Ultraviolet (UV) filters – which are increasingly found in personal care products, and in additives in plastics and packaging – represent a new class of micropollutants in water.

In this Chinese study, an electro-ultrafiltration (EUF) process was used to separate a representative UV filter, 4-methylbenzylidene camphor (4-MBC), from water, by applying an electric field across the membrane to remove these substances more effectively and minimise fouling.

The researchers investigated modification of the polyvinylidene fluoride (PVDF) membrane, the effects of the electric field on the filtration performance, including resistance and retention, and possible intermediates produced during the EUF process.

The membrane had a rougher surface, and the pore size increased due to the PVDF membrane modifications induced by the electric field. The decrease in contact angle demonstrated the improved hydrophilicity in the PVDF membrane surface after the EUF treatment.

The results clearly indicate that the combination of the electric field with ultrafiltration can increase 4-MBC rejection and reduce filtration resistance.

In addition, the mechanism of 4-MBC degradation in the electrofiltration was examined theoretically, by calculating the frontier electron densities of the 4-MBC molecule.

The C5 atom in the 4-MBC structure was demonstrated to be the most reactive site, which is consistent with the intermediate results identified by gas chromatography–mass spectrometry (GC-MS) analysis.

Desalination, Volume 311, 15 February 2013, Pages 211–220.