Preparation and catalytic performance of porous ceramic filter membranes by biomimetic structure design

Porous ceramic membranes are widely used in the chemical, energy, environmental and other industries due to their high thermal stable, low thermal conductivity and corrosion resistance performance. The structure of porous ceramic membranes can be applied to gas-solid separation and liquid-solid separation, and the separation efficiency depends on the parameters of the pores (diameter, thickness, surface morphology, etc). In gas-solid separation application, the high-temperature or high-pressure gases with particles is filtered by the porous ceramic membrane, and the particles is captured in the channel structure of ceramic membrane. For example, porous cordierite ceramics are widely used in the manufacture of diesel particulate filter (DPF) in vehicle exhaust treatment, which is usually designed with the wall-flow structure. The filtering efficiency, and filtering precision of high-temperature filtration system are determined by the pore structures of porous ceramic filters. According to the particle diameter (dp), the size of PM can be divided into 4 categories, shown as follows: PM10, dp < 10 μm; fine particles, dp < 2.5 μm; ultrafine particles, dp < 0.10 μm; nanoparticles, dp < 0.05 μm. Many investigations indicate that ultrafine particles are airborne and penetrate deep into the lungs, which is more harmful for human health than larger particles. However, the porous ceramic filter manufactured by the traditional processes could not efficiently separate ultrafine particles, like the separation of nano-particles is a serious trouble when the diameter of particles is much less than the diameter of filter. The filtration performance of a porous ceramic was strongly influenced by the pore structure, such as pore size, porosity, pore channel structure and so on. In view of this, for the sake of improving the filtration performance, modify the surface of cordierite is needed to adjust the pore structure of filter. In our presentation, the innovative porous ceramic surface/interface were prepared by molten salts synthesis (or gaseous growth) methods. The increasing of ceramics pore wall surface roughness is beneficial for finer particles capturing, this process is similar with the cilia of ciliated cells in human respiratory epithelial tissue filter particulate matter in the air. This type porous ceramics microstructure has extensively application in the liquid-solid separation and the gas-solid separation fields. From the perspective of surface free energy changes, it establishes a criterion for distinguishing the surface of traditional porous ceramics and the surface/interface of this type porous ceramics, and it will provide the basic theoretical support for the microstructure controlling of porous ceramic surfaces.