BSA and lysozyme adsorption on homoionic montmorillonite: Influence of the interlayer cation

•Adsorption of model proteins on homoionic montmorillonite was investigated.•Adsorption constants have been obtained by Langmuir model•Strong influence of interlayer cation on maximum adsorbed amount has been observed.•The adsorption constants do not follow strictly the Hofmeister series.

This study aims to investigate the influence of interlayer cation alkali metal series (Li+, Na+, K+, Rb+, Cs+) and alkali earth metal (Mg2 +, Ca2 +, Ba2 +) on adsorption of model proteins (lysozyme and bovine serum albumin). The localizations of both proteins and their conformational modifications in the interlayer space of the natural clay mineral were studied by X-ray diffraction, transmission electronic microscopy and fluorescence experiments. Based on Langmuir model isotherms, a strong influence of interlayer cation on maximum adsorbed amount and adsorption equilibrium constant has been observed. However the usual kosmotrope/chaotrope classification cannot be used to describe protein adsorption.