Fabrication of recoverable plant polyphenol-based surfactants for efficient removal of uranyl ions from skin and cotton fabric

With the increasing demand for uranium in the nuclear industry, the unintended uranium contamination of skin or clothing for individuals involved in nuclear activities has raised public health concerns. Herein, a plant polyphenol-based surfactant (sulfonated bayberry tannin surfactant, SBTS) was fabricated by modifying the hydrophobic groups in the sulfonated bayberry tannin (SBT) structure using a simple Friedel–Crafts alkylation reaction. The surfactant modified with tetradecane chloride showed superior foaming ability and emulsifying properties compared with SBT. The characterization of SBTS by FT-IR spectroscopy confirmed that hydrophobic chains were successfully grafted on SBT molecules via covalent bonds. As expected, SBTS could disperse in water under near-neutral pH condition, and showed good foaming and emulsifying properties. Moreover, the surfactant exhibited effective removal ability for UO₂²⁺-contaminated cotton fabric and skin in a broad application range, reaching a removal rate of 99 % for low amounts of UO₂²⁺, and even above 55 % for high UO₂²⁺ amounts. More importantly, SBTS after reacing with UO₂²⁺ could be easily separated from aqueous systems after standing for 60 min in acidic and neutral conditions, which is a favorable feature to avoid secondary pollution. In vitro cytotoxicity tests suggested that SBTS was much safer than commonly used synthetic surfactants. Based on XPS and FT-IR measurements, we propose a decontamination mechanism mainly originating from the chelation effect between the phenolic hydroxyl group of SBTS and UO₂²⁺. This study highlights the potential of plant tannin surfactants as effective materials for the removal of UO₂²⁺ from skin or clothing of individuals involved in various nuclear-related activities.