| Membrane separation is widely used in the water treatment due to the advantages of low energy consumption,no phase change and high efficiency.However,the traditional membrane separation process is often suffering from membrane fouling and the trade-off between the selectivity and permeability,which affects the efficiency of and limits the further application of membrane separation technology.To address those problems,carbon nanotubes(CNTs)/ceramic membrane were prepared and coupled with electro-assistance to improve the separation performance in this work.Influence of electro-assistance such as electrostatic effect and electrochemical oxidation were systematically investigated.Besides,the electro-assisted CNTs/ceramic membrane equipment was designed to make a comprehensive evaluation of the electro-assisted membrane separation technology.The results were showed as followed:(1)A CNTs/flat sheet ceramic membrane was prepared by coating CNTs on ceramic substrate and cross-linked by polyvinyl alcohol(PVA)and butanedioic acid.The fabrication of membranes were adjusting by the parameters of CNTs loading,cross-linking time and heat treatment temperature.The CNTs/ceramic membrane exhibits a good permeability and conductivity with the pure water flux is 468 468 L/(m~2·h·bar),the average pore size is 92 nm and the conductivity is 764.8 S/m when the 4 g/m~2 CNTs loading,20 min cross-linking time and heat treatment at 250°C.Besides,the CNTs/ceramic membrane possesses remarkable mechanical stability with no exfoliation of CNTs layer from the CNTs/ceramic membrane in the ultrasonic shock test and the elastic strength and hardness are 2.7±0.3 GPa and 119±20MPa,respectively.(2)The performance of CNTs/ceramic membrane under electro-assistance was investigated by humic acid(HA)separation.The effects of the electrode distance,applied cell voltage and operating pressure on the anti-fouling ability of the membrane were studied.The results implying that the flux loss is decreased as the electrode distance or operating pressure decreases.With the membrane served as cathode and the cell voltage of 2.0 V,the membrane exhibited 49%higher permeate flux and 9%higher HA removal efficiency than that without the electro-assistance.When the membrane served as anode and the cell voltage of 3.0 V,the membrane exhibited 45%higher permeate flux and 22%higher HA removal efficiency than that without the electro-assistance.In addition,it is found that when negative bias is applied on the membrane,the electric repulsion can affect the separation performance and the HA can be decomposed on the positive bias applied membrane surface by electrochemical oxidation.(3)The electro-assisted membrane filtration equipment with a capacity of 1 t/d was self-designed to evaluate the performance of the CNTs/ceramic membrane for sewage water filtration(feed water from a municipal sewage treatment plant in Dalian).Compared to the membrane without electro-assistance,the water production was increased by 21%and the removal efficiencies of TOC and turbidity were improved by 11%and 39%when the CNTs/ceramic membrane applied 2 V cell voltage(membrane as cathode).Furthermore,the electro-assisted CNTs/ceramic membrane filtration can reduce the energy consumption by 14%compared with the CNTs/ceramic membrane filtration without electro-assistance.In summary,the CNTs/ceramic flat sheet membrane exhibits a good electroconductivity and mechanical stability.The electro-assisted CNTs/ceramic flat sheet ultrafiltration membrane can efficiently enhance the antifouling and separation performance.This work offers a feasible approach for membrane fouling mitigation and effluent quality improvement and suggests that the electro-assisted CNTs/ceramic membrane filtration process has great potential in the application of water treatment. |
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