Kinetics and Mechanisms of Rare Earth Complexation

Sastri, V. S.; Bünzli, Jean‐Claude G.; Rao, V. Ramachandra; Rayudu, G.V.S.; Perumareddi, Jayarama R.

doi:10.1016/b978-044451010-5/50021-3

Cited by 4 publications

(5 citation statements)

References 5 publications

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“…Since data for La(NO 3 ) 3 in acetonitrile were unavailable to us, we have drawn for comparison the constants for the corresponding perchlorate. For La(ClO 4 ) 3 in the same solvent, only a cation LaClO 4 2+ was reported, with p K diss = 1.56 . Though our acetonitrile solutions contained 10% toluene, which may somewhat increase the cation–anion association, the working concentrations of the salts are mainly in the millimolar region, and the possibility of their incomplete dissociation can be ignored.…”

Section: Resultsmentioning

confidence: 96%

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Formation, Stability, and Coagulation of Fullerene Organosols: C₇₀ in Acetonitrile–Toluene Solutions and Related Systems

Mchedlov‐Petrossyan

Marfunin

2021

Langmuir

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This paper is aimed at better understanding the nature of C70 aggregates in organic solvents. As liquid media, acetonitrile–toluene mixed solvents were chosen. At a high content of CH3CN, e.g., 90 vol %, colloidal particles with a size of ca. 225 ± 10 nm are formed with a negative ζ-potential of −(55 ± 5) mV and are stable over time. The interaction with electrolytes containing single-, double-, and triple-charged cations was examined using dynamic light scattering and UV–visible spectra. Additional experiments were carried out with methanol and benzene instead of acetonitrile and toluene, respectively. For comparison, data were obtained with C60 organosols. It was found that coagulation obeys the classical Schulze–Hardy rule. The specificity of the coagulating power of various single-charged cations was explained by their different abilities to adsorb on negatively charged C70 aggregates. The overcharging effect is expressed not only for Ca2+ and La3+ ions but even for Li+ and is caused by poor solvation of such cations in a cationophobic solvent, acetonitrile. After introduction of the cryptand [2.2.2], a substantial increase in the critical concentrations of coagulation for Na+, Li+, and Ca2+ was observed owing to conversion of “bare” metal cations into their cryptates. The application of the Derjaguin–Landau–Verwey–Overbeek theory allowed for evaluation of the Hamaker constant of the C70–C70 interaction in vacuum, A FF, which lies in the interval of 5.8–16.6 × 10–20 J. Such an estimate, close to that made previously for C60 organosols, was received after withdrawing electrolytic systems where the hetero- and mutual coagulation were highly likely. However, it is impossible to completely exclude the interfering influence of the latter phenomena. Based on the obtained A FF values, two approaches to understanding the behavior of fullerenes in water were proposed.

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Section: Resultsmentioning

confidence: 96%

“…2+ was reported, with pK diss = 1.56. 43 Though our acetonitrile solutions contained 10% toluene, which may somewhat increase the cation−anion association, the working concentrations of the salts are mainly in the millimolar region, and the possibility of their incomplete dissociation can be ignored.…”

Section: Resultsmentioning

confidence: 99%

Formation, Stability, and Coagulation of Fullerene Organosols: C₇₀ in Acetonitrile–Toluene Solutions and Related Systems

Mchedlov‐Petrossyan

Marfunin

2021

Langmuir

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“…For formation of LaClO 4 + , the corresponding value is 2.59. 31 Though the exact value of the ionic strength in the electrolyte-free systems is unknown, it is extremely low. Hence, in such cases the Huckel−Onsager equation, ς = 1.5u e η/ε r ε 0 , was used.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Indeed, the logarithms of the association constants of Na + , TBA + , Ca 2+ , and Ba 2+ cations with the ClO 4 – ion in methanol at 25 °C are 1.28, 1.73, 2.44, and 2.68, respectively. For formation of LaClO 4 + , the corresponding value is 2.59 …”

Section: Resultsmentioning

confidence: 99%

Interactions of Nanosized Aggregates of Fullerene C₆₀ with Electrolytes in Methanol: Coagulation and Overcharging of Particles

et al. 2016

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Contrary to numerous studies on the stability of fullerene aqueous colloidal solutions in the presence of electrolytes, the corresponding issue for the organosols was until recently almost unexplored. In this article, the state of C in methyl alcohol and the regularities of the coagulation of colloidal solution in this solvent were examined in the presence of electrolytes. Alcosols with a fullerene concentration of 4 × 10 M were prepared by the dilution of the C saturated solution in toluene by methanol. The ca. 300 nm-sized aggregates possess a negative electrokinetic potential value, ζ = -37 ± 8 mV. To determine the critical coagulation concentrations, CCC, the size increase of the species was followed up using the dynamic light scattering method. The analysis of the coagulation in terms of the Fuchs function, W, was accompanied by zeta potential monitoring. The consideration of the data for 1:1 electrolytes NaClO and N(n-CH)ClO allows a rough estimate of the Hamaker constant of fullerene-fullerene attraction. Whereas in the case of these two electrolytes the colloidal species are negatively charged at the CCC, expressed overcharging of up to ζ = +36 mV by H, Ca, Ba, and La ions was observed. The action of HClO should be attributed to the interfacial acid-base reaction, whereas the excessive attraction of metal cations is caused by poor solvation in methanol; the negative charge is restored when the metal cations are shielded by a macrocyclic ligand.

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“…According to the hard-soft-acid-base (HSAB) theory [73], the functional groups of modifiers on the adsorbent surface are hard Lewis bases and an increase in their hardness is in the following order: Cyanex-272 < HDEHP < TBP [74][75][76]. The acidity of REEs decreases from heavy to light rare earth elements [77]. Taken together with the pK a values presented earlier (Section 3.2), these results may provide an explanation of the selectivity principle; namely, the softer the base group, the lower the selectivity for coordination with heavier REE ions, which is in line with the distribution and selectivity coefficients, presented in Tables 2 and 3, respectively.…”

Section: Selectivity Testsmentioning

confidence: 99%

Selective recovery and separation of rare earth elements by organophosphorus modified MIL-101(Cr)

Kavun

Veen

Repo

2021

Microporous and Mesoporous Materials

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Development of state-of-the-art selective adsorbent materials for recovery of rare earth elements (REEs) is essential for their sustainable usage. In this study, a metal-organic framework (MOF), MIL-101(Cr), was synthesized and post-synthetically modified with optimised loading of the organophosphorus compounds tributyl phosphate (TBP), bis(2-ethylhexyl) hydrogen phosphate (D2EHPA, HDEHP) and bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex®-272). The materials were characterized and their adsorption efficiency towards Nd 3+ , Gd 3+ and Er 3+ from aqueous solutions was investigated. The MOF derivatives demonstrated an increase in adsorption capacity for Er 3+ at optimal pH 5.5 in the order of MIL-101-T50 (37.2 mg g − 1 ) < MIL-101-C50 (48.9 mg g − 1 ) < MIL-101-H50 (57.5 mg g − 1 ). The exceptional selectivity of the materials for Er 3+ against transition metal ions was over 90%, and up to 95% in the mixtures with rare earth ions. MIL-101-C50 and MIL-101-H50 demonstrated better chemical stability than MIL-101-T50 over 3 adsorption− desorption cycles. The adsorption mechanism was described by the formation of coordinative complexes between the functional groups of modifiers and Er 3+ ions.

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Kinetics and Mechanisms of Rare Earth Complexation

Cited by 4 publications

References 5 publications

Formation, Stability, and Coagulation of Fullerene Organosols: C₇₀ in Acetonitrile–Toluene Solutions and Related Systems

Formation, Stability, and Coagulation of Fullerene Organosols: C₇₀ in Acetonitrile–Toluene Solutions and Related Systems

Interactions of Nanosized Aggregates of Fullerene C₆₀ with Electrolytes in Methanol: Coagulation and Overcharging of Particles

Selective recovery and separation of rare earth elements by organophosphorus modified MIL-101(Cr)

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Kinetics and Mechanisms of Rare Earth Complexation

Cited by 4 publications

References 5 publications

Formation, Stability, and Coagulation of Fullerene Organosols: C70 in Acetonitrile–Toluene Solutions and Related Systems

Formation, Stability, and Coagulation of Fullerene Organosols: C70 in Acetonitrile–Toluene Solutions and Related Systems

Interactions of Nanosized Aggregates of Fullerene C60 with Electrolytes in Methanol: Coagulation and Overcharging of Particles

Selective recovery and separation of rare earth elements by organophosphorus modified MIL-101(Cr)

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Formation, Stability, and Coagulation of Fullerene Organosols: C₇₀ in Acetonitrile–Toluene Solutions and Related Systems

Formation, Stability, and Coagulation of Fullerene Organosols: C₇₀ in Acetonitrile–Toluene Solutions and Related Systems

Interactions of Nanosized Aggregates of Fullerene C₆₀ with Electrolytes in Methanol: Coagulation and Overcharging of Particles