# Facile Separation of Gadolinium(III) from Samarium(III) and Lanthanum(III) by Emulsion Liquid Membrane and the Optimization with the Box‐Behnken Design Method

## TL;DR

This paper presents a new method to efficiently separate the rare earth element gadolinium from samarium and lanthanum using an emulsion liquid membrane and optimization techniques.

## Contribution

The study introduces an optimized emulsion liquid membrane method for separating Gd(III) from Sm(III) and La(III) using the Box-Behnken design.

## Key findings

- Gadolinium was successfully separated with 84.18% efficiency and 89.24% selectivity under optimized conditions.
- Optimal parameters included 4.2% surfactant, 1.4% ligand, 2.3 M internal aqueous concentration, and pH 1 external aqueous phase.
- The method achieved 75.12% recovery and 22.59% purity of gadolinium.

## Abstract

Rare earth elements (REEs) are important topics and receive considerable attention, because of their unique properties, high economic value and are widely applied in various fields. Gadolinium is an REE, commonly used as a contrast agent for magnetic resonance imaging. However, its presence is still mixed with other REE like samarium and lanthanum so it's necessary to separate gadolinium from the mixture. The purpose of this research is to separate gadolinium from samarium and lanthanum and to determine the optimum conditions of various parameters that affect their separation. This separation is carried out by emulsion liquid membrane method using tributyl phosphate extractant, span‐80 and tween‐80 surfactants, kerosene solvent and nitric acid as internal and external phases. Parameter optimization is carried out with Box‐Behnken design (BBD) which can predict the optimum value efficiently. The results are analyzed using visible spectrophotometer with alizarin red sulfonate. In this research, gadolinium is successfully separated from samarium and lanthanum with optimum conditions: surfactant concentration 4.2%, ligand concentration 1.4%, internal aqueous concentration 2.3 M, and external aqueous pH 1. The results obtained gadolinium with a value of %E and %S being 84.18% and 89.24%, while the recovery and purity are 75.12% and 22.59%.

Facile separation of Gd(III) from Sm(III) and La(III) is achieved using an emulsion liquid membrane with tributyl phosphate as extractant. Optimization by Box‐Behnken design reveals critical parameter interactions, enabling improved selectivity and efficiency, highlighting the potential of this approach for rare earth element purification. © 2025 WILEY‐VCH GmbH