Cationic Forms Research Articles

Direct capture of the alanine ghost in alanine-doped triglycine sulfate crystals.

In this report, ghostly ultra-trace amounts of alanine in alanine-doped triglycine sulfate crystal were directly observed by solid-state nuclear magnetic resonance, and the presence of two chemical states in the cation form and neutral form in the doped alanine was revealed. As the result, the crystal structure of alanine-doped triglycine sulfate was determined for the first time.

PE/PP fibrous adsorbents with bifunctional groups of tertiary amine and phosphate prepared by electron beam induced co-grafting for heavy metal adsorption of both cationic and anionic forms in acidic conditions.

A novel fabric adsorbent having bifunctional groups of tertiary amine and phosphate was prepared by co-graft polymerization of 2-diethylaminoethyl methacrylate (NMA) and 2-hydroxyethyl methacrylate phosphate (PMA) onto a polyethylene/polypropylene nonwoven fabric (PE/PP NF) under low-energy electron beam acceleration. The process involved pre-irradiating the fabric and immersing it in the comonomer solution for grafting. The kinetics of radiation-induced graft polymerization at a total dose of 100 kGy was investigated. For pre-irradiation at 100 kGy, the optimum condition offering highest degree of grafting was at 12 wt% of NMA, 8 wt% of PMA and 4 h of reaction time. The adsorption of anions using hydrogen chromate (HCrO4−) or Cr(VI) and cations using lead (Pb(II)), cadmium (Cd(II)) and copper (Cu(II)) in aqueous solution was carried out. The results demonstrated that the bifunctional adsorbent was able to adsorb both heavy metal anionic and cationic ions from water. The co-grafted adsorbents with tertiary amine and phosphate were able to adsorb 85% Cr(VI) anion and 29% Pb(II) cations from mixed Cr(VI) and Pb(II) solution at pH 3.0 and 71% Pb(II), 13% Cd(II) and 31 % Cu(II) from mixed Pb(II), Cd(II) and Cu(II) solution at pH 5.0. The unique achievement of this study is its hypothesis that a bifunctional adsorbent can be prepared from radiation-induced graft polymerization of two different monomers onto NF, along with proof that the prepared bifunctional adsorbent can actually absorb both cationic or anionic heavy metals forms. Additionally, the adsorbent's preparation offers a rapid and straightforward one-step grafting technique. Therefore, the new bifunctional adsorbents can remove heavy metal ions in aqueous solution, either in the cation or anion form, thus offering highly promising applications in industrial wastewater treatment.

Electrochemical and electrocatalytic properties of hemihexaphyrazine and its trinuclear cobalt complex

The electrochemical and electrocatalytic properties of hemihexaphyrazine and its trinuclear cobalt complex were studied by cyclic voltammetry. The possibility of detecting cationic and anionic forms of compounds in the process of polarization of electrodes in the region of potentials 0.5 ÷ -1.5 V has been established. It is shown that the synthesized cobalt complex has a sufficiently high catalytic activity in the oxygen reduction reaction in an alkaline solution.

As, Pb and Cu Stabilization By a Mixture Type of Mg-Fe Layered Double Hydroxide (LDH) with Oyster Shell: Laboratory and Field Evaluations

Oyster shell has been studied as effective stabilizer for heavy metals that exist as cationic forms in soil-aqueous system, but its stabilization capacity for arsenic was very low because of its anionic existence forms. Layered double hydroxide (LDH) shows excellent oxyanion As fixation capacity in soil because of interlayer anion (or complex) exchange, but has relatively low fixation capabilities for other heavy metals. Because of different main mechanism to fix arsenic in the stabilizer compared to other heavy metals, there are limitations in applying only a single stabilizer to the site contaminated with both the arsenic and other heavy metals. The use of a powdered type stabilizer in the field could also be limited because of the risk of suffering mass loss, fugitive dust generation, and low sustainability of the stabilization effect. To overcome these problems, the granular and the slurry type of Mg-Fe LDH mixed with oyster shell were manufactured as the stabilizer to fix As, Pb, and Cu in the soil at the same time and their stabilization efficiencies were investigated by field scale demonstration tests in this study. Results from experiments confirmed that when a mixed granular type stabilizer was added into the soil, the extraction reducing efficiency for all three, As, Pb and Cu, from soil was more than 75%, which indicated that the mixed stabilizer has great potential to fix all of them in soil at the same time. In field demonstration tests (a total of 3 test beds; each bed: 3 m × 3 m × 2 m), the concentration of As and Pb in groundwater from treated test beds decreased by more than 60%, and their extraction reducing efficiencies were higher than 40%. Both As and Pb fractionation transition to more stable phases in test beds by the mixed stabilizer was clearly observed, supporting the Mg-Fe LDH mixed with oyster shell could be successfully used as a single stabilizer for sites contaminated with both heavy metals and As.

Theoretical perspectives on CO2 separation by ionic liquids: Addressing crucial questions

The global population explosion necessitates more natural resources for energy, making it a major factor in climate change. CO2 is a leading actor in the greenhouse gas effect, and advancements in CO2 capture processes have attracted researchers in recent years. Numerous technologies are practiced for CO2 separation. Nevertheless, due to the intricate nature of gases and different process conditions, most of them continue to face challenges. To overcome these challenges, researchers focus on finding or designing innovative materials compatible with various processes. From the discovery of high CO2 solubility of ionic liquids (ILs), these unique compounds have rapidly gained popularity for different applications like gas separation. Molecular simulations play a crucial role in supporting researchers in understanding the connection between the properties and chemical structure of newly developed materials as ILs in a time-efficient manner. Despite the growing number of molecular simulation studies, there is a gap in the review papers that effectively highlight the benefits and feasibility of the theoretical approach. Up to date, mostly experimental studies mainly focusing on gas transport mechanisms and the relationship between chemical composition and properties were summarized. Herein, we concentrated on molecular simulation studies investigating the adsorption- and membrane-based CO2 separation performance of confined ILs. We systematically addressed prominent questions posed by researchers in each simulation study, demonstrating how to examine confined ILs and interpret the resulting data in relation to gas separation performance. The most pertinent inquiries encompass the influence of ion type (cation or anion) on gas adsorption at the gas–liquid interface and through the confined IL phase, the significance of the confined form of cation or anion in gas transport, the impact of IL thickness on gas separation, and the discernible effects of the material in which ILs are confined. Therefore, we hope to guide researchers in developing innovative membranes or adsorbents by leveraging insights obtained from the answers to these questions derived from molecular simulations of confined ILs.

Theoretical Design of New Grafted Molecules d-Glucosamine-Oxyresveratrol-Essential Amino Acids: DFT Evaluation of the Structure-Antioxidant Activity.

In the pursuit of innovative high-performance materials suitable for antioxidant applications, the density functional theory was employed to design a series of compounds derived from small biodegradable organic molecules. This study involved grafting the negatively charged unit d-glucosamine (GleN) and essential amino acids onto the 3 and 4' carbons of the backbone of trans-2,4,3',5'-tetrahydroxystilbene (trans-OXY), respectively. The aim was to prevent trans-OXY degradation into the cis region and enhance its electronic and antioxidant properties. Theoretical calculations using DFT/PW91/TZP in water revealed that the designed biomolecules (GleN-OXY-AA) outperformed both free OXY units and essential amino acids in terms of antioxidant efficacy, as indicated by the bond dissociation energy (BDE) findings. Notably, GleN-OXY-Ile and GleN-OXY-Trp compounds exhibited an average BDE of 66.355 kcal/mol, translating to 1.82 times the activity of t-OXY and 1.55 times the action of ascorbic acid (Vit C). AIM analysis demonstrated that the proposed biomaterials favored the formation of quasi-rings through intramolecular H···O hydrogen bonds, promoting π-electron delocalization and stabilization of radical, cationic, and anionic forms. Quantum calculations revealed the release of hydrogen atoms or electrons from sites of reduced electronegativity, visually identified by MEP maps and estimated by Hirshfeld atomic charges.

Structure and intermolecular interactions in ionic liquid 1-ethyl-3-methylimidazolium bromide and its aqueous solutions investigated by vibrational spectroscopy and quantum chemical computations.

The recently developed efficient protocol to explicit quantum mechanical modeling of structure and IR spectra of liquids and solutions (S. A. Katsyuba, S. Spicher, T. P. Gerasimova, S. Grimme, J. Phys. Chem. B 2020, 124, 6664) is applied to ionic liquid (IL) 1-ethyl-3-methylimidazolium bromide (EmimBr), its C2-deuterated analog [Emim-d]Br and its aqueous solutions. It is shown that the solvation strongly modifies frequencies and IR intensities of the CH/CD stretching vibrations (νCH/νCD) of the imidazolium ring. The main vibrational spectroscopic features of the neat IL are reproduced by the simulations for a cluster (EmimBr)9, in which all three imidazolium CH moieties of the solvated cation form short contacts with three Br- anions, and another two Br- anions are located on top and bottom of imidazolium ring. Cluster models of aqueous solutions reproduce the experimental vibrational frequencies of actual solutions, provided that the Br- anion of solvated contact ion pair (CIP) is situated on top of imidazolium ring, and CH/CD moieties of the latter participate in short contacts with surrounding water molecules. Both structural and spectroscopic analysis allow to interpret the short contacts CH/CD⋯Br- and CH/CD⋯OH2 as hydrogen bonds of approximately equal strength. Enthalpies of bonding of these liquid-state H-bonds, estimated with the use of empirical correlations, amount to ca. 1.4 kcal⋅mol-1, while the analogous estimates obtained for the gas-phase charged species [Emim]2Br+ increase to 5.6 kcal⋅mol-1. It is shown that formation of solvent-shared ion pair (SIP) in aqueous solution, where the counterions of IL are separated by two water molecules H-bonded to a Br- anion, produces frequency shifts ΔνCH/CD, strongly different from the case of CIP formation. This difference can be used for IR/Raman spectroscopic differentiation of the type of solvated ion pairs of EmimBr or other related ILs.

The analysis of sarcosine phosphate single crystal based on polarized IR and Raman spectra

For the first time, the room temperature polarized IR reflection and Raman spectra of sarcosine phosphate (sar)·H3PO4, in the form of an oriented single crystal have been measured. The polarized spectra are discussed with respect to the crystal structure (X-ray diffraction) data and the literature data on the normal coordinate analysis of the zwitterionic and cationic forms of the sarcosine molecule. Based on the analysis of the spectra and transition dipole moment calculations for each internal mode with respect to the experimental X(a), Y(b) and Z(c) axes, we have been able to determine the directionality and strength of the complicated hydrogen bonds network in the crystal. The A-B-C band structure of the OH stretching vibrations in the strongest hydrogen bonds (HBs) has been assigned. Independent interactions of each HB with light are confirmed based on their polarization properties. The differences within the band of carboxyl group components are ascribed to a rather strong Davydov-type interaction between the carboxyl groups in the title crystal, they may also be caused by participation of the carboxyl-oxygen atom in the medium-strong HB with phosphate-oxygen. These studies are interesting from the point of view of designing strategy for the molecular engineering of new compounds with strong hydrogen bonds, new phase-change materials, as well as crystals with improved optical, magnetic and nonlinear optical properties.

Magnesium(II) Porphyrazine with Thiophenylmethylene Groups-Synthesis, Electrochemical Characterization, UV-Visible Titration with Palladium Ions, and Density Functional Theory Calculations.

The presented studies aimed to evaluate the peripheral coordinating properties of a novel porphyrinoid family representative preceded by its synthesis for potential sensing purposes. Two synthetic pathways were employed to a obtain maleonitrile derivative, further used as a starting material in the cyclotetramerization reaction. In the first one, DAMN was used in sequential double-reductive alkylation with 2-thiophene-carboxyaldehyde and sodium borohydride. In the second, DAMN was used in a one-pot reaction with 2-thiophene-carboxyaldehyde in the presence of a 5-ethyl-2-methylpyridine borane complex in methanol and acetic acid. Following the Linstead approach, the cyclization reaction led to a novel symmetrical magnesium(II) octaaminoporphyrazine with methyl(2-thiophenylmethylene) substituents. The macrocycle's electrochemical properties were assessed by cyclic and differential pulse voltammetries revealing one reduction and two oxidation peak potentials. The additional spectroelectrochemical measurements showed formation of a cationic form of the macrocycle at an applied potential of 0.6 V. The coordinating properties due to the palladium ion of novel porphyrazines were measured with the use of titration combined with UV-vis spectrometry. The titration of Pd2+ revealed the good sensing activity of porphyrazine in the range of 0.1 to 5 palladium molar equivalents. In addition, Pd2+ ions coordination was also assessed by electrochemical studies, indicating the peak potential shift of 0.1 V in the presence of metal cations. DFT calculations showed the good agreement between theoretical and experimental data in the UV-vis and 1H NMR studies.

Method and mechanism for efficient radium isolation from bulk thorium based on anion exchange

In recent years, targeted-α-nuclide therapy (TAT) has been widely concerned in the world. As one of the few representative TAT nuclides, 212Pb showed good efficacy in cancer treatment; however, the amount remains scarce. Separating 228Ra and 224Ra from 232Th is expected to fundamentally solve this issue, since they both are the parent nuclides of 212Pb and can be used in generators. In this work, an efficient method for trace radium isolation from bulk thorium was proposed and verified through a systematic investigation of the adsorption behaviors of an anion exchanger denoted IRA900 toward thorium and barium/radium. Batch experiments suggested that IRA900 had unique selectivity for thorium in nitric acid solution, with almost no barium adsorbed. The thorium adsorption performance kept improving with increasing concentration of nitric acid and decreasing temperature. The adsorption kinetics and adsorption isotherm could be well fitted by the pseudo-second-order kinetic model and the Langmuir model, respectively. Column experiments suggested that thorium could be effectively immobilized by a column packed with IRA900, while barium was directly penetrated. For desorbing the fixed thorium, 0.1 M HNO3 was optimal. A final hot test demonstrated the successful radium isolation from bulk thorium, with high chemical yield and purity. The selective separation mechanism was attributed to the formation of an anionic [Th(NO3)5]− complex, while barium or radium existed in the cationic form in any nitric acid concentration. This work provides a promising method for separating trace radium from thorium, which will be significant for promoting the large-scale utilization of 212Pb.

Graphene-Based Material Supports for Ni- and Ru- Catalysts in CO2 Hydrogenation: Ruling out Performances and Impurity Role.

Laboratory-prepared Gnp using molten salt, commercial Gnp and reduced graphene oxide (rGO) have been characterized and utilized as support for CO2 hydrogenation catalysts. Ni- and Ru- catalysts supported over Gnp, commercial Gnp and rGO have been deeply characterized at different stages using Raman, IR, XRD, FE-SEM-EDXS, SEM-EDXS, XPS, and TEM, also addressing carbon loss before reaction and evolved species, thus allowing a better comprehension of the produced materials. Ni and Ru/rGO were inactive while Gnp-supported ones were active. Ru has been found almost completely selective toward reverse Water Gas Shift to CO, approaching the forecasted thermodynamic equilibrium at 723 K, in the tested conditions (YCO~55 %), with an apparent activation energy in the range of 70-90 kJ/mol. Exhaust catalysts pointed out the presence of sulfur partially linked to the carbon matrix and partially producing the corresponding metal sulfide with the detection of surface oxidized species in the cationic form and adsorbed species as well. The metal-based nanoparticles displayed a quite narrow size distribution, confirming the promising behavior of these catalytic systems for CO2 utilization.

Determination of the Electronic Structure, Charge-transfer, and Optical Properties of Neutral, Anionic, and Cationic Perfluoropentacene

Perfluoropentacene ( is an n-type organic semiconductor made by fluorination of p-type semiconductor Pentacene and can find applications in molecular thin film devices. In this work, a theoretical study of Perfluoropentacene was carried out based on density functional theory (DFT) and time dependent (TD-DFT) as implemented in Gaussian 09 package using B3LYP/6-311++G (d, p) and B3LYP/6-31+G(d) basis sets. The electronic, charge transfer, Linear and nonlinear optical properties of the molecule were calculated and reported for the neutral, anionic, and cationic forms of the molecule. The results show that the cationic state of the molecule has the strongest bond length at R(28,32) using the basis sets B3LYP/6-311++G (d,p) and the weakest bond length was found at R(4,6) in the ionic state with 6-31+G (d) basis set. The energy gap obtained for the neutral molecule using 6-31+G (d) and 6-311++G (d,p) basis sets are 2.00eV, 1.99eV respectively. The results show a strong agreement with a previously related work that reported the energy gap as 2.02eV thus indicating high stability of the molecule. Perfluoropentacene has the highest value of chemical hardness of 1.3929eV in its anionic state (Beta MO), so is considered to be harder and more stable than the neutral and cationic. The findings also revealed that with toluene as solvent, the strongest absorption was found at wavelength of 738.38, highest oscillator strength of 0.0599 and the lowest excitation energy of 1.6791eV. The calculated results of polarizability, first and second hyperpolarizability confirm that this molecule is a good non-linear optical material. On the whole, the molecule could be a good material for optoelectronic applications.

Quercetin encapsulation and release using rapid CO2-responsive rosin-based surfactants in Pickering emulsions

Emulsion-based delivery systems are extensively employed for encapsulating functional active ingredients, protecting them from degradation, and enhancing bioavailability and release efficiency. Here, a CO2-responsive surfactant synthesized from rosin displays rapid responsiveness to CO2 at room temperature, transitioning reversibly switches between active and inactive states multiple times. The dual tertiary amines on the rosin rigid structure contributes to its CO2 sensitivity. When in its active cationic form, in conjunction with silica nanoparticles, it exhibits desired Pickering emulsification performance across various oil phases. In the Pickering emulsion loaded with quercetin, the encapsulation efficiency and loading efficiency reached 80.50% and 0.69%, respectively, with stability lasting at least 30 days. The system provides robust protection for quercetin against external factors, such as UV and heat, revealing sustained release effects. This study investigated the potential of using rosin-based CO2-responsive surfactants alongside nanoparticles to design stable Pickering emulsion systems for active substance encapsulation and sustained release.

In Ukrainian

An important environmental problem is the removal of contaminants and the purification of domestic and industrial water from pollutants of various nature. There is a separate issue of cleaning the effluents of pharmaceutical enterprises. Various chemical and physical methods are used to solve these problems, such as settling, coagulation, filtration, and sorption techniques. Adsorption with using efficient and reusable adsorbents is the most effective and cheap. In recent years special attention has been paid to the use of sorption materials based on hydrolysis lignin, which has a high sorption activity in relation to ions of some heavy metals, dyes, organic compounds and pharmaceuticals. The use of lignin as an adsorbent simultaneously solves two problems: the disposal of paper production waste and the purification of sewage from various types of pollutants. The aim of this work was to study the sorption properties of hydroylysis lignin in aqueous solution in relation to some medical substances of different chemical nature, existing in solution in cationic, anionic or neutral forms. The point of zero charge of hydrolysis lignin was determined, which is equal to рНPZC = 4.95. The adsorption of rivanol, proflavin, doxorubicin, levofloxacin, furacilin, and salicylic acid by hydrolysis lignin was studied as dependence on the pH of the solutions and the concentration of adsorbates. It was found that adsorption largely depends on the structure of the pharmaceuticals and the pH values of the solutions. It is shown that the studied medical compounds, which exist in the solution in the form of cations, are adsorbed the best (rivanol, proflavin, doxorubicin). Adsorption of these substances occurs mainly due to electrostatic interaction with negatively charged surface groups. Adsorption of anionic form (salicylic acid) is the smallest and is observed only at quite low pH values. Levofloxacin is adsorbed mainly in the form of zwitter ions, and furacilin is in neutral form. The adsorption of these both compounds occupies an intermediate value of adsorption amount. The obtained adsorption isotherms are well lined up in Langmuir coordinates. Quantitative parameters of adsorption values - of maximum adsorption and equilibrium constants were calculated. Quite high values of these parameters indicate that hydrolysis lignin can be used as an adsorbent for the removal of these pharmaceuticals.

Performance of density-functional-theory and random-phase-approximation methods on the study of transition-metal clusters: the Tan clusters as an example

Recently developed density-functional-theory (DFT) and random-phase-approximation (RPA) methods are used to study competing isomers of some negatively charged Ta clusters, namely Ta12 - and Ta10 -, in an attempt to find a suitable strategy towards accurate studies of transition-metal clusters based on DFT. Also the neutral and cationic forms Ta12 (0,+) of the twelve-atom cluster are studied. The results are compared with experimental information obtained by several methods that differ in the property under study and the total electric charge of the clusters. We find that a careful choice of the density functional, the use of relativistic two-component methods, eventually in combination with all-electron basis sets, and the application of RPA-type methods, may all be necessary steps for a good assessment. Such an assessment should be made in relation to several experimental properties as much as possible.

Stable, while Still Active? A DFT Study of Cu, Ag, and Au Single Atoms at the C3N4/TiO2 Interface.

Hybrid DFT calculations are employed to compare the adsorption and stabilization of Cu, Ag, and Au atoms on graphitic C3N4 and on the heterojunction formed by g- C3N4 and TiO2. While Cu and Ag can be strongly chemisorbed in form of cations on g- C3N4, Au is only weakly physisorbed. On g- C3N4/TiO2, all coinage metal adatoms can be strongly chemisorbed, but, while Cu and Ag forms cations, Au form an Au- species. Ab Initio Molecular Dynamics simulations confirm that the metal adatoms on g-C3N4 are highly mobile at room temperature, while they remain confined in the interfacial spacing between C3N4 and TiO2 on the heterojunction, being both stably bound and reachable for the reactants in a catalytic cycle. Doping g- C3N4/TiO2 with metal single atoms permits thus to generate catalytic systems with tunable charge and chemical properties and improved stability with respect to bare C3N4. Moreover, the changes in the electronic structure of g- C3N4/TiO2 induced by the presence of the metal single atoms are beneficial also for photocatalytic applications.

Phenyl-bridged N,N,N'N'-Tetrasubstituted bis(2-amino-5-thiazolyl) diamine: Synthesis and applications in electrochromism and photocatalytic nitrobenzene reduction

A novel type of triphenylamine derivatives, phenyl-bridged N,N,N′,N′-tetrasubstituted bis(2-amino-5-thiazolyl) diamine (4) and its cationic form (5) were synthesized via the Hantzsch reaction. The UV–Vis spectroscopy, cyclic voltammetry (CV) and density functional theory (DFT) calculation results showed that the diamine possesses excellent redox properties and a narrow optical energy gap (∼1.85 eV). As an electrochromic material, compound 4 exhibits a notable color change from colorless to blue. It maintains stable cycling performance for up to 175 cycles, even within a higher voltage range of −2.4 to 2.4 V. In addition, as a catalyst, compound 5 exhibits good substrate compatibility and an aniline conversion rate of up to 89 % during the photocatalytic reduction of nitrobenzene. These results would contribute to understand the synthesis of triphenylamine electrochromic materials and expand their applications in the field of photocatalysis.

Organoclays Based on Bentonite and Various Types of Surfactants as Heavy Metal Remediants

The rapid industrial development of civilization has led to the need for the development of new materials to clean up chemically contaminated wastewater and soils. Organoclays, based on smectite minerals and various types of surfactants, are one of the most effective sorbents for adsorbing organic and inorganic pollutants. Organoclays are clay minerals that have been modified by the intercalation or grafting of organic molecules. The main mechanism of interaction between organic substances and organoclays involves the adsorption of the substances onto the surface of the clay mineral, which has an expanded structural cell. Various types of surfactants can be used to synthesize organoclays, including cationic, anionic, and amphoteric surfactants. Each type of surfactant has different properties that affect the clay’s ability to sorb. Cationic forms of trace elements, such as heavy metals, can also be adsorbed by organoclays. Data on the adsorption of these substances by organoclays are provided, along with information on how to synthesize them using various surfactants. This review also discusses the main mechanisms of interaction between these substances and clays and the various methods used to create organoclays. It is clear that the adsorption of heavy metals by organoclays is not influenced by their structure or properties, as they belong to the category of surfactant, but rather by their overall chemical structure and characteristics. The wide variety of surfactant types leads to different effects on the adsorption properties of trace elements.

Integrating diffusion dialysis for sustainable acid recovery from ion exchange regeneration stages: Characterization of metal and non-metal ions migration

Seawater mining presents a potential option for recovering the European Union’s Critical Raw Materials (CRMs), but direct extraction from seawater is challenging due to their low concentrations, as most of them are Trace Elements (TEs) (at levels of mg/L or µg/L). Saltworks bitterns (ultraconcentrated brines resulting from the sea salt production process) offer an alternative solution, naturally concentrated up to 40 times more than seawater. These bitterns can be further processed with chelating Ion Exchange (IX) sorbents to selectively extract TEs. However, this process requires an acidic elution stage with strong acids, followed by neutralization, to recover TEs through precipitation, demanding extensive chemicals consumption. Diffusion Dialysis (DD) could be used to recover the excess acid without external reagents, using an acid-resistant Anion Exchange Membrane (AEM). This study evaluates DD through batch and once-through tests for acid recovery from simulated IX eluate generated in the elution stage of TEs (B, Ga, Ge, Co, Sr) recovery from saltworks bitterns.Batch tests achieved high recoveries for HCl (45–50 %) and H2SO4 (30–37 %), being the theoretical maximum attainable recovery equal to 50 %. B and Ge only partially permeated through the membrane (82 % rejection) by a diffusion mechanism in their neutral form (H3BO3(aq), H4GeO4(aq)). Ga, Co and Sr, in cationic form, were highly rejected (>96 %). Permeability followed the order Ga < Sr < Co ≪ Ge < B, due to the relevant charge and size. HCl permeability correlated linearly with concentration, while H2SO4 was inversely proportional. Once-through tests showed higher acid (74 % HCl, 62 % H2SO4) and oxoacid (66 % H3BO3(aq), 52 % H4GeO4(aq)) recovery at a low specific flow rate, or apparent flux, (0.38 L/(m2membrane·h)) due to increased residence time. Water to acid flow rate ratios did not affect species transport when an excess of water was guaranteed. Conversely, an influence was observed when the ratio was below 1, with a minimum at 0.18, where a very low passage of species was observed due to the reduced dilution volume of the dialysate solution (water). A 1D transport model, incorporating the solutes permeabilities determined experimentally, effectively described the system performance, especially for HCl and B, albeit slightly overestimating the other TEs’ transport.

Computational Insights Into Betanin for Dsscs: Unraveling Deprotonation Variations and Identifying Optimal Anchoring Sites on TiO2

AbstractBetanin (Bn), a natural dye in the Betalains family, predominantly takes on a cationic form known as Bn+. However, it exists in a neutral state as Bn_C2, Bn_C15, and Bn_C17 by losing an H+ from one of its carboxylic acids. Density functional theory (DFT) and Time‐dependent density functional theory (TD‐DFT) studies evaluate the efficiency of each betanin form and pinpoint the most probable anchoring point to TiO2. The Bn_C17 variant stands out as a highly promising candidate for DSSC cells, demonstrating a distinctive combination of electron injection efficiency, electrochemical performance, hole transport capabilities, and photovoltaic behavior. Considering factors like adsorption energy, binding mode, structural compatibility, electronic properties, and absorption characteristics, Bn_C17@TiO2 emerges as the most favorable dye@TiO2 complex among the studied betanin forms for DSSC applications. Contrastingly, the C2‐COOH anchoring point presents challenges with monodentate binding, a different orientation, and potential load distribution issues. This behavior, resembling that of a p‐type dye, differs from the n‐type behavior exhibited by the C15‐COOH and C17‐COOH forms, making the latter two more suitable as sensitizers. Consequently, C2‐COOH may not be the optimal anchoring point for TiO2 in the investigated betanin forms, especially when compared to the more favorable C17‐COOH anchoring point.