Basic Anion Research Articles

The Efficiency Improvement of Electrodeposition of High-Purity Zn by a Proper Electrolyte Solution Preparation from Spent Pickling Liquor by Anion-Exchange Separation

A better procedure for recovering high-purity Zn from the SPL solution has been devised. To provide a suitable electrolyte for the efficient cathodic deposition of high-purity Zn, complete anion-exchange purification had been done by chromatographic technique. The process was then continued by galvanostatic electrodeposition to determine the efficiencies. As the SPL needs to be neutralized before any attempts of Zn electrodeposition, NaCl may provide the required source of Cl- ions for complex formation. The equilibrium studies of the anion-exchange distribution in such solutions showed similar tendencies to those already known in HCl media. The anion-exchange chromatographic separation was devised – with the finer tuning of the parameters – according to the equilibrium result, but other physical parameters were also examined for improving the efficiency of separation and the recovery of Zn. The devised anion-exchange separation in chloride media can purify the SPL, containing Zn as the valuable component and higher concentrations of Fe as the main impurity. The most important impurities (Fe, Mn, Ni, Al and Co) can be efficiently separated in a dissolved state. At the same time, Zn is sorbed in the strongly basic anion[1]exchange resin at a moderate Cl- ion concentration (~ 2 M). Stirring with Fe chips provides a reduction of iron to the Fe(II) state. The remaining problem is minor copper contamination in the same effluent fraction as Zn, which however can be eliminated by a simple additional step of cementation or directly by pre-electrolysis.

Anionic Effects on Li-Ion Activity and Intercalation Kinetics in Highly Concentrated Electrolytes

Certain highly concentrated electrolytes (HCEs) enhance the charge-transfer reaction rate at the electrode/electrolyte interface in Li-ion batteries. The solvation structure of Li+ in HCEs significantly affects the electrochemical interfacial reaction kinetics.1 However, the effects of different anions on these kinetics have not yet been fully understood. In this study, we investigated the effects of anionic species on the liquid structure and electrochemical reactions of HCEs composed of various Li salts and propylene carbonate (PC).2 Raman spectra revealed that both PC and anions were coordinated to Li+ ions in HCEs and that the concentration of uncoordinated (free) PC changed depending on the anionic species. Consequently, the activity of Li+ in the electrolyte changed depending on the anionic species. The use of Li salts with weakly Lewis basic anions increased the activity of Li+ and decreased the concentration of free PC in HCEs.The activity of Li+ in the electrolyte significantly affected the Li+ intercalation/deintercalation reaction rate of the LiCoO2 thin-film electrode. Electrochemical impedance spectroscopy revealed that the interfacial reaction rate of LiCoO2 was enhanced in the HCEs with anions having weaker Lewis basicity owing to the higher Li+ ion activity. In addition to the Li+ ion activity, the electrolyte viscosity also gives a significant effect on the charge-transfer kinetics at the electrode/electrolyte interface. The effects of salt concentration and anionic species on Li+ ion activity, electrolyte viscosity, and reaction kinetics in the HCEs will be discussed in detail. Acknowledgements : This study was partially supported by the JSPS KAKENHI (Grant No. JP19H05813, JP21H04697, and JP22H00340). References Y. Kondo et al., ACS Appl. Mater. Interfaces 2022, 14, 22706-22718.Y. Ugata et. al., J. Phys. Chem. C 2023, 127, 3977-3987.

Nanoconfinement boosts affinity of hydrated zirconium oxides to arsenate: Surface complexation modeling study

Nanoscale hydrated zirconium oxide (HZO) holds great potential in groundwater purification due to its ability to form inner-sphere coordination with arsenate. Despite being frequently used, especially as encapsulations in host materials for practical application in water treatment, the adsorption mechanisms of solutes on HZO are not appropriately explored, in particular for arsenate adsorption. In this study, we investigated the Zr–As coordination configuration and identified the most credible Zr–As configuration using surface complexation modeling (SCM), XPS and FT-IR analysis. The corresponding intrinsic coordination constants (Kintr) values was calculated by SCM, and the nanoconfinement effects were distinguished by comparing bare HZO with the HZO nanoparticles (NPs) encapsulated inside the strongly basic anion exchanger D201. Potentiometric titration suggests that the surface Zirconium hydroxyl groups (≡ZrOH) mainly exist in protonated form (≡ZrOH2+). Batch adsorption experiments demonstrate that the D201 hosts could adsorb As(V) through ion exchange by the quaternary ammonium groups under the low ionic strength (≤0.01 M NaNO3) and at pH > 6. The nanocomposite (HZO@D201) exhibits a higher adsorption capacity in a wide range of pH (3-10) and ionic strength (0.001–0.1 M NaNO3) than bare HZO. SCM simulations reveal that the coordination configuration of diprotonated monodentate mononuclear (MM-H2) dominates at pH 3–6, while deprotonated bidentate binuclear (BB–H0) dominates at pH > 7. For each configuration, the intrinsic coordination constants (Kintr) of HZO@D201 (10−0.66 and 10−16.10, respectively) are significantly higher than those of bare HZO (10−12.24 and 10−44.42, respectively), indicating a superior chemical bonding affinity caused by nanoconfinement. The obtained Kintr values are used to predict arsenate adsorption isotherms in pH 3 and 9, and the results align with the SCM simulation outcomes. This study may offer a feasible method for investigating the nanoconfinement effect of emerging nanocomposite adsorbents from a thermodynamic perspective, and provide reference coordination equilibrium constants of HZO for research and practical application.

A New Azomethine Chemosensor for Naked-Eye Detection of CN− and AcOˉ: Application to Determination of Cyanide in Some Agro-Products and Poisoned Human Blood Samples

A new symmetrical azomethine probe, H2L, has been synthesized via a condensation reaction of N, N´-Ethylene bis (3-formyl-5-methyl salicylaldimine), with Isonicotinic hydrazide in EtOH. The anion recognition studies exhibited that H2L acts as a chemosensor for the detection of CN− and AcO− in pure DMSO and DMSO/H2O 90:10(V/V) media over other basic anions such as F−, Cl−, Br−, I−, N3 −, SO4 2−, SO3 2−, PO4 3−, H2PO4 −, HSO4 −, NO2 −, and NO3 −. The ability of the H2L for rapid colorimetric sensing of CN− and AcOˉ was studied using UV–Vis, and 1H NMR titration methods. The detection limits of H2L toward CN− and AcO− in the semi-aqueous medium were found to be 2.12 and 2.63 μM, respectively, which are lower than the LOD of some existing azomethine probes. Effectively, H2L was used to qualitatively and quantitatively detect cyanide ions in the human-poisoned blood and some of the agro-products containing cyanogenic samples without relying on expensive instruments.

Correlation between absorbed acetylene spectral characteristic and nature of ionic liquids studied by in situ ATR-FTIR spectroscopy

Ionic liquids (ILs) are believed to be a prospective replacement for molecular solvents and are suggested to be used for storing and/or purifying acetylene. Systematic studies of the nature of the interaction between acetylene and different ILs may be necessary to predict new types of ionic liquids. Therefore, in order to investigate the absorption of acetylene by ionic liquids, in situ ATR-FTIR spectroscopy has been applied for the first time. Two series of ILs, such as [C2‍–‍10MIM][BF4] and ILs based on imidazolium with various anions, have been considered. A detailed analysis of the spectra of absorbed acetylene is given, with special attention being paid to the basicity of IL anions as well as the influence of the cation alkyl chain length. It has been found that the magnitude of the band shift associated with the CH stretching vibration and the antisymmetric CH bending vibration of absorbed acetylene correlates well with the change in the Kamlet-Taft β parameter of the ILs. Moreover, neither the free volume nor the IL polarity plays a key role in acetylene solubility. In addition, the enthalpy and entropy of absorption have been calculated for several ILs.

Tyrosine Amino Acid as a Foulant for the Heterogeneous Anion Exchange Membrane.

The features of organic fouling have been revealed for highly basic anion exchange membranes during prolonged electrodialysis in solutions containing the aromatic amino acid tyrosine. With increased operation time when using MA-41 heterogeneous membranes in tyrosine solution, an increase in hydrophobicity and roughness characteristics of the material surface is detected. A reduction in tyrosine flux through the membrane occurs which is caused by its pores plugging and deposition of the amino acid at the membrane surface induced by tyrosine adsorption and local supersaturation of the solution in the membrane phase. The long-term contact of the anion exchange membrane with a solution of tyrosine leads to some structural changes in the anion exchange material. An accumulation of the studied amino acid with phenolic fragment and tyrosine oxidation products (DOPA, DOPA-quinone) is found and confirmed by IR- and UV-spectroscopy techniques. The organic fouling is accompanied by an increase in density and a decrease in moisture content of the studied membrane. A comparative analysis of the chemical and electrochemical cleaning results for fouled samples of the MA-41 membrane demonstrates a partial restoration of the material transport characteristics using electrochemical cleaning in the intensive current mode of electrodialysis. The best efficiency of regeneration is reached when carrying out chemical cleaning with a solution of hydrochloric acid, providing almost complete restoration of the membrane characteristics.

Deoxyfluorination of phenols for chemoselective 18F-labeling of peptides.

The challenge of forming C-18F bonds is often a bottleneck in the development of new 18F-labeled tracer molecules for noninvasive functional imaging studies using positron emission tomography (PET). Nucleophilic aromatic substitution is the most widely employed reaction to functionalize aromatic substrates with the radioactive fluorine-18 but its scope is restricted to arenes containing electron-withdrawing substituents. Furthermore, many protic functional groups are incompatible with basic fluoride anions. Peptide substrates, which are highly desirable targets for PET molecular imaging, are particularly challenging to label with fluorine-18 because they are densely functionalized and sensitive to high temperatures and basic conditions. To expand the utility of nucleophilic aromatic substitution with fluorine-18, we describe two complementary procedures for the radiodeoxyfluorination of bench-stable and easy-to-access phenols that ensure rapid access to densely functionalized electron-rich and electron-poor 18F-aryl fluorides. The first procedure details the synthesis of an 18F-synthon and its subsequent ligation to the cysteine residue of Arg-Gly-Asp-Cys in 10.5 h from commercially available starting materials (189-min radiosynthesis). The second procedure describes the incorporation of commercially available CpRu(Fmoc-tyrosine)OTf into a fully protected peptide Lys-Met-Glu-(CpRu-Tyr)-Leu via solid-phase peptide synthesis and subsequent ruthenium-mediated uronium deoxyfluorination with fluorine-18 followed by deprotection, accomplished within 7 d (116-min radiosynthesis). Both radiolabeling methods are highly chemoselective and have conveniently been automated using commercially available radiosynthesis equipment so that the procedures described can be employed for the synthesis of peptide-based PET probes for in vivo imaging studies according to as low as reasonably achievable (ALARA) principles.

The Effect of DBU on Microstructure and CO2 Absorption of EmimCl‐TEG and BmimCl‐TEG Deep Eutectic Solvents

AbstractMicrostructure of deep eutectic solvents (DESs) based on EmimCl or BmimCl ionic liquid (IL) and triethylene glycol (TEG) was studied by FT‐IR spectra. The influence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) on CO2 absorption behavior and mechanism of DESs was investigated. FT‐IR spectra of pure EmimCl‐TEG and BmimCl‐TEG DESs show that O−H⋅⋅⋅Cl− hydrogen bond interaction formed by IL and TEG gradually strengths with the increase in the molar ratio of IL to TEG, resulting in a corresponding increase in viscosity. Due to the lack of a chemical interaction site, the CO2 absorption capacity of pure DESs at 313.2 K and 1.0 bar is only between 0.15 and 0.56 mol kg−1. Surprisingly, the addition of equimolar DBU to DESs can significantly improve the CO2 absorption capacity, which is up to 2.94 mol kg−1 at the maximum and similar to that of amine‐functionalized DESs. CO2 absorption mechanism characterized by FT‐IR spectra indicates that DBU can form hydrogen bond with O−H of TEG, which leads to deprotonation of O−H of TEG into basic anion under the synergistic effect of O−H⋅⋅⋅Cl− hydrogen bond to achieve efficient CO2 chemisorption via carbonate formation. The obtained results provide a strategy for effectively improving the CO2 capture capacity of EmimCl‐TEG and BmimCl‐TEG DESs.

Labeling of Highly Reactive Tetrazines using [18F]SuFEx

AbstractPretargeted imaging is an emerging technique to study the in vivo biodistribution of nanomedicines. Currently, the tetrazine ligation is considered the most promising bioorthogonal reaction for pretargeting. Recently, Zheng et al. described an ultrafast late-stage radiolabeling of tetrazines based on sulfur 18F-fluoride exchange click chemistry ([18F]SuFEx). However, bispyridyl and H-tetrazines—the most promising structures for in vivo pretargeted applications—cannot be labeled using the proposed reaction conditions as they lead to decomposition of the tetrazine core. Here, we report improved conditions, exploiting basic preconditioning conditions for the quaternary methyl ammonium (QMA) cartridge and the use of low basic anions that allow 18F-labeling of bispyridyl and H-tetrazines using SuFEx. This strategy resulted in fast and efficient radiolabeling of highly reactive tetrazines with radiochemical conversions of up to 85% and radiochemical purity above 95%. This opens up the possibility to use SuFEx to 18F-label tetrazines, which are suitable for in vivo pretargeted imaging.

Water-Soluble Squaramide-Functionalised Copolymers for Anion Recognition.

A series of ethylene glycol-based squaramide-containing copolymers were synthesised via a post-polymerisation functionalisation strategy. Conversion of polymeric amines to squaramides was found to proceed in good yields, representing a versatile method of incorporating squaramides into polymers for anion recognition. Analysis of the polymers by UV-Vis and fluorescence spectroscopy revealed that anion binding takes place similarly to that of small-molecule squaramides. The presence of a fluorescent sensing group on polymer-bound squaramides allowed for a fluorescent sensing mechanism for anions that followed a similar trend in selectivity in aqueous DMSO solution, with selectivity observed for H2 PO4 - , AcO- and SO4 2- over other common anions tested. The anion response and selectivity towards anions was similar to that of analogous small-molecule squaramides, however polymeric squaramides exhibited a greater resistance to deprotonation by more basic anions, which was attributed to the closer proximity of individual squaramides on a macromolecule. The squaramide containing polymers exhibited good water solubility, overcoming a common problem for anion sensors which are typically not sufficiently soluble in water to function in many required applications. Despite no anion binding being observed in water, this represents a simple and effective method of creating fully water-soluble anion receptors which may be adapted to give improved binding affinity and selectivity depending on the anion binding moiety. This article is protected by copyright. All rights reserved.

Transformation of CuO and Cu2O particles into CuxS within the polymeric matrix of anion exchangers, and its structural and morphological implications

The study demonstrates the process of anion exchanger modification in order to obtain a reactive organic polymer containing CuxS dispersed within its matrix. As starting materials, two strongly basic commercial anion exchangers were used – macroreticular and gel-type – previously modified by deposition of cuprite or tenorite within their structure. The pre-formed composites were sulphidated using an Na2S solution to obtain materials containing CuxS (5.3–6.7 wt% Cu and 4.5–6.7 wt% S), which were further studied using Raman and XPS spectroscopy, and XRD and SEM/EDS analyses. Depending on the sulphidation precursor, Cu2O or CuO, its distribution within the polymeric matrix, and the porous structure of the supporting anion exchanger, products with different CuxS content were obtained. The main sulphidation product – covellite – was accompanied by admixtures of copper-rich phases such as digenite and djurleite, but products of sulphide oxidation were also identified. The conversion of Cu2O into CuS was more efficient and selective in comparison to CuO. The sulphidation process remained within the initial distribution of the precursor particles within the polymeric matrix. The morphology of the obtained covellite particles was strongly dependent on the porous structure of the supporting anion exchanger. The conversion of the Cu2O and CuO within the macroporous matrix led respectively to spiky burr-like CuS and more densely packed elongated needle-shaped CuS particles, while the CuS particles obtained in the gel-type matrix were spherical. The spherical particles obtained from Cu2O conversion exhibited a hollow structure, which was the result of solid-state diffusion during the sulphidation, the so-called Kirkendall effect.

Fluorescent Nanoassembly of Tetrazole-Based Dyes with Amphoteric Surfactants: Investigation of Cyanide Sensing and Antitubercular Activity.

Tetrazole-based easily synthesizable fluorogenic probes have been developed that can form self-assembled nanostructures in the aqueous medium. Though the compounds could achieve detection of cyanide ions in apolar solvents, such as, THF, significant interference was observed from other basic anions, such as F-, AcO-, H2PO4-, etc. On the other hand, a highly specific response was observed for CN- ions in the aqueous medium. However, the sensitivity was so poor that it could hardly be useful for real-life sample analysis. Interestingly, the co-assembly of such probe molecules with hydroxyethyl-anchored amphoteric surfactants could drastically improve the sensitivity toward CN- ions in water without dampening their excellent selectivity. Also, it was observed that the degree of fluorescence response for CN- ions depends on the nature of the polyaromatic scaffolds (naphthyl vs anthracenyl), the nature of the surfactant assembly (micelle vs vesicle), etc. The mechanistic investigation indicates the hydrogen bonding interaction between the tetrazole -NH group and cyanide ions in the aqueous medium, which can effectively change the electronics of the tetrazole unit, resulting in alteration in the extent of charge transfer interaction. Then, the biocompatible composite materials (dye-surfactant assemblies at different ratios) were tested for antituberculosis activity. Fortunately, in a few cases, the compositions were found to be as effective as the commercially available antituberculosis drug, ethambutol.

Isomerization of Hemicellulose Aldoses to Ketoses Catalyzed by Basic Anion Resins: Catalyst Screening and Stability Studies

Isomerization of aldoses to ketoses is an essential step in carbohydrate valorization routes in biorefineries to produce a wide variety of bioproducts. In this work, selective isomerization of aldoses into ketoses was investigated using different commercial Brønsted basic anion resins at low temperature conditions. Weak and strong basic resins were tested under different reaction conditions. Amberlite IRA-900 and Amberlyst A-26 (strong resins) and Amberlite IRA-67 and Amberlyst A-21 (weak resins) were tested to assess their catalytic properties. Strong basic resins provided high yields of fructose. IRA-900 was also tested in the isomerization of different sugar monosaccharides conventionally present in lignocellulosic biomass (xylose, arabinose, galactose, glucose and mannose) aiming to explore the performance of this material in hemicellulose-derived sugar mixtures. Very promising performance was observed for IRA-900, yielding fructose selectivity higher than 75% and fructose yield of 27% in the isomerization reaction. Notably, basic anionic resins were not suitable for reuse in different reaction cycles, although the use of organic cosolvents, specifically ethanol, improved the reusability of the tested resins.

Multimodal Sensing of Acetate Anion by Using Anthraimidazoledione‐Based Redox‐Active Amphiphilic Dye in Aqueous Environment

AbstractAnthraimidazoledione based amphiphilic dye is synthesized that exhibits pH‐responsive chromogenic response in aqueous environment. This entices us to investigate its anion‐responsive behavior. In pure water, the compound shows no optical response towards anions (poor sensitivity), whereas interaction with multiple anions is witnessed in acetonitrile medium (poor selectivity). Interestingly, changes in solution color from yellow to orange is observed explicitly upon addition of acetate anion, accompanied by fluorescence turn‐off response. Further, it is revealed that the acetate engaged in hydrogen bonding interaction with both imidazole −NH group and hydroxyl unit. The high basicity of acetate anion along with ‘Y‐shaped’ structure might be responsible for such unique selectivity. The present system has been involved in analyzing residual acetate in natural water samples. Low‐cost, reusable paper strips have been designed for equipment free, rapid on‐location detection of acetate.

Green oxidative esterification of furfural over nano-Au supported on highly basic anion exchange resin beads

Au nanoparticles with an average diameter of 3.7 nm supported on the macroporous anion exchange resin beads with cationic –CH2N+Me3 functional groups and OH−as counter anions were first prepared, for catalyzing the oxidative esterification of biomass-derived furfural in methanol using green O2 as an oxidant. The main product methyl furoate with a high yield of 98% was obtained at 130 °C for 2 h in the absence of soluble alkali additives. The catalyst beads possessed a particle size range of 560∼700 μm inherited from the shaped support, enabling the separation of catalyst and liquid reaction medium by a simple decantation method. Catalyst poisoning experiments demonstrated Au activated superoxide radical O2·− and the basic OH− stored in the anion exchange resin are the decisive active components for the oxidative esterification, and the main product methyl furoate with a yield of 20% and a high selectivity of 96% was obtained under N2 atmosphere revealed the reaction in this catalytic system followed an oxidative dehydrogenation route. In all catalytic cases except for the catalyst poisoning experiments and the cases of low catalyst dosages, the by-product acetal was almost completely suppressed, probably attributed to the presence of the alkaline OH− in the anion exchange resin of the catalyst.

Multifunctional Composite Materials Based on Anion Exchangers Modified with Copper Compounds-A Review of Their Synthesis Methods, Characteristics and Applications.

As copper and its compounds are of fundamental importance for the development of innovative materials, the synthesis of composites intended for water purification was undertaken in which submicron copper containing particles were dispersed within the matrix of a strongly basic anion exchanger, with a macroporous and gel-like structure. Due to their trimethylammonium functional groups, the host materials alone exhibited an affinity to anionic water contaminants and antimicrobial properties. The introduction of such particles as CuO, Cu2O, metallic Cu, CuO/FeO(OH), Cu4O3, Cu(OH)2, Cu4(OH)6SO4, Cu2(OH)3Cl increased these properties and demonstrated new properties. The composites were obtained unconventionally, in ambient conditions, using eco-friendly reagents. Alternative synthesis methods were compared and optimized, as a result of which a new group of hybrid ion exchangers was created (HIXs) containing 3.5-12.5 wt% of Cu. As the arrangement of the inorganic phase in the resin matrix was atypical, i.e., close to the surface of the beads, the obtained HIXs exhibited excellent kinetic properties in the process of oxidation and adsorption of As(III), as well as catalytic properties for the synthesis of triazoles via click reaction, and also antimicrobial properties in relation to Gram-positive Enterococcus faecalis and Gram-negative Pseudomonas aeruginosa and Escherichia coli, preventing biofilm formation. Using thermogravimetry, the effect of the inorganic phase on decomposition of the polymeric phase was evaluated for the first time and comprehensively, confirming the relationship and finding numerous regularities. It was also found that, depending on the oxidation state (CuO, Cu2O, Cu), copper-containing particles affected the textural properties of the polymeric phase endowing a tighter structure, limiting the porosity and reducing the affinity for water.

Tuning basic poly(ionic liquid) solutions towards atmospheric pressure CO2 capture

Ionic liquids and poly(ionic liquid)s are interesting materials for CO2 capture, however, the deployment of their industrial application has been delayed on account of economic and technical issues that demand further optimization. The control over viscosity has serious consequences over the process, therefore, this work is focused on the study of imidazolium and pyrrolidinium-derived ILs and PILs with basic anions, such as acetate, hydroxide, and imidazolate that were synthesized and characterized by NMR, ATR-FTIR, TGA, and DSC. Different solvents and concentrations were tested in the preparation of PIL and IL solutions, which were used to capture CO2 by bubbling this gas at room temperature and atmospheric pressure (1 atm). The evaluation of the CO2 sorption capacity of each sample was carried out through the analysis of quantitative 13C NMR. The poly(1-vinyl-3-ethylimidazolium) acetate showed and sorption capacity of 5.68 mmol CO2/g PIL, and also the capacity to capture CO2 from exhaust gas mixture and the possibility to be recycled at least 5 times.

Preparation of exopolysaccharides by heat-resistant Weizmannia coagulans using anion exchange resins

Weizmannia coagulans with high temperature tolerance and stability was selected for the production of exopolysaccharides (EPS) at the fermentation temperature of 52 °C. The weak basic anion exchange resin was employed in the fermentation for the construction of buffer system to neutralize some lactic acid and form intermolecular hydrogen bonds with hydroxyl groups on capsular polysaccharides of bacteria via tertiary amine groups, resulting in the increased growth space for capsular polysaccharides. In addition, the fermentation at relatively high temperature significantly decreased the adsorption of Ca2+ derived from CaO used for pH adjustment to the resin and sustained the ion exchange capability of the resin available for the formation of intermolecular hydrogen bonds with capsular polysaccharides. The concentration of EPS obtained achieved up to 19.8 g/L, which was increased by approximately 20-fold as compared to the concentration of EPS obtained by conventional fermentation. The conversion rate of carbohydrates to EPS reached up to 35.1%. The EPS produced under the optimized fermentation condition included neutral and acidic heteropolysaccharides with a molecular mass of 3.4 × 104–1.5 × 106 Da. The concentration and molecular mass distribution of EPS exhibited good reproducibility. This study provides a novel method for the industrial production of EPS.

Preparation of Eco-Friendly Chelating Resins and Their Applications for Water Treatment.

In the present study, two chelating resins were prepared and used for simultaneous adsorption of toxic metal ions, i.e., Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Pb2+ (MX+). In the first step, chelating resins were prepared starting with styrene-divinylbenzene resin, a strong basic anion exchanger Amberlite IRA 402(Cl-) with two chelating agents, i.e., tartrazine (TAR) and amido black 10B (AB 10B). Key parameters such as contact time, pH, initial concentration, and stability were evaluated for the obtained chelating resins (IRA 402/TAR and IRA 402/AB 10B). The obtained chelating resins show excellent stability in 2M HCl, 2M NaOH, and also in ethanol (EtOH) medium. The stability of the chelating resins decreased when the combined mixture (2M HCl:EtOH = 2:1) was added. The above-mentioned aspect was more evident for IRA 402/TAR compared to IRA 402/AB 10B. Taking into account the higher stability of the IRA 402/TAR and IRA 402/AB 10B resins, in a second step, adsorption studies were carried out on complex acid effluents polluted with MX+. The adsorption of MX+ from an acidic aqueous medium on the chelating resins was evaluated using the ICP-MS method. The following affinity series under competitive analysis for IRA 402/TAR was obtained: Fe3+(44 µg/g) > Ni2+(39.8 µg/g) > Cd2+(34 µg/g) > Cr3+(33.2 µg/g) > Pb2+(32.7 µg/g) > Cu2+ (32.5 µg/g) > Mn2+(31 µg/g) > Co2+(29 µg/g) > Zn2+ (27.5 µg/g). While for IRA 402/AB 10B, the following behavior was observed: Fe3+(58 µg/g) > Ni2+(43.5 µg/g) > Cd2+(43 µg/g) > Cu2+(38 µg/g) > Cr3+(35 µg/g) > Pb2+(34.5 µg/g) > Co2+(32.8 µg/g) > Mn2+(33 µg/g) > Zn2+(32 µg/g), consistent with the decreasing affinity of MX+ for chelate resin. The chelating resins were characterized using TG, FTIR, and SEM analysis. The obtained results showed that the chelating resins prepared have promising potential for wastewater treatment in the context of the circular economy approach.

Preconcentration of Zinc, Cadmium, and Mercury(II) Ions on a Polymeric Modified Adsorbent Based on a Highly Basic ARA-8p Anionite and a Rhodanine Derivative

We studied the conditions for the adsorption of zinc, cadmium, and mercury(II) ions on a modified adsorbent based on an ARA-8p highly basic anion exchange resin and a Rhodanine derivative, 5-(4-carboxyphenyl-azo)rhodanine (ARA-8p-p-KBAR), in a batch mode. The values of pH, phase contact time, and adsorbate concentration at which the maximum recovery of zinc, cadmium, and mercury(II) ions was achieved were determined. The adsorption capacity of the adsorbent for the adsorbed ions was determined from the obtained adsorption isotherms. The calculated value of the free energy shows that adsorption proceeds with the formation of an ionic bond. Eluents were selected to ensure the quantitative desorption of zinc, cadmium, and mercury(II) ions. The interfering effect of macrocomponents and trace elements of water was studied; zinc, cadmium, and mercury(II) ions were quantitatively adsorbed by this adsorbent from a solution of a complex composition. A procedure was developed for the adsorption–atomic-absorption determination of zinc, cadmium, and mercury(II) ions in various water samples.