A facile strategy to enhance PVDF ultrafiltration membrane performance via self-polymerized polydopamine followed by hydrolysis of ammonium fluotitanate

In this study, to overcome the inherent hydrophobicity and improve the comprehensive performance of polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes, hydrophilic TiO2 particles were utilized to modify PVDF UF membranes. To obtain the strong binding force and homogenous TiO2 distribution on PVDF UF membranes, polydopamine (pDA) as the "bio-glue" was architecturally built between TiO2 and PVDF membranes, and the modification process was facilely designed via self-polymerization of dopamine and subsequent hydrolysis of ammonium fluotitanate. Water contact angle tests proved the significant improvement in the hydrophilicity of PVDF membranes after modification. The morphologies of various membranes before and after modification were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) and the chemical reactions during different modification stages were evaluated by X-ray photoelectron spectroscopy (XPS) tests. It was found that the pDA layer via self-polymerization of dopamine on PVDF membranes could assist TiO2 to lightly and homogeneously bind onto PVDF surface for improving the stability and anti-fouling property of membranes because of the coordination bond (C-O center dot center dot center dot Ti) formed between TiO2 and pDA, and the pore sizes of PVDE. membranes obviously decreased after modifications. The possible mechanisms during modifications were discussed. The comprehensive properties of PVDF membranes after such facile modifications had been greatly enhanced according to the results of water flux, bovine serum albumin (BSA) rejection, antifouling performance, and TiO2 binding performance characterizations. Both the water flux and BSA rejection could be simultaneously improved at the optimized hydrolysis time. Furthermore, the static and dynamic BSA adsorption tests were carried out. Interestingly, the amounts of BSA adsorption onto modified membranes demonstrated the opposite trends for the static and dynamic BSA adsorption tests. The possible reason was clarified based on the competition between the improved hydrophilicity and the adsorption ability of TiO2. Therefore, TiO2 modified PVDF UF membranes developed by this novel strategy have attractive potential for water environmental remediation. (C) 2014 Elsevier B.V. All rights reserved