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18. Simple Removal of Iron by Non-ionic Resin of Macro-reticular Type from Chloride Solution
Kiyoko Imai, Kazuo Watari and Takao Morimoto*
(*Japan Chemical Analysis Center)
Keywords: simple removal, iron, non-ionic resin, chloride solution, hydrochloric acid
Solvent extraction is widely used as a separation or purification method in the fields of chemistry, pharmaceutice and biology. In particular, extraction by ether is often used for the removal of iron prior to radiochemical analysis, because ferric hydroxide is a coprecipitant of many radionuclides in various solutions. However, experimental techniques for solvent extraction are usually rather troublesome and time-consuming. Moreover, use of organic solvents has recently become an issue because of concerns with health effects, waste disposal and fire prevention.
We preciously found that 59Fe, 68Ga, and 198Au as chloro complex anions (MCl4-) were peculiarly adsorbed on non-ionic macro-reticular resin (XAD-7 resin) from concentrated chloride solutions. An adsorption method using a granular resin is more effective and simpler than conventional solvent extraction and other methods. This report deals with the removal of iron by an adsorption method with XAD-7 in the place of solvent extraction by ether.
Effect of agitation time on adsorption of iron was first examined by a batch method, using 0.1g of XAD-7 and 10 ml of 8-9M hydrochloric acid containing 0.1mg of iron spiked with 59Fe. Adsorption reached equilibrium within a 24-hour agitation.
Next, effect of concentration of iron carrier on adsorption was studied using 0.1g of XAD-7 and 10ml of 9M hydrochloric acid solution containing 0.02- 20.0mg of iron with a 24-hour agitation. Adsorption of iron was quantitative on XAD-7 from the solution with iron carrier below 0.1mg, and decreased with increasing iron carrier. From these results, we saw that the adsorption capacity of XAD-7 for iron is about 30mg per 1.0g of dried resin.
Under the same conditions, other elements, such as cobalt, zinc, nickel, were not adsorbed.
Based on the results obtained in the batch experiments, adsorption of iron by column operation was carried out using a column (1.2cm in diameter) containing 3.0g of XAD-7. One hundred ml of 8M hydrochloric acid solution containing 0.1 mg of iron carrier were passed through the column at various flow rates. Iron was adsorbed quantitatively at a flow rate below 1.5ml/min.
The iron adsorbed on the XAD-7 column was easily eluted with 0.1- 0.2M nitric acid solutions. We concluded that adsorption and desorption behaviors of iron on XAD-7 provide similar results as by extraction with ether and back extraction behavior with nitric acid.
The effect of hydrochloric acid concentration on adsorption of iron on XAD-7 and extraction of iron with isopropyl ether is shown in Fig.13. Adsorption and extraction of iron are similar in that they increase with concentration of hydrochloric acid and their maxima appear in 8-10M hydrochloric acid.
From this study, we showed that non-ionic resin (XAD-7) can be used for the effective separation of iron in place of solvent extraction by ether.
