Sponge-like Ca-alginate/Lix-84 beads for selective separation of Mo(VI) from some rare earth elements

In this investigation, a novel alginate complex was developed for the selective separation of molybdenum (Mo (VI)) ions from some rare earth elements (REEs). In this regard, alginate as a natural polysaccharide was impregnated and modified with 2-hydroxy-5-nonylacetophenone oxime (Lix-84) and characterized using FT-IR, TGA/DTA and SEM-EDX. The relation between medium acidity, adsorption kinetics, sorbent dose, isotherm models, temperature and Mo(VI) recovery was investigated. It was concluded that the impregnation stage promoted the Mo(VI) separation. The kinetics and isotherm data were well-fitted and matched with the pseudo-firstorder model and Langmuir isotherm model; respectively. The Langmuir maximum adsorption capacity of Mo(VI) reached 72.2 mg/g. The developed material showed excellent separation performance towards Mo ions over the investigated REEs. The desorption and recovery of the loaded Mo(VI) ions were achieved using 1.0 M HCl. Reutilization of Alg/Lix-84 was confirmed up to three adsorption-desorption cycles with no damage of the beads as proved with SEM analysis. The adsorption mechanism of molybdenum onto Alg/Lix-84 was elucidated through FTIR and XPS measurements and was found to be governed by both electrostatic interaction and ion exchange. Therefore, the developed material has a promising potential for the selective separation of molybdenum from REEs-containing solution.

Automated summary

A novel alginate complex was developed for selective separation of molybdenum from rare earth elements, showing excellent adsorption capacity and recovery performance for Mo(VI) ions. The material was characterized and investigated, confirming its potential for selective separation of molybdenum from REEs-containing solutions and demonstrating good reusability over multiple cycles. The adsorption mechanism was elucidated to be governed by electrostatic interaction and ion exchange.