CZ200676A3 - Method of separating thallium from aluminium salts - Google Patents

Abstract

The method of removing the thalium ion from a solution of aluminum salts, in particular aluminum sulphate and alumina-ammonium, wherein the thalium ion present selectively separates the ion exchanger containing a substance selected from the group consisting of thiouronium functional groups, functional groups -SH and functional groups -SH with at least one co-present group -SO.sub.3.nH

Description

The invention relates to a process for the separation or concentration of thallium ions from acidic solutions of aluminum salts, in particular aluminum sulphate and aluminum ammonium alum.

BACKGROUND OF THE INVENTION

Due to the low thallium content, easy hydrolysis of aluminum ions, and often large volumes of treated solutions, thallium based industrial processes do not appear to be suitable post-processes based on precipitation, extraction or electrochemical processes. The use of selective ion exchangers has proved to be a preferred procedure. The separation of thallium from various types of industrial wastewater using ion exchangers containing thiol or thiouronium functional groups is discussed in U.S. Pat. No. 5,296,204. Under appropriate conditions, thallium can be separated from the elements Zn, Cd, Ni, Co,. Pb, Fe, Cu, Sb, As, alkali and caustic earth elements. Similarly, patent EP 0442778. Similarly, Australian patent 634 853 uses an IMAC-GT 73 ion exchanger containing thiol functional groups for thallium sorption. The thallium content of waste water containing Zn, Cd, Ni, Co, Pb, Bi, As can be reduced below 0.1 mg TI / L under appropriate conditions.

An interesting sorbent for the separation of thallium from solutions in the electrolytic production of zinc is disclosed in U.S. Pat. No. 5,419,882. Fine ground manganese dioxide is used to selectively sorb thallium present in the solution to be treated. The disadvantage of the process is the need to use only certain allotropic modifications of manganese dioxide. Separation of the sorbent used from the purified solution also causes difficulties. Amidoxime group transducers (U.S. Pat. No. 3,088,798) or sorbents containing macrocyclic cryptands (U.S. Pat. No. 5,393,892) are also proposed as sorbents for the separation of thallium together with the other elements present in the solution to be treated.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a process for removing thallium ions from solutions of aluminum salts, in particular aluminum sulfate and ammonium alum. SUMMARY OF THE INVENTION The thallium present is selectively separated by an ion exchanger comprising a substance selected from the group consisting of thiouronium functional groups,

the -SH function groups and the -SH function groups with at least one present -SO 3 H group present. Commercially available ion exchangers with a declared -SH function group contain a small, uncontrollable amount of the - SO 3 H groups that get there during inverter synthesis.

The process utilizes sorption of thallium on ion exchangers containing thiol or thiouronium functional groups or derivatives thereof in acidic solutions of aluminum salts, which does not hydrolyze the aluminum ions and the sorption of thallium is selective. The thallium separation process is suitable for both dilute and highly concentrated solutions. The thallium content can be lowered below 0.05 mg TI / L. The elution of the thallium trapped by the sorbent can be carried out with a solution of mineral acid, preferably sulfuric acid, at a concentration of 0.5 - 3 molar. Functional groups of the ion exchanger can be protected against oxidation by setting the appropriate redox potential of the solution, preferably e.g. adding SO _2i soluble sulfites and bisulfites.

EXAMPLE 1 190 g of crude alum ammonium alum was dissolved in a 2000 ml volumetric flask and the pH of the solution was adjusted to 2.0 by addition of sulfuric acid. The initial thallium concentration in the prepared solution was 4.5 mg TI / L.

To protect the functional groups of the converter, the solution also contained 5.0 g of anhydrous Na ₂ SO ₃ . The purified solution was transported by a peristaltic pump to a column containing 12.5 ml of a swollen Amberlite GT 73 ion exchanger. The column column was 135 x 10 mm. The column flow rate was maintained at 50.0 ml / 40 minutes. The penetration curve was measured. The effluent was collected after 50 ml fractions. The thallium content of the individual fractions was determined by anodic dissolution voltammetry with a hanging mercury drop electrode. From the measured values of the penetration curve, 350 ml {i. 28 BV) at a TI content of <0.1 mg TI / L effluent. The initial value of 4.5 mg TI / L was reached on the penetration curve after 1000 ml of the original alum solution flow.

The aluminum ions present were not sorbed by the converter, ♦

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Example 2

Thallium sorption was carried out with the same solution as in Example 1.

For thallium sorption, a Lewatit Monoplus TP 214 transducer containing thiouronium functional groups was used, the ion exchange column containing 12.5 ml of a swollen transducer.

The column flow rate, volume fraction collected and analytical procedures used were the same as described in Example 1. The volume of the purified alum solution when the thallium concentration reached 0.1 mg TI / L effluent was 95 ml (ie only 52% volume). solution of alum cleaned with Amberlite GT 73). The initial thallium concentration (4.5 mg TI Z L) was achieved after flowing 300 ml of purified alum solution.

Example 3

Under laboratory conditions, 6000 ml of a solution of crude aluminum sulfate containing 244 g of anhydrous salt in 1000 ml of solution was prepared. The thallium content of the prepared solution was 28.4 mg of Ti from L. A commercially available Amberlite GT 73 (containing -SH groups) ion exchange resin of 25.0 ml in the swollen sorbent was used for thallium sorption. The transducer was used in H * form. After transfer to the column, the height of the inverter column was 17.5 cm. The purified solution was transported to the column by a peristaltic pump at a rate of 20.0 ml Z12 min. (4 BV Z hours). The effluent was collected in 20 ml fractions and analyzed for thallium content. Thallium penetration in efluentubyl was detected at a flow rate of 1000 ml of purified solution (0.01 mg TI Z L). The initial concentration of T1 in the effluent was reached after a flow of 5000 ml of purified aluminum sulfate solution. The captured thallium was eluted from the transducer with 500 ml of a 3 M sulfuric acid solution at a flow rate of 3 BV per hour.

Example 4

Purification of the aluminum sulfate solution.

The supplied aluminum sulfate solution (DIAMO) was used as the purified solution.

Al ₂ (SO ₄ ) 3 content: 220 g of the anhydrous salt of L.

TI content: 16 mg TI of L.

pH of the solution: 1.37.

About 50 liters of Amberlite GT 73 were used as sorbent.

The inverter column was about 110 cm high.

Flow rate of purified solution through the column: 70 L Z hr (1.55 BV Z hr).

The penetration of TI into the effluent (0.05 mg TI / L) was recorded after 12 hours of experiment at a flow rate of 840 liters of purified solution. The 0.2 mg TI / L in the effluent was achieved after 13 hours of the experiment, when 910 liters of aluminum sulfate solution were purified. After 25 hours of experiment, a thalia concentration in the effluent of 7.5 mg TI / L was recorded after a flow rate of 1750 liters of purified solution.

Example 5

Equilibrium sorption of thallium on Amberlite GT 73 in dependence on sulfuric acid concentration at constant aluminum sulphate concentration.

Table 1 - Effect of sulfuric acid concentration on thallium equilibrium sorption

Equilibrium sorption of thallium on Amberlite GT 73 depending on sulfuric acid concentration Ion exchange weight: 0,2000 g i.e. dry matter : 0.1901 g Total system volume 20,00 ml System initial thallium concentration: 19.76 mg ί Concentration acid M Equal. conc. TI in mg solution Equal. conc. TI in the ion exchanger mg 0.05 11.7. 8.04 0.1 13.68 6.08 0.15 14.6 5.16 0.25 15.2 4.8 0.35 15.48 4.28 0.75 17.04 2.72 1 17.04 2.72 1.5 17.1 2.66

Industrial applicability

Large amounts of aluminum salts, which arise during the elimination of the consequences of hydrometallurgical uranium mining, eg in northern Bohemia, contain small amounts of thallium, which must be removed before their further use. By using the invention, thallium can be removed from solutions of aluminum salts, in particular aluminum sulphate, to the extent that it can subsequently be used for water or other purposes, for example in the construction, glass, leather, paper, zeolite or various types of special ceramics. The process can also be used to treat various types of process water, in particular waste water, containing the elements.

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Claims (1)

A process for the removal of thallium ions from solutions of aluminum salts, in particular aluminum sulphate and ammonium alum, characterized in that the present thallium is selectively separated by ion exchangers containing a substance selected from the group consisting of thiouronium, -SH and functional groups. -SH with at least one -SO 3 H group present at the same time