Metal organic framework UiO-66 and activated carbon composite sorbent for the concurrent adsorption of cationic and...

A composite sorbent for the simultaneous removal of both Hg²⁺ and SeO₃^2- from aqueous media was produced from the solvothermal synthesis of a zirconium metal organic framework, UiO-66, in the presence of activated carbon. The composite sorbent has a large surface area of 1051 m² g^-1 with crystalized porous structures and has strong thermal stability up to 600 °C. The contaminant uptake of the sorbent follows a Langmuir adsorption isotherm with maximum sorption capacity of 205 mg g^-1 and 168 mg g^-1 for Hg²⁺ and SeO₃^2-, respectively. Scanning electron microscopy-energy dispersive spectroscopy results show that the Se regions overlap exclusively with Zr-rich regions suggesting that SeO₃^2- adsorption depends entirely on the exposed UiO-66 surface. In addition, X-ray photoelectron spectroscopy spectra of Se 3d and Hg 4f showed the association of SeO₃^2- and Hg²⁺ on the UiO-66 and carbon surfaces, respectively. The sorbent could facilitate the development of a single process for the simultaneous removal of cationic Hg and anionic Se as well as other similar ionic metals with opposite charges from aqueous media.