Synthesis of a green ALG@KLN adsorbent for high-efficient recovery of rare earth elements from aqueous solution

The increasing consumption of rare earth elements (REEs) and disposal of REE-containing wastes pose a threat to resources and environment. Hence, it is important to achieve efficient REEs recovery while use eco-friendly methods. Herein, natural kaolinite is loaded on alginate hydrogel to prepare ALG@KLN composites via a facile one-step cross-link reaction without any hazardous chemicals. The characterizations of ALG@KLN, adsorption isotherms, adsorption kinetics, and desorption were investigated by SEM-EDS, XPS, FT-IR, and Zetapotential. The maximum adsorption capacity of Gd (III), Y (III), Ho (III), and Nd (III) reached 74.40, 84.48, 85.18, and 75.17 mg/g, respectively. The adsorption kinetics and isotherm were well fitted to pseudo-secondorder model and Langmuir model, respectively. The -2 mm diameter ALG@KLN can be easily collected and reused. The presence of Na+, Mg2+, and Al3+ has a minor effect on the adsorption of REEs. The adsorption mechanism is mainly via the chemical chelation of oxygen-containing functional groups and electrostatic interaction on negatively charged surface of ALG@KLN. In addition, the cost of ALG@KLN is as low as -0.041 USD/gram. This work greatly contributes to the development of economical and eco-friendly REE adsorbents, which plays an important role in sustainable development.

Automated summary

In this study, a natural kaolinite loaded onto alginate hydrogel was used to prepare ALG@KLN composites, which achieved efficient recovery of rare earth elements (REEs) using an eco-friendly method. ALG@KLN exhibited high adsorption capacity and reusability, and the adsorption mechanism was mainly through chemical chelation and electrostatic interaction. This research is of great significance for the development of economical and eco-friendly REE adsorbents.