NAMS 2002 Workshop - ICOM 2008

Drinking and Wastewater Applications II – 2
Tuesday July 15, 3:00 PM-3:30 PM, Maui
Adsorption Behavior of Perfluorinated Compounds on Thin-film Composite
Membranes
Y. Kwon (Speaker), Stanford University, Palo Alto, California, USA - kwonyn@stanford.edu
K. Shih, University of Hong Kong, Hong Kong, China
C. Tang, Nanyang Technological University, Singapore
J. Leckie, Stanford University, Palo Alto, California, USA
Perfluorinated compounds (PFCs), emerging contaminants, are globally
distributed due to their persistent and bioaccumulative characteristics. The static
adsorption behavior of PFCs on BW30, NF90, and NF270 membranes and the
effect of the physico-chemical properties of the membranes and structure of
Perfluorinated compounds (PFCs) on interactions between them have been
thoroughly investigated. Two classes of PFCs were evaluated: perfluorosulfonic
acid (PFOS) and perfluoroalkanoic acid with 5, 7, 9, and 11 carbon atoms.
Adsorption of PFCs increased with increasing ionic strength, and decreasing pH
due to decreased electrostatic repulsion between membrane surfaces and PFCs.
The extent of PFOS adsorption on each membrane was higher than the extent of
comparable perfluorononanoic acid (PFNA) adsorption. This is attributed to the
easy migration of PFOS to the membrane surface from aqueous solution
compared with PFNA. The adsorption of PFCs on thin-film composite
membranes strongly depended on the material composing the active layer of the
membranes. NF270 membranes (a piperazine based membrane) showed higher
adsorption of PFOS and PFNA compounds compared with BW30 and NF90
membranes (polyamide based membranes). The BW30 polyamide membrane,
which has a coating layer with aliphatic carbon and hydroxyl groups, had less
interaction with PFOS and PFNA than the NF90 polyamide membrane.
Increased chain length of PFCs increased adsorption.
This research shows that the adsorption behavior of PFCs on commercial thinfilm
composite membranes depends on the electrostatic interaction of both
membranes and PFCs as a function of the applied solution chemistry, the active
layer material of the membranes, and the chain length/functional group of PFCs.