Functionalized Construction Of Cellulose-based Composite Membranes And The Separation Performance For Te(Ⅳ)

In recent years,tellurium and its compounds have been widely used in semiconductors,new energy batteries,optical disks and glass,resulting in considerable amount of tellurium-containing wastewater being discharged into the environmental water system,causing people’s concern to the environment and health.Tellurium is mainly present in solution as tellurite（Ⅳ）and tellurate（Ⅵ）.It has been proved that inorganic tellurium compounds are more toxic than organic tellurium compounds in the environment,especially tellurite（Ⅳ）,which is toxic to most microorganisms at low concentration and can inhibit their metabolism.Moreover,it will cause central nervous system lesions.Therefore,the effective treatment of tellurium-containing wastewater before wastewater reclamation is of great significance for environmental protection and sustainable development of water resources.Nowadays,the methods of tellurium-containing wastewater treatment mainly include biological method,adsorption and membrane separation.Among them,membrane separation technology has attracted wide attention due to its advantages of high efficiency,low energy consumption,no phase change and easy operation.Recently,biomass materials such as cellulose have been increasingly used in the development of separation membrane materials due to their wider sources,higher biodegradability and biocompatibility than synthetic polymers.However,original cellulose membranes suffer from less active sites,inhomogeneous pore size distribution,and low separation efficiency in practical separation.It is difficult to achieve satisfactory separation efficiency for ionic contaminant Te（Ⅳ）.In this work,cellulose acetate,cellulose nanofibers and corn straw cellulose were used to construct cellulose-based composite membrane materials by introducing functional materials and surface modification for Te（Ⅳ）separation.The main contents of this work are as follows:（1）Research on the preparation of MgO@CAM composite membrane and its separation performance for Te（Ⅳ）Magnesium oxide modified cellulose acetate composite membranes（MgO@CAM）with layered porous structure were prepared by hydrothermal,physical blending and phase inversion method for the Te（Ⅳ）separation.The surface morphology,elemental composition and structure of MgO@CAM were analyzed by SEM,EDS,XRD,FT-IR,and XPS and the separation mechanism was studied by the structure and composition changes.The results showed that the separation of Te（Ⅳ）by MgO@CAM was mainly based on the substitution of-OH by Te（Ⅳ）on the membrane.It was more conducive to separation under acidic condition,and the maximum separation efficiency reached 97.6%.In addition,the separation performance of MgO@CAM under the interference of coexisting ions and the antifouling performance were investigated,which provided ideas for the Te（Ⅳ）separation.（2）Research on the preparation of LCUM/D composite membrane and its separation performance for Te（Ⅳ）To improve the Te（Ⅳ）separation efficiency and membrane permeability,composite membranes（LCUM/D）based on layered double hydroxide（LDHs）were prepared using dopamine（DA）as the binder and cellulose nanofibers（CNFs）as the backbone and substrate.The effects of CNFs,LDHs and DA on the Te（Ⅳ）separation efficiency and water permeability were systematically investigated,and the separation mechanism was studied.The results showed that the mechanism of separation of Te（Ⅳ）by LCUM/D was mainly based on ion exchange,electrostatic interaction and hydroxyl substitution.Furthermore,the ratio of LDHs to CNFs was the primary factor affecting the separation efficiency and water permeability,and the appropriate amount of DA enhanced both the separation efficiency and permeability.The separation efficiency of LCUM/D for Te（Ⅳ）could reach 97.18%when the water flux was 59.27 L/（m²·h·bar）.LCUM/D effectively improved the problem of low separation efficiency of cellulose membrane at high flux,and provided a new idea for the application of cellulose membrane in the removal of ionic contaminant from water.（3）Research on the preparation of TSNTCM composite membrane and its separation performance for Te（Ⅳ）To further improve the Te（Ⅳ）separation efficiency and reusability of cellulose composite membranes,NH₂-MIL-125 and surface modified synergistically modulated regenerated cellulose composite membranes（TSNTCM）were prepared by co-blending,phase inversion and interfacial polymerization using corn straw as raw material.The separation mechanism and the effects of NH₂-MIL-125 and separation layer on the separation efficiency and water flux were investigated.The results showed that NH₂-MIL-125 and the separation layer effectively enhanced the physical and chemical interaction of TSNTCM with a maximum Te（Ⅳ）rejection of 99.16%.In addition,TSNTCM exhibited a rejection of more than 90%with the present of multiple co-existing ions and could still achieve a rejection of 90.46%after 6 times of consecutive separation/desorption,showing excellent selectivity and reusability.Moreover,the results of water flux showed that NH₂-MIL-125 significantly compensated for the flux reduction due to interfacial polymerization.Furthermore,TSNTCM exhibited excellent anti-fouling properties,providing a new strategy for the high-value utilization of agricultural waste and the design of cellulose-based composite membranes and their application in wastewater reclamation.