Post-modification of UiO-66-NH2 by resorcyl aldehyde for selective removal of Pb(II) in aqueous media

Abstract A new metal organic framework UiO-66-RSA (UiO-66 with hydroxyl) was prepared by the post-modification of UiO-66-NH2 (UiO-66 with amino) with resorcyl aldehyde and was employed for the efficient and selective separation and removal of Pb(II) in aqueous media. The maximum adsorption amount of UiO-66-RSA was 189.8 mg/g at an optimal pH of 4. The adsorption isotherm and kinetic were well described by Langmuir/Dubinin-Radushkevich and pseudo-second-order models respectively. Adsorption process was monolayer chemisorption. UiO-66-RSA was regenerated by thiourea/nitric acid and the removal rate was only decreased by 3.7% after five successive cycles. The analysis of X-ray photoelectron spectroscopy suggested the adsorption mechanism lay on the complexation reaction between hydroxyl/nitrogen-containing groups and Pb(II). The UiO-66-RSA bound Pb(II) by forming double/quadri coordinated complexes. Compared with a multitude of usual metal ions, viz., Zn(II), Co(IV), Ni(II), Mg(II), Cd(II), Cu(II) and Ca(II), the Pb(II) could be absorbed selectively by UiO-66-RSA. The results indicated that the UiO-66-RSA sorbent could be of great potential in the removal of Pb(II) from aqueous solutions.