Estimation of effect of amino acid’s sorption on surface state of ion-exchange membranes using atomic-force microscopy data

Atomic-force microscopy is used to study the surface morphology of different types of cationexchange membranes (MF-4SK homogeneous and MK-40 heterogeneous) in hydrogen and lysine forms. Irregularities of various scales are visualized on the membrane surface. The differences in the surface structure of heterogeneous and homogeneous membranes are found and the features of the effect of sorption of a lysine amino acid on the supramolecular structure of the ion-exchange membranes under study are revealed. The absorption of amino acids by a heterogeneous membrane leads to a decrease in the amount and size of both large defects and nanopores; the surface becomes more homogeneous. In the case of a homogeneous perfluorinated membrane, on the contrary, the sorption of the amino acid makes the surface more heterogeneous due to the formation of supramolecular aggregates.