Preparation Of Ceramic Membrane With Catalytic Ozonation Capability And Its Performance In Water Treatment

Ceramic membrane has attracted plenty of attention for application in watertreatment since its producing cost was greatly reduced in the past decades. But there were still many problems that hindered the further development and application of ceramic membranes, among which post-treatment of retentate and membrane fouling were the most important problems which were mainly ascribed to the incapability of membrane separation process in degradation of organic pollutants. Catalytic ozonation was effective in degradation and mineralization of organic pollutants, but the problems in catalyst running-off and recycling have hindered the wide application of this technology. However, the combination of catalytic ozonation with ceramic membrane separation probably resulted in synergetic effects on enhancing the removal of organic pollutants and reducing the membrane fouling, and simultaneously, avoiding the catalyst running-off.In this work, two kinds of catalytic ceramic membranes were developed and used as key devices in the combined membrane-ozone system. And the main results were as below:Ce-Ti composite ceramic membrane was fabricated with sol-gel method. In the preparation process, the membrane thickness was controlled by adjusting the viscosity of the Ce-Ti mixed sol. The obtained Ce-Ti composite membrane was a typical asymmetric structured membrane, and the Ce-Ti composite layer was not only a separation layer, but also a catalytic layer. Treatment of tetracycline contaminated surface water showed the combined membrane-ozone system with Ce-Ti composite membrane as a key device displayed synergetic effect in the removal of tetracycline and HA. In the continuous mold reaction, when the initial concentration of tetracycline and HA were5mg/L and10mg/L, and the ozone dose was2.5mg/L, the removal rate of tetracycline and HA were about80%and72%, respectively, which were36%and17%higher than the sum of removal rate in single ozonation and membrane separation. The catalytic ozonation process occurred on the surface of Ce-Ti catalytic layer was proved to be the most important reason. The generation of hydroxyl redicals by decomposition of ozone on the surface of Ce-Ti composite catalyst dramatically increased the decomposition of organic pollutants.For further improving the catalytic capability of ceramic membrane and increasing the catalyst loading capacity and effective surface area, hierarchical porous catalytic ceramic membrane (HPCM) was designed and fabricated. The membrane layer was composed by TiO2nanorods assembled macroorous bone structure and mesoporous Ti-Mn catalytic substructure. The membranes were prepared by vaccum dip-coating method with TiC>2nanorods assembled ceramic membrane as supports. The pore structure and catalyst loading capacity were controlled by the viscosity and the particale size of the sol. The results of treatment of Red-3BS contained simulated dye water showed that the usage of HPCM in the combined ozone-membrane system could significantly increase the color and CODcr removal. For the influent with CODcr of195.3mg/L, the removal of color and CODcr were100%and74.3%, respectively, and the permeate flux was higher than that of support membrane at the same condition. The ozonation and catalytic ozonation were found to be the most important reasons for the increase in membrane-fouling reduction and pollutants degradation. Besides, the specific structure of hierarchical porous catalytic membrane also played important role in the combined ozonation-membrane filtration system.On the basis of Ce-Ti composite ultrafiltration membrane and porous Ti-Mn catalyst modified microfiltration membrane, the pilot-scale experiments were designed and performed with micropolluted surface water in Lingshui resevior as a target. The results shown that with Ce-Ti composite ultrafiltration membrane, the membrane fouling was substantially reduced, and the removal of UV254and CODMn were also increased to about80%. For porous Ti-Mn catalyst modified microfiltration membrane in the combined ozonation-membrane filtration system, the membrane fouling was reduced and the back-washing time interval was increased from4h for support to8h for catalytic membrane. Besides, the removal of UV254and CODMn was also increased.In summary, the two types of ceramic membrane with catalytic ozonation capability developed in this work were effective in the process of combined ozone and membrane and resulted in enhancement of the removal rate of organic pollutants and reduction of membrane fouling. We foresee that the process integrated ultrafiltartion and catalytic ozonation using the as-prepared novel membranes with catalytic capability as a key device may open an innovative way for enhanced water purification.