Preparation Of Functional Materials Of Metal Organic Frameworks And Removal Of Arsenic In Water

Arsenic exists here and there,once the concentration in water exceeds a certain range,it will pose a huge threat to ecology and human health.Therefore,how to efficiently remove arsenic from aqueous solutions is particularly important.However,the treatment effect of single adsorbent on arsenic is limited,especially for As（Ⅲ）.This paper takes advantage of Fe₂O₃ onto the surface of metal-organic framework materials（MOFs）to overcome the shortcomings of easy agglomeration.Three types of functional materials were designed to explore the relationship between material structures and removal of arsenic.The relationship between the internal adsorption mechanism is revealed by XRD,SEM,EDS,FT-IR,the details mainly as follows:（1）Similar deprotonated"phenol"materials,it was studying the treatment of arsenic in aqueous solution by MOF-74,MOF-74@Fe₂O₃,UTSA-74,UTSA-74@Fe₂O₃.The results showed that the removal of As（Ⅲ）forms were all H₂AsO₃^-;The removal of As（Ⅴ）forms on MOF-74,UTSA-74,MOF-74@Fe₂O₃ were H₂AsO₄^-,and UTSA-74@Fe₂O₃ was HAsO₄^2-.After comparison,the series of MOF-74 could remove As（Ⅲ）faster,while UTSA-74 removed As（Ⅴ）faster.They were both in line with pseudo-second-order kinetics.Except for UTSA series materials,the removal of arsenic by other materials conformed to the Langmuir isotherm adsorption model,and it was more inclined to single-layer chemical adsorption.The XRD of the material before and after adsorption was unchanged,indicating that the material had a certain stability.The FT-IR showed that when MOF-74 adsorbed As（Ⅲ）,the vibration peak appeared at 883cm^-1.A vibration peak appeared at a wavenumber of 881 cm^-1 when adsorbed As（Ⅴ）,which may be the formation of the Zn-O-Asbond,which promoted the adsorption experiment.UTSA-74 also formed Zn-O-Asbonds after adsorbing As（Ⅲ）and As（Ⅴ）.The specific positions were at 680 cm^-1 and 660 cm^-1,respectively.When two types of materials were loaded with Fe₂O₃,the vibrational peak of arsenic adsorption shifted slightly.It can be obtained that MOF-74 series are more suitable for quickly removing As（Ⅲ）from the environment,and UTSA-74 series materials are more suitable for As（Ⅴ）.（2）Larger pores and more deprotonated"phenol"materials.It was researched that the effect of Zn₂（olz）and Zn₂（olz）@Fe₂O₃ on As（Ⅴ）.Compared the materials with and without Fe₂O₃ loading,the corresponding instruments and equipment were used to characterize the materials before and after adsorption,to explore the adsorption mechanism.The results showed that the type of materials were mainly used for the removal of As（Ⅴ）,and the form of arsenic adsorbed is HAsO₄^2-.After loading Fe₂O₃,the adsorption time of arsenic by material was shortened,and the q_e increased.Among them,Zn₂（olz）and Zn₂（olz）@Fe₂O₃ adsorbed arsenic and generated Zn-O-As bonds at830 cm^-1 and 862 cm^-1,respectively.When Fe₂O₃ on the surface of Zn₂（olz）,it could improve the adsorption performance of Zn₂（olz）and promote the hydrolysis to achieve the purpose of synergistic removal of As（Ⅴ）.（3）Protonated"phenol"materials,It was realized that the effects of UiO-66（OH）@Fe₂O₃ and UiO-66（OH）₂@Fe₂O₃ on arsenic treatment and used different methods and formulas fitting to reveal the adsorption mechanism to lay the theoretical foundation for the design of new materials.The results showed that the efficiency of removal of As（Ⅴ）by UiO-66（OH）@Fe₂O₃was higher than UiO-66（OH）₂@Fe₂O₃.The removal of As was HAsO₄^2-;UiO-66（OH）₂@Fe₂O₃ was more efficient to removing H₂AsO₃^-.The removal of arsenic satisfied quasi-second-order kinetics and Langmuir isothermal adsorption model,thenΔG<0,indicating that the performance satisfied monolayer chemical adsorption and the reaction proceeded spontaneously.When UiO-66（OH）@Fe₂O₃ adsorbed As（Ⅲ）,a small peak existed at 805 cm^-1;when it adsorbed As（Ⅴ）,a small vibration peak occurred at a wavenumber of 810 cm^-1.It may be the Zr-O-As bond formed after the material adsorbs arsenic.Zr-O-Asbonds also appeared at822 cm^-1 and 828 cm^-1 for UiO-66（OH）₂@Fe₂O₃ after arsenic adsorption.For UiO-66（OH）@Fe₂O₃ materials with low hydroxyl content and high protonation in the material,it is suitable for removing HAsO₄^2-,and UiO-66（OH）₂@Fe₂O₃ is more suitable for removing H₂AsO₃^-.Selecting different materials for different forms of arsenic in the environment can achieve the purpose of efficient pollutant removal.