Enhancing of transport parameters and antifouling properties of PVDF membranes modified with Fe3O4 nanoparticles in the process of proteins fractionation

Polyvinylidene fluoride (PVDF) possesses a broad range of applications, including membrane separation used for water and wastewater treatment. However, the natural hydrophobic character of PVDF causes fouling problems which limit the applicability of this material. For that reason, various experimental protocols focused on the PVDF modification are in the spotlight of the recent research. This work focuses on PVDF membranes, modified with iron (II, III) oxide nanoparticles (NPs). The structural and morphological properties of membrane materials have been evaluated using FTIR, SEM, SEM-EDX, AFM, and contact angle (CA) measurements. The modified membrane demonstrated improved hydrophilicity as the contact angle value decreased from 68°± 2° to 51°± 2°. Transport parameters of the obtained membranes were investigated during the dead-end ultrafiltration (UF) process. Compared to the pristine PVDF membrane, the mass transport coefficient of the modified membrane increased twice owing to the ability of Fe3O4 to move in a magnetic field, which allowed to enhance transport parameters and reduce the fouling and concentration polarization phenomena. The modification process improved pure water permeability from 45 L·m−2·h−1·bar−1 for a pristine PVDF membrane to 72 L·m−2·h−1·bar−1 for PVDF with immobilized Fe3O4 NPs. The appropriateness of magnetically active membrane materials in UF of various proteins was also discussed in terms of protein separation and fractionation. The developed magnetoactive PVDF membrane can be used in the process of proteins fractionation owing to its property to prevent the accumulation of lysozyme on the membrane surface at the alkaline medium: the rejection of lysozyme was only 5.3 % at the pH equal to 12.