We report in this paper the synthesis and characterization of a new class of biopolymer−clay nanocomposites based in the assembling of chitosan to sepiolite, which is a natural magnesium silicate showing a microfibrous texture. CHN and ICP/AES chemical analyses, XRD, FTIR spectroscopy, 13C solid-state NMR, LT-SEM, and thermal analysis have been employed in the characterization of the resulting nanocomposites. The adsorption isotherm of chitosan on sepiolite in acidic medium reveals a significant coverage of the biopolymer at high equilibrium concentration values indicating a multilayer adsorption. The arrangement of chitosan chains on the surface of the silicate microfibers is discussed on the basis of physicochemical data obtained by application of the different techniques. The potentiometric response of this new type of bio-nanocomposites incorporated in carbon paste electrodes toward aqueous salt solutions was employed for the first time as a valuable technique for a rapid assessment of the ion-exchang...