Design Of Indium-based MOF Membrane And Its Photocatalytic Removal Of Cr(Ⅵ) And Tetracycline From Water

Due to the increasing complexity of the water pollution situation,the current commonly used water treatment methods no longer meet the requirements.Photocatalytic technology is a promising method in the field of water treatment because of its safety,efficiency and environmental friendliness.The key to photocatalytic technology lies in the selection of catalysts,but most of the existing photocatalytic materials are in the form of powder,photocatalytic materials,there are easy to gather,difficult to recover,difficult to separate and other disadvantages,which restrict the development of photocatalytic materials.To address this situation,we use photocatalytic materials loaded onto metal woven webs by in situ growth to form membrane materials to solve the shortcomings of powder photocatalytic materials.In this study,we selected In as the central ion to generate MOF films in situ on metallic copper mesh.This membrane material can reduce Cr（Ⅵ）to Cr（III）on the one hand,which facilitates the recovery of chromium,and on the other hand,it can be a good alternative method for the removal of tetracycline,which is difficult by biological methods.The specific work is as follows:（1）MIL-68（In）-NH₂@Cu membrane was designed and prepared.The morphological structure and photoelectrochemical properties of MIL-68（In）-NH₂@Cu films were systematically characterized by SEM,XRD,FT-IR,BET,XPS and UV-vis DRS.The results show that MIL-68（In）-NH₂@Cu film is a visible-light responsive photocatalytic material with a large number of needle-like microcrystals densely encapsulated on a metallic copper mesh and an optical band gap（Eg）of 2.66 e V.Compared with MIL-68（In）-NH₂,MIL-68（In）-NH₂@Cu film has a higher electron transfer rate and a better electron-hole pair separation efficiency.（2）The performance and mechanism of the photocatalytic reduction of Cr（Ⅵ）in water by MIL-68（In）-NH₂@Cu membrane were investigated.The experiments showed that the removal of Cr（Ⅵ）by MIL-68（In）-NH₂@Cu membrane could reach 98.28%at 300 ml,50mg/L under the condition of p H=2 and 300μL of ethanol trapping agent,and the removal of Cr（Ⅵ）could still reach 96.9%after five replicate tests.In addition,·O₂^-and e^-are the active substances for the photocatalytic reduction of Cr（Ⅵ）,and e-plays the main role.（3）A cyclic reactor for photocatalytic reduction of Cr（Ⅵ）and its resource-based recovery was designed.The reactor consists of a reaction cell,an alkali cell,an acid cell,a connecting assembly and an automatic dosing system,and is based on the full utilization efficiency of the prepared MIL-68（In）-NH₂@Cu membrane for the efficient reduction of Cr（Ⅵ）and its resource-based recovery.Its construction is simple,easy to use,and at the same time can recycle chromium slag without causing secondary pollution to the environment.（4）The performance and mechanism of MIL-68（In）-NH₂@Cu membrane photocatalytic degradation of tetracycline in water were investigated.The test showed that the removal efficiency of MIL-68（In）-NH₂@Cu membrane could reach 78.89%for 300 m L,20 mg/L of tetracycline at p H=8,and the tetracycline removal rate could still reach 75%after five replicate tests.In addition,·O₂^-,h⁺and·OH were the active substances for photocatalytic degradation of tetracycline,and the effect was·O₂^->h⁺>·OH.The MIL-68（In）-NH₂@Cu membrane synthesized by in situ growth overcomes the disadvantages of powder MOFs such as easy aggregation,secondary contamination,difficult separation and recovery,and also improves the removal performance of Cr（Ⅵ）and tetracycline（TC）from water.In addition,MIL-68（In）-NH₂@Cu membrane can unconditionally reduce Cr（Ⅵ）to Cr（III）,which creates conditions for the recovery of chromium.And based on the suitability of membrane materials and the need of resource utilization,a photocatalytic Cr（Ⅵ）reduction cycle reactor was designed to enable the reduction of Cr（Ⅵ）and its resourceful recovery.In summary,this study has searched for a new angle of development of photocatalysis technology and made a contribution to photocatalysis technology in water treatment.Figure[37]Table[4]Reference[126]...