Diglycolamic acid modified silica gel for the separation of hazardous trivalent metal ions from aqueous solution

• Synthesis of diglycolamic acid modified silica gel (Si-DGAH).
• Characterization of Si-DGAH.
• Extraction of hazardous Am(III) and Eu(III) in Si-DGAH.
• Kinetics of extraction and isotherms.
• Feasibility of using Si-DGAH for separation.

The surface of the silica gel was modified with diglycolamic acid moieties and the product (Si-DGAH) was characterized by elemental analysis, TG–DTA, 1H and 29Si NMR and scanning electron microscopy (SEM). The adsorption behavior of hazardous americium (III) and europium (III) in Si-DGAH was studied from aqueous nitric acid medium to examine the feasibility using the modified silica for the separation of Am(III) and Eu(III) from aqueous wastes. In this context, the effect of various parameters such as the duration of equilibration, and concentrations of europium, nitric acid, sodium nitrate and diethylenetriaminepentaacetic acid (DTPA) in aqueous phase, on the distribution coefficient (Kd) of Am(III) and Eu(III) was investigated. The distribution coefficient of ∼103 mL/g (>99.9% extraction) was obtained for both Am(III) and Eu(III) at pH 3, and the Kd values decreased with increase in the concentration of nitric acid. Rapid kinetics of extraction in the initial stages of equilibration, followed by the establishment of equilibrium occurred within 30 min. The extraction data were fitted into Langmuir adsorption model and the apparent europium extraction capacity was determined. Europium loading capacity of the sorbent was determined at various feed pH by column method. The study indicated the possibility of using diglycolamic acid-modified silica for the separation of Eu(III) and Am(III) from aqueous wastes.

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