The selective extraction of dispersed metallic germanium (Ge(IV)) from wastewater offers significant economic and environmental benefits. In this work, a novel Zr-based metal-organic framework composites (UIO-66-NMG) was prepared for enhanced selective uptake of Ge(IV) by N-methyl-D-glucosamine ligand rich of several o-hydroxyl groups. The capture performance of UIO-66-NMG on Ge(IV) was superior at pH 9. In the case of coexistence of multiple metal ions Ga(III), Zn(II), Ni(II), Co(II), Mn(II) and Cr(III), the selectivity coefficients (K) of Ge (IV) to these ions by UIO-66-NMG were all higher than 20, demonstrating significant capture selectivity and salt resistance. The adsorption kinetics and isotherms implied that the separation of Ge(IV) was better described by pseudo-second-order model and Langmuir model than the other kinetic and isotherms models. The fitting results of the EDR-IDR and AOAS mass transfer models suggested that the external mass transfer efficiency of Ge(IV) in UIO-66-NMG was significantly higher than that of internal mass transfer, and chemical adsorption dominated the entire process. Moreover, UIO-66-NMG showed good stability and reproducibility after five adsorptiondesorption cycles with a high Ge(IV)capture rate of 89.18%. Density functional theory calculations (DFT) analyses indicated that the strong interactions between UIO-66-NMG and Ge(IV) ions could be attributed to the ionexchange reaction of GeO(OH)3- with the neighboring hydroxyl group and chelation of -NH. This work showed the application value of organic ligands to improve the MOFs in the field of selective capture of dispersed metallic ions.

Weathered rare earth ores are an important strategic mineral resource in China, and they are the primary source of medium and heavy rare earths (MHRE). The efficient recovery of MHRE is of great significance from an industrial standpoint. In this study, fulvic acid (FA) was employed as a precipitant to investigate the precipitation of rare earth (RE). The results indicate that the precipitation rates (w) of RE range from 89.69 wt% to 99.86 wt% with the pH of 9, the molar ratio of 2, and the temperature of 40 degrees C, except for Lu3+, the w reaches 97.33 wt% with the pH of 9, the molar ratio of 3, and the temperature of 25 C. The w of RE in the ammonium acetate rare earth leaching solution ranges from 95.99 wt% to 98.54 wt%, with the MH/L of the rare earth distribution after precipitation increasing from 0.77 to 0.80. The use of FA as a precipitant is demonstrated to yield effective precipitation of RE, particularly those of MHRE. FA complexes with RE3+, where deprotonation of COO- increases the surface electron density of oxygen atoms, creating additional active sites for electron-deficient RE3+. The mechanism provides a theoretical basis for using carboxylic acid compounds as new precipitants. Further, a novel technology for FA complexation precipitation of RE from lignite extract is proposed. (c) 2025 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.

The removing of fine inclusions in molten metals plays a significant role on improving quality of metal materials. In this work, the interception behavior of Al2O3 ceramic foam filter (Al2O3 CFF) for fine inclusions in molten metals under supergravity field was accessed through both molten metal filtration and water simulation. The analysis via response surface methodology (RSM) in water simulation presented that mere filtration in deep bed of Al2O3 CFF can not trap the inclusions completely, and the increase in liquid volume elevates the separation efficiency. Combined with molten metal filtration of primary aluminum and galvanized zinc, the observation showed that the aggregation between particles and intermetallics and the cake layer wrap for inclusions on the surface of Al2O3 CFF both extremely promote the separation efficiency. The inclusion particles below 20 mu m in molten metals was almost removed completely by using Al2O3 CFF of H = 20 mm and P = 130 ppi or 170 ppi under supergravity field.

Weathered crust elution-deposited rare earth ores (WCE-REOs) are the primary global source of medium and heavy rare earth elements (M/HREEs). The recent discovery of high-altitude (1500–2500 m) WCE-REOs in southern Yunnan Province, China, presents new opportunities for the development of M/HREE resources. This study investigates the enrichment and fractionation mechanisms of rare earth elements (REEs) in these deposits through a systematic analysis of three representative weathering profiles associated with the Lincang granite batholith. The analytical results indicate that the profiles consist mainly of clay minerals (kaolinite, halloysite, illite, minor montmorillonite) and iron oxides, with high SiO2 (64.10–74.40 wt.%) and Al2O3 (15.50–20.20 wt.%) and low CaO/MgO—typical of weathered REE deposits. The total REE contents (238.12–1545.53 ppm) show distinct fractionation: LREE-enriched upper layers and HREE-enriched deeper zones. Sequential extraction revealed that the REEs in the Lincang granite weathering profiles predominantly occur in ion-exchangeable, residual, and iron-manganese oxide-bound states (>95% total REEs). Ion-exchangeable REEs showed depth-dependent enrichment (peaking at 819.96 ppm), while iron-manganese oxides exhibited a strong REE affinity (up to 47% total REEs), with amorphous phases that were preferentially enriched in Ce (partitioning >80%). Fissure systems exerted critical control over the redistribution of elements, particularly REEs.

This study explores the use of alkaline earth metal carboxylates as sustainable alternatives to conventional ammonium-based lixiviants for the eco-friendly extraction of weathered crust elution-deposited rare earth ores. We investigated the impact of lixiviant concentration, pH, and leaching temperature on the extraction efficiency of rare earths and aluminum, utilizing magnesium acetate and calcium acetate alongside traditional ammonium salts. The results showed that a leaching rate exceeding 91% for rare earths was achieved, while aluminum leaching remained under 30% at 298 K, pH 6.5–7.0, and 0.20 mol/L concentration of carboxylates. Notably, magnesium acetate was particularly effective in extracting medium and heavy rare earths at lower concentrations. A double electric layer model was used to clarify the leaching mechanism, indicating that zeta potential and double electric layer thickness were significantly affected by the concentration and pH of the leaching agents. Overall, this method presents an efficient approach for low-impurity extraction, offering valuable insights for sustainable mineral resource development.

This paper investigates the rare earth (RE) leaching process of weathered crust leached rare earth ores (WCE-DREOs) with different ore particle sizes. Ore particles were categorized into seven distinct size ranges: −0.106 mm, +0.106 mm to −0.15 mm, +0.15 mm to −0.25 mm, +0.25 mm to −0.85 mm and +0.85 mm. The study examined the correlation between the thickness of the electrical double layer (EDL) and the RE content, as well as the swelling ratio of clay minerals. The findings demonstrated that the order of RE content with respect to varying particle sizes was as follows: C−0.106>C+0.106~−0.15>C+0.15~−0.25>C+0.25~−0.85>C+0.85 (C represents RE content). The RE content of full particle size was found to be 7.93 mg/g, with the particle size −0.106 mm exhibiting the highest RE content of 2.02 mg/g. In the fitting of the relationship between the RE content and the thickness of the EDL, it was observed that the particle size −0.106 mm exhibited a consistent correlation with the Logistic function y=2.03−0.43/(1+1.49x172.39). In the study of the swelling performance of the WCE-DREOs, the order of the swelling ratio of ore samples in different particle sizes was δ−0.106>δ+0.106~−0.15>δ+0.15~−0.25>δ+0.25~−0.85>δ+0.85(δ represents the swelling ratio), and the swelling ratio was 3.34%, 2.92%, 2.33%, 1.55% and 0.01%, respectively. In the fitting of the relationship between the swelling ratio of clay minerals and the thickness of the EDL, it was observed that a particle size of −0.106 mm corresponded to the exponential function y=3.65−99.89·exp⁡−x/0.12. The results of the study provide useful assistance in the mining of the WCE-DREOs.

In order to reveal the influence of ammonium salts on the rare earth leaching process of weathered crust elution-deposited rare earth ores, ammonium acetate, ammonium chloride, and ammonium sulfate were used as leaching agents. The effects of the leaching agent on the rare earth leaching efficiency and the expansion, dissolution, and transformation behavior of clay minerals in the rare earth leaching process were studied. The results showed that rare earth leaching efficiency followed the order ammonium acetate > ammonium chloride > ammonium sulfate, with values of 90.60%, 85.96%, and 84.12%, respectively. The swelling ratio of clay mineral followed the order ammonium acetate < ammonium chloride < ammonium sulfate; the clay mineral swelling ratio was 2.09% when ammonium acetate was the leaching agent. Thermogravimetric analysis showed that the interlayer water content was the lowest when ammonium acetate was used as the leaching agent. Under the conditions of different leaching agents, the clay mineral contents changed from illite and halloysite to smectite and kaolinite. When ammonium acetate was used as the leaching agent, the relative conversion of illite was 1.49%, and that of smectite was only 0.17%. SEM analysis showed that the clay minerals expanded and dissolved obviously when ammonium chloride and ammonium sulfate were used as the leaching agents. Meanwhile, the clay mineral layered structure was relatively complete when ammonium acetate was used as the leaching agent. Therefore, when ammonium acetate was used as the leaching agent, it had the least effect on the swelling, dissolution, and transformation of clay minerals. This can provide a theoretical basis for the safe production of weathered crust elution-deposited rare earth ore, and for the screening of green and efficient leaching agents.

为了缓解风化壳淋积型稀土矿浸取过程存在的浸取周期长、浸出剂用量大和稀土拖尾等问题,以非离子型表面活性剂为助浸剂,氯化镁为浸出剂,对稀土浸出过程进行研究,研究复配浸出剂溶液性质,分析浸矿前后矿物粒径分布,探讨表面活性剂的促渗机理.研究结果显示,加入表面活性剂后,稀土浸出率提高,渗透速度加快,溶液的表面张力和接触角均减小,黏度增大,矿物颗粒的中值粒径明显减小,矿物表面Zeta电位增大,其中加入吐温40后稀土浸出率提高至86.38％,表面张力减小19.00％,接触角减小53.19％,溶液黏度减小4.29％,溶液性质变化最大.加入表面活性剂后可使溶液更容易润湿矿物,进入孔隙的阻力变小,扩散层厚度减小,黏土矿物的膨胀受到抑制,使得溶液浸出稀土的效果更好,其中吐温40对溶液浸出稀土的渗流效果影响最大,助渗效果最好.

To reveal the regularity of variation in the rare earth occurrence states of weathered crust elution-deposited rare earth ores, ore samples from different weathering crust layers were obtained by performing the sequential extraction procedure. The order of rare earth contents firmly obeyed the following sequence: the weathered layer > humic layer > partly weathered layer. The occurrence states of rare earth elements were mainly the ion exchange state, carbonate bound state, iron–manganese oxide state, organic binding state and residual state. The proportions of rare earth elements found in the rare earth ion exchange state of the weathered layer, humic layer and partly weathered layer were 78.55%, 73.53% and 53.88%, respectively. The light rare earth elements (LREEs) found in the rare earth ion exchange state were enriched in the upper part of the weathering crust, while the heavy rare earth elements (HREEs) were enriched in the lower part. There were also obvious negative anomalies in the content of cerium in the ion exchange state. The content of rare earth elements found in the carbonate bound state was small, and the rare earth partition pattern was basically consistent with that of the ion exchange state, which had little effect on the differentiation of the rare earth elements. The iron–manganese oxide state was mainly enriched with cerium, and the content of cerium increased with the depth of the weathering crust. The iron–manganese oxide state was the main factor causing the phenomenon of the anomaly in the cerium content. Meanwhile, the iron oxides in the iron–manganese oxide state were mainly hematite and goethite. The organic binding state mainly beneficiated yttrium and cerium by complexation and certain adsorption. The content of elements found in the rare earth residual state was related to the degree of weathering and reflected the release sequence of rare earth elements in the mineralization process. Clarifying the rare earth occurrence states is conducive to better revealing the metallogenic regularity of weathered crust elution-deposited rare earth ores. In addition, the results can provide a valuable reference for expanding the available rare earth resources and the efficient comprehensive utilization of rare earth ore.

采用化学共沉淀法制备铁锰复合氧化物作吸附剂,通过静态和动态吸附实验探究了不同吸附条件对铁锰氧化物吸附稀土离子的影响,对铁锰氧化物吸附稀土离子过程进行了等温吸附模型拟合和吸附动力学、吸附活化能分析,探究了稀土离子在铁锰氧化物上的吸附机理.结果表明,稀土离子在铁锰氧化物上的吸附过程符合Langmuir等温吸附模型;稀土离子在铁锰氧化物上的吸附过程符合准二级动力学模型,属于单层均匀的化学吸附过程,吸附速率控制步骤由化学吸附决定,且温度对吸附动力学影响程度最大;吸附热力学分析表明铁锰氧化物吸附稀土离子是吸热的化学吸附过程,吸附活化能分别为ELa3+=11.04 kJ/mol、EGd3+=16.85 kJ/mol和Ey3+=16.67 kJ/mol;稀土离子与铁锰氧化物上的羟基发生了交换形成了内层络合物,稀土离子取代表面羟基是主要的吸附机制.

为解决工业上铵盐回收稀土工艺所带来的环境污染问题,对氧化镁沉淀镁盐稀土浸出液过程进行研究,探索了氧化镁加入方式、氧化镁用量、沉淀温度以及沉淀时间对镁盐稀土浸出液中稀土沉淀的影响.结果表明,相同氧化镁用量下,氧化镁浆液的稀土沉淀率优于氧化镁粉末.采用氧化镁浆液沉淀氯化镁和硫酸镁稀土浸出液时,重稀土沉淀率均高于轻稀土,最佳氧化镁用量比(氧化镁实际用量/理论用量)分别为1.4和1.1,最佳沉淀温度分别为35℃和25℃,稀土沉淀反应达到平衡时间均为180 min,氯化镁和硫酸镁稀土浸出液中稀土沉淀率分别为97.11％ 和94.12％.研究结果对镁盐稀土浸出液中回收稀土工艺具有一定的指导意义.

Rare earths are mainly adsorbed on the clay minerals as ion-exchangeable phase which could be extracted by the ion-exchange method in weathered crust elution-deposited rare earth ore. The clay minerals would swell after adsorbing electrolyte solution during the rare earth leaching process, which would easily lead to the occurrence of landslides and other geological disasters. In this study, to alleviate the expansion of the clay minerals, swelling kinetics curves of the ore samples in the three anti-swelling agents: urea, NH4Cl and NH4NO3 were investigated. Synergy effects of these three anti-swelling agents in binary and ternary systems were also studied. Results showed that the lowest swelling ratio was obtained in the urea/ NH4Cl/NH4NO3 system: 3% wt NH4Cl and NH4NO3 with mass ratio: 7:3 and 6% wt urea at the optimum value of pH 5.0. The Swelling ratio of clay minerals increased with the increase of the temperature in the ternary system. Additionally, swelling kinetics equation delta = A.e(-B/t) of the clay minerals in different anti-swelling agents were also determined by mathematical regression analysis. The SEM, TG, FTIR and XRD analysis of rare earth tailing leached by ternary system verified the antiswelling function of urea in the leaching process.

As a kind of rare-earth oxide, CeO2 has been considered as a great potential material for its abundant oxygen vacancies and catalysis activity in wastewater treatment. In this study, three ceria samples with different morphological structure were prepared, and their effect on contaminates degradation in electro-Fenton (E-Fenton) system was investigated. It is found that the morphology of CeO2 has great influence on promoting the performance of E-Fenton process. The rod-like CeO2 (ReCeO2) induced EFenton system shows higher azo dye X3B removal and mineralization rates than cubs (CeCeO2) and octahedrons (OeCeO(2)), and the degradation kinetic rate constants are 0.28, 0.169 and 0.181 min(-1) respectively, already surpass that of the blank one (0.120 min(-1)). The H2O2 generation capacity of ReCeO2 induced E-Fenton system is also superior to the others, and the corresponding Faraday current efficiency even increases to 166.2% at 2.5 min. Characterizations by scanning-transmission electron microscopy (STEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), Raman spectroscopy were conducted to disclose the mystery behind this phenomenon. The results indicate that the difference of surface oxygen vacancy density in different shaped CeO2 acts as a magic driving force for the accelerated oxygen reduction, and then leads to the enhanced degradation efficiency of E-Fenton system. This work provides a new insight into the development and application of rare-earth elements based catalyst in E-Fenton technology. (c) 2022 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.

研究了以碳酰胺为助浸剂的风化壳淋积型稀土矿浸取稀土工艺.通过柱浸方式模拟原地浸出过程,在单因素试验基础上,采用响应曲面法建立二次多项数学模型,以稀土浸取率为响应值,探究助浸剂碳酰胺浓度、浸取温度和浸取剂溶液pH对稀土浸取率的影响,分析各因素间的交互作用.结果表明,影响稀土浸取率从强到弱的因素依次是浸取剂溶液pH、碳酰胺浓度、浸取温度.在浸取剂乙酸铵浓度0.10 mol/L条件下,最佳工艺参数为碳酰胺浓度0.59 mol/L、浸取温度25.03℃、浸取剂pH=5.51,该条件下稀土浸取率响应值为97.50％.实际试验稀土浸取率为96.36％.两者误差较小,表明采用响应曲面模型得到的工艺参数是基本可靠的.

To improve the leaching process of rare earth and reduce the impurities in the leachate, the carboxylate ammonium, such as ammonium acetate, ammonium citrate and ammonium tartrate, were selected as lixiviant to compare the effects of concentration, flow rate, pH and temperature on leaching mass process of rare earth and aluminum. Meanwhile, the leaching behaviors of rare earth and aluminum leached by three kinds of carboxylate ammonium were analyzed by chromatographic plate theory. The relationship between the flow rate and height equivalent (HETP) could fit well with the Van Deemter equation and there was an optimal flow rate (u(opt)) for the leaching of the rare earth and aluminum. Besides, the conditions of carboxylate ammonium lixiviant were optimized. The optimum concentrations of ammonium acetate, ammonium tartrate and ammonium citrate were 15 g/L, 25 g/L and 5 g/L respectively, the leaching flow rate was 0.50 mL/min, the pH value was approximatively 7.00 and the leaching temperature was 293 K to 303 K. At these conditions, the mass transfer efficiencies of three ammonium carboxylates for rare earth and aluminum was in the order of ammonium acetate > ammonium tartrate > ammonium citrate. Moreover, the ammonium acetate could commendably inhibit aluminum ions entering the lixivium.