Preparation And Performance Of MOFs For Adsorption Of Metal Oxyanions In Water

Water is one of our most essential natural resources indispensable to life.Metal oxyanions pose serious threats to human health and the natural environment due to their high persistence,mobility and toxicity.Effective removal of such pollutants has become a critical issue.So far,adsorption is one of the most promising technologies for purification of polluted water.Therefore,the development of new adsorption materials has attracted extensive attention.Metal-organic frameworks(MOFs)have the advantages of tunable porosity,high specific surface area and abundant functional groups,which are unmatched by traditional adsorbents.In order to solve the serious hazard caused by metal oxyanions to the aquatic environment,several MOFs and their composites were successfully designed and synthesized in this paper.perrhenate(Ⅶ)and vanadate(Ⅴ)were used as the target targets,their adsorption properties were explored,and the corresponding adsorption mechanism was obtained through a series of characterization analyses.The specific results of this study were described as follows:1.Using formic acid as a modulator,the pure BUC-17 crystals with regular hexagonal prism shape were successfully prepared via hydrothermal method.It was proved to be cationic MOFs BUC-17 by X-ray single crystal diffractometer and powder X-ray diffraction.And the adsorption properties of non-radioactive ReO4-which is widely selected as radionuclide TcO4-analog were explored.The experimental results showed that BUC-17 is an efficient adsorbent for ReO4-removal,and the maximum sorption capacity of BUC-17 was 401.9 mg g-1 at 298 K which was appreciably higher than those of most counterpart adsorbents reported previously.In a wide range of pH(4～10)and in the presence of excess co-existing ions(SO42-,NO3-,etc.),BUC-17 could still exhibit excellent removal effect.The SPE column packed with BUC-17 powder could continuously eliminate ReO4-solution,which provided the possibility to accomplish potentially large-scale application.Finally,the possible adsorption mechanism was proposed by XPS analysis and other characterizations.2.In order to further reduce the synthesis cost of MOFs and use them to solve the pollution problems existing in the actual water environment.In this chapter,a green and economical Fe-based MOFs MIL-88A(Fe)was prepared by room-temperature method with less energy consumption,and the adsorption performance of MIL-88A(Fe)for vanadate(Ⅴ)was explored.The results showed that MIL-88A(Fe)is an excellent adsorbent for V(Ⅴ)removal,which could be lower than the limit in drinking water sources in China for the low concentration of Ⅴ in the actual groundwater.The adsorption of Ⅴ(Ⅴ)onto MIL-88A(Fe)was fitted to the pseudo-second-order kinetic model and Langmuir isotherm,and the maximum adsorption capacity was 170.36 mg g-1 at 298 K.And in a wide pH range(311)and the presence of co-existing ions(SO42-,NO3-,Cl-)showed excellent removal effect.At last,its value in industrial applications was explored through packing the SPE column experiment with MIL-88A(Fe)powder for continuous Ⅴ(Ⅴ)removal.This study provided a possibility for the remediation of actual Ⅴ-contaminated groundwater.3.In order to enhance the practical application value and adsorption performance of the material.MIL-88A(Fe)was successfully loaded on absorbent cotton by in situ synthesis method to obtain MIL-88A(Fe)/cotton.This method was modified on the basis of previous work.With the amount of immobilized MIL-88A(Fe)on cotton as high as 100～120 mg g1 it was used as an adsorbent to explore the adsorption performance for vanadate(Ⅴ).The results showed that the maximum adsorption capacity of MIL-88A(Fe)/cotton for Ⅴ(Ⅴ)at 298 K was 269.70 mg g-1,which is much higher than that of MIL-88A(Fe)powder of 170.36 mg g-1.In addition,MIL-88A(Fe)/cotton showed excellent removal effect in a wide pH range(3～11)and in the presence of co-existing ions(SO42-,NO3-,Cl-,etc).The simulated Panzhihua actual wastewater after adsorption could meet the concentration limit of vanadium in drinking water source in China.Finally,the removal effect of MIL88 A(Fe)/cotton in pure water and tap water was compared using a fixed-bed column experiment.This study further promotes the application of MOFs in the field of groundwater remediation in actual Ⅴ-contaminated areas.