Cross-flow filtration membrane and method for manufacturing the same

摘要

The thickness (e) of the separation layer (4) decreases in the direction of flow (f) of the fluid. The membrane has an inorganic rigid porous support (2) defining at least one circulation channel (3) for the fluid to be treated to circulate in a given direction (f). The surface of the channel is covered with at least one layer (4) for separating the fluid, with a fraction called the permeate passing through the layer and support. The thickness of the separation layer decreases continuously or in steps in the direction of flow. The steps each have the same length in the direction of flow. The channel has a cylindrical or polygonal section. Process for making such a membrane, by covering the surface of the channel with a separation layer of decreasing thickness in the direction of flow of the fluid. The thickness decreases as a function of the gradient of the fluid pressure so the flow of permeate is constant along the channel. The length of each channel is divided into sections of equal length and the surface of each channel is covered with a separation layer by depositing it, starting with the section at the inlet end of the channel and reducing the length for each successive deposit. Alternatively, the porous support is placed vertically and each channel is filled with a suspension of the deposit of the separation layer and the channel is emptied progressively so the deposit time for one end of the channel is greater than that of the other.