The sorption of uranyl ions on silica-titania mixed-hydroxide gels

SiO₂–TiO₂ mixed hydroxide gels were prepared and the apparent adsorption capacity for Na⁺ (1.30–1.60 mmol/g dry sample) determined by pH titration. The effect of solution pH on the sorption ability of the binary gels was studied. It is found that: (1) the sorption mechanism depends upon the pH, and the two most important factors are the nature of both counter ions in bulk solution and the surface of silica-titania gels, (2) the best pH range for the sorption of uranyl ions is 4–7. The thermodynamic functions were evaluated, suggesting that the reaction is chiefly attributed to physical adsorption rather than chemical one, and the opposite is the case of the reaction.