Adsorption of cationic “gemini” surfactants at the TiO2-solution interface

Adsorption isotherms of cationic pyridinium surfactants at the solid/liquid interface were obtained on aqueous dispersions of titanium dioxide as a function of the electrification features of the adsorbent. The surfactants, prepared in the laboratory, were a symmetric 'gemini-like' dimer (1,1'-bidodecyl-4,4'bipyridinium chloride) and its related simple monomeric salt (1-dodecyl-4-methylpyridinium chloride). X-ray photoelectron spectroscopy analyses were performed both on the bare adsorbent and in the presence of the adsorbates. The XPS regions of Ti 2p, O 1s, N 1s, and C 1s were specifically investigated. The nature of the interactions supporting the adsorption and the molecule orientation/co-area are discussed in the light of the different experimental evidence.