Exchange adsorption of electrolytes on titanium dioxide

Author

Richard Algimantas Slepetys, New Jersey Institute of Technology

Document Type

Thesis

Date of Award

6-30-1957

Degree Name

Master of Science in Chemical Engineering - (M.S.)

Department

Chemical Engineering

First Advisor

George C. Keeffe

Second Advisor

Saul I. Kreps

Third Advisor

C. L. Mantell

Abstract

During the manufacture of titanium dioxide pigments many processing steps are carried out in solutions of electrolytes. Adsorption of these electrolytes strongly affects properties of the finished pigments.

Adsorption of electrolytes Was studied on titania samples prepared by controlled neutralization of titanium tetrachloride solutions with ammonium hydroxide, and one sample of commercial sulfate process rutile titania. In analogy to zirconia--as reported by Kraus and Phillips?^22,23 titania also behaved as a weak anion exchanger in acid solutions and as a weak cation exchanger in basic solutions. Acid or base liberated was approximately equivalent to ions exchanged. On the best sample the exchange capacity was 0.8 milliequivalents per gram for sodium, 1.1 for barium, and 0.7 for sulfate. These values compare with the exchange of 1.4 millimoles of chromate ions per gram of zirconia, reported by Kraus end Phillips.²³

The isotherm data were best correlated by the use of Langmuir's equation because it postulates conditions corresponding to ion exchange; is e., monolayer adsorption on active sites. Since Freundlich's equation does not take into account the saturation of adsorbent with adsorbate, it applied only at lower concentrations. The modified BET equation was good because only low relative saturations were reached.

Hofmeister series essentially applied to about 0.3 N solutions at higher concentrations the order Changed to Ba⁺⁺>Na⁺>Li⁺>K⁺.

As it is typical of true ion exchange, temperature increase (25°C. to 70°C.) had no effect on the capacity of a laboratory-prepared sample. The capacity of the plant titanic sample decreased with temperature, indicating weaker attraction for the ions.

The few articles dealing with adsorption of electrolytes on titanium dioxide disagree about the nature of this adsorption: some investigators have reported strong adsorption of anions with little or no adsorption of cations (Bhatia and Ghosh,³ Kargin and Tolstaya ¹⁸) while others have round the opposite to be true (Verkhovskii³⁶ and coworkers). These discrepancies in the literature can be explained now on. the basis of amphoteric behavior of titania: cation exchange was reported in basic solutions and anion in acid ones.

Recommended Citation

Slepetys, Richard Algimantas, "Exchange adsorption of electrolytes on titanium dioxide" (1957). Theses. 2597.
https://digitalcommons.njit.edu/theses/2597