Superhydrophobic porous polyvinylidene fluoride monolith with outstanding environmental suitability for high-efficient continuous oil/water separation under harsh conditions

Abstract

The actual cleanup of oil spill and chemical leakage is usually implemented in harsh environments, thus oil absorbents possessing excellent environmental suitability are urgently required for high-efficiency oil/water separation. Herein, a novel three-dimensional porous polyvinylidene fluoride (PVDF) monolith with multi-environmental tolerance was facilely prepared via thermally impacted nonsolvent-induced phase separation method. In view of its unique pore structure and low surface energy, the PVDF monolith owned super-hydrophobicity (water contact angle = 154°) and super-oleophilicity (oil contact angle = 0°) without any modification. As an oil absorbent, the porous monolith exhibited outstanding oil/water separation performance for various oils/organic solvents, such as preeminent separation efficiency, high saturation absorption capacity (21.3 g g−1) and rapid absorption speed (reaching saturation state within 15 s). More importantly, the monolith revealed stable and prominent oil/water separation capability under harsh conditions involving intense ultraviolet radiation (72 h), rapidly alternating temperature (−20 to 65 °C), extreme pH, oil-water emulsion, strongly turbulent water, suspended solids (sand and tea leaf). It is worth noting that the monolith was capable of continuously and efficiently separating oil/organic solvent from water by a simple pump-assisted system (soybean oil flux reached 3520 L m−2 h−1 at 0.06 MPa). A small piece of PVDF monolith (0.132 g) was able to continuously separate at least 16,000 times its own weight of soybean oil and could be reused for 5 cycles. Based on the superior environmental suitability and continuous oil/water separation capability, the porous PVDF monolith has a tremendous potential to clean up large-scale oil contaminants in leakage accidents.