Thiodiacetic acid-functionalized Zr-MOFs as a robust adsorbent for efficient removal of Hg(II) and Pb(II) from aqueous solution

Heavy metal pollution has always been a problem that can not be ignored in the environment. In view of the high toxicity and ubiquity of Hg(II) and Pb(II), a new zirconium-based adsorbent (Zr-TDA) was successfully prepared by a one-step method and used in adsorption experiments. The results showed that the adsorption effect of Zr-TDA was the best at pH = 5.0. The adsorption process conformed to the pseudo-second-order kinetic model, and the maximum adsorption amounts calculated by the Hill model were 605.5 (Hg) and 212.7 (Pb) mg/g at 298 K, respectively, and increased with the increase of temperature. The adsorbent exhibited excellent selectivity with distribution coefficients of 16.814 (Hg) and 1.064 (Pb), respectively. After four repeated experiments, the removal rate decreased by only 15.57% (Hg) and 8.18% (Pb), respectively. In addition, XPS analysis showed that the adsorbent efficiently removed heavy metal ions in solution through chelation, and the functional groups containing O and S had a cooperative effect.