************ The 18th Lab Seminar **************************************

Title : Depth Heterogeneity of Fully Aromatic Polyamide Active Layers in 
Reverse Osmosis and Nanofiltration Membranes
(O. Coronell, B. J. Marinas, and D. G. Cahill, Environ. Sci. Technol., 
2011, 45, 4513-4520)

Speaker : Suzuki Yuichi

Date : Fri. Feb. 22th, 1:30 pm

Abstract :
We studied the depth heterogeneity of fully aromatic polyamide (PA) 
active layer s in commercial reverse osmosis (RO) and nanofiltration (NF) 
membranes by quantifying near-surf ace (i.e., top ~6nm) and volume-
averaged properties of the active layers using X-ray photoelectron 
spectrometry (XP S) and Rutherford backscattering spectrometry (RBS), 
respectively. Some membranes (e.g., ESPA3 RO) had active layers that 
were depth homogeneous with respect to the concentration and pKa 
distribution of carboxylic groups, degree of polymer cross-linking, 
concentration of barium ion probe that associated with ionized carboxylic 
groups, and steric effects experience d by barium ion. Other membranes 
(e.g.,NF9 0 NF) had active layers that were depth heterogeneous with 
respect to the same properties. Our results therefore support the 
existence of both depth-homogeneous and depth-heterogeneous active 
layers. It remains to be assessed whether the depth heterogeneity 
consists of gradually changing properties throughout the active layer 
depth or of distinct sub layers with different properties.


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