| The membrane separation, which has efficient separation characteristics, is a kind of new technology of emerging rapidly. This technology has been widely used in water treatment, biotechnology, food, pharmaceutical, chemical industry and other fields. However, during the process of membrane separation, organic materials are easy to deposite on the membrane surface, and can block the pores of the membrane, which causes a decline in membrane flux. At present, physical cleaning and chemical cleaning are the commonly used methods, easing the membrane fouling. While, the frequent purging, which increases the operating cost, is not conducive to the production process. Photocatalysis and electrocatalysis called environmentally friendly catalytic oxidation technologies can effectively degrade pesticides, dyes, phenols and other organic substances, which could be mineralized to carbon dioxide and water. And what’s more, the synergic effect of photocatalytic and electrocatalytic technology is benefical for the improvement of catalytic activity. In order to solve the problem of membrane fouling and increase the membrane’s life, this article focuses on the combination of photoelectrocatalysis and membrane separation.In this paper, graphene/Sb-N-TiO2/Sb-SnO2/A-type zeolite/Al2O3 composite ceramic membrane and graphene/Zn-Sb-SnO2/A-type zeolite/Al2O3 composite ceramic membrane have been successfully prepared.The graphene/Sb-N-TiO2/Sb-SnO2/A-type zeolite/Al2O3 composite ceramic membrane was made by scraping slurry, hydrothermal synthesis, sol-gel, and dip-coating methods. And stannous chloride, tetrabutyl titanate and graphene oxide served as precursors. The surface features of this membrane were characterized by SEM, EDX, XPS, XRD, TQ IR, UV-Vis and CV analysises. The results showed that the graphene/Sb-N-TiO2/Sb-SnO2 layer, having an excellent photoelectrocatalytic performance, had been successfully loaded on the composite film surface. The crystalline pattern of SnO2 and TiO2 were rutile and anatase, respectively. And the anatase TiO2 has the best photocatalytic performance. The surface of the composite ceramic membrane with an average pore size of 2 run was smooth and uniform.The voltage, salt content, pressure and other factors were studied during the treatment process of high salinity direct red 31 dye wastewater. With the process of 0.7 MPa, voltage of 1.2 V, light source current of 15A, NaCl content of 4%, solution pH 6, direct red 31 initial concentration in the range of 20～30 mg· L-1, the membrane flux increased by more than 100%, compared with the membrane separation process without photoelectric catalysis(power sources alternate between run 1 h and close 1 h), which helped to ease the membrane fouling in the membrane pores and on the membrane surface. With the direct red 31 dye retention rate of over 99%, inorganic salt NaCl rejection rate of less than 1%, the osmotic solution was colorless and transparent, achieving the separation of salts and organic matters.The graphene/Zn-Sb-SnO2/A-type zeolite/Al2O3 composite ceramic membrane was prepared by scraping slurry, hydrothermal synthesis, sol-gel, and dip-coating methods. Stannous chloride, zinc acetate and graphene oxide served as the precursor. The composite ceramic membrane was characterized by SEM, EDX, XRD, TG, IR, UV-Vis and CV analysises. And the results showed that the graphene/Zn-Sb-SnO2 layer, giving the composite ceramic membrane an excellent photoelectrocatalytic performance, had been successfully loaded on the surface of the membrane. There were SnO2 and ZnO on the film surface. In addition, Zn element had also been doped into SnO2 lattice, existing in the form of ZnSnO3. And this could help to increase the crystal structure defects and enhance the electrocatalytic properties. The surface of the composite ceramic membrane was uniform and smooth. And the average pore size of this composite ceramic membrane was 2 nm.The pressure, voltage, salt content and other factors have a significant influence on the ceramic membrane separation performance. With the process of 0.7 MPa, voltage of 1.2 V, light source current of 15A, NaCl content of 4%, solution pH 7, direct red B initial concentration in the range of 20～30 mg · L-1, the membrane flux increased by more than 100%, compared with the membrane separation process without photoelectric catalysis(power sources alternate between run 1 h and close 1.5 h). Due to the combination of photoelectrocatalysis and membrane separation, the membrane fouling caused by the pollutants, existing in the membrane pores and on the membrane surface, had been greatly alleviated. With the direct red B dye retention rate of more than 99%, inorganic salt NaCl rejection rate of less than 1%, the osmotic solution was colorless and transparent, achieving the separation of salts and organic matters. And this is conducive to the recycling of dyes and salts. |
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