Surfactant-modified hydrous titanium oxide gels

Abstract

In a previous paper [H. Z. Chen and E. Ruckenstein, J. Colloid Interface Sci. 145, 581 (1991)] it was demonstrated that a hydrous oxide gel containing a surfactant can have increased adsorption power compared with one free of surfactant. In addition, it was observed that an optimum surfactant concentration exists for which the adsorption power is maximum. To explain these observations and to characterize the material, the effect of the addition of sodium n-dodecylbenzene sulfonate (SDBS) on the crystallographic structure, morphology, surface chemistry, and mechanical strength of air dried hydrous titanium oxide gels is investigated. The changes with increasing amount of surfactant in the crystallographic structure were followed by X-ray powder diffraction analysis, and the ratios of surface atoms have been determined by X-ray energy-dispersive spectroscopic analysis measurements. Compressive strength measurements provided information on the mechanical strength, and scanning electron microscopy observations provided information on the morphology of the material. Finally, Fourier transform-infrared spectral analysis has allowed identification of the adsorption active sites of the gel. The experiments have shown that there exists an optimum surfactant concentration for which the size of the particles that constitute the gel is the smallest and the surface area and the mechanical strength are the largest. A possible explanation for the existence of an optimum surfactant concentration is suggested.