Species In Aqueous Solution Research Articles

Characterization of the Fe(III)-Tiron System in Solution through an Integrated Approach Combining NMR Relaxometric, Thermodynamic, Kinetic, and Computational Data.

The Fe(III)-Tiron system (Tiron = 4,5-dihydroxy-1,3-benzenedisulfonate) was investigated using a combination of 1H and 17O NMR relaxometric studies at variable field and temperature and theoretical calculations at the DFT and NEVPT2 levels. These studies require a detailed knowledge of the speciation in aqueous solution at different pH values. This was achieved using potentiometric and spectrophotometric titrations, which afforded the thermodynamic equilibrium constants characterizing the Fe(III)-Tiron system. A careful control of the pH of the solution and the metal-to-ligand stoichiometric ratio allowed the relaxometric characterization of [Fe(Tiron)3]9-, [Fe(Tiron)2(H2O)2]5-, and [Fe(Tiron)(H2O)4]- complexes. The 1H nuclear magnetic relaxation dispersion (NMRD) profiles of [Fe(Tiron)3]9- and [Fe(Tiron)2(H2O)2]5- complexes evidence a significant second-sphere contribution to relaxivity. A complementary 17O NMR study provided access to the exchange rates of the coordinated water molecules in [Fe(Tiron)2(H2O)2]5- and [Fe(Tiron)(H2O)4]- complexes. Analyses of the NMRD profiles and NEVPT2 calculations indicate that electronic relaxation is significantly affected by the geometry of the Fe3+ coordination environment. Dissociation kinetic studies indicated that the [Fe(Tiron)3]9- complex is relatively inert due to the slow release of one of the Tiron ligands, while the [Fe(Tiron)2(H2O)2]5- complex is considerably more labile.

Review on Electrocatalytic Coreduction of Carbon Dioxide and Nitrogenous Species for Urea Synthesis.

The electrochemical coreduction of carbon dioxide (CO2) and nitrogenous species (such as NO3-, NO2-, N2, and NO) for urea synthesis under ambient conditions provides a promising solution to realize carbon/nitrogen neutrality and mitigate environmental pollution. Although an increasing number of studies have made some breakthroughs in electrochemical urea synthesis, the unsatisfactory Faradaic efficiency, low urea yield rate, and ambiguous C-N coupling reaction mechanisms remain the major obstacles to its large-scale applications. In this review, we present the recent progress on electrochemical urea synthesis based on CO2 and nitrogenous species in aqueous solutions under ambient conditions, providing useful guidance and discussion on the rational design of metal nanocatalyst, the understanding of the C-N coupling reaction mechanism, and existing challenges and prospects for electrochemical urea synthesis. We hope that this review can stimulate more insights and inspiration toward the development of electrocatalytic urea synthesis technology.

Quenching of the Photoluminescence of Gold Nanoclusters Synthesized by Pulsed Laser Ablation in Water upon Interaction with Toxic Metal Species in Aqueous Solution

Sensors for the detection of heavy metal ions in water are in high demand due to the danger they pose to both the environment and human health. Among their possible detection approaches, modulation of the photoluminescence of gold nanoclusters (AuNCs) is gaining wide interest as an alternative to classical analytical methods based on complex and high-cost instrumentation. In the present work, luminescent oxidized AuNCs emitting in both ultraviolet (UV) and visible (blue) regions were synthesized by pulsed laser ablation of a gold target in NaOH aqueous solution, followed by different bleaching processes. High-resolution electron microscopy and energy-dispersive X-ray scattering confirmed the presence of oxygen and gold in the transparent photoluminescent clusters, with an average diameter of about 3 nm. The potentialities of the bleached AuNCs colloidal dispersions for the detection of heavy metal ions were studied by evaluating the variation in photoluminescence in the presence of Cd2+, Pb2+, Hg2+ and CH3Hg+ ions. Different responses were observed in the UV and visible (blue) spectral regions. The intensity of blue emission decreased (no more than 10%) and saturated at concentrations higher than 20 ppb for all the heavy metal ions tested. In contrast, the UV band emission was remarkably affected in the presence of Hg2+ ions, thus leading to signal variations for concentrations well beyond 20 ppb (the concentration at which saturation occurs for other ions). The limit of detection for Hg2+ is about 3 ppb (15 nmol/L), and the photoluminescence intensity diminishes linearly by about 75% up to 600 ppb. The results are interpreted based on the ligand-free interaction, i.e., the metallophilic bonding formation of Hg2+ and Au+ oxide present on the surface of the UV-emitting nanoclusters.

Recent progress in C–N coupling for electrochemical CO2 reduction with inorganic nitrogenous species in aqueous solution

The electrocatalytic CO2 reduction in aqueous solution mainly involves bond cleavage and formation between C, H and O, and it is highly desirable to expand the bond formation reaction of C with other atoms to obtain novel and valuable chemicals. The electrochemical synthesis of N-containing organic chemicals in electrocatalytic CO2 reduction via introducing N sources is an effective strategy to expand the product scope, since chemicals containing C–N bonds (e.g. amides and amines) are important reactants/products for medicine, agriculture and industry. This article focuses on the research progress of C–N coupling from CO2 and inorganic nitrogenous species in aqueous solution. Firstly, the reaction pathways related to the reaction intermediates for urea, formamide, acetamide, methylamine and ethylamine are highlighted. Then, the electrocatalytic performance of different catalysts for these several N-containing products are summarized and classified. Finally, the challenges and opportunities are analyzed, aiming to provide general insights into future research directions for electrocatalytic C–N coupling.

Recent advances of the thermodynamic behavior of tin species in aqueous solution

Thermodynamic behavior has been extensively used to evaluate the stability of materials and predict the direction of the chemical reaction at different pH values, temperatures, potentials, and ion concentrations. Although researching efforts on Sn species in an aqueous solution system (Sn/H2O) of acid, alkali, and salt have been reported, scattered data leads to the inefficiency of a thermodynamic method in the practical application. This article provides a brief review on the potentialpH diagram for Sn/H2O system, which reflects the thermodynamic behavior of Sn species in an aqueous solution and extracts thermodynamic data for the practical application of Sn species. Firstly, the relationship of the thermodynamic behavior, potential-pH diagram, and equilibrium relations of Sn species for Sn/H2O system was overviewed. Additionally, the potential-pH diagram of Sn/H2O system at different temperatures (298 K, 373 K, and 550 K), dissolved Sn activities (1, 10?1, 10?3, and 10?6), and the potential-pH diagram of the Sn species in a chloridion aqueous solution (Sn/H2O-Cl) was summarized. Finally, the application prospect of the potential-pH diagram for Sn/H2O system was investigated in the intelligent simulation of Sn metallurgy and the practical application of Sn materials.

Excited states of polonium(IV): electron correlation and spin-orbit coupling in the Po4+ free ion and in the bare and solvated [PoCl5]- and [PoCl6]2- complexes.

Polonium (Po, Z = 84) is a main-block element with poorly known physico-chemical properties. Not much information has been firmly acquired since its discovery by Marie and Pierre Curie in 1898, especially regarding its speciation in aqueous solution and spectroscopy. In this work, we revisit the absorption properties of two complexes, [PoCl5]- and [PoCl6]2-, using quantum mechanical calculations. These complexes have the potential to exhibit a maximum absorption at 418 nm in HCl medium (for concentrations of 0.5 mol L-1 and above). Initially, we examine the electronic spectra of the Po4+ free ion and of its isoelectronic analogue, Bi3+, in the spin-orbit configuration interaction (SOCI) framework. Our findings demonstrate that the SOCI matrix should be dressed with correlated electronic energies and that the quality of the spectra is largely improved by decontracting the reference states at the complete active space plus singles (CAS + S) level. Subsequently, we investigate the absorption properties of the [PoCl5]- and [PoCl6]2- complexes in two stages. Firstly, we perform methodological tests at the MP2/def2-TZVP gas phase geometries, indicating that the decontraction of the reference states can be skipped without compromising the accuracy significantly. Secondly, we study the solution absorption properties by means of single-point calculations performed at the solvated geometries, obtained by an implicit solvation treatment or a combination of implicit and explicit solvation. Our results highlight the importance of saturating the first coordination sphere of the PoIV ion to obtain a qualitatively correct picture. Finally, we conclude that the known-for-decades 418 nm peak could be attributed to a mixture of both the [PoCl5(H2O)]- and [PoCl6]2- complexes. This finding not only aligns with the behaviour of the analogous BiIII ion under similar conditions but also potentially provides an explanation for previous discrepancies in the literature.

Response Surface Methodology for the Optimization of Zn-Contaminated Soil Remediation by Soil Washing with Water-Soluble Chitosan.

Soil washing is an important method for the remediation of contaminated soil. This research presents the optimization of soil washing conditions in the remediation of Zn-contaminated soils with water-soluble chitosan (WSCS). Response surface methodology (RSM) was used to optimized the washing conditions after single factor experiments. The central composite design (CCD) with three factors and five levels was applied to the optimization of the removal efficiency of Zn from soils, and WSCS concentration, pH value, and washing time were evaluated variables in the washing process. Results indicated that the pH value (p < 0.0001) was the most significant factor which mainly affected the distribution and content of metal species in aqueous solution, ion exchange and adsorption/desorption behavior of metals, solubility of chelating agent, as well as readsorption of metal complexes. The optimal conditions for the Zn removal from soils were WSCS concentration of 1.5%, pH of 3.3, and washing time of 72 min. The removal efficiency could reach 65.4% under the optimized conditions, which was close to the predicted value of 68.3% by the response surface method. Therefore, it could be found that the response surface methodology was an effective method to determine the optimal conditions for the removal of metals from contaminated soils by soil washing.

A new version of the Langelier-Ludwig square diagram under a compositional perspective

The Langelier-Ludwig square diagram is a commonly used diagnostic tool in groundwater chemistry. Suitable groupings of cations and anions are selected and plotted as percentages of milliequivalents with the sums of the selected cations and anions plotted on the y- and x-axes, respectively. It displays relative ratios rather than absolute concentration whereby each axis ranges from 0 to 50 meq%. However, the sample space in which data are represented in a Langelier-Ludwig square diagram is indeed given by the simplex. Incorrect conclusions may be drawn when the compositional nature of compositional data is not taken into account, i.e., a change in one value in one component changes all other values due to due to the constant sum constraint of the measured chemical elements. Correlations are thus influenced by the presence of negative bias in the covariance structure and linear or nonlinear patterns on the square diagram can be misinterpreted. A new version of the Langelier-Ludwig square diagram based on a well-chosen coordinate representation of cations and anions is proposed. The advantage of the revised diagram is that all the information is contained in the log-ratios describing the intricate relationship between chemical species in aqueous solutions. It is shown that the geochemical interpretation of this new diagram – based on the relative dominance of major ions and distance from the (robust) barycenter of the data – provides a better and unbiased understanding of water-environment interactions. To further aid interpretation, (robust) tolerance ellipses show the correlation structure in the new version of the Langelier-Ludwig square diagram, and clustering algorithms can be applied to divide the data into groups beforehand. A bunch of different plotting options and interactive representations complete the implementation in free open-source software. It is recommended to replace the classic Langelier-Ludwig diagram with the new version.

A Water-Soluble Leggero Pillar[5]arene.

The study of aqueous-phase molecular recognition of artificial receptors is one of the frontiers in supramolecular chemistry since most biochemical processes and reactions take place in an aqueous medium and heavily rely on it. In this work, a water-soluble version of leggero pillar[5]arene bearing eight positively charged pyridinium moieties (CWP[5]L) was designed and synthesized, which exhibited good binding affinities with certain aliphatic sulfonate species in aqueous solutions. Significantly, control experiments demonstrate that the guest binding performance of CWP[5]L is superior to its counterpart water-soluble macrocyclic receptor in traditional pillararenes.

Rapid, Selective Fluorescent Determination of Copper (II) in Aqueous Solution and Living Cells Using a Dansyl-Based Click Probe

A novel 1,2,3-triazole based dansyl fluorophore has been designed and synthesized for detecting Cu2+ as a fluorescent probe (P1). The probe P1 exhibited high sensitivity and selectivity for Cu2+ compared to other selected species in aqueous solution within a wide pH span (5 to 14), which showed that P1 may be applied in the entire alkaline pH window. The limit of detection (LOD) was measured to be as low as 5 × 10−7 mol/L for Cu2+. A 1:2 binding ratio and association constant of 4.6 × 104 M−1 between P1 and Cu2+ were determined. Additionally, rapid response to Cu2+ was demonstrated in less than 3 seconds and the linear concentration range was from 0.5 to 2.5 µmol/L. Moreover, probe P1 showed good biocompatibility and cell membrane permeability and was successfully applied for imaging Cu2+ in water samples and living cells, which demonstrates the application of P1 in complicated environments.

Complexing properties of 2-pyridylphoshonate and 2-pyridylsulfonate ligands for Zn2+ and Ag+ central atoms

The Zn2+/Ag+-pypo and pysu (pypo = 2-pyridylphosphonate, pysu = 2-pyridylsulfonate) complexes speciation in aqueous solution at I = 0.1 M (KNO3) and 25 °C is described in detail under our experimental synthetic conditions. Protonation and stability constants were determined, and distribution diagrams show protonated and deprotonated complexes formation in the case of Zn2+/Ag+ pypo/pysu binary system, respectively. Moreover, the new complex, {[Zn(H2pypo)2(H2O)2]}n(ClO4)2n·2nH2O, was isolated and its spectral and structural properties were determined. An unusual pypo bidentate coordination mode is described and compared with published ones.

The simultaneous reduction and adsorption for V(V) and Cr(VI) anionic species in aqueous solution by polyethyleneimine cross-linked titanate nanotubes

Treating water containing hazardous V(V) and Cr(VI) by using a efficient and simple method is an urgent need, but still a challenge. Novel binary composites (PEI-TNTs) were successfully synthesized by introducing polyethyleneimine (PEI) onto titanate nanotubes (TNTs) in a cost-effective and facile route, where TNTs and PEI existed as an interior core and an exterior shell. The removal efficiency of PEI-TNTs was highly reliant on the initial solution pH according to the batch adsorption experiments, and the maximum adsorption capacity for V(V) reached 1280.36 mg g−1 at pH 3.0 and for Cr(VI) reached 980.39 mg g−1 at pH 2.0 calculated by the Langmuir model. And PEI-TNTs effectively resisted the interference of various coexisting anions and cations. In simulated mining wastewater experiments, PEI-TNTs still remained fine V(V) and Cr(VI) adsorption capability; and PEI-TNTs could be regenerated and reused for 5 cycles without significantly reducing its removal efficiency. The excellent removal performance mainly owned to the high stability of inorganic skeleton and high surface activity from polymer modification. A comprehensive mechanism was proposed for the adsorption process associating with electrostatic attraction, redox reaction, and chelation. This work provides the theoretical and practical information for the novel inorganic–organic nanomaterials based on titanate nanotubes and polymers for the efficient reduction and adsorption of heavy metal anionic pollutants in water.

Chromium removal from tannery wastewaters with a strong cation exchange resin and species analysis of chromium by MINEQL+

Chromium (III) salts are highly applied for tanning purpose in tannery industries. The purpose of this study was removal and recovery of chromium(III) from tannery wastewater with a strong cation exchange resin. For this purpose, Amberlite 252 ZU was chosen as a strong cation exchange resin. In the first part of this study, The MINEQL+ computer program was applied depending on the optimum concentration and pH for determining Cr species in aqueous solutions. The second part of the work consists of measuring the exchange equilibrium of H+ ions and Cr(III) ions. Therefore, solutions containing fixed amounts of chromium were brought into contact with different amounts of resins. The evaluation of the obtained equilibrium parameters was done by surface complexing theory. Retention and regeneration steps were successfully performed in the column without any significant change up to 10 cycles. Efficiency was between 90 and 98% in removal studies, and between 81 and 92% in recovery studies. The results showed that a strong cation exchange resin Amberlite 252 ZU can be successfully used for chromium removal and recovery.

Electrocatalytic Reduction of Nitrogen Oxyanions with a Redox-Active Cobalt Macrocycle Complex.

The cobalt complex, [Co(CR)Br2]+, where CR is the redox-active macrocycle 2,12-dimethyl-3,7,11,17-tetraazabicyclo-[11.3.1]-heptadeca-1(17),2,11,13,15-pentaene, has been investigated for the electrocatalytic reduction of aqueous NO2- and NO3-. At neutral pH, the bromide ligands are hydrolyzed, providing [Co(CR)(OH2)(OH)]2+ as the major species in aqueous solution. In the presence of nitrite, [Co(CR)(NO2)2]+ is formed as the major species in solution and is a precursor to the electrocatalytic reduction of NO2-, which is selectively converted to ammonium with high Faradaic efficiency. There is evidence for both homogeneous and heterogeneous electrocatalysis. Although similar NO3- binding is not observed, electrocatalytic reduction to ammonium also occurs, albeit with a lower Faradaic efficiency. In this case, NO2- is generated as an intermediate product of NO3- reduction.

Metal-Organic Framework-Based Materials for Adsorption and Detection of Uranium(VI) from Aqueous Solution.

The steady supply of uranium resources and the reduction or elimination of the ecological and human health hazards of wastewater containing uranium make the recovery and detection of uranium in water greatly important. Thus, the development of effective adsorbents and sensors has received growing attention. Metal–organic frameworks (MOFs) possessing fascinating characteristics such as high surface area, high porosity, adjustable pore size, and luminescence have been widely used for either uranium adsorption or sensing. Now pertinent research has transited slowly into simultaneous uranium adsorption and detection. In this review, the progress on the research of MOF-based materials used for both adsorption and detection of uranium in water is first summarized. The adsorption mechanisms between uranium species in aqueous solution and MOF-based materials are elaborated by macroscopic batch experiments combined with microscopic spectral technology. Moreover, the application of MOF-based materials as uranium sensors is focused on their typical structures, sensing mechanisms, and the representative examples. Furthermore, the bifunctional MOF-based materials used for simultaneous detection and adsorption of U(VI) from aqueous solution are introduced. Finally, we also discuss the challenges and perspectives of MOF-based materials for uranium adsorption and detection to provide a useful inspiration and significant reference for further developing better adsorbents and sensors for uranium containment and detection.

Solution- and gas-phase behavior of decavanadate: implications for mass spectrometric analysis of redox-active polyoxidometalates.

Decavanadate (V10O28 6- or V10) is a paradigmatic member of the polyoxidometalate (POM) family, which has been attracting much attention within both materials/inorganic and biomedical communities due to its unique structural and electrochemical properties. In this work we explored the utility of high-resolution electrospray ionization (ESI) mass spectrometry (MS) and ion exclusion chromatography LC/MS for structural analysis of V10 species in aqueous solutions. While ESI generates abundant molecular ions representing the intact V10 species, their isotopic distributions show significant deviations from the theoretical ones. A combination of high-resolution MS measurements and hydrogen/deuterium exchange allows these deviations to be investigated and interpreted as a result of partial reduction of V10. While the redox processes are known to occur in the ESI interface and influence the oxidation state of redox-active analytes, the LC/MS measurements using ion exclusion chromatography provide unequivocal evidence that the mixed-valence V10 species exist in solution, as extracted ion chromatograms representing V10 molecular ions at different oxidation states exhibit distinct elution profiles. The spontaneous reduction of V10 in solution is seen even in the presence of hydrogen peroxide and has not been previously observed. The susceptibility to reduction of V10 is likely to be shared by other redox active POMs. In addition to the molecular V10 ions, a high-abundance ionic signal for a V10O26 2- anion was displayed in the negative-ion ESI mass spectra. None of the V10O26 cations were detected in ESI MS, and only a low-abundance signal was observed for V10O26 anions with a single negative charge, indicating that the presence of abundant V10O26 2- anions in ESI MS reflects gas-phase instability of V10O28 anions carrying two charges. The gas-phase origin of the V10O26 2- anion was confirmed in tandem MS measurements, where mild collisional activation was applied to V10 molecular ions with an even number of hydrogen atoms (H4V10O28 2-), resulting in a facile loss of H2O molecules and giving rise to V10O26 2- as the lowest-mass fragment ion. Water loss was also observed for V10O28 anions carrying an odd number of hydrogen atoms (e.g., H5V10O28 -), followed by a less efficient and incomplete removal of an OH• radical, giving rise to both HV10O26 - and V10O25 - fragment ions. Importantly, at least one hydrogen atom was required for ion fragmentation in the gas phase, as no further dissociation was observed for any hydrogen-free V10 ionic species. The presented workflow allows a distinction to be readily made between the spectral features revealing the presence of non-canonical POM species in the bulk solution from those that arise due to physical and chemical processes occurring in the ESI interface and/or the gas phase.

A molecular dynamics investigation of La3+ and Lu3+-ligand speciation in aqueous solution

Ion-pair association of rare earth elements (REE) with ligands is important for its mobilization, enrichment, and fractionation during hydrothermal transport process, which is of great significance to study REE ore genesis, weathering process, the origin and evolution of earth and other related geoscience issues. However, reliable experimental data are limited to a specific system or ambient conditions, which hampered our understanding of the geochemical behavior of REE. In the present study, classical molecular dynamics simulations were carried out to calculate the potential of mean force (PMF) between La3+/Lu3+ and ligands of Cl−, F−, OH−, HCO3−, CO32− and SO42− in dilute aqueous solutions from ambient to supercritical thermodynamic conditions. Stability constants were calculated from the PMFs and compared with literature reported and thermodynamic calculated data. The analyses of the PMFs and stability constants suggest smaller or highly charged ions are easier to form stable complexes. For both La3+ and Lu3+ containing systems, the stability of ion pair decreases in the order of CO32− > OH− > SO42− > F− > HCO3− > Cl−. The smaller Lu3+ is to form more stable aqueous complexes at all thermodynamic conditions and these stability difference may lead to significant fractionation between La (light) and Lu (heavy). The trends of PMFs calculated stability constants are consistent with thermodynamic calculated values and provide association constants of ligands for which no experimental data exist.

PH-dependent structural changes of arsenic oxoacids in solution and solid phase: Raman spectrometry and computational studies

Reliably knowledge of the arsenic oxoacids in solution and solid-state and any possible relationship between them at different pHs is of concern in various scientific fields. This work compares the experimental Raman spectra of the inorganic arsenic oxoacids in aqueous solutions under acidic, neutral and alkaline conditions with the dry precipitates obtained from the corresponding aqueous solutions. Further, we explore the ability of quantum chemical methods to model the Raman spectra of the arsenic oxoacids in solution by considering explicit water molecules and conformational sampling, fitting reasonably well with the experimental spectra in the whole pH range covered. Hydrogen bridges and the coexistence of arsenic oxoacids facilitate strong overlapping in the Raman spectra of the As(III) aqueous samples compared with the As(V) ones. Some Raman shifts of the dry arsenic precipitates correlate well with the corresponding Raman spectra of the same arsenic species in aqueous solutions, allowing a practical use of the Raman spectrometry for indirect screening purposes of arsenic speciation in both condensed phases.

Quantification of mineral reactivity using machine learning interpretation of micro-XRF data

Accurate characterizations of mineral reactivity require mapping of spatial heterogeneity, and quantifications of mineral abundances, elemental content, and mineral accessibility. Reactive transport models require such information at the grain-scale to accurately simulate coupled processes of mineral reactions, aqueous solution speciation, and mass transport. In this work, millimeter-scale mineral maps are generated using a neural network approach for 2D mineral mapping based on synchrotron micro x-ray fluorescence (μXRF) data. The approach is called Synchrotron-based Machine learning Approach for RasTer (SMART) mapping, which reads μXRF scans and provides mineral maps of the same size and resolution. The SMART mineral classifier is trained on coupled μXRF and micro-x-ray diffraction (μXRD) data, which is what distinguishes it from existing mapping tools. Here, the SMART classifier was applied to μXRF scans of various sedimentary rock samples including consolidated shales from the Eagle Ford (EFS1), Green River (GRS1), Haynesville (HS1), and New Albany (NAS1) formations and a syntaxial vein from the Upper Wolfcamp formation. The data were obtained using an x-ray microprobe at beamline 13-ID-E at the Advanced Photon Sources. Individual mineral maps generated by the SMART classifier well-captured distributions of both dominant and minor phases in the shale rocks and revealed EFS1 and GRS1 to be carbonate rich shales, and NAS1 and HS1 to be sulfide rich shales. The EFS1 was further characterized for its trace mineral abundances, grain sizes, trace element composition, and accessibility. Approximately 4.4 wt% of the rock matrix were found to be pyrite, with a median grain size of 3.17 μm in diameter and 62% of the grains predicted to be smaller than 4 μm. Quantifications of trace elements in pyrite revealed zinc concentrations up to 4.2 wt%, along with minor copper and arsenic copresence. Mineral accessibility was examined by contact with other phases and was quantified using a new type of image we are calling an adjacency map. Adjacency analyses revealed that of the total pyrite surface present in the EFS1, 28% is in contact with calcite. The adjacency maps are useful for quantifying the likelihood that a mineral could be exposed to fluids after dissolution of a contacting reactive phase like calcite. Lastly, pooling data from different samples was demonstrated by training a classifier using two sets of coupled μXRF-μXRD data. This classifier yielded an overall accuracy of >96%, demonstrating that data pooling is a promising approach for applications to a wide suite of rock samples of different origin, size, and thickness.

Derivation of limiting ion mobility equation based on the application of solvation effect-incorporated Poisson-Boltzmann equation

Interaction potential energy between ion and solvent molecular dipole moments in solvation shell around ion was derived on basis of the application of the solution of linear SEI-PB (Solvation Effects-Incorporated Poisson-Boltzmann) equation. Based on application of the solution of linear SEI-PB equation, distribution of solvent molecules in solvation shell around ion in electrolyte solution at thermodynamic equilibrium was derived. In case approaching to limit of infinite dilution, analytical expression for evaluating limiting ion mobility is derived from the boundary condition that the average number of solvent molecules accompanying with translational motion of ion is equal to the mean solvation number of ion. The derived limiting ion mobility formula is different from the Stokes–Einstein relation and lies in relation to direct proportion with the cube of dynamic size of ion in solution, depending not only on the viscous coefficient, dielectric constant, the density and molecular weight of solvent but also on temperature.By virtue of the equation, it was possible to estimate dynamic sizes of ions in solution. It was found the estimated dynamic sizes of ions in aqueous solution to be compatible with the average ion–water distances, and to be always greater than crystallographic ionic radii in size.A new relation between the limiting ion mobility and the solvent molecular dipole moment in solvation shell was established based on the interaction potential energy between ion and solvent molecular dipole moments in solvation shell around ion. By virtue of the proposed relation, we could find out the average water molecular dipole moment in hydration shell to be different more or less in size from that in bulk solution according to ionic species in aqueous solution.