SORPTION–PHOTOMETRIC METHOD FOR DETERMINING TRACES OF TITANIUM IN AN ALCOHOL–WATER MEDIUM

R. D. Glukhovskaya, Yu. L. Lel’chuk, L. L. Skripnova,
E. D. Lukker

(Presented by the scientific seminar of KhTF)

A large number of works are known in the literature devoted to the separation and concentration of titanium using ion-exchange resins. These include, for example, methods for separating titanium from iron, aluminum, chromium, molybdenum, vanadium, tungsten, etc. on cation exchangers [1—8] or anion exchangers [9—11]. We [10, 11] also proposed a method for concentrating titanium and separating it from copper and iron.

All the methods listed use water as the solvent and therefore can be used for separating and concentrating titanium from aqueous solutions, but are unsuitable for determining titanium in the presence of organic solvents.

In view of the fact that one of the objects of our investigation is alcohol, it was necessary to study the influence of this solvent on the sorption of titanium.

In practice, ion exchange is used not only in aqueous solutions but also in aqueous–organic and organic media. A number of works [12—19] are known that demonstrate an increase in the efficiency of ion exchange upon addition of an organic solvent, in particular alcohol. As early as 1941, Wigner [19] showed that the rate of exchange of alkali metals on permutite in aqueous–alcohol solutions increases with increasing alcohol concentration. Materova et al. [12] confirmed this conclusion for the exchange of sodium for barium on wofatite C and obtained a linear dependence of the equilibrium constant on the concentration of ethyl alcohol. Other investigators came to the same conclusions (14, 15, 17).

Panchenkov et al. [13] further found that, under otherwise equal conditions, ethyl alcohol affects the equilibrium constant more strongly than methyl alcohol.

When using an aqueous–alcohol medium, the authors of all these works focused their attention mainly on the exchange of ions of alkali and alkaline-earth metals.

The aim of the present work is to study the sorption of titanium in aqueous–alcohol solutions and to develop a sorption–photometric method for determining traces of titanium in certain model media.

The resin chosen was the cation exchanger KU-2–8 h. A small column [10, 11] packed with a 3—4 cm layer of cation exchanger, 1 cm in diameter, was used for the work. The resin was washed with a 10% solution of hydrochloric acid and then with water.

Equilibrium was studied under both static and dynamic conditions in aqueous and aqueous–alcohol media at various pH values of the solution.

Into flasks with ground-glass stoppers were placed 0.5 g of dry resin charged in the \(H\)-form, a titanium solution with a concentration of \(8.3\cdot10^{-4}\ M\), hydrochloric acid to create the required acidity of the solution, the required amount of ethyl alcohol, and the volume was brought up with water to 50 ml. The flasks were shaken from time to time, and after equilibrium had been reached (after 6 days), titanium was determined in aliquot portions of the solution [10, 11] and the distribution coefficient was calculated [5]. The results are given in Table 1.

As can be seen from the table, the addition of alcohol in all cases increases the efficiency of exchange; however, at very high contents—

Table 1

Distribution coefficient of titanium

—of alcohol (75%) the solution became turbid, and it became impossible to determine titanium. The greatest degree of absorption of titanium by the resin is observed at a solution acidity equal to 0.1 N and an alcohol content of 50%.

Studying sorption under dynamic conditions, we confirmed that titanium is sorbed within the permissible errors from aqueous and water–alcohol solutions (at a water-to-alcohol ratio of 1:1) and at a solution acidity of 0.1 N. The sorbed titanium is completely eluted with 12–15 ml of 2 N HCl.

Verification of the sorption and desorption of titanium was carried out on solutions of pure titanium salts with the addition of 50% alcohol and hydrochloric acid to pH 1. To 10 ml of a water–alcohol solution containing a definite amount of titanium, 1 N HCl was added to pH = 1. The solution was passed through a column with KU-2, previously washed with 0.1 N HCl, at a rate of 2–3 ml per minute. The sorbed titanium was washed with 18 ml of 2 N HCl into a 25 ml volumetric flask. To it were added 1 ml of a 7% solution of ascorbic acid, 2 drops of a 5% solution of copper sulfate, and 5 ml of a 5% solution of diantipyrylmethane in 1 N HCl, and the volume of the solution was brought to the mark with 5 N HCl. The mixture was stirred, and after 30–40 minutes the optical density of the solution was measured on a FEKN-57 with a blue light filter having a transmission maximum of 413 mµ (Table 2).

Table 2

Determination of titanium in salt solutions

The developed procedure was applied for the determination of traces of titanium in model media:

1. 0.5% hydrochloric acid solution;
2. 0.8% aqueous solution of sodium chloride;

1. in a 70% ethyl alcohol solution;
2. in solutions with pH = 5 and pH = 8, containing in 100 ml of distilled water 0.2 g of potassium chloride, 0.1 g of magnesium sulfate, 2.0 g of urea, and 0.05 g of uric acid.

The experiments were carried out both in aqueous and in water–alcohol media. The results of the analysis are summarized in Table 3.

Table 3

Conclusions

A procedure has been developed for the sorption–photometric determination of traces of titanium in certain model media of rubber and latex products enterprises, with a sensitivity of \(10^{-6}\)—\(10^{-7}\%\). The duration of the analysis is 1—1.5 hours. The relative error does not exceed 10%.

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