Preparation Of Metal Organic Framework Composites And Study On Their Treatment Of Dye Wastewater

Metal organic frameworks?MOFs?are a kind of porous three-dimensional network structure formed by metal clusters or metal ions as nodes and organic ligands as connectors through strong chemical bonds.MOFs have great potential in wastewater treatment due to its high porosity,large specific surface area,functional modification and adjustable crystal structure.However,the physical and chemical stability of most MOFs is not high,so its application in photocatalytic,adsorption and other fields is limited.Therefore,the researchers combined MOFs materials with other functional materials,trying to combine the good properties of the two materials,and maximize composite material function through the synergistic effect between them.Therefore,this paper synthesized three kinds of MOFs composite materials,and explored their application in dye wastewater treatment,the main research contents are as follows?1?The Dawson type heteropoly acid H₆P₂W₁₈O₆₂ was introduced in the process of preparing Metal Organic Framework MIL-101?Fe?,the composite H₆P2W 18O62/MIL-101?Fe?was synthesized by encapsulating H₆P2W 18O62 in MIL-101?Fe?framework.The effect of initial concentration of methylene blue,initial pH of solution and the amount of H₆P₂W₁₈O₆₂ on the adsorption performance of Methylene Blue?MB?dye was investigated.The results showed that H₆P₂W₁₈O₆₂/MIL-101?Fe?had the best adsorption effect on methylene blue when the pH of solution was four and the dosage of H₆P₂W₁₈O₆₂ was 0.4 g.At 303 K,the maximum adsorption capacity of H₆P₂W₁₈O₆₂/MIL-101?Fe?for MB was 148.14 mg/g The data of kinetic model and isothermal adsorption model show that the adsorption process is consistent with Langmuir isothermal adsorption model and pseudo second-order kinetics.The results of ?G<0 and ?H>0 in thermodynamic data show that the adsorption process is a spontaneous endothermic process?2?A simple and effective self-assembly technology was used to encapsulate Dawson type heteropoly acid H₆P₂Mo₁₅W₃O₆₂ in Metal Organic Framework MIL-96?Al?resulting in H₆P₂Mo₁₅W₃O₆₂/MIL-96?Al?composite material.The charge on the composite surface was adjusted by introducing heteropolyanion[P₂Mo₁₅W₃O₆₂]6" with high negative charge into MIL-96?Al?.The high negative charge in H₆P₂Mo₁₅W₃O₆₂/MIL-96?Al?composite can effectively adsorb cationic dye through electrostatic action.The adsorption properties of H₆P₂Mo₁₅W₃O₆₂/MIL-96?Al?composite were studied with Methylene Blue?MB?as the target dye.The results showed that pH=4 and the dosage of H₆P₂Mo₁₅W₃O₆₂ was 0.4 g,which was the best condition for H₆P₂Mo₁₅W₃O₆₂/MIL-96?Al?to adsorb methylene blue.At a temperature of 303 K,the maximum adsorption capacity of H₆P₂Mo₁₅W₃O₆₂/MIL-96?Al?on MB is 228.83 mg/g.The kinetic study indicated that the adsorption of MB onto H₆P₂Mo₁₅W₃O₆₂/MIL-96?Al?followed the pseudo second-order model well.The isothermal adsorption curve is combined with Langmuir isothermal adsorption model.The thermodynamic data ?G<0 and ?H<0 indicate that the adsorption is a spontaneous exothermic process?3?The composite photocatalyst Bi₂WO₆/UiO-66 was synthesized by solvothermal method.The morphology of UiO-66 was controlled by acetic acid,and the effect of the ratio of bismuth?Bi?and zirconium?Zr?on the photocatalytic activity of the composite was investigated.Rhodamine B?RhB?was used as the target dye to study the degradation efficiency of Bi₂WO₆/UiO-66 under visible light.The results show that the photocatalytic activity of Bi₂WO₆/UiO-66 is the strongest when the ratio of Bi to Zr is 2:1.The removal rate of RhB by Bi₂WO₆/UiO-66 was 98.5%after 50 min irradiation in visible light.According to the experimental data of free radical capture,the key active substance in photocatalysis is hole?h+?.UV Vis DRS and VB XPS were used to characterize the forbidden band width and valence band position Therefore,the possible photocatalytic mechanism was proposed:the photogenerated electrons?e'?produced by RhB and B12WO6 were excited by visible light transitioned to the LUMO orbitals of UiO-66 to promote the generation of holes?h1?in the Bi₂WO₆ valence band,thus enhancing the photocatalytic activity.