Structure and size of complete hydration shells of metal ions and inorganic anions in aqueous solution

The structures of nine hydrated metal ions in aqueous solution have been redetermined by large angle X-ray scattering to obtain experimental data of better quality than those reported 40-50 years ago. Accurate M-OI and M-(OI-H)⋯OII distances and M-OI(H)⋯OII bond angles are reported for the hydrated magnesium(II), aluminium(III), manganese(II), iron(II), iron(III), cobalt(II), nickel(II), copper(II) and zinc(II) ions; the subscripts I and II denote oxygen atoms in the first and second hydration sphere, respectively. Reported structures of hydrated metal ions in aqueous solution are summarized and evaluated with emphasis on a possible relationship between M-OI-OII bond angles and bonding character. Metal ions with high charge density have M-OI-OII bond angles close to 120°, indicative of a mainly electrostatic interaction with the oxygen atom in the water molecule in the first hydration shell. Metal ions forming bonds with a significant covalent contribution, as e.g. mercury(II) and tin(II), have M-OI-OII bond angles close to 109.5°. This implies that they bind to one of the free electron pairs in the water molecule. Comparison of M-O bond distances of hydrated metal ions in the solid state with one hydration shell, and in aqueous solution with in most cases at least two hydration shells, shows no significant differences. On the other hand, the X-O bond distance in hydrated oxoanions increases by ca. 0.02 Å in aqueous solution in comparison with the corresponding X-O distance in the solid state. A linear correlation is observed between volume, calculated from the van der Waals radius of the hydrated ion, and the ionic diffusion coefficient in aqueous solution. This correlation strongly indicates that monovalent metal ions, except lithium and silver(I), and singly-charged monovalent oxoanions have a single hydration shell. Divalent metal ions, bismuth(III) and the lanthanoid(III) and actinoid(III) ions have two hydration shells. Trivalent transition and tetravalent metal ions have two full hydration shells and portion of a third one. Doubly charged oxoanions have one well-defined hydration shell and an ill-defined second one.

Environmental chemistry response of beryllium to diverse soil-solution conditions at a waste disposal site

This study evaluated how the variation in different sorption conditions of beryllium (Be) in soil-water systems (electrolytes; ionic strengths; competing, counter, and co-existing ions; concentrations of Be and soil; and temperature) affected Be's environmental behaviour. For this reason, potentially contaminated soil was collected from a legacy waste site near Sydney, Australia. The sorption-desorption plateau for Be was found at >12.5 g L^-1 (soil/solution), considering higher sorption and limited desorption. Variable surface charges developed by different added ions (competing ions, counter ions, and co-existence of all ions) were not always correlated with Be sorption. However, effects of added ions in Be sorption (increased by counter ions and decreased by competing ions) primarily occurred at low pH, with no noticeable changes at pH > 6 due to the hydration and precipitation behaviour of Be at higher pH. Both laboratory data and modelling indicated the substantial effect of counter ions on increased sorption of Be. Relatively higher amounts of sorption under the co-existence of all added ions were suggested from synergistic actions. Sorption was favourable (K_L > 0, and 0 < R_L < 1) across all concentrations and temperatures at pH 5.5, and high retention (84-97%) occurred after four desorption cycles indicated specific sorption. The sorption process was exothermic (ΔH > -43 kJ mole^-1), while desorption was endothermic (ΔH > +78.4 kJ mole^-1). All sorption-desorption reactions were spontaneous (ΔG = -Ve), and executed without any structural deformation (ΔS = nearly zero) of soil particles. However, the effect of temperature on desorption was influenced by the concentrations of Be. Higher retention and different sorption-desorption parameters (K_d-desorption > K_d-sorption; K_f-desorption > K_f-sorption; n_desorption/n_sorption < 1) indicate limited mobility of Be and the presence of desorption hysteresis in the studied soil under the experimental conditions.

Role of beryllium in the environment: Insights from specific sorption and precipitation studies under different conditions

In this study, we examined factors influencing the environmental behaviour of Be, specifically considering soils collected from a legacy radioactive waste disposal site near Sydney (Australia). The precipitation study showed the formation of Be(OH)₂ (amorphous) from ICP standard solution, but a mixture of Be(OH)₂ (alpha), Be(OH)₂ (beta) and ternary Na/S-Be (ΙΙ)-OH(s) solid phase were formed from BeSO₄ solutions. The precipitation of Be started at relatively lower pH at higher concentrations than at the lower Be concentration as indicated by both laboratory data and simulation. Across the pH range, the Be sorption curve was divided into three phases, these being pH 3-6, pH 6-10, and pH > 10, within which sorption of Be with soil was 9-97%, 90-97%, and 66-90%, respectively. Beryllium solubility was limited at pH > 7, but a sorption study with soil showed chemisorption under both acidic and alkaline pH (pH 5.5 and 8) conditions, which was confirmed by FTIR and XPS analysis. At pH 5.5 (specifically relevant to the study site), sorption of Be was 72-95%, in which 77% and 46% Be was respectively sorbed by separated fulvic and humic acid fractions. The irreversible chemisorption mechanism was controlled by SOM at higher pH, and by metal oxyhydroxides at lower pH. Both organic and inorganic components synergistically influence the specific chemisorption of Be at the intermediate pH 5.5 of field soil.

Systematic Evaluation of Ion Diffusion and Water Exchange

As a fundamental property of all fluids, diffusion plays myriad roles in both science and our daily lives. Diffusive properties of many liquids including water have been extensively studied both experimentally and theoretically, while for transition metal ions, there exist significant experimental data that have not been extensively studied theoretically. Hence, high-confidence predictions for challenging systems like radioactive ions that are biohazardous cannot be reliably generated. In this work, a workflow named ISAIAH (Ion Simulation using AMBER for dIffusion Action when Hydrated) was designed to accurately simulate the diffusion coefficients of 15 monoatomic ions with charges varying from -1 to +3 in four water models. As the results indicate, good agreement with experimental values was achieved, leading us to select ²³⁹Pu⁴⁺ (for which no experimental data are available) as a candidate ion to make a theoretical prediction of its diffusion coefficient in water. Among all the force field parameter sets, the ones parametrized using an augmented 12-6-4 Lennard-Jones (LJ) potential showed lower average unsigned errors (AUE) for ions of various radii and electron configurations relative to some 12-6 LJ parameters. This observation agrees well with the fact that diffusion is affected by both the hydration free energy (HFE) and the ion-oxygen distance (IOD) between solute and solvent molecules, both of which are handled well by the 12-6-4 model.

Desorption and Migration Behavior of Beryllium from Contaminated Soils: Insights for Risk-Based Management

Factors influencing the desorption, distribution, and vertical migration behavior of Be in contaminated soils are not fully understood. This study examined the desorption and migration of Be in a soil profile from a legacy radioactive waste disposal site using different batch leaching [monofilled waste extraction procedure (MWEP); synthetic precipitation leaching procedure (SPLP); simulated acid rain solution (SARS); and toxicity characteristic leaching procedure] and sequential leaching [community bureau of reference (BCR)] methods for insights relevant to the application of risk-based management. The results showed that Be desorption was higher in the presence of organic than the inorganic leachate composition (MWEP < SPLP < SARS < TCLP < BCR first-step). The desorption followed three diffusion control mechanisms, which resulted in three desorption rate constant estimates of 157, 87.1, and 40.4 Be/kg.h^0.5, and the estimated desorption maximum was 556 μg/kg. The desorption process was, spontaneous (ΔG > 0), enthalpically and entropically influenced. Increasing the incubation period and heat treatment resulted in a decrease of Be desorption and migration. The soil clay content and pH were the primary factors influencing Be desorption, and the results suggested that Be was desorbed from metal oxyhydroxides and surfaces of silicates (e.g., reactive surfaces of clay minerals), organic matters, and soil pores. Because of high K _d values, the mobility of Be was limited, and no exceedances of ecological or human health risk index or guidelines were determined for the current contamination levels at the site. However, Be released from the waste trenches has the ongoing potential to increase Be concentration in the soil.

Sorption of beryllium in cementitious systems relevant for nuclear waste disposal: Quantitative description and mechanistic understanding

Beryllium has applications in fission and fusion reactors, and it is present in specific streams of radioactive waste. Accordingly, the environmental mobility of beryllium needs to be assessed in the context of repositories for nuclear waste. Although cement is widely used in these facilities, Be(II) uptake by cementitious materials was not previously investigated and was hence assumed negligible. Sorption experiments were performed under Ar-atmosphere. Ordinary Portland cement, low pH cement, calcium silicate hydrated (C-S-H) phases and the model system TiO₂ were investigated. Sorption kinetics, sorption isotherms and distribution ratios (R_d, in kg⋅L^-1) were determined for these systems. Molecular dynamics were used to characterize the surface processes driving Be(II) uptake. A strong uptake (5 ≤ log R_d ≤ 7) is quantified for all investigated cementitious systems. Linear sorption isotherms are observed over three orders of magnitude in [Be(II)]_aq, confirming that the uptake is controlled by sorption processes and that solubility phenomena is not relevant within the investigated conditions. The analogous behaviour observed for cement and C-S-H support that the latter are the main sink of beryllium. The two step sorption kinetics is explained by a fast surface complexation process, followed by the slow incorporation of Be(II) in C-S-H. Molecular dynamics indicate that Be(OH)₃^- and Be(OH)₄^2- are sorbed to the C-S-H surface through Ca-bridges. This work provides a comprehensive quantitative and mechanistic description of Be(II) uptake by cementitious materials, whose retention properties can be now reliably assessed for a wide range of boundary conditions of relevance in nuclear waste disposal.

Luminescence Properties of Tetrahedral Coordinated Mn2+; Genthelvite and Willemite Examples

The cause of the split of 4A4E(4G) Mn2+ excited level measured on minerals spectra is discussed. It is our view that ∆E = |4E(4G) − 4A(4G)| should be considered an important spectroscopic parameter. Among the possible reasons for the energy levels splitting taken under consideration, such as the covalent bond theory, the geometric deformation of the coordination polyhedron and the lattice site’s symmetry, the first one was found to be inappropriate. Two studied willemite samples showed that the impurities occur in one of the two available lattice sites differently in both crystals. Moreover, it was revealed that the calculated crystal field Dq parameter can indicate which of the two non-equivalent lattice sites positions in the willemite crystal structure was occupied by Mn2+. The above conclusions were confirmed by X-ray structure measurements. Significant differences were also noted in the Raman spectra of these willemites.

The influence of soil properties on sorption-desorption of beryllium at a low level radioactive legacy waste site

This study examined the influence of soil physicochemical properties on the sorption, desorption and kinetics of beryllium (Be) uptake and release on soils from a legacy waste site in Australia. This information is needed to help explain the current distribution of Be at the site and evaluate potential future environmental risks. Sorption was determined by a batch study and key soil properties were assessed to explain Be retention. The soil was favourable for sorption of Be (up to 99%) due to organic content, negative surface charge, soil oxyhydroxides (Fe/Al/Mn-O/OH) and the porosity of the soil structure. Lesser sorption was observed in the presence of a background electrolyte (NaNO₃). Sorption closely followed pseudo second order kinetics and was best described by the Langmuir model. FTIR analysis suggested that chemisorption was the predominant mechanism of Be sorption. Desorption was very low and best described by the Freundlich model. The low desorption reflected the high K_d (up to 6624 L/kg), and the presence of hysteresis suggested partially irreversible binding of Be with active surfaces of the soil matrix (minerals, SOM, oxyhydroxides of Fe/Al/Mn etc.). Intra-particle diffusion of Be and entrapment in the pores contribute to the irreversible binding. The sorption behaviour of Be helped to explain the relative immobility of Be at the site despite the significant quantities of Be disposed. Soil physicochemical properties were significant for Be sorption, through influencing both the uptake and desorption, and this demonstrates the implications of these measurements for evaluating potential future risks to the environment.

Ab Initio Molecular Dynamics Investigation of Beryllium Complexes

Structures of aqueous [Be(H₂O)₄]²⁺, its outer-sphere and inner-sphere complexes with F^-, Cl^-, and SO₄^2-, and dinuclear complexes with a [Be₂(κ-OH)(κ-SO₄)]⁺ core have been studied through Car-Parrinello molecular dynamics (CPMD) simulations with the BLYP functional. According to constrained CPMD/BLYP simulations and pointwise thermodynamic integration, the free energy of deprotonation of [Be(H₂O)₄]²⁺ and its binding free energy with F^- are 9.6 and -6.2 kcal/mol, respectively, in good accord with available experimental data. The computed activation barriers for replacing a water ligand in [Be(H₂O)₄]²⁺ with F^- and SO₄^2-, 10.9 and 13.6 kcal/mol, respectively, are also in good qualitative agreement with available experimental data. These ligand-substitution reactions are indicated to follow associative interchange mechanisms with backside (S_N2-like) attack of the anion relative to the aquo ligand it is displacing. Outperforming static density functional theory computations of the salient kinetic and thermodynamic quantities involving simple polarizable continuum solvent models, CPMD simulations are validated as a promising tool for studying the structures and speciation of beryllium complexes in aqueous solution.

Aqueous solubility of beryllium(II) at physiological pH: effects of buffer composition and counterions

Beryllium ion elicits p53-mediated cell cycle arrest in some types of human cancer cells, and it is a potent inhibitor of GSK3 kinase activity. Paradoxically, Be²⁺ is regarded to have almost negligible aqueous solubility at physiological pH, due to precipitation as Be(OH)₂. This study demonstrates that the interaction of Be²⁺ with serum proteins greatly increases its effective solubility. In typical serum-supplemented mammalian cell culture medium, Be²⁺ was soluble up to about 0.5 mM, which greatly exceeds the concentration needed for biological activity. Some biochemical studies require protein-free Be²⁺ solutions. In such cases, the inclusion of a specific inorganic counterion, sulfate, increased solubility considerably. The role of sulfate as a solubility-enhancing factor became evident during preparation of buffered solutions, as the apparent solubility of Be²⁺ depended on whether H₂SO₄ or a different strong acid was used for pH adjustment. The binding behavior of Be²⁺ observed via isothermal titration calorimetry was affected by the inclusion of sodium sulfate. The data reflect a "Diverse Ion Effect" consistent with ion pair formation between solvated Be²⁺ and sulfate. These insights into the solubility behavior of Be²⁺ at physiological and near-physiological pH will provide guidance to assist sample preparation for biochemical studies.

Ab-initio investigation on ion-associated species and association process in Li[B(OH)4] solution

In this paper, the factors determining the spectroscopic characteristics of v_sym-B(OH)₄^- band including coupling effect, hydrogen bonding effect, and direct contact effect in Li[B(OH)₄] solutions are investigated by using ab initio calculation. The coupling effect between the liberations of water and [B(OH)₄^-] has a larger effect on v_sym-B(OH)₄^- in solvent-shared ion pair (SIP) and monodentate contact ion pair (MCIP), but the smaller effect in bidentate contact ion pair (BCIP). Water molecule tends to hydrate to the middle position between the first sphere of B(OH)₄^- and outer-sphere of [Li(H₂O)₄⁺] and has a different effect on v_sym-B(OH)₄^- in ion pairs. The direct contact effect and polarization effect lead to 19.7 cm^-1 red shift of v_sym-B(OH)₄^- in MCIP, and 0.4 cm^-1 blue shift in BCIP. The association process in Li[B(OH)₄] solution was also introduced by using Raman spectral evolution of v_sym -B(OH)₄^- in the dehydration process.

Coordination of Be and Mg Centres by HCN Ligands - Be…N and Mg…N Interactions

ωB97XD/aug-cc-pVTZ calculations were performed for clusters of Z2+ cations (Z=Be and Mg) and HCN molecules (up to six molecules). The clusters of Be(CH3 )2 and Mg(CH3 )2 with HCN species were also calculated to analyse the influence of the Be/Mg-C formally covalent bonds on interactions of Be or Mg centre with ligands. The beryllium and magnesium centres possess different areas of a positive electrostatic potential that depend on a number of HCN ligands in the cluster considered. Numerous correlations between geometrical, energetic and topological parameters of the clusters considered are discussed since various theoretical approaches are applied; Quantum Theory of 'Atoms in Molecules', Natural Bond Orbital method and decomposition of the energy of interaction. The Be/Mg…N interactions classified as beryllium and magnesium bonds possess numerous characteristics which are known for the hydrogen bonds. Different types of coordination of Be and Mg centres analysed here exist also in crystal structures.

Synthesis, IR spectroscopy and crystal structure of [(UO2)2{Be(H2O)2(PO4)2}]·(H2O), the first compound with a trimer beryllophosphate anion

The first uranyl beryllophosphate, [(UO2)2{Be(H2O)2(PO4)2}]·(H2O), has been synthesized under hydrothermal conditions at 200°C. The monoclinic unit-cell parameters are: a=9.3361(1), b=8.8545(4), c=9.6592(10) Å, β=93.211(1)°, V=797.21(6) Å3, space group P2/n, Z=2. The crystal structure has been solved by direct methods and refined to final R 1=4.92% using 1294 I>3σ(I) reflections in the anisotropic approximation. The structure consists of sheets of UrO5 pentagonal bipyramids and PO4 tetrahedra. UrO5 bipyramids are linked by edge-sharing to form infinite chains. Adjacent chains of UrO5 bipyramids are connected by sharing alternating edges of uranyl bipyramids with PO4 tetrahedra. The resulting sheets are based on the well-known uranophane anion-topology. Be atoms are tetrahedrally coordinated by two oxygen atoms of PO4 tetrahedra and two water molecules in the interlayer space. One isolated water molecule also occurs in the interlayer space, where it is held in position by H bonds. The connection between the phosphorus and beryllium tetrahedra leads to formation of an unbranched trimer [BeP2O8(H2O)2]4− observed for the first time in inorganic oxysalts.

A facile synthesis for BeCl2, BeBr2and BeI2

A facile synthesis for anhydrous berylliumhalides is presented and their vibrational spectra have been measured for the first time.

Vibrational spectroscopic studies and DFT calculations on NaCH3CO2(aq) and CH3COOH(aq)

NaCH₃CO₂(aq) and CH₃COOH(aq) were studied using Raman and infrared spectroscopy over a large concentration range, in the terahertz region and up to 4000 cm⁻¹. Band assignments for CH₃CO₂⁻(aq) and CH₃COOH(aq) were carried out under guidance of DFT frequencies.

Cooperativity between hydrogen bonds and beryllium bonds in (H2O)(n)BeX2 (n = 1-3, X = H, F) complexes. A new perspective

The interaction of BeX(2) (X = H, F) with water molecules has been analyzed at the B3LYP/6-311+G(3df,2p)//B3LYP/6-311+G(d,p) level of theory. The formation of strong beryllium bonds between water molecules and the BeX(2) derivative triggers significant electron density redistribution within the whole system, resulting in significant changes in the proton donor and proton acceptor capacity of the water molecules involved. Hence, significant cooperative and anti-cooperative effects are present, explaining why there is no case in which the global minimum corresponds to a tetracoordinated beryllium atom. In fact, the most stable clusters can be viewed as the result of the attachment of BeX(2) to the water trimer and the water dimer, respectively, and not as the result of the solvation of the BeX(2) molecule. We have also shown that the decomposition of the interaction energy into atomic components is a reliable quantitative tool to describe all the closed-shell interactions present in the clusters investigated herein, namely hydrogen bonds, beryllium bonds and dihydrogen bonds. Indeed, we have shown that the changes in the atomic energy components are correlated with the changes in the strength of these interactions, and they provide a quantitative measure of cooperative effects directly in terms of energies.