Gd³⁺ Adsorption over Carboxylic- and Amino-Group Dual-Functionalized UiO-66

Abstract

Owing to the growing industrial demand worldwide and limited mineral deposits, the recovery of low-concentration rare earth elements (REEs) from waste sources is being considered, which also helps to reduce water pollution. In this work, the adsorption of gadolinium ions (Gd 3+ ) in aqueous solutions over a functionalized metal−organic framework (MOF), UiO-66, was investigated. Initially, the MOF structure was synthesized solvothermally using a ligand mixture of terephthalic and trimellitic acids to produce coordination-free −COOH groups on the UiO-66 framework. Subsequently, the −COOH group was reacted with ethylenediamine to introduce additional −NH 2 groups onto the MOF. The optimized product (denoted as UiO-66-COOH-ED) showed an equilibrium adsorption capacity of 79 mg/g for Gd 3+ compared with 16 mg/g by pristine UiO-66. This improvement in adsorption by a factor of 4.9 was a consequence of the coordination of Gd 3+ ions with the electron-abundant oxygen and nitrogen atoms of −COOH and −NH 2 groups. A solution pH between 6.0 and 7.0 was found to be the best for Gd 3+ capture, and a selectivity of 75% toward Gd 3+ was observed against other competing alkali or transition metal ions coexisting in the solution. UiO-66-COOH-ED was reusable for at least five cycles without any noticeable deterioration in its adsorption capacity.

Ultra-High Performance of Hyper-Crosslinked Phosphate-Based Polymer for Uranium and Rare Earth Element Adsorption in Aqueous Solution

“…A comparison of the Gd adsorption capacity with other adsorbents is listed in Table . Obviously, the Gd adsorption capacity of HCPP is compared with the recently reported polymer-grafted silica, higher than most of adsorbents. − …”

A Facile One-Pot Strategy to Functionalize Graphene Oxide with Poly(amino-phosphonic Acid) Derived from Wasted Acrylic Fibers for Effective Gd(III) Capture

“…In addition, the selectivity of PAMGO-3 for Gd(III) over them was compared on a percentage basis, which can be estimated by investigating the distribution coefficient value (K D ). 8 The calculation for the K D values were depicted in the SIII. As shown in Figure 5c, the selectivity for Gd(III) uptake is nearly 87%, whereas those of the other rare earth metal ions are all less than 7%.…”

“…Table 2 provides the results of comparative study of PAMGO-3 with other adsorbents for Gd(III) removal from an aqueous solution. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]17,18 Gratifyingly, it can be found that the PAMGO-3 is a good candidate as an adsorbent with the second highest Gd(III) adsorption capacity, which is probably attributed to the large specific surface area, the abundant PAPA functional groups on PAMGO-3, and excellent surface complexation between PAGMO-3 and Gd(IIII) ion during the sorption process. Although the GO/CNt shows a slightly higher Gd(III) uptake, its separation requires a dialysis bag, and the special and more complex procedures for the Gd(III) adsorption in these systems may hinder their practical application.…”

“…The selectivity of Gd­(III) among various REM ions (La 3+ , Nd 3+ , Ce 3+ , Y 3+ , and Eu 3+ ) was also investigated at all testing metals ion concentration of 50 mg/L. In addition, the selectivity of PAMGO-3 for Gd­(III) over them was compared on a percentage basis, which can be estimated by investigating the distribution coefficient value ( K D ) . The calculation for the K D values were depicted in the SIII.…”

“…As an important rare earth metal (REM), gadolinium (Gd) is widely used in many industries such as medical imaging, information, metallurgy, and nuclear. , However, Gd­(III) ions effluents discharged from such industries has aroused wide concern because of its high toxicity, carcinogenicity, and bioaccumulation. − Therefore, the uptake of Gd­(III) from wastewater is essential before disposal, and adsorption is considered to be the most promising method for its recovery from low-concentration sources of Gd­(III), because of the straightforward advantages such as high efficiency, simple operation, and low-cost. − A variety of adsorbents for Gd­(III) removal have been developed accordingly, including porous metal–organic frameworks (MOFs), − silica-based materials, ,, polymers, ,,, carbons, ,, and metal oxides . Among them, graphene oxide, the oxidation product of graphene with abundant oxygen-containing functional groups, high mechanical stability, and large specific surface area has attracted special attention owing to the exhibition of significantly higher potential for such treatment. , For example, Chen et al used GO-based adsorbent to remove Gd­(III) in aqueous solution by surface complexation of Gd­(III) with −COOH functional groups in GO.…”