The most common method in the membrane material forming stage is the phase inversion method (NIPS, non-solvent-induced phase separation). This method typically involves dissolving polymer materials (such as PVDF, PES, etc.) in an organic solvent to create a casting solution, which is then formed by extrusion or coating. The solution is then placed in an aqueous coagulation bath to undergo phase separation, resulting in a membrane layer with a microporous structure. This process determines the membrane's pore size distribution, porosity, and initial flux performance.
The structure conditioning stage usually involves adding pore-forming agents or modifying additives to improve the membrane's hydrophilicity and antifouling properties. Simultaneously, by controlling the coagulation bath temperature, solvent evaporation rate, and stretching process, the mechanical strength and pore structure uniformity of the membrane fibers or sheets can be adjusted. For hollow fiber membranes, a double-layer structure needs to be formed simultaneously during spinning to improve pressure resistance and filtration performance.
The module encapsulation stage requires bundling and fixing the prepared membrane fibers or sheets to form a complete membrane module. Common methods include epoxy resin potting or hot-melt encapsulation, fixing the membrane fibers in end plates or water collection pipes to ensure reliable sealing of the permeate channel. Finally, after cleaning, soaking, and performance testing, the membrane module can be applied to the Membrane bioreactor system to achieve stable solid-liquid separation.