Polyvinylidene fluoride-alkali lignin blend: A new candidate for membranes development

• Alkali lignin (AL) proved to be an efficient natural hydrophilizing agent for polyvinylidene fluoride (PVDF). • Hydrophilic PVDF/AL membranes are fabricated using a one-step blending method combined with a non-solvent induced phase separation technique. • The inclusion of AL leads to structural alterations, improved mechanical properties, and enhanced water permeance in the membrane. • PVDF/AL 1:1 membrane demonstrates exceptional performance, effectively retaining oil droplets from a stable oil-in-water submicron emulsion even under high volume reduction factors (VRF). New blend membranes consisting of a tuned ratio of polyvinylidene fluoride (PVDF) and alkali lignin (AL) were studied. Through the use of a green solvent like dimethyl sulfoxide, effective mixing between PVDF and AL was achieved, leading to the development of highly hydrophilic membranes with robust mechanical stability. Characterization methods confirmed the suitability of the blend for membrane preparation and its hydrophilic nature. A key aspect of the strategy involved hydrophilizing PVDF during the preparation process by blending it with AL in the pot. This approach aimed to streamline production by reducing the number of steps compared to post-treatment methods such as grafting or coating. The presence of hydrophobic/hydrophilic groups in the AL structure addressed the challenge of compatibility between PVDF and conventional hydrophilic polymers, enhancing interaction between the components. The resulting hydrophilic material exhibited improved pure water permeance and demonstrated resistance to irreversible fouling. The membrane's ability to process wastewater streams and its resistance to fouling was demonstrated by separating stable and uniform submicron oil-in-water emulsions with high rejection (>99.9 %) up to a volume reduction factor (VRF) of 7.7.