Synthesis of a zinc–imidazole metal–organic framework (ZIF-8) using ZnO rods grown on cotton fabrics as precursors: arsenate absorption studies

A Zn-imidazolate metal–organic framework, ZIF-8, was synthesized using ZnO nanorods grown on cotton fibers as precursors. We monitored the synthesis path via X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The fibers were evaluated by their capacity to absorb arsenate from aqueous solutions and we used scanning transmission electron microscopy–high angle annular dark-field (STEM–HAADF) imaging to observe the transport gradient of arsenate across the ZIF layer and the ZnO interface. The uptake of arsenate in the fibers coated with ZIF-8 on top of the ZnO rods, at pH 7, was of 70% while the uptake of the fibers coated only with ZnO rods was 38%. In addition to the enhanced uptake capacity, the fibers containing ZIF-8 also exhibited lower amounts of Zn leaching into the arsenate solutions. These results provide insights on the synthesis of Zn-imidazole metal–organic frameworks and confirm the potential use of ZIF-8 in the removal of arsenate from contaminated water streams.