Adsorption Of Rare Earth Ions Research Articles

Recovery of rare earth elements from sedimentary rare earth ore via sulfuric acid roasting and water leaching

Rare earth elements were extracted using a sulfuric acid roasting-water leaching process. The effect of acid roasting on a new type of low-grade sedimentary rare earth ore found in Guizhou Province, China was analyzed using X-ray diffraction and scanning electron microscopy. A systematic study was conducted on process parameters such as amount of acid, roasting temperature, roasting time, water leaching temperature, and leaching time. The results reveal that the total recovery of rare earth elements reaches 81.37%, which is 3.1 times higher than that achieved through direct acid leaching, under the optimal conditions. In addition, the leaching rate of heavy rare earth elements reaches 72.53%. Rare earth elements and some other valuable metals are transformed into soluble sulfate through the local decomposition of clay minerals under the action of the sulfuric acid attack. The dissolution rates of aluminum, iron, and titanium ions are 34.94%, 17.05%, and 62.77%, respectively. The precipitation rate of Ti reaches 99%, and the loss of rare earth ions in the solution is less than 1%. Meanwhile, the results of a leaching kinetics analysis indicate that the leaching process of rare ions is controlled by diffusion. Precious metal ions such as iron and aluminum in the leaching solution can reduce the adsorption of rare earth ions by kaolinite. This study efficiently recovered rare earth ions under conditions of low calcination temperature and direct water leaching, resulting in reduced energy consumption of the extraction process and acidity of the leaching solution. These findings provide a solid foundation for the further separation and extraction of rare earth ions.

Influence of Sulfate and Nitrate for Lanthanum (III) Adsorption on Bentonite: Implications for Rare Earth Wastewater Disposal

The direct discharge of rare earth wastewater causes the waste of resources and heavy metal pollution. This paper compared the adsorption behaviors of lanthanide ions on bentonite under sulfate and nitrate systems by examining the factors affecting the adsorption, such as adsorption time, pH, background electrolyte concentration, and initial rare earth ion concentration. It was shown that the sulfate system was more favorable for the adsorption of rare earth ions on the bentonite surface. The maximum adsorption capacity in the sulfate system was about 1.7 times that in the nitrate system. In contrast, the adsorption under the nitrate system was more sensitive to the changes in pH and background electrolyte concentration. The adsorption processes under both systems are spontaneous physical adsorption processes (ΔGθ are from −27.64 to −31.48 kJ/mol), and both are endothermic (ΔHθ are 10.38 kJ/mol for the nitrate and 7.53 kJ/mol for the sulfate) and entropy-increasing (ΔSθ are 61.54 J/mol for the nitrate and 76.24 J∙mol−1 for the sulfate) processes. This study helps to provide information about the optimizing process parameters for the adsorption treatment of rare earth wastewater using bentonite.

An environment-friendly capacitive deionization recovery strategy for rare-earth (La/Nd/Ce/Pr) ions based on nickel foam

Rare earth (RE) is a non-renewable strategic resource widely used in many high-tech fields, it is crucial to develop clean and efficient separation technologies for RE elements. In this work, the RE ions (RE=La, Nd, Ce and Pr) in single or mixed simulated solution are recovered using nickel foam (NF) as an adsorptive electrode by capacitive deionization (CDI) technology. The adsorption capacity of NF from solution of the studied RE is amounted to 1347.7 mg g−1 for La(NO3)3, 841.9 mg g−1 for Nd(NO3)3, 810.7 mg g−1 for Ce(NO3)3 and 1082.0 mg g−1 for Pr(NO3)3 within 300 min, indicating the strong effect of an electric field force on the mobility of RE ions. The obtained products are designated as La(OH)3, CeO2, Pr(OH)3 and Nd(OH)3, respectively. Changes in pH and conductivity occur due to the adsorption of RE ions and water hydrolysis. The respective precipitates are deposited on the ribs and in the void of NF electrode, leading to an increase in reaction impedance and reducing the adsorption rate. By monitoring the adsorption, La, Ce, and Pr are indicated to follow the second order kinetics, while Nd follows the first order kinetics. Furthermore, the RE elements are simultaneously adsorbed from mixed solutions, and the electrode can be reused for several times without Ni corrosion. RE3+ ions can be recovered rapidly within a few minutes without any other chemical agents, making this an inexpensive and environment-friendly way to recover or enrich RE elements.

Adsorption Behaviors of Lanthanum (III) and Yttrium (III) Ions on Gibbsite

The enrichment process of rare earth elements in ion-adsorbed rare earth ores and bauxite is potentially related to the adsorption of rare earth elements by gibbsite. In this paper, lanthanum and yttrium were selected as surrogates of light rare earth elements and heavy rare earth elements, respectively. The effects of adsorption time, solution pH, and background electrolyte concentration on the adsorption of rare earth ions by gibbsite were investigated through batch adsorption experiments. The results showed that the adsorption of rare earth ions by gibbsite can approach equilibrium in 72 h. There is mainly electrostatic repulsion between gibbsite and rare earth ions at pH 4–7, and the adsorption efficiency increases with the increase in solution pH value and background electrolyte concentration. The adsorption process of rare earth ions by gibbsite is more consistent with the pseudo-second-order kinetic and Langmuir single-layer adsorption models. Moreover, based on the structural correlation between clay minerals and gibbsite, the causes for the differences in the adsorption behaviors of rare earth elements on the minerals are discussed. The results of this study help to understand the role of aluminum hydroxide in the migration and fate of rare earth elements in epigenetic environments.

Adsorption of rare earth ions from synthetic seawater and hot spring water using phosphorylated yeast

In a previous study, a metal-adsorbing yeast with chemically modified phosphate groups (referred to as P-yeast) was developed. The adsorption performance of P-yeast was evaluated using synthetic seawater and hot spring water for extracting rare earth elements (REEs) from nature. In the case of synthetic seawater containing Dy3+, 90% of the ions were adsorbed while the adsorption of Na+ and Mg2+ present at high concentrations was suppressed. Furthermore, the performance of P-yeast was examined using strongly acidic hot spring water (from Tamagawa hot spring, Japan) containing several tens of ppb of REEs (Ce3+, La3+, Dy3+, and Gd3+). A part of Al3＋ and Fe2＋ present at high concentrations in hot spring water was removed as a precipitate after pH adjustment while 60%–80% of REEs remained in the solution. Ce3+, the most abundant REE, was contained at 37 ppb. P-yeast could adsorb REEs from the solution after the treatment and, in combination with a desorption phase using acid, these elements could be concentrated 10–19 times with a recovery of 20%–37%. It was strongly suggested that P-yeast is a practical microbial adsorbent, as selective adsorption and concentration were achieved even in environmental water, which has a low concentration of target substances and many contaminants. In the future, P-yeast made from industrial waste such as surplus yeast is expected to be applied to recover rare earth ions.

Modified tailings of weathered crust elution-deposited rare earth ores as adsorbents for recovery of rare earth ions from solutions: Kinetics and thermodynamics studies

Weathered crust elution-deposited rare earth ores tailings are mainly composed of clay minerals, which can be used as efficient adsorption materials. In order to explore the possibility of recovering rare earth ions using tailings from mine waste liquid, the weathered crust elution-deposited rare earth ores tailings were modified to adsorb La3+ and Y3+ with respect to initial concentrations of La3+ and Y3+, temperatures and impurity ions, and the adsorption kinetics and thermodynamics were further discussed to analyze the adsorption behavior. The results show a higher adsorption capacity of heavy rare earth Y3+ than that of light rare earth La3+. The presence of impurity ions does not adversely affect adsorption of rare earth ions by the modified tailings. The adsorption performance is well fitted with the Langmuir adsorption isotherm model rather than the Freundlich adsorption isotherm model, and the maximum adsorption capacity is 0.0226 mmol/g and 0.0197 mmol/g for Y3+ and La3+, respectively. Pseudo-first-order, pseudo-second-order, intraparticle diffusion and Elovich model were applied to fit the adsorption results. The results show that the adsorption process of modified tailings for La3+ and Y3+ is more in line with the pseudo-second-order kinetic model, suggesting the dominated chemical adsorption. The adsorption activation energies of La3+ and Y3+ on modified tailings are 11.60 KJ/mol and 7.60 KJ/mol, respectively. Thermodynamic studies show that the adsorption process of modified tailings for La3+ and Y3+ is a spontaneous endothermic reaction in the experimental temperature range. The recovery of rare earth ions form the modified tailings can be carried out by the leaching solution of weathered crust elution-deposited rare earth ores, 0.2 mol/L (NH4)2SO4 solution. In addition, the modified tailings are reversible and keep functionality to reuse in several cycles after elution process.

A novel polystyrene-poly(hydroxamic acid) interpenetrating polymer network and its adsorption towards rare earth ions

A novel polystyrene-poly(hydroxamic acid) interpenetrating network resin (PS-PHA IPNs) was successfully synthesized by suspension polymerization and interpenetrating network technology. The effects of various experimental parameters, including pH, contact time and initial concentrations of rare earth ions on the adsorption capacity were discussed in detail. Under the condition of pH 4.0 (La3+), 1.0 (Ce3+) and 3.0 (Y3+), respectively, PS-PHA IPNs can reach equilibrium adsorption in 6 h and get maximum adsorption capacities (1.08, 1.43 and 1.36 mmol/g). The adsorption process of PS-PHA IPNs for La(III), Ce(III) and Y(III) ions can be described by liquid membrane diffusion, particle diffusion and chemical reaction. The adsorption process is a spontaneous and endothermic process and can be better simulated by Langmuir adsorption isotherm. The studies of SEM-EDS indicate that rare earth ions are adsorbed on the surface of PS-PHA IPNs. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis further prove that rare earth ions are chemisorbed on the surface of PS-PHA IPNs. These results reveal that the as-prepared PS-PHA IPNs is a promising adsorbent for adsorption of rare earth ions due to their higher adsorption capacity than other adsorbents.

Highly efficient enrichment and adsorption of rare earth ions (yttrium(III)) by recyclable magnetic nitrogen functionalized mesoporous expanded perlite

A magnetic mesoporous expanded perlite-based (EPd-APTES@Fe3O4) composite was designed and synthesized as a novel adsorbent for enrichment of rare earth ions in aqueous solution. Effect of various factors including the pH of solution, contact time and adsorbent dosage on the adsorption behaviors of yttrium(III) by the EPd-APTES@Fe3O4 nano-material composites from aqueous solution was investigated. The maximum adsorption capacity of the as-prepared materials for yttrium(III) ions was 383.2 mg/g. Among the various isotherm models, the Freundlich isotherm model could well described for the adsorption of the rare earth ions at pH 5.5 and 298.15 K. The kinetic analysis indicated that the adsorption process followed the pseudo-second order kinetics model, and the rate-determining step might be chemical adsorption. Thermodynamic parameters declared that the adsorption process was endothermic. In addition, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and the quantum chemical calculation indicated that the yttrium(III) ions were captured on the EPd-APTES@Fe3O4 surface mainly by coordination with functional group of -NH2. More importantly, the adsorption-desorption studies indicated that the EPd-APTES@Fe3O4 nano-material composites had a high stability and good recyclability.

Selective adsorption of rare earth ions from aqueous solution on metal-organic framework HKUST-1

Recovery of rare earth ions from wastewater holds an important strategy for the use of the precious resources. In this study, we found that a metal-organic framework (MOF), HKUST-1, exhibited a high affinity and selectivity towards adsorptive recovery of rare earth ions (Ce3+ and La3+) in aqueous solutions. The adsorbent showed a remarkable adsorption capacity of 234 mg/g and 203 mg/g for Ce3+ and La3+ at pH = 6, respectively. More importantly, its adsorption selectivity of the rare earth ions was about 87% against other metal ions. The adsorption isotherm, kinetics, and mechanism in the process were also investigated. The adsorption process can be better fit by the Freundlich model in isotherm and the pseudo-second-order model in kinetics. A plausible mechanism for the adsorption of metal ions on the HKUST-1 was proposed by considering ion exchange and the covalent bonding between the adsorbent and metal ions. The selectivity can be attributed to the different bonding abilities to metal ions.

Nano-quantitative ion character–activity relationships of adsorption of rare earth ions on multi-walled carbon nanotubes

ABSTRACTIn this study, the maximum adsorption capacities (qmax) of multi-walled carbon nanotubes (MWCNTs) for 16 rare earth ions were estimated from the experimental data using Langmuir isotherm model. The Langmuir model fitted the experimental data very well, with R2 > 0.98. To explore the impact of ion properties of their adsorption onto MWCNTs, Quantitative Ion Character–Activity Relationships (QICAR) method was applied. The experimental values of qmax were used as dependent variable and the rare earth ions properties were considered as independent variables. Based on covalent index, a new variable was defined which is highly correlated to qmax (correlation coefficient of 0.776). Different variable selection techniques and wrapper models were applied to choose the best subset of variable. Among all developed linear and non-linear models constructed using support vector machine regression (SVR), neural networks, random forest and multiple linear regression, the SVR model presents the best statistical performance. The result of the Wrapper-SVR developed model, with R2c = 0.993 and R2p = 0.794, was excellent than those of other models. The importance of some thermodynamic parameters, Gibbs free energy (ΔG0f) and enthalpy of formation (ΔH0f) of the trivalent lanthanide ions (M+3) at 25°C, indicated the role of thermodynamic aspects on adsorption mechanism. Atomic radius, ionisation energy and electronegativity of rare earth ions should also be considered.

Density functional theory based studies on the adsorption of rare-earth ions from hydrated nitrate salt solutions on g-C3N4 monolayer surface

This article represents density functional theory (DFT) based comparative analysis on six trivalent rare-earth ions (RE3+; RE: Y, La, Ce, Sm, Eu and Gd) absorption, from the respective nitrate-hexahydrate salts, on graphitic carbon nitride (g-C3N4) 2D monolayer, and the photocatalytic properties of the RE3+ adsorbed g-C3N4 systems (g-C3N4/RE3+) based on the ground-state electronic structure calculations. Structure, stability and coordination chemistry of two configurations of each hydrated RE-salt system are discussed in detail. Both DFT (B3LYP/SDD) and semi-empirical (Sparkle/PM7) calculations identify the central N6 vacancy of pristine g-C3N4 as the most suitable site for RE3+ adsorption. Bader’s QTAIM, Mayer bond order and charge population analyses (ADCH, CHELPG and DDEC) are performed to describe the bond characteristics within the systems under study. Thermochemical calculations suggest that the adsorption process is thermodynamically more feasible for higher atomic number (Z) RE3+ [Sm3+, Eu3+ and Gd3+], compared to lower-Z RE3+ [Y3+, La3+ and Ce3+] ions. Besides, the better photocatalytic properties of higher-Z RE3+ adsorbed g-C3N4 systems are revealed from better HOMO-LUMO delocalization, decreased HOMO-LUMO gap, increased softness, higher electrophilicity and electron transfer parameter, compared to pristine or lower-Z RE3+ adsorbed g-C3N4 systems, as obtained from Hirshfeld orbital compositions, density of states and condensed Fukui function analyses.

Accumulation and Release of Rare Earth Ions by Spores of Bacillus Species and the Location of These Ions in Spores.

Two rare earth ions, Tb3+ and Dy3+, were incorporated into spores of Bacillus species in ≤5 min at neutral pH to 100 to 200 nmol per mg of dry spores, which is equivalent to 2 to 3% of the spore dry weight. The uptake of these ions had, at most, minimal effects on spore wet heat resistance or germination, and the ions were all released upon germination, probably by complex formation with the huge depot of dipicolinic acid (DPA) released when spores germinate. Adsorbed Tb3+/Dy3+ were also released by exogenous DPA within a few minutes and faster than in spore germination. The accumulation of Tb3+/Dy3+ was not reduced in Bacillus subtilis spores by several types of coat defects, significant modification of the spore cortex peptidoglycan structure, specific loss of components of the outer spore crust layer, or the absence of DPA in the spore core. All of these findings are consistent with Tb3+/Dy3+ being accumulated in spores' outer layers, and this was confirmed by transmission electron microscopy. However, the identity of the outer spore components binding the Tb3+/Dy3+ is not clear. These findings provide new information on the adsorption of rare earth ions by Bacillus spores and suggest this adsorption might have applications in capturing rare earth ions from the environment.IMPORTANCE Biosorption of rare earth ions by growing cells of Bacillus species has been well studied and has attracted attention for possible hydrometallurgy applications. However, the interaction of spores from Bacillus species with rare earth ions has not been well studied. We investigated here the adsorption and/or desorption of two rare earth ions, Tb3+ and Dy3+, by Bacillus spores, the location of the adsorbed ions, and the spore properties after ion accumulation. The significant adsorption of rare earth ions on the surfaces of Bacillus spores and the ions' rapid release by a chelator could allow the development of these spores as a biosorbent to recover rare earth ions from the environment.

One-step fabrication of imprinted mesoporous cellulose nanocrystals films for selective separation and recovery of Nd(III)

Previously, we investigated imprinted silica films templated by cellulose nanocrystals for the selective adsorption of rare earth ions from acidic systems, but the cost of organosilane limits the application of silica film adsorbents. Considering the cost and outstanding properties of cellulose, converting this renewable biological resource into an adsorbent material is a vital step towards sustainable development. One-step fabrication of imprinted mesoporous cellulose nanocrystals films (IMCFs) was implemented via ionic imprinting technology and they were applied to efficiently and selectively separate neodymium ions [Nd(III)]. Transmission photographs clearly demonstrated there is a highly ordered mesoporous structure after removal of silicon source. Nitrogen adsorption measurements showed two obtained materials possess high specific surface area, providing a good premise for efficient separation. When employed as absorbents, the maximum adsorption capacity of IMCFs is almost three folds than that of NIMCFs, reaching 18.22 mg g−1. The distribution coefficient of IMCFs for Nd(III) reached 435.46 mL g−1, much higher than other interfering ions. Repeatability tests showed IMCFs retained 81.55% of initial adsorption capacity after five adsorption cycles. In summary, this work presents a new avenue to construct imprinted mesoporous cellulose nanocrystals films for separation of rare earth ions.

Preparation of diglycolamide polymer modified silica and its application as adsorbent for rare earth ions

ABSTRACTThree novel diglycolamide monomers were synthesized and polymerized on silica. The diglycolamide polymer grafted silica were used as adsorbents for rare earth ions. The effects of acid concentration, structure of monomer, initial solution concentration, contact time and coexisting ions on adsorption of rare earth ions were investigated in detail. It was shown that the adsorption capacity increased with increasing acid concentration. Three adsorbents exhibited selectivity for middle and heavy rare earth over light rare earth in different extent. The adsorbent prepared from the monomer having the largest alkyl substituent showed the lowest adsorption capacity but the highest selectivity for different rare earth elements (REEs). Adsorption data were well fitted to the Langmuir isotherm and pseudo-second-order models. The presence of high concentrations (100 fold) of coexisting metal ions, K(I), Cr(II), Cu(II) or Fe(III), does not decrease the adsorption for rare earth ions seriously.

Preparation of Diglycolamide Based Hydrogel and Its Application as Adsorbent for Rare Earth Ions

A novel hydrogel based on diglycolamide compound was prepared for the adsorption of rare earth ions. The hydrogel shows high adsorption capacity in 0.1 M HNO3, from the lowest 128 mg g−1 for La to ...

Effect of pore structure parameters of porous glass on luminescence properties of Eu2+/Dy3+ co-doped high silica luminescence glass

The Eu2+/Dy3+ co-doped high silica luminescence glasses were prepared through sintering porous glasses which have adsorbed rare earth ions previously and the effect of pore structure parameters including average pore size, specific surface area, and pore volume on luminescence properties of high silica glass were analyzed by utilizing BET method and emission spectra. The results show that the pore parameters of porous glasses do not affect the shapes of emission spectra but affect the luminescence intensities of high silica glasses. The luminescence intensities of high silica glass increase when the specific surface area of porous glasses increases, which can be interpreted by mechanism of adsorption of rare earth ions onto porous glass. The average pore size and pore volume indirectly affect the luminescence intensities through influencing specific surface area of porous glass.

Role of oxygen on the interfacial adsorption sites of Lu and La in β-Si3N4

Molecular dynamics computer simulations show the important role of oxygen replacing nitrogen at surface sites in the prismatic surface of β-Si3N4 on the adsorption of rare-earth ions from the intergranular film. Such adsorption affects the grain morphology, which plays an important role in mechanical properties. The simulations successfully obtain the correct Lu sites Lu1 and Lu2 on the prismatic surface with O replacement at specific combinations of N surface sites. The results match the experimental high angle annular dark field scanning transmission electron microscopy data. Unlike the Lu results, surface oxidation does not have a large effect on La adsorption sites on the prismatic surface, but does have an influence on the La surface occupancy. The simulation results provide the mechanisms for both the experimental variances observed for the adsorption sites of these two rare-earth additives in the intergranular films and can be used to explain the different grain growth behavior seen experimentally.

Synthesis and characterization of a new low-cost composite for the adsorption of rare earth ions from aqueous solutions

We synthesized and characterized a novel composite, poly(acrylamide-expanded perlite) [P(AAm-EP)] and investigated its adsorptive features for Tb3+. We achieved the synthesis by using free-radical polymerization and a number of structural characterization methods, including scanning electron microscopy (SEM) and BET-porosity swelling tests. We successfully performed free-radical polymerization of acrylamide (AAm) over expanded perlite (EP). We cross-linked expanded perlite with acrylamide to enhance its chemical resistance. P(AAm-EP) composite has a specific surface area of 31.7m2/g. We evaluated the composite of adsorptive features for Tb3+ in light of the dependency of the ion concentration, pH, temperature, time, and reusability. The composite was able to bind Tb3+ ions with strong chemical affinity. The adsorption results were fitted to the classical Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) sorption models. The composite was used in the removal studies of the Tb3+ ions. The adsorption of Tb3+ ions increased as the pH increased and reached a plateau value at around pH 3.0. Variations in the ΔH and ΔS values showed that the sorption process was spontaneous (ΔG<0), endothermic (ΔH>0), and had increased entropy (ΔS>0). We also found that the adsorption kinetics followed the pseudo-second order model and that the rate-controlling step was chemical adsorption. We were able to reuse the composites 5 sequential times.

Adsorption of rare earth ions onto the cell walls of wild-type and lipoteichoic acid-defective strains of Bacillus subtilis

The aim of this study is to investigate the potential of cell walls of wild-type and lipoteichoic acid-defective strains of Bacillus subtilis 168 to adsorb rare earth ions. Freeze-dried cell powders prepared from both strains were used for the evaluation of adsorption ability for the rare earth ions, namely, La(III), Eu(III), and Tm(III). The rare earth ions were efficiently adsorbed onto powders of both wild-type strain (WT powder) and lipoteichoic acid-defective strain (∆LTA powder) at pH 3. The maximum adsorption capacities for Tm(III) by WT and ∆LTA powders were 43 and 37 mg g(-1), respectively. Removal (in percent) of Tm(III), La(III), and Eu(III) from aqueous solution by WT powder was greater than by ∆LTA powder. These results indicate that rare earth ions are adsorbed to functional groups, such as phosphate and carboxyl groups, of lipoteichoic acid. We observed coagulated ∆LTA powder in the removal of rare earth ions (1-20 mg L(-1)) from aqueous solution. In contrast, sedimentation of WT powder did not occur under the same conditions. This unique feature of ∆LTA powder may be caused by the difference of the distribution between lipoteichoic acid and wall teichoic acid. It appears that ∆LTA powder is useful for removal of rare earth ions by adsorption, because aggregation allows for rapid separation of the adsorbent by filtration.

Preparation and photoluminescence properties of Vycor glasses impregnated with Tb 3+ and Ce 3+(or Gd 3+)

Vycor glasses impregnated with Tb 3+ and Ce 3+(or Gd 3+) were prepared as vacuum ultraviolet (VUV) and ultraviolet (UV) luminescent materials by adsorption of rare-earth ions into a special porous Vycor glass followed by reduction sintering in a CO atmosphere. In the presence of Ce 3+(or Gd 3+), the Tb 3+ emissions under VUV and UV excitation were significantly enhanced owing to energy transfer from Ce 3+(or Gd 3+) to Tb 3+. Furthermore, it was found that the intensity of Tb 3+ emissions depended on the solution concentration of Ce 3+(or Gd 3+) ions under the excitation at 160 nm but not at 231 nm. The reason may be due to the direct and indirect excitation of Tb 3+ under UV and VUV lights, respectively.