Freeze-Casting Synthesis and Life Cycle Assessment of Closed-Loop Recyclable and High-Flux Polyvinylidene Fluoride Organogels

The development of sustainable materials with simultaneous high permeability and closed-loop recyclability remains a critical challenge in separation technology. Herein, a closed-loop recyclable polyvinylidene difluoride (PVDF) organogel with a high flux for oil-water separation was developed by directional freeze-casting. The effects of solvent, freezing temperature, solid content, and nonsolvent were investigated to obtain a PVDF organogel with well-aligned channels. The highly ordered channels provide an effective way for oil to pass through with low mass transfer resistance. A PVDF organogel with a 5 wt % PVDF content and a freezing temperature of -100 °C demonstrates a separation flux of 385 L m^-2 h^-1 and a half-life of 870 min for an oil-water emulsion. The physically cross-linked network of PVDF organogels enables sustainable closed-loop recycling through a dissolution-gelation process, exhibiting no decline in the separation flux after four recycling cycles. The life cycle assessment indicates that the effect of the freezing temperature on the carbon emissions during the manufacturing stages of PVDF organogels is minor. The carbon emission for the first production of the PVDF organogel is 92.4 kg CO₂e/kg. Sustainable recycling reduces life cycle carbon emissions remarkably, exhibiting a decrease of 59% after 10 recycling cycles. This study provides a strategy to develop low-carbon, high-performance, and sustainable materials for water treatment.