This work analyzed the extraction of Zn 2+ , Cd 2+ , and Fe 3+ from aqueous hydrochloride solutions using ionic liquids in the absence of chelating agents. For this purpose, ionic liquids based on 1-(n-alkyl)-3-methylimidazolium and tetraalkylammonium cations and several anions (hexafluorophosphate, bis[(trifluoromethyl)sulfonyl]imide, tetrafluoroborate, and chloride) were tested. It was found that the ionic liquid methyltrioctylammonium chloride, [MTOA + ][Cl -], allowed almost complete removal (extraction percentage > 94) of Zn 2+ , Cd 2+ , and Fe 3+ from the aqueous solutions. Furthermore, efficient selective separation of Zn 2+ /Fe 3+ and Cd 2+ /Fe 3+ was achieved using 1-methyl-3-octylimidazolium tetrafluoroborate, [omim + ][BF 4 -], since high extraction percentages were reached for Zn 2+ and Cd 2+ (extraction percentage > 90) while this parameter was very low for Fe 3+ . These results indicate that the use of ionic liquids as an alternative to traditional extraction agents in liquid/liquid extraction of heavy metal ions is very promising.
The use of ion exchange technology was studied to remove chromium (III) from acidic waste solution by Amberlite IR-120 resin. Batch and column experimental tests were conducted to provide data for theoretical models and verify the system performance of the adsorption process. Results of batch equilibrium tests indicated that Langmuir isotherm describes well the adsorption process, whereas experimental data also provide evidence that, under the present experimental conditions, chromium (III) adsorption by Amberlite IR-120 resin is film-diffusion controlled; on the other hand, the theoretical model used in the present investigation was found to predict reasonably well the ion exchange breakthrough performance.
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