Preparation Of N-doped TiO₂Ceramic Membranes And Research Of The Treatment Of Wastewater With Salinity By Photocatalysis

As a high efficiency technology, membrane separation has been widely used in many fields such as petrochemical and environmental. However, both the adsorption of organic matter happened on membrane surface and the blockage of channel pore directly caused a decline of membrane flux, reducing the efficiency of membrane separation. The drawbacks of membrane single function as well as its fouling have been the main obstacles for extended application. In order to solve the problem of membrane fouling, membrane has to be cleared from time to time during operation. But, frequent disassemble and cleaning waste a lot of time, affecting the production process. TiO2photo catalysis is regarded as an efficient and environmental benign technology, and has been widely used for photo degradation of various pollutants and inactivation of diverse bacteria in aquatic environments. Over the past decades, intensive investigations have been devoted to developing and improving the photo catalytic activity of TiO2-based photo catalysts. However, the issue concerning on its recycle and reuse is an inherent and significant drawback.TiO2-based ceramic membranes are proposed to provide a possible and beneficial solution to these problems because it provides unique multifunction of membrane separation and photo catalytic degradation concurrently. Dyes, phenols, halides, hydrocarbons, pesticides and other toxic organic pollutants can be completely degraded into water, carbon dioxide and other mineral acids by photocatalysis method. At present, combination of photocatalytic technology and membrane separation has become a research hotspot. In the coupling process, photocatalytic technology can mitigate or eliminate participation of membrane fouling, thus increasing the membrane flux; photocatalytic degradation products can be quickly removed from the reaction system by membrane separation, which breaks the mass transfer equilibrium in the reaction, promotes the reaction process.In this paper, the N-TiO2/SiO2/Al2O3photo catalytic ceramic membranes were prepared by the dip-coating method, which used flat membranes as the carrier and titanium tetraisopropoxide and ethyl silicate as the raw materials. The membrane surface morphology and cross-section composition of the ceramic membrane were characterized by using XRD, SEM and EDAX analysis. The results showed that the prepared membranes possess uniform microstructures with good interconnectivity between grains. The doping of N hindered the growth of crystalline particles and prevented the crystal of TiO2transferred from anatase to rutile. The membranes exhibit average pore size distribution centered at pore diameter8.7nm, excellent chemical stability and higher fluid permeation.The experiment demonstrated that the rejection of Rhodamine B dye was greater than95%and the retention of inorganic salt was less than10%, decolorization rate of wastewater came close to100%. Anti-fouling ability of membrane by filtration concurrent photo catalysis is mainly due to photo catalytic degradation of foulants by UV irradiation. Compared with in dark, the transition in fouling mode from initial pore blocking to cake filtration occurs much slower by UV irradiation on membrane surface. Coupled photo catalytic membrane separation technology in salt dye wastewater treatment process showed good synergistic effect, the permeate flux of the composite membrane under irradiation was increased by100%, compared with the processes of membrane separation without irradiation.