Benign separation, adsorption, and recovery of rare-earth Yb(III) ions with specific ligand-based composite adsorbent

This study developed a ligand-based composite adsorbent (ComA) for efficient Ytterbium (Yb(III)) adsorption and recovery from waste samples. The organic ligand of 1E,1`E,1``E,1```E (tetrakis(3-carboxysalicylidene)) naphthalene-1,2,5,5-tetramine (TSNT) was synthesized and TSTN was successfully immobilized onto mesoporous silica by a direct immobilization approach. The experiment conditions were optimized based on contact time, solution acidity, initial Pb(II) concentration pH value, and diverse metal salt concentrations. The Europium (Eu(III)) ion was selected from the lanthanides (Ln(III)) series for green and robust adsorption and recovery based on the adsorption, complexation, and selectivity tendency from the standpoint of the pH-dependent factor. The chemical compound of TSTN consisted of O- and N-donor atoms and was able to make stable complexation with Ln(III) ions in optimum conditions due to the open functionality of the ComA. The experimental data revealed that the maximum Yb(III) adsorption was possible at pH 5.0. The presence of other cations and anions did not adversely affect the Yb(III) capturing by the adsorbent. The bonding mechanism suggested that O- and N-donor atoms of TSTN were strongly coordinated to Eu(III) with a 2:1 ratio complexation. The maximum adsorption capacity was determined to be as high as 149.27 mg/g. The extraction of Yb(III) ions from the saturated adsorbent was possible with 0.25 M HNO3. The regenerated adsorbent that remained maintained the high selectivity to Yb(III) ions and exhibited almost the same adsorption capacity as that of the original adsorbent. However, the adsorption efficiency slightly decreased after several cycles. Therefore, the proposed adsorbent offered a cost-effective material and may be considered a viable alternative for effective adsorption and recovery of Yb(III) ions from water samples.

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