Kaolinite is the primary mineral in ion-adsorption rare earth ores, and improving our understanding of the adsorption state of REEs on kaolinite will benefit efforts to leach REEs from these ores. In order to explain why Eu³⁺ ions exhibit stronger pH-dependent desorption behavior than Lu³⁺, molecular dynamics simulations were applied to investigate the adsorption mechanism of Eu³⁺ and Lu³⁺ on a deprotonated kaolinite (001) surface. The simulation results show that the hydration numbers of Eu³⁺ and Lu³⁺ are comparable, whereas the ordering degree of water molecules around Eu³⁺ is higher than that of Lu³⁺, which is beneficial to the movement of Eu³⁺ to preferentially occupy favorable adsorption sites on the kaolinite surface, following which coordination bonds are formed between Eu³⁺ and the surface. As a result, the desorption rate of Eu³⁺ decreases sharply with the increase in leaching pH, while the desorption rate of Lu³⁺ is only slightly affected by pH.

Tungsten is a crucial strategic metal that plays a significant role in various fields, such as the defense industry, fine chemicals, and the preparation of new materials. During the practice of numerous tungsten smelting processes, a large amount of acidic wastewater containing low concentrations of WO₃ is generated. The adsorption method, known for its simplicity, effectiveness, and ease of operation, represents the most promising approach for tungsten recovery and is vital for the sustainable development of the tungsten industry. In this study, D318 macroporous resin was used as an adsorbent to investigate its effectiveness in adsorbing WO₃ from acidic solutions. Static adsorption experiments revealed that the adsorption capacity of D318 resin for WO₃ was 683 mg·g⁻¹. Kinetic analysis indicated that the controlling step for the adsorption of WO₃ from acidic solutions by D318 resin was intraparticle diffusion. Thermodynamic analysis demonstrated that the adsorption process was endothermic and could occur spontaneously. By fitting the isothermal adsorption equation, it was found that the Langmuir model was more suitable for describing the adsorption process of WO₃ on D318 resin in acidic solutions. The results of dynamic adsorption experiments showed that under optimized conditions, the dynamic adsorption capacity for WO₃ was 529 mg·g⁻¹; when using NaOH as the desorbent for cyclic desorption, the desorption rate for WO₃ was 98.21%. XPS and SEM-EDS testing and analysis confirmed that D318 macroporous resin exhibited excellent adsorption performance for tungsten in acidic solutions.

SmF₃ cannot be reduced to metallic samarium by aluminum due to variable valence states of Sm. This study investigates the reduction products of SmF₃ via an aluminothermic reduction. The effect of molar ratios of Al/SmF₃ on the morphology, elemental distribution, crystal structure, and chemical valence of the samples were investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The thermodynamic results show that it is feasible for SmF₃ reduction by Al to form SmF₂ in 933~1356 K. SmF_2.413, AlF₃, and Sm(AlF)₅ are obtained under the condition of the molar ratio of Al to SmF₃ at 1:3, 2:3, 3:3, 4:3, and 5:3. The samarium of the reduction products exhibits mixed valence states of Sm³⁺ and Sm²⁺, with the ratio δ of F to Sm determined by a(δ) = −0.1794δ + 5.819 (0 ≤ δ ≤ 0.4615). The presence of adsorbed oxygen in the products facilitates the oxidation process from Sm²⁺ to Sm³⁺. These findings may provide a theoretical basis on the development of valence states for other rare earth elements in aluminothermic reduction.

Deep-sea mud is expected to be a novel and potential rare earths resource that supplements terrestrial rare earths, and has received international attention. In this work, the leaching kinetics and behavior of rare earths from deep-sea mud with sulfuric acid was investigated. The results revealed that the rare earth elements (REEs) could be leached out via a sulfuric acid leaching process. A optimized REEs leaching percentage of 82.83% was obtained by using 1.0 mol/L sulfuric acid as leaching agents with a liquid-solid ratio of 4:1 and stirring speed of 250 rpm at 60℃ for 30 min. Under the optimized leaching conditions, the lea­ching kinetics analysis showed that the leaching process was conformed to the shrinking-core model which contained two stages as follows: 1) From 0 min to 4 min, the reaction was controlled through an external diffusion process, and could be described as X = 0.5491·e–4569/RT·t (Ea = 4.569 kJ/mol); 2) From 4 min to 30 min, due to the increase of solid calcium sulfate products, the reaction gradually transformed into an internal diffusion-controlled process, and could be described as 1 – 2/3X – (1 – X)2/3 = 0.0577·e–7083/RT·t (Ea = 7.083 kJ/mol).