This is due to the surface of cotton fibres that was modified by a highly branched aliphatic poly(imine) which concealed the effect due to the presence of Na+.
Moreover, it could be seen that although NaC has no effects on lac dye adsorption on PEI-treated cotton fibres the amount of lac dye adsorbed on the PEI-treated cotton remained high with respect to that on the untreated and the BSA-treated cotton fibres