Detachable and hierarchical assemblies for recyclable and highly efficient oil-fouling removal

Large-scale use of detergents to remove oil-fouling in industry continuously generates tremendous amounts of wastewater and thus leads to both economic and environmental problems. To develop recyclable oil-fouling removal strategy is an appealing solution but a challenging task. Herein, a kind of dynamic imine-based surfactant has been constructed by 2-formylbenzenesulfonic acid sodium salt (FBSS) and linear amines (C_nNH₂, n = 6, 7, 8, 10, and 12). Owing to high interfacial activity and strong assembly ability, dynamic FBSS/C₈NH₂ system can remove oil-fouling on multiple substrates for at least 10 cycles, largely reducing the toxicity to ecosystem. At basic pH, the hierarchical assemblies (from vesicle to network and hollow sphere) are formed and boost surfactant molecule enrichment around oil-fouling, leading to highly efficient emulsification. When pH is changed to acidic condition, the surfactant molecules dissociate due to the breaking of imine bonds, and accordingly the emulsion is destroyed and the released oil droplets float to the top layer. After removing the oil-fouling and adjusting the solution back to basic pH, the surfactant assemblies are reconstructed and used for the next oil-fouling cleaning cycle. This study provides a recyclable, efficient and eco-friendly oil-fouling removal approach, satisfying the need of sustainable development.