Novel bimodal micro-mesoporous Ni50Co50-LDH/ UiO-66-NH2 nanocomposite for Tl(I) adsorption

Abstract

Ni50Co50-layered double hydroxide/UiO-66-NH2 metal–organic framework nanocomposite (Ni50Co50-LDH/UiO-66-NH2 NC) was synthesized through a facile ultrasonic-assisted hydrothermal method. UiO-66-NH2 MOF nanocrystals were in situ grown on the surface of ultrathin 2-dimensional functionalized Ni50Co50-LDH nanosheets. Using this method, a uniform nanocomposite architecture was obtained by uniformly distributing MOF nanocrystals on Ni50Co50-LDH. The synthesized LDH/MOF NC possesses essential properties of potential nanoadsorbent such as high surface area (907 m2 g−1), large pore volume (0.91 cm3 g−1), bimodal micro-mesoporous structure, and chemical functionality. Accordingly, Ni50Co50-LDH/UiO-66-NH2 NC was used as an adsorbent for the uptake of toxic thallium (I) from water. Isotherm, thermodynamic, and kinetic studies were conducted to gain a better insight into the adsorption mechanism (s) involved in the removal process. Langmuir and pseudo-first-order models present a better fit to the isotherm and kinetic data, respectively, and the maximum Langmuir adsorption capacity was found to be 601.3 mg g−1 after non-linear fitting analysis (pH=7.0, solution volume=30 mL, initial thallium (I) concentration=50 mg L–1, contact time=15 min, solution temperature=293 K). Thermodynamic parameters were estimated (=+64.979 kJ mol−1, =+0.335 kJ mol−1 K−1, =–33.176 to –39.876 kJ mol−1) and it was found that the adsorption is endothermic and spontaneous with a physicochemical adsorption nature.