Mechanism Research For ZrO₂Dynamic Membrane Formation At The Crossflow Microfiltration

Dynamic membrane (DM) is a kind of hysteromorphous membranes that can be formed on the surface of porous supports such as ceramic, carbon and polymeric membranes. As particles in solution are similar in size to the support pores, the particles are rejected and deposited on the porous support surface to form a dynamic layer, which is characterized by easy preparation, cleaning and operation. Both dynamic layer and support constitute an asymmetrical structure, improving the anti-fouling ability of the support, and overall rejection performances are superior to the support, which has properties of ultrafiltration or microfiltration membranes.Now investigations of the DM mainly focused on experimentally examining the effects of operating conditions such as trans-membrane pressure difference, feed flow rate, cross-flow velocity and feed concentration on permeate process. Most blocking model is used to fitting to the data of the experiments for theoretical research which is found that most process accord with a standard filter model and filter cake filtering model and the further theoretical research remains to be strengthened.At present about dynamic membrane predicting model research is less. The shear-stress diffusion model and concentration polarization model can simply be used to predict permeate flux variations of the DM. Available force balance model only took the unidirectional forces acted on particles into account. There is still lack of a comprehensive model considering the multi-directional forces, especially in the particle deposition and DM formation.On the basis of experimental results,the paper overall begin dynamic membrane formation mechanism of theoretical and experimental research.First of all, through analyzing the experimental phenomenon and rule and theoretically forcing on particle in tube.First, the critical particle size model was developed through analyzing the forces acting on a single particle base on the experimental phenomenon and rule on the directions of axial, radial and circumferential considering the influence on critical particle size of temperature, penetration rate and cross-velocity.Second, with the critical particle size model as the core to build dynamic membrane formation predicting model..Finally, the DM preparation experiments were carried out in a porous tubular carbon support with ZrO2particles as coating materials. The effects of feed temperature, cross-flow velocity and permeate flux on the critical particle sizes were theoretically and experimentally investigated, and mechanisms of the particle deposition were discussed.