Recycling and Reuse of a Sugar-Based Nonionic Surfactant Enabled by Redox-Switchable Precipitation-Dissolution

Due to environmental concerns and resource waste associated with large-scale surfactant discharge, developing efficient recycling and reuse strategies for surfactants is of great importance. Here, a novel switchable Se-containing sugar-based nonionic surfactant, N-dodecylselenosulfonylpropyl gluconamide (NDSeOPGA), is synthesized, which can be reversibly transformed between an ON state (NDSeOPGA, water-soluble) and an OFF state (N-dodecylselenolpropyl gluconamide, NDSePGA, insoluble in both water and oil) upon alternating reactions with H₂O₂ and Na₂SO₃ (or N₂H₄), leading to the formation of ─SeO─ and ─Se─ moieties, respectively. This distinctive property not only enables the surfactant to behave as a conventional one for preparing micellar solutions, emulsions and microemulsions but also enables demulsification and phase separation readily. Moreover, solid NDSePGA can be recovered (over 95%) simply by filtration from solutions or demulsified oil-water systems at room temperature and reused (more than 10 cycles) through reaction with H₂O₂. This work establishes a new paradigm for developing recyclable and reusable intelligent nonionic surfactants with broad implications for green chemistry.