Ion-exchange Phase Research Articles

Quantitative study of competitive and selective immobilization of Pb(II)-Ni(II)-Zn(II)-MB(I) by biogenic monohydrocalcite composite and its potential environmental effects

The study of the competitive and selective immobilization properties and mechanisms of pollutants immobilized by metastable biogenic monohydrocalcite is of great importance for the assessment of the eco-environmental effects and applications of hydrated calcite at the Earth’s poles. Microbial culture technology was used to induce the synthesis of biogenic monohydrocalcite (BMHC), and mineral characterization, batch adsorption experiments and chemical analyses were further used to investigate the sequestration characteristics, action mechanism, and environmental effects of BMHC on Pb(II)-Ni(II)-Zn(II)-methylene blue (MB) compound pollution. The results show that BMHC is an organic-inorganic mineral composite (about 3.60 % organic matter, Mg/Ca ≈ 0.07). The adsorption and immobilization processes of Pb(II), Ni(II), Zn(II), and MB(I) by BMHC are all better fitted by the pseudo-second-order kinetic equation. The passivation ability of BMHC for contaminants is ranked as Pb(II) ≫ Zn(II) > Ni(II) > MB(I). BMHC exhibits an excellent selective sequestration capacity of Pb(II) (k ≥ 31.89), which is related to the solubility product of the carbonate minerals, the initial concentration of Pb(II), ion exchange and mineral phase transformation. Based on these results, it is proposed that the synthesis and transformation of monohydrocalcite under global warming at the Earth's poles may influence the biogeochemical cycling of environmental pollutants. The study provides a theoretical basis for the environmental effects and geochemical action of biogenic monohydrocalcite and its applications.

A highly stable and leach resistant sodium copper titanate based ion-exchanger for immobilizing strontium: Comprehensive studies on preparation, characterization, adsorption and material stability

A leach resistant, stable strontium (Sr) specific solid phase ion exchange material that could be used as a matrix for immobilizing Sr-bearing nuclear waste was developed, and different studies were conducted to establish the material's stability. Sodium copper titanate (SCT) that was prepared by a simple solution synthesis method exhibited a high Sr removal tendency from pH 4 to 8, and is therefore capable of removing Sr from alkaline aqueous waste in the pH range. Sr adsorption was modeled using Langmuir, Freaundlich, Tempkin, and D-R isotherm models and the diffusion based reaction kinetics models have also been explored by modeling adsorption kinetics. Subsequent to Sr exchange to SCT at room temperature, the material was calcined at 673 K and 1273 K. Material stability of the Sr loaded SCT matrix was studied using thermogravimetric, SEM, X-ray diffraction and Raman spectrometric methods. Soxhlet leaching experiments were performed on the Sr-loaded SCT established the stability of the studied material under harsh conditions.

An improved synthesis of alkyl AMP esters

Enzymes belonging to the Acyl-CoA/NRPS/Luciferase (ANL) superfamily of enzymes, are significant targets in drug development. One member of this superfamily is Acetyl-CoA Synthetase (ACS). This enzyme is an emerging target for the treatment of various infectious diseases and cancer. Alkyl AMP esters have emerged as potent inhibitors of ACS. Previous methods for synthesizing these esters often involved water-based reactions or necessitate purification through reverse phase prep-HPLC or ion-exchange chromatography. To address these challenges, we developed a new approach utilizing 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) to couple 5′-adenylic acid to the corresponding alcohol, utilizing triethylamine as the base. This method yielded primary, secondary, unsaturated, and cyclic alcohols in excellent yields. Importantly, we optimized the reaction conditions to achieve excellent yield and purity without the need for reverse phase prep-HPLC or ion exchange chromatography. Instead, purification was achieved through silica gel chromatography using Biotage ® Sfar spherical silica gel.

Research on Modification of Oxygen-Producing Adsorbents for High-Altitude and Low-Pressure Environments

In oxygen production on plateaus, pressure swing adsorption (PSA) oxygen production is currently the most commonly used oxygen production method. In plateau regions, low pressure leads to a decrease in adsorbent nitrogen–oxygen separation performance, which affects the performance of PSA oxygen production, so it is particularly important to enhance adsorbent nitrogen–oxygen separation performance. In this paper, Li-LSX (lithium low-silicon aluminum X zeolite molecular sieve) adsorbents were modified using the liquid phase ion exchange method, and five kinds of modified adsorbents were obtained, namely AgLi-LSX, CaLi-LSX, ZnLi-LSX, CuLi-LSX, and FeLi-LSX, respectively. The influences of different metal ions and modification time lengths on the adsorbent nitrogen adsorption and nitrogen–oxygen separation coefficients were analyzed. Through theoretical calculations, the nitrogen and oxygen adsorption and separation performances of the modified adsorbents at different altitudes and low adsorption pressures were investigated. It is shown that the nitrogen adsorption capacity of the AgLi-LSX-1 adsorbent obtained from the modification experiment reaches 27.92 mL/g, which is 3.24 mL/g higher than that of Li-LSX; the nitrogen–oxygen separation coefficients of S1 and S2 are 19.24 and 7.54 higher, respectively; and the nitrogen–oxygen separation coefficients of S4 are 20.85 and 7.54 higher than those of Li-LSX, respectively. With the increase in altitude from 50 m to 5000 m, the nitrogen–oxygen separation coefficient of the AgLi-LSX-1 adsorbent increased rapidly from 20.85 to 57, and its nitrogen–oxygen separation coefficient S4 exceeded that of the Li-LSX adsorbent to reach 47.61 at an altitude of 4000 m. Therefore, the modified adsorbent AgLi-LSX-1 in this paper can enhance the performance of the PSA oxygen process for oxygen production in plateau applications.

Porous heterojunction CoSe2–MoSe2 nanosheet arrays for electrocatalytic oxygen evolution

Oxygen evolution reaction (OER) is an important half-reaction of many actual processes, which has the slow kinetics of four-electron process. Interface engineering as an effective method can accelerate the slow kinetics of oxygen evolution reaction. In this paper, CoSe2–MoSe2 porous nanosheet arrays with heterostructures were synthesized on carbon cloth by ion exchange and vapor phase selenization using Co-MOF as template. Due to the porous two-dimensional structure, the electron diffusion path is shortened and the self-supporting electrode has excellent conductivity. When catalyzing OER in 1 M KOH solution, the CoSe2–MoSe2 delivers an overpotential of 278 mV at 10 mA cmm2, and Tafel slope of 61.2 mV dec−1, making catalytic activity a better result than commercial RuO2. In addition, the decay of the catalytic activity is negligible after 24 h of continuous electrolysis. This work provides a method for the design of porous bimetallic selenide self-supporting oxygen evolution electrocatalysts.

Use of Commercial Mixed-Mode Stationary Phases and Sorbents in the High-Performance Liquid Chromatography Analysis and Solid-Phase Extraction of Ionized and Hydrophilic Bioactive Compounds.

Mixed-mode high-performance liquid chromatography (HPLC) is increasingly used for the analysis of ionic and highly hydrophilic drugs, which are difficult to separate by conventional single-mode HPLC. In the former case, chromatographic separation is achieved using one of the several commercially available mixed-mode stationary phases, typically combinations of reversed and ion-exchange phases. Moreover, mixed-mode stationary phases can be used as solid-phase extraction (SPE) sorbents. This review focuses on the recent applications of mixed-mode stationary phases in the chromatographic analysis of bioactive compounds, such as drugs, herbicides, and pesticides. Specifically, we briefly summarize HPLC methods utilizing mixed-mode stationary phases and SPE pretreatment procedures utilizing mixed-mode sorbents developed in the last decade, thus providing a reference work for overcoming the difficulties in analyzing ionized or hydrophilic drugs by conventional reversed-phase chromatography.

Developing Green Sorbents Derived from Natural Materials for Microextraction and Determination of Emerging Contaminants

Developing Green Sorbents Derived from Natural Materials for Microextraction and Determination of Emerging Contaminants

Thermal‐Triggered Phase Separation and Ion Exchange Enables Photoluminescence Tuning of Stable Mixed‐Halide Perovskite Nanocrystals for Dynamic Display

AbstractFlexible regulation of bandgap of perovskite nanocrystals (PNCs) is fundamentally critical for desirable optoelectronic functions and applications. Here, regulating chemical composition and emission wavelength of PNCs in glass by a simple heat‐treatment process are reported, which is established to rely on the thermal‐trigger phase separation and ion exchange. The first principle calculations are overall performed to reveal the mechanism of bandgap engineering and optimization of emission performance. The PNCs exhibit excellent stability against thermal, ultraviolet irradiation, and organic molecules. The bandgap of PNCs in the heat‐treated glass can also be re‐modulated by ultrafast laser irradiation. Ultrafast laser direct writing of multi‐color patterns and holographic dynamic displays are achieved, which hold great potential in the application of encryption‐decryption and emissive devices.

A performance comparison of photo-fenton decolorization of methylene blue by using bentonite/iron composites prepared by liquid phase and solid phase ion exchange method

Nowadays, there is a wide range of pollutants present, which requires the treatment of wastewater. The photo-Fenton method has been recognized as valuable in this area. In this study, iron/bentonite composites were created using both liquid phase and solid phase iron exchange techniques, and they were utilized as a photocatalyst for the degradation of methylene blue through photo-Fenton process. Various factors affecting the photocatalytic decolorization were investigated, including the initial concentration of the dye, weight of the catalyst, pH of the solution, and concentration of hydrogen peroxide. The decolorization efficiency of the iron/bentonite composites prepared using the solid phase and liquid phase ion exchange approaches was found to be 99% and 95%, respectively. Based on the data, it can be concluded that the performance of both catalysts was almost equally influenced by the initial dye concentration, catalyst weight, solution pH, and hydrogen peroxide concentration. Moreover, the solid phase ion exchange method demonstrated greater reusability compared to the liquid phase ion exchange method. Consequently, it can be stated that the solid phase ion exchange approach is a suitable and straightforward alternative to the conventional liquid phase ion exchange method for producing a photo-Fenton catalyst.

Моделирование процессов переноса с учетом химических взаимодействий в программном комплексе GeRa

The paper considers a transport model with geochemical couplings implemented in the GeRa software. It evaluates the scope of application typical for such models focused on the safety assessment of nuclear facilities. The paper presents a few typical case studies to demonstrate the accountability of different chemical processes: ion exchange, surface complexation, dissolution and mineral phase precipitation. It overviews some typical radionuclide transport problems with an account taken of sorption, as well as the one of concrete decalcification.

Strengthening rare earth and inhibiting aluminum leaching in magnesium salt-acetic acid compound system from ion-adsorption type rare earth ore

The leaching process of rare earth (RE) from ion-adsorption type rare earth ore (IATREO) using ammonium salt or magnesium salt as leaching agents presents challenges to inefficient leaching of RE elements and simultaneous leaching of ion-exchangeable phase aluminum (Al). This paper introduced acetic acid (HAc) into the leaching process of IATREO, to enhance the leaching of RE elements and inhibit the leaching of ion-exchangeable phase Al. The results show that RE elements and HAc mainly existed in the form of REAc2+, with a relative proportion of approximately 15 %. The presence of the HAc-Ac- conjugate acid-base pair provided a buffer capacity. In the MgSO4-HAc compound system, column leaching was controlled by internal diffusion, and the supplementation of HAc decreased the activation energy of the RE leaching reaction to 7.11 kJ/mol while increasing the leaching rate. Besides, the HAc-Ac- buffer system increased the pH of the leaching process and promoted the hydrolysis of ion-exchangeable phase Al, thereby inhibiting its leaching. Single-factor experiments indicated that under the optimal conditions, the leaching efficiency of RE elements reached 98.40 %, while the leaching efficiency of Al was 66.61 %. Compared with the ammonium and magnesium salts leaching systems, the leaching efficiency of RE elements increased by more than 6 %, while the leaching efficiency of Al was reduced by 23.33 %. This paper plays an important role in promoting the efficient and green extraction of IATREO.

Alkali-Induced Phase Transition to β-Spodumene along the LiAlSi2O6-LiAlSi4O10 Join

Due to the refractory nature of α-spodumene (LiAlSi2O6) and petalite (LiAlSi4O10), two major lithium minerals, conventional lithium recovery processes involve a high-temperature pre-treatment (>1000 °C) to induce a phase transition to tetragonal β-spodumene, an open structure allowing easier access to lithium through ion exchange. Considering that these high temperatures are not dictated by thermodynamics but rather sluggish kinetics, the study investigates the mechanisms enhancing the rate of transformation to β-spodumene at lower temperatures while minimizing the growth of metastable hexagonal β-quartz typically observed at the onset of the conversion. The heat treatment of natural α-spodumene revealed that rapid growth of β-spodumene veinlets is achieved at ≤600 °C by activation of alkali-rich fluid inclusions, through a dissolution–recrystallization process. For petalite, the mechanism of the phase transition, initiated at ≈750 °C is a solid-state transformation keeping crystallographic coincidence with the mineral host. Synthetic growth experiments along the LiAlSi2O6-LiAlSi4O10 join indicate a compositional dependence on the resulting β-phase structure, where minor sodium doping strongly favors β-spodumene, as the tetrahedral framework of β-quartz does not allow the extent of deformation to accommodate the larger alkali. These findings open opportunities for energy-efficient lithium recovery pathways where the phase transition and ion exchange can be achieved simultaneously without a high-temperature pre-treatment.

Effect of the Preparation Method on Cu-MOR/g-C3N4 for Direct Methanol Synthesis from Methane Oxidation by Photothermal Catalysis

Copper-based zeolite catalysts are widely used in methanol synthesis from methane oxidation, but their photothermal catalytic properties have seldom been explored. This study examines the effect of the preparation method on Cu-based zeolite composite graphite-phase carbon nitride catalysts (Cu-MOR/g-C3N4) for direct methanol synthesis from methane oxidation by photothermal catalysis. Four different preparation methods are employed: liquid phase ion exchange (Cu-MOR/g-C3N4-IE), isovolumetric impregnation (Cu-MOR/g-C3N4-IM), solid-state ion exchange (Cu-MOR/g-C3N4-GR), and hydrothermal synthesis (Cu-MOR/g-C3N4-HT). Cu-MOR/g-C3N4-IE shows the highest methanol yield (3.09 μmol h−1 gcat−1) due to strong interactions between the CuxOy species and g-C3N4, as well as smaller interfacial charge transfer forces. This study provides a new method for the design and synthesis of catalysts for the conversion of methane.

Activated Ni-O-Ir Enhanced Electron Transfer for Boosting Oxygen Evolution Reaction Activity of LaNi1-x Irx O3.

Tuning the structure of the active center of catalysts to atomic level provides the most efficient utilization of the active component, which plays an especially important role for precious metals. In this study, the liquid phase ion exchange method is used to introduce atomic Ir into LaNiO3 perovskite oxide, which shows excellent catalytic performance in the oxygen evolution reaction (OER). The catalyst, LaNi0.96 Ir0.04 O3 , with the optimal concentration of Ir, displays an overpotential of just 280mV at 10mAcm-2 . The introduced Ir enriches the surface electron density significantly, which not only improves site-to-site electron transfer between O and Ni sites but also allows stable adsorption of the intermediates. Theresults of cyclic voltammetry tests reveal the superior overpotential and remarkable efficiency of the OER process because of the strong interactions in Ni-O-Ir. Moreover, the Ir atom inhibits the participation of a lattice oxygen oxidation mechanism (LOM) in LaNiO3 that guarantees the stability of the catalyst in alkaline conditions. It is anticipated that this work will be instrumental for the preparation and study of a broad range of atomic metal-doped perovskite oxides for water splitting.

A novel and versatile Hybrid HILIC and Ion Exchange Phase for the LC/MS Analysis of Polar Compounds

LebensmittelchemieVolume 76, Issue S2 p. S2-140-S2-140 Analytik (ATW-A) A novel and versatile Hybrid HILIC and Ion Exchange Phase for the LC/MS Analysis of Polar Compounds S.H. Liang, S.H. Liang Restek Corporation, 110 Benner Circle, Bellefonte, PA, 16823 United StatesSearch for more papers by this authorC. Flannery, C. FlannerySearch for more papers by this authorD. Li, D. LiSearch for more papers by this author S.H. Liang, S.H. Liang Restek Corporation, 110 Benner Circle, Bellefonte, PA, 16823 United StatesSearch for more papers by this authorC. Flannery, C. FlannerySearch for more papers by this authorD. Li, D. LiSearch for more papers by this author First published: 01 September 2022 https://doi.org/10.1002/lemi.202259097AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume76, IssueS2September 2022Pages S2-140-S2-140 RelatedInformation

Coordination–reduction leaching process of ion-adsorption type rare earth ore with ascorbic acid

The magnesium sulfate (MgSO4)–ascorbic acid (Vc) compound leaching technique can extract rare earth elements (REEs) existing in ion-exchangeable phase and colloidal phase from ion-adsorption type rare earth ore through the synergy effect of coordination and reduction, but its reaction process and mechanism remain unclear. In this paper, the coordination–reduction leaching mechanism was analyzed from the perspectives of leaching thermodynamics and kinetics, which provide theoretical guidance for the compound leaching process. In the case of neodymium, about 45% of dissolved neodymium will exist as the complex species of NdVc3(aq) in Nd–Vc–sulfate system. Based on this, it is deduced that the Gibbs free energy of the leaching reaction of ion-exchangeable phase REEs will change to a more negative value through the coordination of REEs cations and Vc anions in the MgSO4 leaching process. In addition, the Eh–pH diagrams of Ce–SO42––H2O and Fe–SO42––H2O together with the dissolution experiments confirm that the added Vc initiates the leaching process of colloidal phase REEs through reduction–dissolution reaction. Through the study of leaching kinetics, the leaching of REEs is controlled by diffusion and chemical reaction in the compound leaching system since colloidal phase REEs are leached. Therefore, the addition of Vc can shift the leaching equilibrium to a more favorable state and accelerate leaching process. The rare earth leaching efficiency of ion–exchangeable phase and colloidal phase can be effectively improved by increasing the reaction temperature, the concentrations of leaching agent and Vc, and the leaching agent acidity.

Modification of Beta Zeolites and Their Application in Catalytic Oxidation of Propane

AbstractIn this manuscript, Beta zeolites are modified by liquid phase ion exchange method and high temperature roasting method to achieve the effect of catalytic degradation of propane. After modification by hydrochloric acid, nickel nitrate and zinc nitrate, the specific surface area, pore size and pore volume of Ni−Zn−H‐Beta zeolites catalyst increased, which greatly improved the catalytic degradation effect of propane. By high temperature roasting, the effect of conventional calcined catalyst is better than that of microwave calcined catalyst. When the gas composition is air and 1 % propane, the gas flow is 100 ml/min, the reaction temperature is 300 °C, the optimum preparation conditions of the catalyst are Ni: Zn=2 : 1, HCl pickling temperature is 70 °C, conventional roasting temperature is 500 °C, and the holding time is 60 min, the catalytic activity of Ni−Zn−H‐Beta zeolites is the best, and the degradation rate of propane is 79.6 %.

Selective Scandium (Sc) Extraction from Bauxite Residue (Red Mud) Obtained by Alkali Fusion-Leaching Method.

Bauxite residue, known as “red mud,” is a potential raw material for extracting rare-earth elements (REEs). The main REEs (Sc, Y, La, Ce, Nd, Nb, and Sm) from the raw bauxite are concentrated in RM after the Bayer leaching process. The earlier worldwide studies were focused on the scandium (Sc) extraction from RM by concentrated acids to enhance the extraction degree. This leads to the dissolution of major oxides (Fe2O3 and Al2O3) from RM. This article studies the possibility of selective Sc extraction from alkali fusion red mud (RMF) by diluted nitric acid (HNO3) leaching at pH ≥ 2 to prevent co-dissolution of Fe2O3. RMF samples were analyzed by X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), electron probe microanalysis (EPMA), and inductively coupled plasma mass spectrometry (ICP-MS). It was revealed that Sc concentration in RMF can reach up to 140–150 mg kg−1. Sc extraction was 71.2% at RMF leaching by HNO3 at pH 2 and 80 °C during 90 min. The leaching solution contained 8 mg L−1 Sc and a high amount of other REEs in the presence of relatively low concentrations of impurity elements such as Fe, Al, Ti, Ca, etc. The kinetic analysis of experimental data by the shrinking core model showed that Sc leaching process is limited by the interfacial diffusion and the diffusion through the product layer. The apparent activation energy (Ea) was 19.5 kJ/mol. The linear dependence of Sc extraction on magnesium (Mg) extraction was revealed. According to EPMA of RMF, Sc is associated with iron minerals rather than Mg. This allows us to conclude that Mg acts as a leaching agent for the extraction of Sc presented in the RMF in an ion-exchangeable phase.

Inhibition on the swelling of clay minerals in the leaching process of weathered crust elution-deposited rare earth ores

Rare earths are mainly adsorbed on the clay minerals as ion-exchangeable phase which could be extracted by the ion-exchange method in weathered crust elution-deposited rare earth ore. The clay minerals would swell after adsorbing electrolyte solution during the rare earth leaching process, which would easily lead to the occurrence of landslides and other geological disasters. In this study, to alleviate the expansion of the clay minerals, swelling kinetics curves of the ore samples in the three anti-swelling agents: urea, NH4Cl and NH4NO3 were investigated. Synergy effects of these three anti-swelling agents in binary and ternary systems were also studied. Results showed that the lowest swelling ratio was obtained in the urea/ NH4Cl/NH4NO3 system: 3% wt NH4Cl and NH4NO3 with mass ratio: 7:3 and 6% wt urea at the optimum value of pH 5.0. The Swelling ratio of clay minerals increased with the increase of the temperature in the ternary system. Additionally, swelling kinetics equation δ = A•e-B/t of the clay minerals in different anti-swelling agents were also determined by mathematical regression analysis. The SEM, TG, FTIR and XRD analysis of rare earth tailing leached by ternary system verified the anti-swelling function of urea in the leaching process.

Phosphorus-doped MoS2 with sulfur vacancy defects for enhanced electrochemical water splitting

MoS2 is a promising electrocatalyst because of its natural abundance and outstanding electrochemical stability. However, the poor conductivity and low activity limit its catalytic performance; furthermore, MoS2 is unable to satisfy the requirements of most industrial applications. In this study, to obtain a P-doped MoS2 catalyst with S vacancy defects, P is inserted into the MoS2 matrix via a solid phase ion exchange at room temperature. The optimal P-doping amount is 11.4 wt%, and the resultant catalyst delivers excellent electrocatalytic properties for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with the corresponding overpotentials of 93 and 316 mV at 10 mA cm−2 in an alkaline solution; these values surpass the overpotentials of most previously reported MoS2-based materials. Theoretical calculations and results demonstrate that the synergistic effect of the doped P, which forms active centers in the basal plane of MoS2, and S vacancy defects caused by P doping intensifies the intrinsic electronic conductivity and electrocatalytic activity of the catalyst. Density functional theory calculations demonstrate that P optimizes the free energy of the MoS2 matrix for hydrogen adsorption, thereby considerably increasing the intrinsic activity of the doped catalyst for the HER compared with that observed from pristine MoS2. The enhanced catalytic activity of P-doped MoS2 for the OER is attributed to the ability of the doped P which facilitates the adsorption of hydroxyl and hydroperoxy intermediates and reduces the reaction energy barrier. This study provides a new environmentally friendly and convenient solid-phase ion exchange method to improve the electrocatalytic capability of two-dimensional transition-metal dichalcogenides in large-scale applications.