High-efficiency foam flotation of bisphenol A using bifunctional MIL-101(Fe) collectors: A structure-performance study on the critical role of alkyl chain length

Bisphenol A (BPA) as a typical endocrine-disrupting chemical has attracted extensive attention due to its persistent pollution and high biotoxicity. Traditional water treatment technologies suffer from low efficiency, high cost and secondary pollution in removing trace BPA. Herein, MIL-101(Fe) was hydrophobically modified with alkyltrimethylammonium bromides (TTAB, CTAB, OTAB) to construct a bifunctional flotation collector, which integrates high adsorption capacity and excellent foam stabilization. The structure-interfacial property-performance relationship was systematically investigated. Results demonstrated that 6 mmol/L OTAB-modified MIL-101(Fe) exhibited optimized amphiphilicity, foamability and adsorption performance, with a maximum BPA adsorption capacity of 185.03 mg/g. Under optimal foam flotation conditions (dosage = 300 mg/L, pH = 4, gas flow = 500 mL/min), the BPA removal efficiency and enrichment ratio reached 93.67% and 13.11, respectively. The material displayed superior selectivity and satisfactory reusability in simulated wastewater. This work provides a promising strategy for highly efficient separation and removal of trace hydrophobic organic pollutants via MOF-based foam flotation.