Preparation And Performance Study Of Polylactic Acid Separation Membrane

With the constant widening applications of membrane separation technology,the demand for membrane material is also increasing.Most of the commercial membrane materials are polysulfones,polyamides,polyesters,and fluoropolymer.However,it would cause environmental pollution and waste of resources when these polymer membrane materials cannot be recycled and reused.As a degradable material,poly(lactic acid)(PLA)has been widely studied due to its good formability,strong plasticity,and good biocompatibility.In this study,PLA was used as the membrane-forming polymer,and the silica(SiO2)/PLA hybrid flat membrane was prepared by non-solvent phase separation(NIPS).Further,the fiber tubular braid-reinforced PLA hollow fiber membrane was prepared by using the tubular braid as reinforcement.The SiO2/PLA hybrid flat membrane was prepared by NIPS with PLA as polymer matrix and hydrophilic nano-SiO2 as additive,and the effect of nano-SiO2 on the structure and properties of hybrid membrane was discussed.The results showed that with the increase of nano-SiO2 content,the cross-sectional finger pore size,surface membrane pore size and porosity first increased and then decreased;The addition of nano-SiO2 improved the crystallinity and thermal stability of the hybrid membrane;The addition of proper amount of nano-SiO2 improved the mechanical properties of the hybrid membrane effectively;With the increase of nano-SiO2 content,the pure water flux(PWF)of hybrid membrane first increased and then decreased,the maximum was 847.5 L·m-2·h-1 and the bovine serum albumin(BSA)rejection first decreased and then increased,the maximum was 95%.Moreover,the hydrophilicity and anti-pollution performance of the hybrid membrane were significantly improved with the water contact angle reduced from 83.7° to 25.6 ° and the flux recovery rate(FRR)increased from 52.6%to 91%.The homogenous(PLA)and heterogeneous(PET)tubular braid-reinforced PLA hollow fiber membranes were prepared by concentric circle method with PLA fiber and PET fiber tubular braids as reinforcements,the PLA as the surface separation layer and different molecular weight polyethylene glycol(PEG)as porogen.The results showed that with the PEG molecular weight increase,the outer surface of the homogenous tubular braid-reinforced(HMR)PLA hollow fiber membrane tended to be dense;With the increase of PEG molecular weight,the PWF first increased and then decreased,the maximum was 135.8 L·m-2·h-1,and the BSA rejection first increased to a certain value and remained stable,the maximum was 96.1%.Moreover,the hydrophilicity and anti-pollution performance of HMR PLA hollow fiber membrane were improved with the FRR increased from 30%to 77.2%.The HMR PLA hollow fiber membrane had excellent mechanical properties with tensile tensile strength of about 15 MPa and bursting strength of about 0.6 MPa.Compared with the heterogeneous tubular braid-reinforced(HTR)PLA hollow fiber membrane,the HMR PLA hollow fiber membrane not only had outstanding axial tensile performance,but also had the good interfacial bonding between the separation layer and the reinforcement,the occurrence of interface slippage or separation during the use of the HTR PLA hollow fiber membrane was avoided.