Renewable and Selective Vermiculite Fixed Bed for the Rare-Earth Dysprosium Recovery

The recovery of dysprosium(III) using a modified phosphorylated chitosan resin by rapid small-scale column testing and its environmental impact assessment

The recent surge in demand for rare earth elements (REEs), essential for advanced technologies, coupled with supply chain challenges, has heightened interest in recovering these metals from alternative sources such as natural saline brine and wastewater streams. Water treatment methods facilitating REE recovery are economically viable and support the transition to a circular economy. In this communication, we report on the recovery of dysprosium(III) (Dy(III)) using a modified phosphorylated chitosan resin (PCs/MB) through rapid small-scale column testing. The optimal recovery conditions were identified, and the associated environmental impacts, from resin fabrication to the recovery process, were assessed. A maximum adsorption capacity (qsat) of 22 mg/g was achieved under optimized conditions, with a Dy(III) feed concentration of 13 mg/L at pH 5.2. Additionally, the use of flow interruption improved the adsorption capacity of Dy(III), bringing it closer to the maximum adsorption capacity observed in batch studies. Complete recovery of Dy(III) from PCs/MB was achieved using 2 L/g of 0.001 M hydrochloric acid over three 12-h desorption cycles. Full recovery of Dy(III) and Nd(III) from a saturated adsorbent was similarly attained within 48 h, with a concentration factor of 1.8x in the first desorption cycle. A preliminary cradle-to-gate life cycle assessment (LCA) of biomass-based PCs/MB production predicted 2.6 times lower energy consumption and substantial reductions in global warming potential (GWP), acidification potential (AP), and eutrophication potential (EP) compared to fossil fuel-derived styrene-based resins. This environmental impact assessment highlights the potential of this method as a sustainable approach for REE recovery.

Capturing Rare-Earth Elements by Synthetic Aluminosilicate MCM-22: Mechanistic Understanding of Yb(III) Capture

We studied the mechanism underlying the solid-phase adsorption of a heavy rare-earth element (HREE, Yb) from acidic solutions employing MCM-22 zeolite, serving as both a layered synthetic clay mimic and a new platform for the mechanistic study of HREE adsorption on aluminosilicate materials. Mechanistic studies revealed that the adsorption of Yb(III) at the surface adsorption site occurs primarily through the electrostatic interaction between the site and Yb(III) species. The dependence of Yb adsorption on the pH of the solution indicated the role of surface charge, and the content of framework Al suggested that the Brønsted acid sites (BAS) are involved in the adsorption of Yb(III) ions, which was further scrutinized by spectroscopic analysis and theoretical calculations. Our findings have illuminated the roles of surface sites in the solid-phase adsorption of HREEs from acidic solutions.

Cerium biosorption onto alginate/vermiculite-based particles functionalized with ionic imprinting: Kinetics, equilibrium, thermodynamic, and reuse studies

Cerium is an essential element for several applications in industry, therefore, recovering it from secondary sources is a promising strategy from an economic and environmental perspective. For this purpose, biosorption is a low-cost and effective alternative. The present work evaluated the recovery of Ce³⁺ from aqueous solutions using alginate/vermiculite-based particles (ALEV) functionalized by ionic imprinting. From the kinetic assays, it was verified that the uptake of Ce³⁺ followed the pseudo-second-order model and was mainly controlled by external diffusion. The Langmuir model better described the equilibrium data, and a maximum biosorption capacity of 0.671 mmol/g at 45 °C was attained. The evaluation of the thermodynamic quantities revealed that the process occurs spontaneously and endothermically. The particles reuse and Ce³⁺ recovery were achieved using 0.1 mol/L HCl or 1.0 mol/L CaCl₂ solutions for up to four cycles of biosorption/desorption. The biosorbent was characterized before and posted Ce³⁺ biosorption to investigate the morphology, textural properties, crystallinity, thermal resistance, composition, and functional groups of the biosorbent.