Membranes have been widely used in water filtration processes. Generally, commercial membranes are directly deployed without any pretreatment. The possible interferences introduced by the membrane itself on water analysis have long been overlooked. In this study, we find that five types of commercial membranes (i.e., polycarbonate, polycarbonate track etch, cellulose acetate, polyethersulfone, and polyvinylidene fluoride membranes) release organic particles into the permeates during the membrane filtration process. With and without vacuum pressure applied, the total organic carbon (TOC) of 8-mL membrane permeates range from 0.32 - 5.8 mg L<sup>-1</sup> and 0.64 - 7.2 mg L<sup>-1</sup>, respectively. Scanning electron microscopy demonstrates that the released particles exhibit irregular morphologies and form agglomerates. Raman spectroscopy analysis shows that the vibrational and fluorescence signatures of the released particles from pristine membranes match with those of the particles from the blue separator papers between membranes, indicating that the released particles from pristine membranes originate from the separator papers. The presence of the organic particles in membrane permeate may affect organic compound analysis when commercial membranes are used for water sample pretreatment. Two pretreatment methods - soaking the membrane in 1-L deionized water for 24 hours and washing the membrane for 30 seconds, both reduced the TOC in membrane permeates up to 90%. Filtrating a relatively large sample volume (&gt;100 mL) can also significantly reduce the concentrations of the released organic particles in membrane permeates. This study suggests that we should carefully interpret the results when using commercial membranes for organic compound analysis to avoid the interferences from the organic particles released from the membranes.

Organic particles released from commercial membranes: Origins, implications, and mitigation strategies

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