Adsorption and desorption properties of D151 resin for Ce(III)

Understanding the Adsorption of Rare-Earth Elements in Oligo-Grafted Mesoporous Carbon

Rare-earth elements (REEs) are 17 elements of the periodic table primarily consisting of lanthanides. In modern society, the usage of REEs is ubiquitous in almost all modern gadgets and therefore efficient recovery and separation of REEs are of high importance. Selective adsorption and chelation of REEs in solid sorbents is a unique and sustainable process for their recovery. In this work, single-stranded oligos with 100 units of thymine were grafted onto carboxylated mesoporous carbon to synthesize a sorbent with phosphorus and oxygen functionalities. The sorbent was characterized by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy-energy-dispersive X-ray spectroscopy. Three different REEs with varying atomic radii and densities, Lu, Dy, and La, were adsorbed onto the carbon from aqueous solutions. It was observed that the adsorbed amounts increased with the increase in the atomic radius or decrease in the atomic density. Calculation of the distribution coefficients for all the equilibrium adsorption amounts suggested that adsorption is more effective in the lower concentration region. The L₃-edge X-ray absorption near-edge structure confirmed a 3+ oxidation state of REEs in the adsorbed phase. Extended X-ray absorption fine structure (EXAFS) confirmed the binding of REEs with oxygen functionalities in the adsorbed phase. The radial distribution functions calculated from the EXAFS data suggest a longer RE-O distance for La compared to those for Lu and Dy. The coordination numbers and Debye-Waller factors have typical values of about 8-9 atoms and 0.01-0.02 Ų, respectively.

Superadsorbent Fe3O4-coated carbon black nanocomposite for separation of light rare earth elements from aqueous solution: GMDH-based Neural Network and sensitivity analysis

A series of nanocomposites adsorbents with different magnetite/carbon black ratios were synthesized by using the co-precipitation method and used for separation of LREEs (Ce, La, and Nd) from aqueous solution. The adsorption efficiency of nanocomposites is strongly dependent on both pH and the loading carbon on nanocomposite. The maximum adsorption capacity (370 mg/g) was reported by nanocomposite with 20% Fe3O4 and 80% carbon in pH 7 for LREE initial concentration of 250 ppm. Results revealed that the LREEs adsorption behavior of the optimal adsorbent fits well with Langmuir isotherm and pseudo-first-order kinetic model. Moreover, the average values of thermodynamic parameters suggest the endothermic and irreversible chemisorption mechanism. An empirical correlation was obtained by using GMDH (Group Method of Data Handling)-based Neural Network to predict the adsorption kinetics of LREEs as a function of ion's electronegativity, molecular weight, and initial concentration. The results showed that the correlation can predict the experimental data mostly lower than 12.5% and it can predict the results of other researches with similar conditions with up to 25% from the experimental values. Finally, the results of sensitivity analysis revealed that the adsorption of LREEs is more sensitive to ions electronegativity and molecular weight at equilibrium conditions.

Static and dynamic studies of lanthanum(III) ion adsorption/desorption from acidic solutions using chelating ion exchangers with different functionalities

Increasing the number of applications of rare earth elements (REEs) has led to increased release of these metals into the environment. Removal of REEs from e-wastes is very important considering the increasing demand for these elements, the limited resource availability of them as well as the significant environmental issues. In this present study, optimization of the La(III) ions sorption from acidic solutions on chelating ion exchangers containing different functional groups, i.e. Amberlite IRC748, Purolite S930, Lewatit® Monoplus TP208, Amberlite IRC747, Purolite S940, and Purolite S950, was carried out. The sorption data was analyzed using the Lagergren pseudo-first order, Ho and McKay pseudo-second order, Weber-Morris intraparticle diffusion, Boyd kinetic models, pore and film diffusion coefficients as well as the Langmuir, Freundlich, and Temkin isotherm models. Additionally, thermodynamic parameters and regeneration abilities of chelating ion exchangers were evaluated. The maximum recovery of La(III) ions was found for HNO₃ concentration equal to 0.2 mol/dm³. The La(III) ions sorption was fast and sorption equilibrium was achieved after about 60 min. The best fitting for the lanthanum(III) ions sorption was obtained using the pseudo-second order kinetic and Langmuir isotherm models. Moreover, breakthrough curves were obtained from dynamic studies. The physicochemical characterization places special emphasis on determination of chemical composition of ion exchangers using ATR/FT-IR and XPS spectroscopy. Furthermore, characterization parameters of ion exchangers such as surface area and porosity (pore size), point of zero charge, and thermal stability were estimated. Chelating ion exchangers with aminophosphonic functional groups are characterized by the best adsorption properties towards La(III) ions so they could be used for the recovery of rare earth elements from spent battery solutions.

Adsorption of Rare Earth Elements onto DNA-Functionalized Mesoporous Carbon

The recovery and separation of rare earth elements (REEs) are of national importance owing to the specific usages, high demand, and low supply of these elements. In this research, we have investigated the adsorption of rare earth elements onto DNA-functionalized mesoporous carbons with a BET surface area of 605 m²/g and a median mesopore width of 48 Å. Three types of single-stranded DNA, one with 100 base units of thymine, another with 20 units of thymine, and the third, a 2000 unit long DNA from salmon milt were grafted on the carboxylated mesoporous carbon surface. All of the DNA-functionalized mesoporous carbons demonstrated higher adsorption of REEs compared to pristine mesoporous carbon and DNA grafted with 100 units of thymine demonstrated slightly higher adsorbed amounts compared to others. Pure neodymium (Nd(III)) adsorption in the aqueous phase demonstrated an adsorbed amount of 110.4 mg/g with respect to the initial concentration of 500 mg/g. A pH variation study with pure Nd(III) demonstrated that the adsorbed amount is higher at elevated pH compared to that at lower pH, thereby suggesting possible recovery at lower pH. Adsorption of a mixture of 16 REEs, including Sc, Lu, Tm, Yb, Er, Ho, Tb, Dy, Y, Eu, Gd, Sm, Ce, Nd, Pr, and La revealed that the adsorbed amount increased with an increase in the atomic weight and metallic radii of elements within the lanthanides. The calculation of the distribution coefficients for all of the equilibrium adsorption amounts suggested that adsorption is more effective in the lower concentration region. The Nd L₃-edge X-ray absorption near edge structure (XANES) confirmed a 3+ oxidation state of Nd in the adsorbed phase. The extended X-ray absorption fine structure (EXAFS) confirmed the local atomic structure relaxation of Nd complexes in the adsorbed phase and shortening of the Nd-O bond distance by about 0.03-0.04 Å, which may be associated with their local complexation at the carbon surface.

Preparation of a Novel Polystyrene-Poly(hydroxamic Acid) Copolymer and Its Adsorption Properties for Rare Earth Metal Ions

In this study, a novel polystyrene-poly(hydroxamic acid) copolymer was synthesized as an effective adsorbent for the treatment of rare earth elements. Through the use of elemental analysis as well as FTIR, SEM, XPS, and Brunauer-Emmett-Teller (BET) surface area measurement, the synthesized polymer was found to have a specific surface area of 111.4 m²·g⁻¹. The adsorption performances of rare metal ions were investigated under different pH levels, contact times, initial concentrations of rare earth ions, and temperatures. The adsorption equilibrium for La³⁺, Ce³⁺, and Y³⁺ onto a polystyrene-poly(hydroxamic acid) copolymer is described by the Langmuir model, which confirms the applicability of monolayer coverage of rare earth ions onto a polystyrene-poly(hydroxamic acid) copolymer. The amount of adsorption capacities for La³⁺, Ce³⁺, and Y³⁺ reached 1.27, 1.53, and 1.83 mmol·g⁻¹ within four hours, respectively. The adsorption process was controlled by liquid film diffusion, particle diffusion, and chemical reaction simultaneously. The thermodynamic parameters, including the change of Gibbs free energy (∆G), the change of enthalpy (∆H), and the change of entropy (∆S), were determined. The results indicate that the adsorption of resins for La³⁺, Ce³⁺ and Y³⁺ was spontaneous and endothermic. The polymer was also used as a recyclable adsorbent by the desorption experiment.

Central composite design optimization of Ce(iii) ion removal from aqueous solution using modified SBA-15 mesoporous silica

HESI-SBA-15 was used as an effective adsorbent for cerium ion removal in real samples.

Monosodium Glutamate Functionalized Chitosan Beads for Adsorption of Precious Cerium Ion

Monosodium glutamate functionalized chitosan (MSGC) beads were synthesized and used as an adsorbent for recovering precious cerium ion from aqueous solutions. Several parameters which can affect adsorption efficiency such as effect of pH and adsorbent dosage have been investigated. The optimum pH for Ce (III) adsorption was 4. The rate of Ce (III) uptake was fast as the time to reach equilibrium was less than 10 min. Based on the applied kinetic model, Ce (III) adsorption onto MSGC fitted well with pseudo-second-order model. The maximum adsorption capacity recorded from the Langmuir isotherm model was 369.0 mg g-1 at 300 K.

Thermodynamic parameters for adsorption equilibrium of heavy metals and dyes from wastewaters

This meta-analysis evaluates adsorption studies that report thermodynamic parameters for heavy metals and dyes from wastewaters. The adsorbents were derived from agricultural waste, industrial wastes, inorganic particulates, or some natural products. The adsorption mechanisms, derivation of thermodynamic relationships, and possible flaws made in such evaluation are discussed. This analysis shows that conclusions from the examined standard enthalpy and entropy changes are highly contestable. The reason for this flaw may be the poor physical structure of adsorbents tested, such that pore transport controlled the solute flux, leaving a surface reaction process near equilibrium.