| The membrane separation has been widely used in desalination, food industrial water purification, pharmaceutical chemical production, etc. In recent years, the membrane separation has been showing unique technical advantages and a broad application future in the field of wastewater treatment. However, during the process of wastewater treatment, the membrane fouling, occuring in the film holes and on the surface of the membrane, caused by pollutions such as particles, organic matter and algae, leads to a decline of membrane flux, and decreases the life of the membrane. At present, the commonly used methods of alleviating the membrane fouling could be divided into two categories:chemical cleaning and physical cleaning. Because of a big energy consumption, a high cost of membrane and a relatively long downtime of film equipment, it is necessary to develop a more energy saving, high efficiency and easy operating technology for membrane fouling inhibition.Electrocatalysis can effectively degrade dyes, benzene, pesticides and other organic materials, which could be degraded into small molecule organic matter or completely oxidized into CO2 and water. The combination of membrane separation and electrocatalysis could ease the membrane fouling and realize the effective separation of organic matter and salt at the same time. Therefore, the dye can be concentrated and recycled.This article selects tin oxide as basic electric catalytic with the highest oxygen evolution overpotential. In order to improve its catalytic properties, the tin dioxide sol is doped with rare earth elements:antimony, bismuth and cerium. The sol-gel method is choosed to prepare the electric catalytic ceramic separation membrane. And then, the Al2O3 film coated with modified tin dioxide sol is used to the operation of the high salt organic wastewater treatment experiment and to explore the coupling inhibition mechanism of membrane and electric catalytic for membrane fouling.In this paper, two composite ceramic membranes are made of different materials. The Sb-Bi-SnO2/Al2O3 composite ceramic ultrafiltration membrane, using sol-gel technology, with stannous chloride as precursor, takes tablet Al2O3 membrane as support system. And it is characterized by scanning electron microscopy (SEM), energy dispersive X-ray detector (EDX), X-ray diffraction (XRD) and infrared spectroscopy (FTIR). The results show that the Bi element has been doped into Sb-SnO2 sol successfully, and it has not been doped into SnO2 lattice, existing in the form of BiCIO on the surface of SnO2. The doping of Bi element inhibits the growth of tin dioxide grains, and promotes the transition of SnO2 to rutile phase. The average grain size of SnO2 is 9.3 nm, and the composite membrane with a smooth surface has an average pore diameter of 3 nm.Experiment results of high salt directly orange S dye wastewater treatment show that the process parameters:initial concentration of waste water, salt content, voltage, and the pressure across the membrane have a significant influence on the ceramic membrane separation performance. With the voltage of 1.0 V, transmembrane pressure difference of 0.4 Mpa, NaCl mass fraction of 20%, direct orange S initial concentration of 40 mg/L, solution pH 5, the intercept rate of direct orange S is 99%, indicating a good effect on dye concentration, and the decolorization rate is closed to 100%. According to the low intercept rate of monovalent inorganic salt of NaCl, which is less than 1%, the separation of the dyes and inorganic salt has been effectively realized. Compared with the single membrane separation of direct orange S dye wastewater treatment, the membrane flux of the electro-catalytic membrane increases by 110%.Scanning electron microscopy (SEM), energy dispersive X-ray detector (EDX), X-ray diffraction (XRD), uv-vis diffuse reflection spectrum (UV-Vis DRS) and TOC are used to analysis the alleviating mechanism of the membrane fouling. The phenomenon of concentration polarization is effectively restrained through the combination of membrane separation and electrocatalysis, and the membrane fouling is alleviated or even eliminated by reducing the organic pollutants blocked on the membrane surface and in the film holes.The second one, using sol-gel and scraping slurry methods, is Sb-Ce-SnO2/4A molecular sieve/Al2O3 composite ceramic nanofiltration membrane. Stannous chloride and tablet Al2O3 membrane serve as precursor and support system respectively. The scanning electron microscopy (SEM), energy dispersive X-ray detector (EDX) and X-ray diffraction (XRD) are carried out on the membrane surface to analysis its characterization. The results show that the element of Ce has been successfully doped into Sb-SnO2 sol, and the doping mole ratio is 1%(Sb:Ce:Sn= 10:1:100), achieving a smooth surface membrane without cracks. Doping Ce element, the growth of tin dioxide grain is inhibited, which promotes the transition of SnO2 to rutile phase. The average grain size of SnO2 is 14.2 nm, and the average pore diameter is 2 nm.Aiming at salty direct orange S, the separation performance of the ceramic membrane has been studied. Initial concentration of dye, pH of the waste water, pressure difference across the membrane and voltage has significant effects on the membrane separation performance. Voltage of 1.4 V, transmembrane pressure difference of 0.7 Mpa, NaCl mass fraction of 10%, initial concentration of direct orange S of 20 mg/L, pH 5, the optimum interception rate with 99% for direct orange S could be obtained, and the decolorization rate is closed to 100%. Because of the low monovalent inorganic salt intercept rate of NaCl, which is less than 2%, the separation of the dyes and inorganic salt has been effectively realized. Comparing with single membrane separation, electric catalytic coupling membrane for the treatment of direct orange S dye wastewater, the membrane flux increased by 100%.The scanning electron microscopy (SEM), energy dispersive X-ray detector (EDX), X-ray diffraction (XRD), uv-vis diffuse reflection spectrum (UV-Vis DRS) and TOC is selected to analysis the alleviating mechanism of membrane fouling. The combination of membrane separation and electrocatalysis perfectly restrain the phenomenon of concentration polarization. If there is no higher transmembrane pressure difference applied on the film, the membrane flux can be kept at a high level for a long time. It is of great significance in the process of the automation separation and recycling for salty dye wastewater. |
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