Behavior and mechanism of graphene oxide-tris(4-aminophenyl)amine composites in adsorption of rare earth elements

Efficient Capture and Release of the Rare-Earth Element Neodymium in Aqueous Solution by Recyclable Covalent Organic Frameworks

Rare-earth elements (REEs) are present in a broad range of critical materials. The development of solid adsorbents for REE capture could enable the cost-effective recycling of REE-containing magnets and electronics. In this context, covalent organic frameworks (COFs) are promising candidates for REE adsorption due to their exceptionally high surface area. Despite having attractive physical properties, COFs are heavily underutilized for REE capture applications due to their limited lifecycle in aqueous acidic environments, as well as synthetic challenges associated with the incorporation of ligands suitable for REE capture. Here, we show how the Ugi multicomponent reaction can be leveraged to postsynthetically modify imine-based COFs for the introduction of a diglycolic acid (DGA) moiety, an efficient scaffold for REE capture. The adsorption capacity of the DGA-functionalized COF was found to be more than 40 times higher than that of the pristine imine COF precursor and more than four times higher than that of the next-best reported DGA-functionalized solid support. This rationally designed COF has appealing characteristics of high adsorption capacity, fast and efficient capture and release of the REE ions, and reliable recyclability, making it one of the most promising adsorbents for solid-liquid REE ion extractions reported to date.

Activated carbon from Camellia oleifera shells for adsorption of Y(iii): experimental and DFT studies

Yttrium is an important rare earth element and is widely used in fields such as special glass preparation, metallurgy, and materials science. However, it is difficult to recover yttrium ion waste from dilute solutions with traditional processes, resulting in a significant waste of rare earth resources. The simple, effective, and easy-to-operate adsorption method is the most promising method for recovering yttrium, which is of great significance for sustainable development of the rare earth industry. In this study, activated carbon was prepared from Camellia oleifera fruit shells (COS) using phosphoric acid activation, and efficient recovery of Y(iii) from the Camellia oleifera fruit shell activated carbon was studied. Adsorption equilibrium data showed that this activated carbon had a Y(iii) adsorption capacity of 35.41 mg g-1, indicating significant potential for recovery of yttrium ions. The adsorption of Y(iii) by the activated carbon prepared from COS was consistent with the Langmuir model, and the adsorption data were consistent with the pseudo second-order kinetic model, indicating that the adsorption process was primarily chemical adsorption. After adsorption, the surface of the activated carbon contained large amounts of N, O, and Y, indicating that Y(iii) was stably adsorbed. The mechanisms for adsorption of Y(iii) on three types of activated carbon were studied through DFT calculations. The results showed that Y(iii) interacted with the carbon atoms on the surfaces to form new chemical bonds. The yttrium ion adsorption capacities for the three different activated carbons decreased in the order C I > C II > C.

Preparation of imprinted bacterial cellulose aerogel with intelligent modulation of thermal response stimulation for selective adsorption of Gd(III) from wastewater

Research on recycling of used rare earth elements has been of great interest. Adsorption is one of the advantageous methods to recover gadolinium with high value. In the process of adsorption and separation of gadolinium from materials, the selectivity of materials for gadolinium can be significantly improved by using ion imprinting technique. However, gadolinium elution process is a traditional pickling process, which may affect the construction of imprinting sites. In this study, bacterial cellulose with three-dimensional spatial structure was used as the base material of aerogel material, and functional materials containing a large number of carboxyl groups were introduced by chemical grafting method. In combination with ion imprinting technology and N-polyacrylamide as intelligent temperature control valve, intelligent imprinting aerogel (PNBC-IIPS) with specific selectivity to gadolinium was prepared. The properties of aerogel materials were analyzed by SEM, FT-IR, and BET characterization. The experimental analysis shows that the desorption of gadolinium can be achieved by controlling the temperature change. The adsorption experiments show that PNBC-IIPS can selectively adsorb gadolinium ions from aqueous solution. The maximum adsorption capacity reached 95.51 mg g-1. Compared with unimprinted aerogel, the maximum adsorption capacity of gadolinium ion is significantly increased, which proves that the introduced ion imprinting technique plays a key role in the adsorption process. Cyclic experiments show that the adsorption capacity of PNBC-IIPS can still maintain 88% of the original adsorption capacity after 5 times of adsorption and desorption. In conclusion, PNBC-IIPS is a green adsorbent for selective recovery of gadolinium ions.

Fabrication of sodium alginate-doped carbon dot composite hydrogel and its application for La (III) adsorption and enhanced the removal of phosphorus

Adsorption is an effective method for the removal of hazardous substances from wastewater. In this work, a low-cost and environmental-friendly composite hydrogel material of sodium alginate doped with nitrogen doped carbon dots (SA@NCDs) was fabricated by impregnation for lanthanide and enhanced phosphorus adsorption in wastewater. The effects of NCDs doping amount, dosage, pH, initial solution concentration, adsorption time and temperature on the process of La (III) adsorption by SA@NCDs were investigated. The adsorption isotherms fitted to Langmuir isotherm model (R2 = 0.9970-0.9989) and the adsorption kinetics followed pseudo-second-order kinetic model (R2 = 0.9992). The maximum adsorption capacity of the adsorbent for La (III) was 217.39 mg/g according to the Langmuir model at 298.15 K. After five cycles, the removal efficiency of La (III) adsorbed by SA@NCDs was still 85.1%. Moreover, the loaded La (III) enhanced the adsorption of phosphorus. The La (III)-SA@NCDs-5 hydrogel adsorbent greatly improved the adsorption capacity for phosphorus compared with the La (III)-free adsorbent, and the adsorption amount can reach 9.64 mg-P/g. The SA@NCDs complex hydrogels for rare earth adsorption were prepared by introducing NCDs rich in amino group into SA hydrogels. The introduction of NCDs increases the adsorption sites of hydrogels, and also overcomes the problem that NCDs itself is difficult to recover in wastewater treatment applications. The lanthanide adsorbed material has a stable structure and can be used to remove phosphorus to deal with waste using the waste. It indicates the SA@NCDs hydrogel composite adsorbent have good potential for wastewater treatment.

Fabrication of magnesium oxide-calcium alginate hydrogel for scaffolding yttrium and neodymium from aqueous solutions

In this research, the possibility of using sustainable nano-MgO/Ca-alginate beads for efficient sorption of some rare earth metal ions such as neodymium(III) and yttrium(III) from an aqueous acidic solution was explored. The nano-MgO/Ca-alginate beads adsorbent was characterized before and after sorption of Nd(III) and Y(III) using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD) techniques. Batch sorption parameters were investigated, such as contact time, initial metal ion concentration, and adsorbent dose (V/m). The calculated experimental results showed that the suitable selected sorption conditions were carried out using 100 mg/L of Nd(III) and Y(III) with nano MgO/Ca-alginate beads (contact time = 90 min, pH = 2, V/m = 0.05 L/g). The maximum sorption capacity of 0.1 g of nano MgO/Ca-alginate was found to be 7.85 mg/g and 5.60 mg/g for Nd(III) and Y(III), respectively. The desorption of Nd(III) and Y(III) from the loaded nano MgO/Ca-alginate was achieved with 1.0 M sulfamic acid and found to be 51.0% and 44.2%, respectively. The calculated thermodynamic parameters for the nano MgO/Ca-alginate/Nd/Y system show that the positive charge of ΔHo confirmed the endothermic nature of the sorption process, ΔSo (positive) indicates an increase in reaction system disordering, and ΔGo (negative) indicates a spontaneous process. These kinetic results indicate that the sorption process of Nd(III) and Y(III) on nano MgO/Ca-alginate beads is performed by the chemisorption process.

Mussel-Inspired Nanocellulose Coating for Selective Neodymium Recovery

Neodymium (Nd) is one of the most in-demand rare earth elements (REEs) for developing the next generation of magnetic medical devices and clean energy. Eco-friendly and sustainable nanotechnology for REE recovery may be highly suitable to address the limited global supply while minimizing the environmental footprints of current practice, such as solvent extraction. Here, we present a novel one-step mussel-inspired nanocellulose coating (MINC) using bifunctional hairy cellulose nanocrystals (BHCNC), bearing dialdehyde and dicarboxylate groups. The dialdehyde groups enable dopamine-mediated orthogonal conjugation of BHCNC to substrates, such as microparticles, while the high content of dicarboxylate groups yields high-capacity and selective Nd removal against ferric, calcium, and sodium ions. To the best of our knowledge, the MINC-treated substrate provides the most rapid selective removal and recovery of Nd ions even at low Nd concentrations with a capacity that is among the highest reported values. We envision that the MINC will provide new opportunities in developing next-generation bio-based materials and interfaces for the sustainable recovery of REEs and other precious elements.

Highly efficient removal of rare earth elements by two-dimensional titanium carbide nanosheets as impacted via water chemistry

The separation and recycling of rare earth elements (REEs) are very important owing to the high demand, limited resource, specific usages, and environmental issues. In this work, two-dimensional Ti3C2Tx MXene was introduced to remove REEs (Nd(III) and La(III)) from water, and its physicochemical properties were conducted by HRTEM, SEM-EDS, XRD, FTIR, and XPS. Various parameters, such as initial pH, REEs initial concentration, contact time, and temperature, were investigated by batch experiment, respectively. Furthermore, the adsorption kinetic and isotherm were examined to analyze the adsorption behavior and adsorption mechanism. Nd(III) and La(III) have a good affinity with Ti3C2Tx MXene surface functional groups (-F, -OH, and containing oxygen groups). The maximum adsorption capacities of Ti3C2Tx MXene for Nd(III) and La(III) were 229.85 mg/g and 175.83 mg/g at T = 333 K, respectively. The adsorption data of Nd(III) on Ti3C2Tx MXene fitted well with the Freundlich isotherms model and pseudo-second-order kinetic model. However, the best fitting for La(III) adsorption on Ti3C2Tx MXene was described by both pseudo-first-order and pseudo-second-order model. Thermodynamic study of Nd(III) and La(III) adsorption on Ti3C2Tx MXene showed that the reaction was a spontaneous and endothermic process. These results indicated Ti3C2Tx MXene had a great potential in extracting REEs from an aqueous solution.

Modification of graphene oxide with imidazolium-based ionic liquid for significant sorption of La(III) and Pr(III) from aqueous solutions

A straightforward ferrocyanide immobilization on the surface of graphene oxide (GO) was conducted for rapid and efficient adsorption capacity for lanthanum and praseodymium from an aqueous solution. The GO was mixed with 1-methyl imidazole in the presence of epichlorohydrin to form GO-imidazole-Cl and thereafter suspended in a potassium ferrocyanide solution to fabricate GO-imidazole-FeCN. The prepared materials were characterized with different advanced techniques confirming the preparation method. The adsorption ability of GO-imidazole-FeCN towards La(III) and Pr(III) ions was evaluated. Moreover, the adsorption isotherm showed that the sorption process was fitted with the Langmuir isotherm model with a considerable maximum adsorption capacity of 781.25 mg g−1 for La(III) and 862.07 mg g−1 for Pr(III). The thermodynamic studies showed that the adsorption of both metal ions was spontaneous and endothermic. In addition, the adsorbent showed excellent adsorption–desorption behavior over 5 times, suggesting that GO-imidazole-FeCN may be considered a potential candidate for La(III) and Pr(III) removal from different metal ions which present in fission products.

Ce(III) and La(III) ions adsorption using Amberlite XAD-7 resin impregnated with DEHPA extractant: response surface methodology, isotherm and kinetic study

In this paper, the removal efficiency of Cerium (Ce(ΙΙΙ)) and lanthanum (La(ΙΙΙ)) ions from aqueous solution using Amberlite XAD-7 resin impregnated with DEHPA(XAD7-DEHPA) was studied in the batch system. The adsorbent ( XAD7-DEHPA) was characterized by SEM-EDX, FTIR and BET analysis Techniques. The response surface methodology based on the central composite design was applied to model and optimize the removal process and evaluate operating parameters like adsorbent dose (0.05-0.065), initial pH (2-6) and temperature (15-55). Variance analysis showed that the adsorbent dose, pH and temperature were the most effective parameters in the adsorption of Ce(ΙIΙ)and La(IΙI) respectively. The results showed that the optimum adsorption condition was achieved at pH = 6, the optimum amount of absorbent and the equilibrium time equal to 0.6 gr and 180 min, respectively. According to the results, the adsorption percentage of Ce(ΙIΙ) and La(ΙΙΙ) ions onto the aforementioned resin were 99.99% and 78.76% respectively. Langmuir, Freundlich, Temkin and sips isotherm models were applied to describe the equilibrium data. From the results, Langmuir isotherm (R² (Ce) = 0.999, R² (La) = 0.998) was found to better correlate the experimental rate data. The maximum adsorption capacity of the adsorbent ( XAD7-DEHPA) for both Ce(IΙI) and La(III) was found to be 8.28 and 5.52 mg g^-1 respectively. The kinetic data were fitted to pseudo-first-order, pseudo-second-order and Intra particle diffusion models. Based on the results, the pseudo-first-order model and Intra particle diffusion model described the experimental data as well. In general, the results showed that ( XAD7-DEHPA) resin is an effective adsorbent for the removal of Ce(IΙI) and La(III) ions from aqueous solutions due to its high ability to selectively remove these metals as well as its reusability.

Inclusion, occlusion and adsorption of rare earth elements from chloride media onto barite-gypsum composite

In this study, a synthetic BaSO4·CaSO4 composite was prepared by co-precipitation technique, characterised and examined for REE sorption. The sorption parameters were; pH = 4, equilibrium time = 20 min, temperature = 303 K, and REE liquor volume to composite mass ratio of 0.2:1 L g−1. The sorption reaction was controlled by pseudo 2nd order kinetic mechanism and Langmuir adsorption isotherm with an adsorption capacity of 168.63 mg g−1. 90.14% of REE (III) was desorbed using 1 mol L−1 HNO3. The process was endothermic and spontaneous. Accordingly, 1:1 barite-gypsum (natural ingredient for BaSO4·CaSO4), with 136 mg g−1 loading capacity, was used for REEs extraction.

Graphene oxide modified with carboxymethyl cellulose for high adsorption capacities towards Nd(III) and Ce(III) from aqueous solutions

This work addresses a simple method to functionalize graphene oxide with sodium carboxymethyl cellulose using tetraethyl orthosilicate as a linker for rapid and significant removal of Nd(III) and Ce(III) from aqueous solutions. The prepared composite (GO–CMC) was characterized by different techniques to confirm the modification and adsorption process. The sorption performance of the GO–CMC was evaluated using Nd(III) and Ce(III) as absorbent materials. The experimental results demonstrated that the sorption process was excellently fitted by the pseudo-second-order kinetic model. The adsorption results were also analyzed by different isotherm models. According to the Langmuir isotherm model, the experimental sorption capacities at pH 3.0 was 661.21 and 436.55 mg/g for Nd(III) and Ce(III), respectively. The thermodynamic results indicated that the sorption process of the two examined metal ions was endothermic and spontaneous. The regenerated GO–CMC composite has a similar removal percentage to the original composite. These results confirmed that the prepared composite (GO–CMC) could be used as an effective adsorbent for Nd(III) and Ce(III) from certain multielement solutions.

Rare Earth Group Separation after Extraction Using Sodium Diethyldithiocarbsamate/Polyvinyl Chloride from Lamprophyre Dykes Leachate

This study presents the first application of sodium diethyldithiocarbamate/polyvinyl chloride (DdTC/PVC) as a novel adsorbent for rare earth element (REE) sorption from leach liquors. DdTC/PVC has higher adsorption properties than other sorbents, the synthesis of DdTC/PVC is more accessible than other resins, and it is considered a more affordable sorbent. The three-liquid-phase extraction technique (TLPE) was applied to separate REEs into light, middle, and heavy rare earth elements as groups. The TLPE is an excellent achievable technique in the separation of REEs. DdTC/PVC was prepared as a sorbent to sorb rare-earth ions in chloride solution. It was described by XRD, SEM, TGA, and FTIR. The factors pH, initial rare-earth ion concentration, contact time, and DdTC/PVC dose were also analyzed. The ideal pH was 5.5, and the ideal equilibration time was found to be 45 min. The rare-earth ion uptake on DdTC/PVC was 156.2 mg/g. The rare-earth ion sorption on DdTC/PVC was fitted to Langmuir and pseudo-2nd-order models. The rare-earth ions’ thermodynamic adsorption was spontaneous and exothermic. In addition, rare-earth ion desorption from the loaded DdTC/PVC was scrutinized using 1 M HCl, 45 min time of contact, and a 1:60 S:L phase ratio. The obtained rare earth oxalate concentrate was utilized after dissolving it in HCl to extract and separate the RE ions into three groups—light (La, Ce, Nd, and Sm), middle (Gd, Ho, and Er), and heavy (Yb, Lu, and Y)—via three-liquid-phase extraction (TLPE). This technique is simple and suitable for extracting REEs.

Mild hydrothermally treated brewer's spent grain for efficient removal of uranyl and rare earth metal ions

The increasing concerns on uranium and rare earth metal ion pollution in the environment require sustainable strategies to remove them from wastewater. The present study reports an eco-friendly approach to convert a kind of protein-rich biomass, brewer's spent grain (BSG), into effective biosorbents for uranyl and rare earth metal ions. The employed method reduces the energy consumption by performing the hydrothermal treatment at a significantly lower temperature (150 °C) than conventional hydrothermal carbonization. In addition, with the aid of the Maillard reaction between carbohydrates and proteins forming melanoidins, further activation processes are not required. Treatment at 150 °C for 16 h results in an altered biosorbent (ABSG) with increased content of carboxyl groups (1.46 mmol g⁻¹) and a maximum adsorption capacity for La³⁺, Eu³⁺, Yb³⁺ (pH = 5.7) and UO₂²⁺ (pH = 4.7) of 38, 68, 46 and 221 mg g⁻¹, respectively. Various characterization methods such as FT-IR, ¹³C CP/MAS NMR, SEM-EDX and STA-GC-MS analysis were performed to characterize the obtained material and to disclose the adsorption mechanisms. Aside from oxygen-containing functional groups, nitrogen-containing functional groups also contribute to the adsorption. These results strongly indicate that mild hydrothermal treatment of BSG could be applied as a greener, low-cost method to produce effective adsorbents for uranyl and rare earth metal ion removal.

Effective biosorbent ABSG is obtained via hydrothermal treatment of BSG at low temperature without activation, minimizing energy consumption and environmental impact.