Views: 69 Author: Site Editor Publish Time: 2022-11-11 Origin: Site
The cross-linking reaction can effectively improve the mechanical strength and water resistance of the membrane, but it will sacrifice the water flux to a certain extent. Adding pore-forming particles or performing hydrophilic treatment on the base membrane can increase the water flux to make up for the loss of hydroxyl groups. What is the water flux of PVA membrane separation performance modification?
Here is the content list:
l Basement membrane pretreatment
l Introduce additives
l Add hyperbranched polyester
The matrix membrane was pretreated with polyethylene glycol, and phosphate additives were added to form a membrane with a porous structure. The hydrophilicity of the membrane after pretreatment was significantly improved, and the pure water flux at 0.1 MPa reached 80 L/(m2 · h). Modified PVA membranes were made by adding different kinds of metal salts. Different salts could improve the flux of the membrane, and LiCl had the best modification effect. The metal salt ions are dispersed in the PVA solution, and the dense structure is destroyed to form pores during the film formation process, which weakens the resistance of water passing through, and the water flux can be improved.
The introduction of nanoparticles helps to form nanopores on the surface and inside of the membrane, which increases the actual contact area between the membrane and water, thereby increasing the water flux. A TiO2-modified PVA-poly piperazine amide composite nanofiltration membrane was prepared, and the nano-TiO2 grafted with an acid chloride group improved the hydrophilicity and surface roughness of the composite membrane, thereby increasing the water flux to 106.7 L/(m·2h). PVA solution and gas-phase SiO2 solution to obtain a composite ultrafiltration membrane, and the pure water flux could reach 165 L/(m·2 h). The blend of PVA and SiO2 forms an ultra-thin skin layer on the surface of the paper base, and the addition of SiO2 forms a porous structure on the skin layer, which increases the water flux. The PVA film is modified by introducing polyvinyl ammonium phosphate. The polyvinyl ammonium phosphate itself contains a large number of hydroxyl groups that can bond with polyvinyl alcohol, and it exists in the film relatively stably; The improvement of water flux is of great help. At 1.0 MPa, the water flux can reach 110 L/(m·2 h), and the retention rate of Na2SO4 is 88%.
Hyperbranched polymers are macromolecular polymers with a highly branched structure with many functional groups attached. Its free volume is large, and there are many nano-holes inside the molecule, which can be used in separation membranes to improve the selectivity and permeability of separation membranes. A nanofiltration membrane was prepared with the synthesized hyperbranched polyester and TMC, and the flux was as high as 79.1 L/(m2 h), indicating that the hyperbranched polyester can be well applied to the composite membrane. The hyperbranched modified composite membrane was prepared. With the increase of hyperbranched polymer content, the mechanical properties and water flux of the modified membrane were improved, and the retention of bovine serum albumin (BSA) was also greatly improved, indicating that hyperbranched polyester can be well used in composite membranes; by blending hyperbranched polyester and PVA solution into membranes, the three-dimensional branched structure of hyperbranched polymers can be introduced to improve water flux and selective permeability, while retaining PVA. membrane properties. The hyperbranched polyester was modified to obtain water-soluble hyperbranched polyester, and the PVA composite film was prepared. The thermodynamic and hydrophilic properties of the film were improved. The improvement of water flux is mainly to improve the hydrophilicity of the membrane surface, opening the pores of the membrane to facilitate the rapid passage of water. The above metal ions, nanoparticles, or hyperbranched polyester are all porogen, which destroys the original dense skin layer of the PVA membrane, reducing the resistance of molecules to pass.
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