test their activity for the removal of agricultural pollutants in water. The hybrid photocatalysts were prepared by an innovative method involving hydrothermal synthesis at 150 ◦C using a mechanochemically syn- thesized zeolitic imidazolate framework (ZIF-8) and titanium tetraisopropoxide as a titanium dioxide (TiO2) precursor. Three composite photocatalysts with different mass fractions of titanium dioxide (5, 50, and 95 wt%) were synthesized and characterized, and their adsorption and photocatalytic properties investigated for the removal of imidacloprid. The equilibrium adsorption test showed that ZIF-8 is a good adsorbent and can adsorb 65% of the model component under the working conditions used in this work, while the hybrid photocatalysts can adsorb 1–3% of the model component. It is assumed that the adsorption is hindered by the TiO2 layer on the surface of ZIF-8, which blocks the interactions of ZIF-8 and imidacloprid. A significant decrease in band gap energies (3.1–3.6 eV) was observed for the hybrid TiO2/ZIF-8 photocatalysts compared to the values obtained with ZIF-8 (5 eV), depending on the mass fractions of TiO2. The highest removal efficiency of imidacloprid was achieved with the hybrid photocatalysts containing 5 wt% TiO2.

imidacloprid; heterogeneous photocatalysis; metal-organic frameworks (MOFs); TiO2; ZIF-8

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