Iron-copper separation in aqueous solution using ion exchange resins

Saha, Shailen (2021) Iron-copper separation in aqueous solution using ion exchange resins. Masters thesis, Memorial University of Newfoundland.

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Abstract

Iron removal is an imperative process in hydrometallurgy processing of non-ferrous metallic ores as iron coexists with these non-ferrous metals in nature; e.g., the common copper mineral chalcopyrite is the sulfide of copper and iron. Precipitation methods and solvent extraction techniques are used to separate iron from copper leach solutions selectively. However, precipitation methods create a plethora of iron precipitates, making it not environment-friendly, and solvent extraction methods have the disadvantages of extractant’s loss and potential fire accidents. Ion exchange resin technology is applied extensively in metal ion recovery or removal at low metal concentrations, e.g., ppm levels. This research studied the efficiency of 24 commercial resins in 14 different functional groups to remove Fe(III) from Cu(II) leach solutions at relatively high metal concentrations. The resin dosage ranged from 0.1 to 0.5 g / mL, to test the effect of resin type and dosage on the separation of iron from simulated copper leach solutions containing 45 g / L Cu(II) and 50 g / L Fe(III) at pH 1.5. The test results showed that resins with the amino-phosphonic functional group and a mixture of phosphonic and sulfonic groups showed the best percentage of Fe(III) removal, while the resin with bis-picolylamine groups obtained more than 92% Cu(II) loading with a moderate amount of Fe(III) removal. Resins with phosphoric, phosphinic acid, and amidoxime functional groups also favoured the loading of Fe(III) over Cu(II) but loaded less percentages of metals. Resins with the carboxylic, quaternary amine, and glucamine groups had the best potential to remove a significant amount of Fe(III), while keeping Cu(II) loading low using multiple adsorption stages. Resins with sulfonic groups, thiol, thiourea, and isothiourium groups did not obtain a notable loading of both metals from the leach solution. However, resins with the iminodiacetic acid group loaded a considerable percentage of both Fe(III) and Cu(II) at the highest resin dosage. After choosing selective resins based on better iron removal and copper recovery performance, single factor optimization tests were conducted by studying the effects of pH, adsorption time, and temperature on metal adsorption. Finally, elution experiments were performed with different acids for the resins having the most selective adsorption of Fe(III).

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