Scale-up construction of stable multifunctional hydrogel interfaces for large-scale purification of complex oil-water emulsions and oil recovery

Inspired by the multi-level structure of grass clumps in nature, a novel filter with plexiform-structured hydrogel interface was constructed using sepiolite-derived silica nanofiber (SiNF) as the supporter and crosslinked polyvinyl alcohol (cl-PVA) hydrogel as the coating. Experimental test, DFT and MD calculations have confirmed that the addition of SiNF can not only enhance oil-water separation efficiency, but also improve the stability of hydrogel coating. The hydrogel interface with excellent stability and superhydrophilic/underwater superoleophobicity can be manufactured on a large copper mesh (1 m × 1.2 m) to achieve large-scale production. The surface-engineered mesh (named cl-PVA/SiNF@Ag-Cu) can be assembled on a self-designed equipment for continuous purification of emulsion wastewater (processing capacity: 576.00 L/day), achieving a high separation efficiency of 99.7% for complex oily emulsion only under the action of gravity, and can simultaneously recover oils. After being treated under extreme conditions such as strong acid/alkali, high/low temperature (100°C, 200°C, and -18°C), high salt concentration, sandpaper wear, and long-term aging, the surface structure of cl-PVA/SiNF@Ag-Cu filter remains stable. The antifouling, antibacterial, and anticorrosion capabilities of the filter give it the potential for long-term and large-scale purification processes. Planting and breeding experiments have confirmed that purified water is harmless to animals and plants.