Study On Synthesis,Modification And Boron Absorption Properties Of Metal Organic Framework Materials

Boron is a trace element necessary for organisms.Excessive amount will cause organisms to produce toxicological reactions.However,the amount of boron contained in untreated domestic sewage exceeds drinking water standards.In addition,in the process of seawater desalination,there are certain requirements for reducing the boron content in seawater.Therefore,it is of great significance to study an efficient method to reduce and remove the boron content in the solution.In this paper,ZIF-67 metal organic framework material and GO@ZIF-67 composite material was prepared.The two materials were characterized by SEM,XRD,FTIR,Zeta potential and XPS.The adsorption behavior of the two materials for boron in solution was investigated.The effects of adsorption temperature,adsorption time and initial pH value of the solution on the adsorption performance were investigated.1.The ZIF-67 metal organic framework material was successfully prepared by liquid-phase diffusion method and the boron adsorption performance and mechanism by ZIF-67 material were explored.The results showed that the amount of boron adsorbed by the material at 25°C was 26.31 mg·g^-1,and the adsorption process reached equilibrium in about 350 minutes.The adsorption kinetics shows that the adsorption process of boron on materials conforms to the pseudo-first-order kinetic model and is controlled by the diffusion step.Adsorption thermodynamics indicates that the adsorption process is controlled by entropy change and that this process is a spontaneous endothermic process.The adsorption isotherms indicates that the adsorption process conforms to the Langmuir model,indicating that the adsorption process is monolayer adsorption.The study on the mechanism shows that there is physical adsorption during the adsorption of boron by the material,mainly the combination of B（OH）₄^-and the positive charge on the surface of the material;there is chemical adsorption during the adsorption of boron by the material,It is mainly composed of B（OH）₄^-and Co2p1 and Co2p3 adsorption sites.2.The improved Hummer method was used to successfully prepare graphene oxide.Using the prepared graphene oxide as a template,ZIF-67 metal organic framework material was grown on it.GO@ZIF-67 composite material was successfully prepared.And the adsorption properties and mechanism of composite material for boron was explored.The results show that the amount of boron adsorbed by the composite material is as high as 66.65 mg·g^-1 at 25°C,and the amount of boron adsorbed by the composite material is 2.5 times that of ZIF-67 metal organic framework materials.The adsorption process reached equilibrium in about 400 min.The adsorption kinetics shows that the adsorption process of boron by the composite material conforms to the pseudo-first-order kinetic model and is controlled by the diffusion step.Adsorption thermodynamics indicates that the adsorption process is controlled by entropy change and that this process is a spontaneous endothermic process.The adsorption isotherm indicates that the adsorption process conforms to the Freundlich model,indicating that the adsorption process is multimolecular layer adsorption.The study on the mechanism shows that there is physical adsorption during the adsorption process of boron by the composite material.On the one hand,B（OH）₄^-is combined with the positive charge on the surface of the composite material,on the other hand,B（OH）₄^-Chelate with the hydroxyl group on the graphene oxide template in the composite material;the composite material has a chemical adsorption effect on the adsorption process of boron,which is mainly combined by the B（OH）₄^-and Co2p3 adsorption sites.The regeneration performance of composite material is good,and the properties of the material are stable before and after adsorption.After 4 cycles,the adsorption amount of boron is only reduced by 22%.