Effect of Different Valence Ions and Coexistence of Cations and Humic Acid on the Separation of Perfluorobutyl Sulfonic Acid by Nanofiltration.

Perfluorobutylsulfonic acid (PFBS) is a biotoxic and persistent pollutant that cannot be effectively removed by conventional drinking water treatment processes. Nanofiltration is an effective method to remove PFBS, which can remove trace small molecular organic pollutants in water. The effects of the coexistence of inorganic ions and cations with humic acid (HA) on the nanofiltration separation of perfluorinated butyl sulfonic acid (PFBS) in nanofiltration membranes at 25°, 0.6M Pa were studied. The experimental results showed that when cations were present in the filtration solution, the removal rate of PFBS by NF membrane ranged from large to small as K+ (92.46%) > Na+ (92.16%) > Ca2+ (91.20%) > Mg2+ (91.07%) > Fe3+ (78.09%). The removal rate of PFBS was PO43− (92.34%) > SO42− (90.15%) when anions were present in the filtered solution. The dominant mechanism of NF membrane removal of PFBS is electrostatic repulsion, while the ionization of cations reduces the negative charge of the membrane surface and PFBS, and the high anions can increase the negative charge of the membrane surface and solute particles, changing the electrostatic repulsion between NF membrane and PFBS. When cations coexisted with HA, the electrostatic repulsion was enhanced, but the concentration polarization generated by the contaminated layer reduced the retention of PFBS. By identifying the leading removal mechanism of PFBS by NF membrane, this study can provide certain theoretical guidance for the selection of NF membrane in the actual water treatment application of NF technology, and the deep purification of drinking water to remove PFBS. [ABSTRACT FROM AUTHOR]

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