Underwater Superoleophobic and Salt-Tolerant Sodium Alginate/N-Succinyl Chitosan Composite Aerogel for Highly Efficient Oil–Water Separation

Materials for oil–water separation under harsh conditions that exhibit high separation efficiency, salt tolerance, and the capability of high-speed separation and reusability are in great demand. In this study, we introduce a series of sodium alginate (SA)/N-succinyl chitosan (NSCS) composite aerogels with outstanding mechanical strength, robust salt tolerance, and high oil–water separation efficiency. These aerogels were well designed and prepared through a combination of a freeze-drying method, ionic cross-linking, and chemical cross-linking. Due to their remarkable mechanical performance and good flexibility, the composite aerogels could achieve oil–water separation under various harsh conditions. The separation efficiency reached 99% owing to the outstanding underwater superoleophobicity and high-porosity structure of the aerogel. More importantly, the aerogels could preserve their high separation efficiency and underwater superoleophobicity after being soaked in a saturated NaCl solution for 30 days or after 30 separation cycles, which suggested their favorable stability under high-salinity conditions. These results indicated that SA/NSCS aerogels were qualified materials for oil–water separation, which gives us hope for their application in oil–water separation under harsh conditions.