Facile preparation of UiO-66@PPy nanostructures for rapid and efficient adsorption of fluoride: Adsorption characteristics and mechanisms

A nanocomposite of a zirconium-based metal-organic framework (UiO-66) @ polypyrrole (PPy) (UiO-66@PPy) was successfully synthesized to eliminate F- from groundwater. The optimum initial pH and adsorbent dose for maximum uptake of F- from aqueous solution were found to be 3.0 and 0.1 g/L, respectively. The fluoride removal performance of UiO-66 was greatly enhanced through the introduction of polypyrrole guests, and the maximum adsorption capacity of UiO-66@PPy, namely, 290.7 mg/g, was reached, which is far superior to those of other previously reported adsorbents. The fluoride adsorption by UiO-66@PPy agreed well with the pseudo-second-order equation model and Langmuir isotherm model. The coexisting PO43- and CO32- substantially influence fluoride removal. The synthesized UiO-66@PPy could be reused five times in adsorption-desorption cycles. The incorporation of conducting polymers opened additional paths for the development of adsorbent materials; thus, UiO-66@PPy could be a viable adsorbent material and contribute to fluoride removal from groundwater.