Preparation And Characterization Of Highly Permeable And Anti-fouling PVDF Ultrafiltration Membran

In recent years,Polyvinylidene fluoride(PVDF)membranes have been widely used in sewage treatment and drinking water purification due to their excellent chemical resistance and high permeability.However,traditional PVDF membranes have some disadvantages such as poor perm-selectivity and poor resistance to foulants,which restrict their further applications.In this work,a deep eutectic solvent was developed as a new blending additive to simultaneously improve the perm-selectivity and antifouling performance of the PVDF membrane,and surface modification of the PVDF membrane was carried out by co-deposition of dopamine and protein to further improve the anti-fouling performance of the membrane.This work mainly focuses on the following:(1)Enhanced perm-selectivity and anti-fouling properties of PVDF ultrafiltration membrane by using deep eutectic solvent(DES)and PEG as novel mixed additivesUrea and zinc chloride were uniformly mixed to form a DES solution under heating and then blended with PEG and PVDF to prepare a casting solution.The PVDF ultrafiltration membrane was prepared by the non-solvent induced phase separation method.The morphology and structure,the perm-selectivity and anti-fouling performance of the PVDF membranes were characterized.By optimizing the addition amount of DES and the molecular weight of PEG in the casting solution,the optimal PVDF ultrafiltration membrane exhibited a super high surface porosity(14.8%)and overall porosity(82.4%),a high water permeation coefficient of 221.4 LMH/bar and a high BSA rejection above 99%,which were far better than the related parameters of the control PVDF membrane without DES.The anti-fouling property of the PVDF membrane was evaluated in a cross-flow ultrafiltration system using BSA as the model foulant.It was found that the anti-fouling performance of the PVDF membrane with DES was improved to a certain extent compared with the control membrane.(2)Antifouling performance of the PVDF membrane modified by co-deposition of bovine hemoglobin(BHb)and dopamine(DOPA)Surface modification of the highly perm-selective PVDF ultrafiltration membrane prepared in the previous work was carried out by the method of co-deposition of BHb and DOPA.Surface properties of the membranes were characterized,and the permselectivity and anti-fouling performance of the membranes were tested.Results demonstrate that BHb could act as a powerful oxidant to accelerate the oxidation and polymerization of DOPA.Moreover,the pristine PVDF ultrafiltration membrane was modified by co-deposition of BHb and DOPA.Compared with the pristine membrane,the hydrophilicity of the modified PVDF ultrafiltration membrane was greatly enhanced,and the membrane surface exhibited less negative charge.Membrane fouling study confirmed that the modified PVDF ultrafiltration membrane achieved a suppressed flux decline rate of 14.3%,which was lower than the pristine membrane(35.4%)without modification.Moreover,the corresponding flux recovery rate of the modified membrane was 88.7%,higher than the values of the pristine membrane(65.4%).In this work,DES worked as multifunctional additives to not only improve the porosity and water permeance of the PVDF membrane,but also simultaneously improve the hydrophilicity and fouling resistance of the PVDF membrane,and it has a great potential to be used in industry.Co-deposition of protein and DOPA on the PVDF membrane surface can not only greatly improve the hydrophilicity and anti-fouling property of the PVDF membrane,but also exhibit the advantages of simple operation and suitable for a variety of substrates,and is expected to be applied for other materials surface modification.