RBS Characterization of Arsenic(III) Partitioning from Aqueous Phase into the Active Layers of Thin-Film Composite NF/RO Membranes

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Abstract
The main objective of this study was to apply Rutherford backscattering spectrometry (RBS) for characterizing the partitioning of arsenic(III) from aqueous phase into the active layer of NF/RO membranes. NF/RO membranes with active layer materials including polyamide (PA), PA-polyvinyl alcohol derivative (PVA), and sulfonated-polyethersulfone (SPES) were investigated. The partition coefficient was found to be constant in the investigated As(III) concentration range of 0.005−0.02 M at each pH investigated. The partitioning of As(III) when predominantly present as H3AsO3 (pH 3.5−8.0) was not affected by pH. In contrast, the partition coefficient of As(III) at pH 10.5, when it was predominantly present as H2AsO3-, was found to be approximately 33−49% lower than that of H3AsO3. The partition coefficients of H3AsO3 and H2AsO3- for membranes containing PA in their active layers were within the respective ranges of 6.2−8.1 and 3.6−5.4, while the corresponding values (4.8 and 3.0, respectively) for the membrane with SPES active layer were approximately 30% lower than the average values for the PA membranes.

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