Acid Cation Exchange Research Articles

Integrated deep eutectic solvent extraction and resin adsorption for recovering polyphenols from citrus reticulata Blanco peels: Process optimization, compositional analysis, and activity determination

The recovery of polyphenols from Citrus reticulata Blanco peels was studied based on integrated deep eutectic solvent (DES) extraction and resin adsorption. The DES prepared with choline chloride and ethylene glycol (molar ratio 1:4) and hydrophobic interaction/weakly acidic cation exchange mixed-mode adsorption resin HD-1 were used as the extractant and adsorbent respectively. The operating parameters of integrated process were optimized using completely randomized design and response surface methodology (RSM). The extraction kinetics was studied and the composition of extract was analyzed by UPLC-MS. Finally, the antioxidant activity of extract and its inhibitory ability on α-glucosidase and α-amylase were determined. Under the optimal operating conditions (liquid–solid ratio of 20:1, extraction temperature of 43 °C, extraction time of 4.8 h, resin amount of 6.6 g), the polyphenols yield of integrated process was increased by 2.15-fold and the time was shortened by 52.48 % compared with that of traditional sequential process. The extraction kinetic curves of both integrated and sequential processes conformed to pseudo-first-order kinetic model, and the extraction speed of integrated process was significantly higher than that of sequential process. The main polyphenols in extract were neohesperidoside, poncirin, narirutin, and hesperidin, etc. The extract exhibited a strong antioxidant capacity with DPPH free radical scavenging rate of extract reached 79.54 % of that of vitamin C. The inhibition ratios of extract against α-glucosidase and α-amylase were 97.81 % and 427 % of that of acarbose respectively. The results indicated that the extract has a potential application for prevention and control of type 2 diabetes mellitus.

The Effective Separation of Gallium, Vanadium, and Aluminum from a Simulated Bayer Solution by Resin Exchange.

The effective recovery of gallium from wastewater discharge in the Bayer process is promising for the long-term development of gallium resources. The adsorption and desorption behavior of gallium (Ga), vanadium (V), and aluminum (Al) ions on a strong acidic styrene cation exchange resin (JK resin) from a simulated Bayer solution was systematically investigated by static experiments. The results showed that the optimum conditions for separating Ga from V and Al were at low temperatures and short contact times, with 78.30%, 15.16%, and 6.63% of the adsorption efficiency at 25 °C and 60 min, respectively, for Ga, V, and Al. The adsorption kinetics of Ga3+ conformed to the pseudo-second order model, and the static saturation adsorption capacity was 18.25 mg/g. The Langmuir model fitted the adsorption isotherm of gallium well, and the maximum adsorption capacity was 1.11 mg/g at 25 °C. FT-IR spectroscopy and XPS showed that the mechanism of the Ga3+ adsorption was only related to the interaction of the oxygen atoms of the amide oxime group (C=NOH). The separation of Ga, V, and Al can be achieved by desorbing 98% of Al with low concentrations of ammonia and 90% of Ga with low concentrations of hydrochloric acid. The results indicate that JK resin is an efficient adsorbent for separating gallium and vanadium in alkaline solutions.

Aqueous Lithium-Ion Battery with Dual Electrolytes at Equilibrium across Cation-Exchange Membrane Separator

Aqueous lithium-ion batteries (ALIBs) have been investigated as a promising safe and low-cost storage device for sustainable energy. For the stability of ALIBs, it is important to expand the electrochemical stability window of aqueous electrolytes. Although “Water-in-salt” electrolytes [1] containing significant amounts of lithium salts have been reported as an effective approach, cost reduction of the aqueous electrolyte remains a major challenge for the industrialization of such ALIBs.Controlling the pH of the aqueous electrolyte is another approach to widen the electrochemical window with a smaller use of lithium salts. The 2 V-class ALIB of Zn-coated Li4Ti5O12/LiMn2O4 was demonstrated using dual aqueous electrolytes having different pH separated by a lithium-ion conductive inorganic solid electrolyte.[2] However, lithium-ion conductive inorganic solid electrolytes may often be unstable in alkaline solutions. A perfluorinated sulfonic acid cation-exchange membrane (CEM) is one of the possible alternatives for separating two different aqueous electrolytes. In principle, the concentration of the entire electrolyte does not change during lithium-ion battery operation where lithium ions shuttle between the cathode and anode. Therefore, the specific compositions of the cathode and anode electrolytes are selected to achieve the Donnan equilibrium across the CEM, and stable battery operation is expected as long as the electrolyte equilibrium is maintained. In this study, the feasibility of this concept was investigated using ALIB cell of the anatase-TiO2/spinel-LiMn2O4.A stable combination of cathode and anode electrolytes was investigated experimentally. Several compositions of cathode and anode electrolytes were prepared, and equal volumes of the cathode and anode electrolytes were faced across the CEM, stored for 10 days at room temperature, and the composition of each electrolyte were determined using inductively coupled plasma atomic emission spectroscopy (ICP-AES). After repeating this procedure, a stable combination of cathode and anode electrolytes was found as 27 g/L of Li and 8 g/L of K for an anode electrolyte, and 24 g/L of Li, 36 g/L of K, 41 g/L of P, and 68 g/L of S for a cathode electrolyte prepared using LiOH, KOH, Li2SO4, and KH2PO4. The pH was 4 and 11 for the cathode and anode electrolytes, respectively.The battery test was demonstrated for the TiO2/LiMn2O4 cells assembled with the cathode/anode electrolyte and the same 2 mol/kg Li2SO4 electrolyte in both sides for comparison. The initial charge/discharge profiles are shown in Fig. 1. The profiles were obtained by constant current of 15 mA/g regarding the weight of the cathode active material with the cutoff voltage of 2.8 V and 1.5 V in charge and discharge processes, respectively. The Coulombic efficiency was reached to 96% in the cells with electrolytes having the pH difference, whereas it was 69% in the cell with the 2 mol/kg Li2SO4. The alkaline anode electrolyte suppressed hydrogen generation sufficiently for the lithiation/delithiation of anatase TiO2, which leads to an excellent reversibility over 2 V operation with an improvement in the Coulombic efficiency of the cell with dual aqueous electrolytes.To further investigate the stability of the aqueous battery, a cycle test was conducted on the cell with the dual electrolytes. Figure 1(b) shows the discharge capacity during 100 charge-discharge cycles obtained by the constant current of 75 mA/g-cathode. The Coulombic efficiency reached >99%, and the capacity retention was calculated to be 75% at 100 cycles, which indicates that the suitable pH of the cathode and anode electrolyte was maintained during repeated charge/discharge cycles.In the presentation, we will discuss the details of the battery operation, including a role of perfluorosulfonated CEM and issues to improve the battery performance.

Elastoplastic properties of ion exchangers based on cross-linked polyelectrolytes

In this paper, we dilatometrically studied the elastoplastic properties of spherical grains of industrial weakly acidic and strongly acidic ion-exchanger in experiments with constant uniaxial compression and a subsequent unload at room temperature, depending on the ionic form and concentration of the electrolyte solution. It was found that the ionic form of polyacrylate and polymethacrylate cross-linked with triethylene glycol dimethacrylate and divinylbenzene, respectively, and the concentration of the external solution affects their elastoplastic properties. In dilute solutions of sodium chloride and calcium chloride, the gels exhibited elastic properties with close relative amplitudes of deformation. The amplitude of deformation of the grain of polymethacrylate crosslinked with divinylbenzene, in the Ni form, in a dilute nickel chloride solution was significantly lower than that of the Ca form, with significant plastic deformation. With an increasing concentration of the external solution of calcium and nickel chlorides under mechanical load on the grain of polymethacrylate cross-linked with divinylbenzene, the total deformation of the granule and the magnitude of elastic deformation decreased, while the residual (plastic) deformations increased. In concentrated solutions of CaCl2 and NiCl2, such an ion-exchanger became an inelastic rigid material. Even under increased mechanical load, the magnitude of its elastic compressive deformation was very small. The K-form of a swollen in water strongly acidic polystyrene cation-exchanger with grafted sulpho groups cross-linked with divinylbenzene is also characterized by elastic deformations, i.e. the polymer is in a highly elastic state. However, the polystyrene matrix is more rigid compared to polyacrylic and polymethacrylic cation-exchangers in the alkali metal ion form, so the amplitude of deformation is significantly smaller. For such a cation-exchanger in Ca- and Ni- forms, elastic deformations prevail even in concentrated solutions.

Inherited Structure Properties of Larch Arabinogalactan Affected via the TEMPO/NaBr/NaOCl Oxidative System.

Arabinogalactan (AG), extracted from larch wood, is a β-1,3-galactan backbone and β-1,6-galactan side chains with attached α-1-arabinofuranosyl and β-1-arabinopyranosyl residues. Although the structural characteristics of arabinogalactan II type have already been studied, its functionalization using 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) oxidation remains a promising avenue. In this study, the oxidation of AG, a neutral polysaccharide, was carried out using the TEMPO/NaBr/NaOCl system, resulting in polyuronides with improved functional properties. The oxidation of AG was controlled by analyzing portions of the reaction mixture using spectrophotometric and titration methods. To determine the effect of the TEMPO/NaBr/NaOCl system, air-dried samples of native and oxidized AG were studied by Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy, as well as by gel permeation chromatography. Compounds that model free (1,1-diphenyl-2-picrylhydrazyl (DPPH)) and hydroxyl radicals (iron(II) sulfate, hydrogen peroxide, and salicylic acid) were used to study the antioxidant properties. It was found that, in oxidized forms of AG, the content of carboxyl groups increases by 0.61 mmol compared to native AG. The transformation of oxidized AG into the H+ form using a strong acid cation exchanger leads to an increase in the number of active carboxyl groups to 0.76 mmol. Using FTIR spectroscopy, characteristic absorption bands (1742, 1639, and 1403 cm-1) were established, indicating the occurrence of oxidative processes with a subsequent reduction in the carboxyl group. The functionality of AG was also confirmed by gel permeation chromatography (GPC), which is reflected in an increase in molecular weights (up to 15,700 g/mol). A study of the antioxidant properties of the oxidized and protonated forms of AG show that the obtained antioxidant activity (AOA) values are generally characteristic of polyuronic acids. Therefore, the TEMPO oxidation of AG and other neutral polysaccharides can be considered a promising approach for obtaining compounds with the necessary controlled characteristics.

Eco-friendly closed-loop recycling of nickel, cobalt, manganese, and lithium from spent ternary lithium-ion battery cathodes

Recycling technology is essential for managing waste and addressing environmental issues related to scrapping power lithium batteries. A closed-loop recycling technique was proposed in this work for maximizing usage of lithium (Li), manganese (Mn), cobalt (Co), and nickel (Ni) resources in spent ternary lithium battery (SNCMB) cathodes. A green and sustainable leaching process utilizes citric acid (CA) and hydrogen peroxide (HP) to efficiently extract Ni, Co, Mn, and Li from SNCMB cathodes. Maximizing leaching rates for Ni (96.69 %), Co (95.38 %), Mn (97.64 %), and Li (98.72 %) under optimal conditions (80 ℃, 4 mol/L CA, 20 g/L solid to liquid (S/L) ratio, 2 vol% HP, 70 min). The Avrami equation models leaching kinetics, requiring a temperature of 80 ℃ to accelerate the process. Hydrogen-type strong acidic cation exchange resin (HR) effectively adsorbs Ni, Co, Mn, and Li ions from leachates through ion exchange under optimal conditions, reducing costs and eliminating the need for separating metals with similar chemical properties. This multi-stage adsorption recycling process renders leachates both economical and eco-friendly. The metal-enriched HR composite (HRC) from the ion-exchange process prepares ternary lithium battery (NCMB) cathodes to maximize metal usage. Microwave heating achieves excellent structure and electrochemical performance of regenerated ternary lithium battery (RNCM) cathodes, with 153.81 mAh/g discharge capacity at 0.1C rate and 90.92 % capacity retention after 50 cycles at 900 ℃ for 4 h. This innovative, efficient, and eco-friendly technique allows for closed-loop recycling of Ni, Co, Mn, and Li from SCNMB cathodes, providing new avenues for lithium battery recycling.

Effect of Fractionation Columns on the Elution of Rare Earth Elements Recovered from Acid Mine Drainage

Rare earth elements (REE) can be found in expressive contents in different secondary sources, such as acid mine drainage (AMD). This work evaluated separation of light and heavy rare earth elements (REE) from an acid mine drainage (AMD) generated in a former uranium mine in Brazil by using ion exchange. This AMD presents pH 3.50, total REE content of 97 mg L−1 and 1.3 g L−1 of sulfate and was used in the REE loading experiments. Loading experiments were carried out in columns using a commercial strong acid cation (SAC) exchange resin. Elution was performed with 0.01 mol L−1 NH4EDTA in systems with one, two and three columns. Regarding the loading step, the resin presented a total loading capacity of 0.58 mmol g−1. The resin proved to be more selective for light REE with adsorption efficiency of 78% and 48% for heavy REE. Regarding elution, high efficiencies between 90 and 100% were achieved for REE. The final REE solution is approximately 10 times more concentrated in the liquor related to the acid mine water. Better fractionation results were achieved for the system with three columns. Although the complete separation of the REE into pure elements was not possible, two distinct fractions of heavy and light REE could be obtained, and La was completely separated from the other REE. In order to improve fractionation and separate the REE into individual ones, the concentrated fractions can proceed to subsequent ion exchange systems.

Removal of heavy metal ions from wastewater using ion exchange resin in a batch process with kinetic isotherm

Techniques such as selective ion exchange can be used to remove traces of heavy metals. The recently created resins provided quicker sorption kinetics and a high resin capacity for metal ions such as Lead (Pb²⁺), Copper (Cu²⁺), Zinc (Zn²⁺), Cadmium (Cd²⁺), and Nickel (Ni²⁺) ions. The elimination of Pb²⁺ and Cu²⁺ ions from aqueous solutions was examined in the current work. Purolite® C100, a strong acid cation-exchange resin, was used in experimental studies. Using packed-column chromatography, the impacts of operating factors on metal ion exchange were examined. These parameters included resin dose, initial pH, residence time, and metal ion concentration with ranges of 40 - 80 gs, 3 - 12, 30 - 90 min, and 50 -150 parts per million respectively. As part of exchange research, different doses of resin are brought into contact with a fixed volume of solution containing different concentrations and pHs of Pb²⁺ and Cu²⁺ ions for different periods. An Atomic Absorption Spectrophotometer (AAS) approach was used to measure the concentrations of metal ions. Experimental data on ion exchange were evaluated using Langmuir, Freundlich, and Temkin models.The results showed that there is a clear competition between lead and copper, as it was found that there is a convergence between the removal rates for both metals under the same conditions. The ion-exchange recovery of Cu approached 94.37 %, but Pb recovery was 92.9 % with Purolite® C100 resin dose range of 40 g to 80 g in the pH range of 3 to 12.

Environmentally safe technology of waste processing of galvanic production

It is known that waste is difficult to purify using existing reagent methods to the standards of the MPC. In addition, the formed sediments contain poorly soluble hydroxy compounds of heavy metals and gypsum, which makes it impossible to dispose of iron- and copper-containing electroplating sludges. The purpose of the study was to study the possibility of ion exchange separate and simultaneous extraction of iron and copper ions from acidic solutions of pickling and copper plating in galvanic production to obtain ferrites. In the course of research, the highly acidic cation exchange resin Dowex HCR S/S in the H+ form was chosen as the cationite. The choice of a strongly acidic cationite is justified, based on the fact that cationites of this type are able to easily lose hydrogen ions due to their displacement from the cationite matrix by other cations of the solution. The sorption processes of iron (II) and copper (II) ions were carried out under dynamic conditions. In the course of experimental studies, it was shown that with an increase in the concentration of sulfuric acid, the full exchangeable dynamic capacity of the cationite significantly decreases both during the sorption of iron ions and during the sorption of copper ions. For iron-containing solutions, full dynamic exchange capacity decreases from 1.39 g-eq/dm3 in the absence of H2SO4 in the initial solution and decreases to 0.3-0.46 g-eq/dm3 at a concentration of sulfuric acid at the level of 1-3 g/dm3. An increase in the concentration of iron (II) ions leads to a significant increase in full dynamic exchange capacity, even with a concentration of sulfuric acid of 8 - 13 g/dm3, full dynamic exchange capacity was at the level of 1.35 g-eq/dm3, which corresponds to the level of sorption of diluted solutions even in the absence of acid. However, the total concentration shows that the efficiency of sorption of metals from acidic solutions remains quite high and increases with the increase of the initial total content of sorbed ions. The main indicator used when choosing an ion exchange method is the possibility of effective regeneration of the cation exchange material. When using 5% solution of sulfuric acid already at the specific consumption of the regeneration solution, it was possible to achieve a degree of regeneration at the level of 95-98%, and when using 10% solution, the degree of regeneration reached 100%. According to the developed technological scheme, regeneration solutions are processed by precipitation into magnetite in a ferritizer reactor. To remove iron ions from concentrated iron-containing regeneration solutions by the ferrite method in order to obtain ferrite particles (magnetite) with maximum magnetic properties, a mixture of Fe (II) and Fe (III) sulfates was used with their concentration ratio K = [Fe2+]/[Fe3+] = 0.5, as a stable relationship between magnetic properties and sediment volume was noted. At maximum magnetic properties, the sediment volume is minimal, and vice versa. Obtaining highly dispersed magnetic particles from a mixture of ferric and ferric sulfates by precipitating them with 10% NaOH solution during heating allows to significantly reduce the duration of the process, simplify it and increase the productivity of the equipment. To obtain magnetic particles of copper ferrites from regeneration solutions by precipitation with alkali at normal temperatures, the concentration ratio K1 = [Fe2+]/[Cu2+] = 3.15-7.76 should be maintained. With an increase in the concentration of Cu2+ ions, there is an increase in the period of crystallization of the obtained sediments and their acquisition of magnetic properties. The formed ferrite material can be used for environmental purposes as a valuable raw material for carbon monoxide neutralization catalysts, as part of alkaline cement for concrete products, or sent for safe disposal. The obtained results on the application of ion-exchange extraction of iron and copper ions from acidic solutions of galvanic production are expedient as the first stage of complex ecologically safe processing of galvanic wastes with the production of ferritic materials for industrial use.

Construction and in vitro/in vivo evaluation of menantine hydrochloride oral liquid sustained-release drug delivery system

Objective The purpose of the present study was to formulate a menantine hydrochloride (MH) sustained-release suspension. Methods Menantine hydrochloride drug resin complex (MH-DRC) was prepared with strong acid cation exchange resin as carrier using water bath method. The MH-DRC was characterized using scanning electron microscopy, X-ray diffraction and infrared spectroscopy. The MH-coated microcapsule (MH-CM) with optimized formulation was further dispersed in a suitable medium to obtain a sustained-release suspension. The rats were given both the MH sustained-release suspension and the commercial MH sustained-release capsule by intragastric administration. The plasma concentration-time curves and related pharmacokinetic parameters were also investigated using a non-atrioventricular model. Results MH and ion-exchange resin were ionically bonded. AmberliteIRP®69 had a higher affinity for MH at the initial concentration of 5 mg·mL−1 and a reaction temperature of 25.0 ± 0.5 °C. In vitro drug release profile showed that both the drug resin complex and the coated microcapsules had a certain level of sustained-release effect. The t1/2 of MH sustained-release suspension was extended from 68.44 h to 72.79 h with the peak blood concentration being decreased to 3.56 μg·mL−1 and the Tmax extended to 12 h compared with the commercial MH sustained-release capsule. The concentration-time curve of the self-made MH sustained-release suspension was flattened and the average relative bioavailability (Fr ) was 116.65% compared with the commercial MH sustained-release capsules. Conclusions The findings showed that the MH sustained-release suspension was successfully formulated with acceptable pharmacokinetic indices for effective treatment of Alzheimer’s disease.

Pertechnetates - A Structural Study Across the Periodic Table.

The number of crystal structures of pertechnetates derived from aqueous solutions has been expanded from seven to over 30. We report the conversion of NH4TcO4 to aqueous HtcO4 via acidic cation exchange. This is followed by the synthesis and structural elucidation of pertechnetate salts of alkaline earth (AE), transition metal I and lanthanoids (Ln) elements. Various degrees of hydration and coordination are discussed. Where possible, a comparison with the perrhenate homologues is made. The described syntheses and materials may be used as novel starting materials for extended technetium research.

STUDYING THE BREAKTHROUGH TIIIIE FOR STRONGLY ACIDIC CATION EXCHANGERS

f-he airn of'this research is to study the breakthrough time for cation exchangers by using a pilot plant of iotr exchange and passing water with different concentrations of hardness. The piiot plant oonsisted of one colurnn containing strongly acidic cation exchanger of styrene divinylLenenzene type. The study covered the effects of the flow rate (1.013 --5.067) L/hr, bed depth (0.1 - 0.5) m, and hardness concentration (200-500) ppm on breakthrough rime for cation -exchangerr. io u column witl: (2.5 cm in diameter. Box-Wilson cornposite ratatable design method was adopted in the designing the experimental work" -I'hi.s method proposed secclnd order polynomial mathernatical moclel and their coefficients are estinLatecl through non -- linear regression analysis to correlate the response function (breakthn:ugh tirne) with the three variables (flow rate, bed depth, trnd hardness concentratiorr).

Commercial turpentine oil enriched with α-terpineol using an acid heterogeneous catalyst

The hydration of α-pinene, limonene, β-pinene, and commercial turpentine oil in the presence of strong acidic cation exchange resin Amberlyst-15 was studied. The acid catalytic hydration was performed in a batch reactor, and the effect of solvent at various temperatures and reaction times was evaluated. The main hydration product obtained from α-pinene was α-terpineol with a yield of 36 % (4 h, 70 °C, 2-propanol as solvent); however, the selected catalytic system was even more active to obtain α-terpineol when β-pinene was used as a substrate, obtaining α-terpineol yield of 38 % in 2 h of reaction. For the hydration of turpentine (70 °C, turpentine:water:2-propanol mass ratio of 1:0.5:2, 15 % w/w catalyst) the composition of reaction mixture after 4 h was 35 % w/w of α-terpineol, 8 % w/w of α-pinene, and 0.5 % w/w of β –pinene, which correspond to a final content of α-terpineol similar to the concentration obtained when α-pinene was used as a substrate (36 % w/w).

Heavy metal adsorption from phosphoric acid 29% P2O5 with Amberlite IRC200 Na resin

ABSTRACT Phosphoric acid plays a major role in our day-to-day life since it is used among other applications to produce fertilizers. Nevertheless, its production from phosphate rock often involves the presence of heavy metals. This study investigates the adsorption of cadmium, zinc, nickel, chromium, arsenic, and vanadium from phosphoric acid on a strongly acidic cation exchange resin, Amberlite IRC200 Na. Amberlite IRC200 Na is an easily regenerated resin with a high selectivity toward divalent cations (Cd, Zn, and Ni) removing 94% of them, while the formation of anionic or neutral complexes with phosphoric acid hinders the adsorption of Cr (70%), As and V (below 20%) on the resin. To model the resin adsorption in a continuous flow, the kinetics and isotherm have been studied. The fast adsorption of metals follows a pseudo-second order kinetic, where the rate is equivalent to the square of the number of remaining adsorption sites. The adsorption isotherm follows a Langmuir equilibrium model, which indicates that the ion exchange can be approximated to a homogeneous adsorption. The kinetic and isotherm results show that the resin is not selective between divalent ions.

Recovery of Ionic Liquid from the Model Solution Mixture Mimicking the Catalytically Hydrolyzed Cellulose Product Utilizing Amberlyst Ion-Exchange Resin

The hydrolysis of cellulose using ionic liquid (IL) has been extensively studied but there is limited understanding of the removal of IL from the biomass hydrolysate. Finding a suitable method for the recovery and reuse of IL is one of the biggest challenges before its large-scale application. Selecting an appropriate combined recovery process is very important. This study proposed a facile ion-exchange combined method for the recovery of IL from the modeled cellulose hydrolysate mixture containing sugars as well as γ-valerolactone (GVL) via an adsorption–desorption mechanism using sulfonic acid cation-exchange (Amberlyst 15 (H)) resin. The results showed that the resin could adsorb more than 94% of 1-ethyl-3-methylimidazolium chloride [Emim]Cl IL at ambient conditions within a contact time of 20 min. The other coexisting constituents like glucose and GVL have no significant effect on the adsorption efficiency of IL. The adsorption of IL on Amberlyst 15 (H) resin was observed to be pseudo-second-order adsorption. The regeneration of the adsorbed IL was possible up to 70% using low-cost, easily available sodium chloride (NaCl) solution. Similarly, despite the interference of other unwanted byproducts in the real biomass hydrolysate sample, an IL adsorption efficiency up to 51% was reached under similar operating conditions. This study thus opens the facile possibility of extracting and recycling IL used in the biomass hydrolysis process.

Study of Sorption of Chlortetracycline Hydrochloride and Its Subsequent Determination by Capillary Zone Electrophoresis

The work deals with the development of an approach to the determination of chlortetracycline, which combines the preconcentration of the analyte with its subsequent determination by capillary zone electrophoresis. The conditions that ensure the lowest value of the limit of determination for chlortetracycline in aqueous solutions using a Kapel-105M capillary electrophoresis system (Lumex, Russia) are determined, i.e., temperature, time and pressure of sample injection, background electrolyte composition, and detection wavelength. It is shown that the stability of a chlortetracycline solution is maximum at a storage temperature of 0.5°С in the absence of buffer systems or in using a dilute ammonium acetate buffer solution. It is found that the recovery of chlortetracycline by strongly acidic cation exchangers KU-1, KU-2 is higher compared to that by KB-4 and KB-4P2, bearing weakly acidic functional groups. The conditions under which the recovery of the analyte by KU-1 from a phosphate buffer solution is about 90% are determined.

Carbonate Associated Sulfate Extraction Method Using Weakly Acidic Cation Exchange Resins

The sulfur (S) mass fraction of carbonate minerals can be used to reconstruct the environmental conditions and S sources at the time of precipitation. As S is present in a wide range of host materials, there is an urgent need to develop a method to extract S from a single mineral phase. We have developed a method to extract structurally substituted sulfate, termed carbonate‐associated sulfate (CAS), from geological and biogenic carbonate minerals using weakly acidic cation exchange resins. Two types of weakly acidic cation exchange resin (methacrylic acid and acrylic acid types) were tested to minimise the blank S contents and decompose carbonate. After repeated cleaning of the resins with high‐purity water or HCl, the blank S contents were reduced to < 0.1 μg, which is < 0.1% of the CAS in the samples. The cleaned resin was used to dissolve 10 and 25 mg of the JCp‐1 carbonate certified reference material (CRM; Japanese National Institute of Advanced Industrial Science and Technology, AIST). Samples and resin were added to 8 ml of high‐purity water at resin/sample ratios of 2, 5, 10 and 20, set on a shaking table, and reacted. The supernatant solutions were sampled sequentially from 0.5 h to 87 h after the start of experiments. The results show that the optimal conditions for decomposing 10 mg of carbonate is a resin/sample ratio of ≥ 10 with a reaction time of ≥ 40 h. Carbonate‐associated S mass fractions were measured for six geological and biogenic carbonate CRMs. The coefficient of variation in carbonate‐associated S mass fractions was ≤ 7%, regardless of the type of resins used. The mass fractions determined with this method recover 74–94% of the total S mass fractions reported in previous studies, suggesting that this method dissolved carbonate, and did not leach other S‐bearing fractions that are not resistant to weak acids. Another benefit of this method is that the decomposed solution can be introduced directly into the ion chromatograph, allowing for more sensitive analyses. We emphasise that this method can also be used for S isotopic measurements, as S contamination from other S‐bearing mineral phases is low.

A novel hollow CuMn-PBA@NiCo-LDH nanobox for efficient detection of glucose in food

Designing a rapid and sensitive glucose detection method is of great significance to public health. Herein, hollow CuMn-PBA@NiCo-LDH nanoboxes (CuMn-PBA@NiCo-LDH NBs) were prepared using acid etching, cation exchange, and reflux method. The modified electrode exhibited outstanding electrocatalytic performance for glucose oxidation due to the unique hollow nanostructure and synergistic effects. The CuMn-PBA@NiCo-LDH NBs electrode displayed excellent electrocatalytic oxidation activity for glucose in an alkaline solution. Under optimal conditions, the electrode achieved a wide linear range (0.0005–1 mmol L–1, and 1–7 mmol L–1) and high sensitivity (10,300 μA L/mmol cm−2 and 5310 μA L/mmol cm−2), with a limit of detection (LOD) of 19 nmol L–1. The feasibility of the sensor applied to the detection of glucose was verified in real food samples through spiked recovery experiments. This electrode material offers an alternative method for the non-enzymatic glucose sensors.

Pre-concentration and partial fractionation of rare earth elements by ion exchange

This work evaluated the pre-concentration and fractionation of rare earth elements (REE) from an acid mine drainage (AMD), by using ion exchange technique. The AMD presents pH 3.50, total REE content of approximately 45.5 mg g−1, 1.3 g L−1 of sulfate and 253 mg L−1 of Ca, Al, Mg as the main impurities. The tests were carried out in columns using a commercial strongly acidic cation exchange resin, LEWATIT® MDS 200H. Regarding the loading step, the resin proved to be more selective for La, Ce, Pr and Nd. A total loading capacity of 0.25 mmol g−1 was obtained for the REE and 2.64 mmol g−1 for the impurities, with efficiencies of 78% and 48%, respectively. Regarding fractionation, the 0.01 mol L−1 NH4EDTA promotes the best elution profiles with more narrow and separated bands. Elution efficiency was greater for the heavy REE, near 100% and only 40% for the light ones. Aluminum and Ca were eluted with an efficiency of approx. 3%. Aluminum was the most difficult impurity to separate from REE.

Mechanism of Water Dissociation on Metal Oxide Surfaces in Bipolar Membrane Electrolyzers: A First-Principles Calculation

Bipolar membranes for water electrolysis, consisting of an acidic cation exchange layer and an alkaline anion exchange layer are a promising means for hydrogen production. The electrolyzer operates the oxygen evolution reaction (OER) under locally basic conditions and the hydrogen evolution reaction (HER) under locally acidic conditions. Water dissociation (WD) occurs within the junction, which is spatially separated from the HER and the OER. It has been shown that the addition of a layer of metal oxide nanoparticles at the junction significantly lowers the overpotential for the process of WD [Science, 2020, 369,1099]. However, the atomistic mechanism by which the metal oxide surface catalyzes the WD is still unclear. We will discuss the theoretical understanding of the WD mechanism at the metal-oxide/water interfaces and investigate the descriptors such as surface pKa, dielectric constants, and adsorption energies, etc. We will combine ab intio molecular dynamics simulations with the electronic structure calculations at the hybrid functional level. Further details of the reaction mechanisms during the WD process will also be explored with the nudged-elastic-band calculations.