Synthesis Of UiO-66-based Materials And Its Enrichment Performance Of U(Ⅵ) And Mechanism

Adsorption is considered as the most promising method for the removal of U（Ⅵ）from wastewater,and it is of great significance to find efficient,rapid and selective U（Ⅵ）separation adsorbents.MOFs are currently attracting tremendous attention due to its high specific surface area,porosity,unsaturated metal coordination and structural diversity.Uio-66 series MOFs have excellent acid resistance,thermal stability and easy functionalization.Therefore,UiO-66-2COOH materials were synthesised with different amounts of acetic acid addition.The increase of acetic acid content could increase the crystallinity order and particle size of the materials.Low concentration acetic acid can increase the specific surface area and porosity.Moreover,the addition of acetic acid increased the number of free carboxyl groups and surface defects,which make UiO-66-2COOHs had more available active sites.The experiment results showed that the adsorption capacity of U（Ⅵ）reached the maximum（172.3mg/g）when the amount of acetic acid addition was 0.1M,which indicated a monolayer adsorption dominated by chemical process.The thermodynamic parameters suggested that the adsorption was a spontaneous and endothermic processes.UiO-66-2COOHs have high selectivity to U（Ⅵ）.Under the condition of pH 3.0,the adsorption process mainly dominated by the of inner-spheres complexation between carbon-containing and oxygen-containing functional groups with U（Ⅵ）.UiO-66-2COOH-0.1M was synthesized by hydrothermal method without organic reagents.The magnetic Fe₃O₄@SiO₂@UiO-66 composite presented high specific surface area,porosity and magnetic separation characteristics.The maximum adsorption capacity of the composite on U（Ⅵ）reached 83.61mg/g at pH 4.0.The isothern showed that the process is homogeneous monolayer adsorption.Ca²⁺、CO₃^2-、SO₄^2-and HA in water have great influence on the adsorption.At low pH,Zr–O clusters and oxygen-containing functional groups adsorb U（Ⅵ）by inner-sphere complexation,while the electrostatic attraction and inner-sphere complexation dominated U（Ⅵ）adsorption under nearly neutral conditions.Due to the fast reaction rate,high adsorption capacity and strong anti-interference ability,the composite have strong potential of practical radioactive wastewater treatment.This paper is expected to provide references for the evaluation of the application of MOFs in radioactive wastewater treatment.