Preparation Of Modified And Calcined MIL-101 And Zr-MOFs Materials For The Adsorption Of Heavy Metal Ions From Aqueous Soultion

With the rapid development of modern industry, China is facing very serious water pollution problems, especially in the industrial wastewater pollution caused by lead, mercury and antimony, because these ions pose a significant threat to the health of humans and other organisms. Metal-organic frameworks（MOFs）, a new class of porous material, has large surface areas, low framework densities, accessible cages, tunnels and modifiable pores, is a kind of potential excellent adsorbent in water treatment. In this paper, MIL-101 and Zr-MOFs are modified by amino and thiol groups, or a new structural metal oxide is obtained by modified Zr-MOFs after high-temperature calcination, thus providing a new thought for adsorption removal of heavy metal ions in wasterwater, and demonstrating a potentially wider future application of MOFs as a novel robust adsorbent for removal of heavy metal ions. The details are summarized as follows:1. In this paper, amino-functionalization of Cr-based MOFs MIL-101 are modified through coordination bonding of unsaturated Cr metal centers with-NH2 group in ethylenediamine, and we demonstrate their excellent performance for the removal of Pb（II） ions from water. Through XRD, FT-IR, SEM, TEM and XPS characterization method proved successful synthesis of ED-MIL-101. The adsorption capacity of ED-MIL-101, which is more than five times that of MIL-101, is 81.09 mg·g-1 for Pb（II） ions from aqueous samples, and the isotherms are well-fitted with the Langmuir isotherms. D-R adsorption isotherm model suggests that chemical adsorption is the primary type of adsorption for Pb（II）.The adsorption kinetics of Pb（II） ions shows that the process fits well with a pseudo-second-order model, and the adsorption equilibrium time is only about 30 min. Moreover, the practical application of ED-MIL-101 achieves almost 97.22% removal efficiency for Pb（II） ions. These results indicate that ED-MIL-101 has great potential in selectively removing Pb（II） ions from water environment.2. In this work, 2,5-dimercapto-1,4-benzenedicarboxylic acid with hard carboxyl and soft thiol functionalities is first synthesized for use as the organic ligand. Thiol-functionalized Zr-based MOF（Zr-DMBD） is later prepared under solvothermal conditions using ZrCl4 and H2 DMBD. X-ray diffraction and scanning electron microscopy indicate that the structure of Zr-DMBD exhibit the UiO-66 topologies, and examination of the Fourier transform infrared spectra verifies that the free thiol groups have been identified in the Zr-DMBD. The maximum adsorption capacities of Zr-DMBD for Cu（II）, Cd（II）, Pb（II）, and Hg（II） are 40.2, 43.8, 97.0 and 171.5 mg·g-1, respectively, which are significantly higher than those of UiO-66.The isotherms for metal ions’ adsorption on Zr-DMBD are well-fitted with the Langmuir isotherms, and the metal ions’ adsorption kinetics are in agreement with the pseudo-second-order model. D-R adsorption isotherm model suggests that chemical adsorption is the primary type of adsorption for the metal ions. Competitive adsorption studies show that Zr-DMBD has a high recognition ability and selectivity for Hg（II） ions. Moreover, fixed-bed column adsorption experiment shows that the effective treatment volume for Hg（II） ions is 840 BV, indicating the Zr-DMBD has a great potential for effective selective adsorption of Hg（II） from aqueous environments.3. In this paper, UiO-66, UiO-66-NH2 and Zr-DMBD are first synthesized, then a series of new structural ZrO₂ is obtained by modified Zr-MOFs after high-temperature calcination. ZrO₂ synthesized by Zr-MOFs calcined at 900℃ has superior adsorption capacity for Sb（III） than other high-temperature calcination obtained ZrO₂. The maximum adsorption capacities of ZrO₂ obtained by UiO-66, UiO-66-NH2 and Zr-DMBD calcined at 900℃ are 46.32mg·g-1,54.29 and 72.10mg·g-1, much higher than ZrO₂ obtained by calcining ZrO（OH）2.The isotherms for Sb（III） adsorption are well-fitted with the Langmuir isotherms.D-R adsorption isotherm model shows that adsorption process is mainly chemical adsorption. Adsorption kinetics show that adsorption rates are very fast within 20 min, and the adsorption kinetics are in agreement with the pseudo-second-order model. In addition, solution pH value has a great influence on adsorption of Sb（III）, and the optimum pH value is 8. These results indicate that ZrO₂ obtained by modified Zr-MOFs calcined at 900℃ has great potential in removing Sb（III） from water environment.