Ion-exchange Mechanism Research Articles

Chiral zwitterionic stationary phases based on Cinchona alkaloids and dipeptides: Application in chiral separation of dipeptides under reversed phase conditions

Chromatographic behavior of novel chiral stationary phases with bonded selectors based on Cinchona alkaloids modified with dipeptides was studied using dipeptides as probe molecules. Buffer-free and salt containing hydro-organic solutions were used as the mobile phases. The selectors exhibit pseudoenantiomeric behavior with respect to the L/D or LL/DD enantiomers and do not behave so with respect to the LD/DL enantiomers. The alkaloid part of the selectors is the driver of enantioselectivity, while the dipeptide substituent plays a modulating role. The quinidine-based selectors demonstrate stronger adsorption affinity and higher enantioselectivity as compared to the quinine-based selectors. The dipeptide analytes containing a glycyl fragment are weaker retained and their enantiomers are worse separated comparing to dipeptides with both units being larger amino acids. Moreover, a phenyl group in the structure of a dipeptide analyte facilitates enantioseparation. The effect of the mobile phase composition on retention depends on the hydrophobicity of an analyte. Hydrophobic dipeptides are better eluted by methanol-rich solvents, hydrophilic dipeptides are better eluted with water-rich solvents, and dipeptides with an intermediate hydrophobicity demonstrate a U-shaped or more complicated dependence of the retention factor on the percentage of methanol. Even a small buffer addition to the mobile phase decreases retention, but the ion-exchange mechanism was not confirmed. The effect of an electrolyte is rather due to the shielding of the charged groups of the selector reducing thereby electrostatic interaction between the selector and analyte. Efficiency of the novel columns is comparable to that of other brush-type chiral columns, the highest achieved number of the theoretical plates per 1 m varying between 30,000 and 40,000.

A contribution to understanding ion-exchange mechanisms for lithium recovery from industrial effluents of lithium-ion battery recycling operations

Industrial effluents or process waters generated from spent lithium-ion batteries (LIBs) recycling operations often contain high concentrations of lithium ions (Li+). This study characterizes the composition of process water obtained from pre-treatment and concentration operations of LIBs recycling. Ion-exchange experiments are conducted using synthetic lithium solutions (1g/L) and industrial waters to understand Li+ recovery. Employing four commercial cationic resins, fast Li+ exchange kinetics are observed fitting the pseudo-second order model. The equilibrium isotherm data corresponds to the Langmuir adsorption model and reveals a Li capacity of 30-32mg/g using AmberliteTM IRC 120 H, 70mg/g using Lewatit® TP 308 H, 37-40mg/g using Lewatit® TP 208 Na, and 37-41mg/g using Lewatit® TP 260 Na. While the resins initially demonstrate moderate affinity for Li+, this can be significantly enhanced by increasing the Li+ concentration. Notably, as LIBs recycling operation effluents typically contain minimal competing ions, these results underscore the potential of employing ion exchange as a viable method to recover and concentrate lithium before precipitation into lithium salts.

Functionalization of Na2Ca2Si3O9/Ca8Si5O18 Nanostructures with Chitosan and Terephthalaldehyde Crosslinked Chitosan for Effective Elimination of Pb(II) Ions from Aqueous Media

Lead poses significant health risks to humans, including neurological and developmental impairments, particularly in children. Additionally, lead pollution in the environment can contaminate soil, water, and air, endangering wildlife and ecosystems. Therefore, this study reports the straightforward fabrication of Na2Ca2Si3O9/Ca8Si5O18 nanostructures (NaCaSilicate) utilizing a sol-gel technique. Additionally, the produced nanostructures underwent further modification with chitosan (CS@NaCaSilicate) and chitosan crosslinked with terephthalaldehyde (CCS@NaCaSilicate), resulting in new nanocomposite materials. These samples were developed to efficiently extract Pb(II) ions from aqueous media through complexation and ion exchange mechanisms. Furthermore, the maximum adsorption capacity for Pb(II) ions by the NaCaSilicate, CS@NaCaSilicate, and CCS@NaCaSilicate samples is 185.53, 245.70, and 359.71 mg/g, respectively. The uptake of Pb(II) ions was characterized as spontaneous, exothermic, and chemical, with the best description provided by the Langmuir equilibrium isotherm and the pseudo-second-order kinetic model. Furthermore, a 9 M hydrochloric acid solution effectively eliminated Pb(II) ions from the synthesized samples, attaining a desorption efficacy surpassing 99%. Additionally, the fabricated samples exhibited efficient reusability across five successive cycles of adsorption and desorption for capturing Pb(II) ions.

Remediation of sediments contaminated by harmful heavy metals using aluminum sulfate: Sustainable approach for practical applications

Chemical washing could be suitable for the remediation of marine sediments contaminated with harmful heavy metals. Considering green and sustainable remediation (GSR), the application of aluminum sulfate (AS) is intended to reduce the costs and environmental impacts. We extracted harmful heavy metals from manganese nodules using an ion exchange mechanism that occurs when AS dissociates in water. AS in the range from 2 % to 5 % was used. The remediation efficiencies using 5 % AS were found to be the highest, at 91.8 % for Ni and ≥ 100 % for other harmful heavy metals. The Pearson's coefficient evaluation showed that increasing elapsed time did not significantly affect the extraction of harmful heavy metals. Pollutants in post-processing products may not cause secondary pollutions if solidification/stabilization and additional treatments are used. Our results can serve as fundamental data for the actual remediation processes using AS not only for deep-sea mining tailings but also contaminated marine sediments.

Deciphering multistep transformation mechanism of cobalt-vanadium bimetallic sulfides anode in sodium storage

Transition metal sulfides as a high specific capacity sodium-ion batteries (SIBs) anode which have been suffering from successive phase transitions bringing about stress changes, poor electronic conductivity and ineffective ion transport kinetics. Combining self-sacrificial templates and ion-exchange transition reaction mechanisms, herein, cobalt, vanadium bimetallic sulfides hollow nano-cubic boxes with nitrogen-doped nanocarbon coating layer (CoV2S4@NC) are designed to solve these symbiosis problems. With a combination of in-situ Raman, ex-situ XPS/TEM, and density-functional theory calculations, the synergistically coordination mechanism between cobalt and vanadium binary metal during multi-step conversion processes is responsible for the faster charge transfer kinetics and boosted Na+ pseudocapacitance storage capability. Furthermore, the hollow cubic structure combined with the carbon shell layer can release the internal stress during phase transitions and avoid the recurrent growth of SEI film by volume change during the electrochemical process, thus realizing a superior electrode/electrolyte interface. Thus, when used as anode materials for SIBs, the prepared anode materials display excellent electrochemical performance, delivering capacity of 492 mA h g−1 at a current density of 10 A g−1 and high capacity stability with 484 mAh g−1 after 1000 cycles at 5 A g−1. More importantly, the assembled full cell (Na3V2(PO4)3//CoV2S4@NC) also shows high capacity of 574 mAh g−1 with 94.7% capacity retention after 85 cycles, suggesting the potential application of bimetallic sulfides in SIBs.

Simultaneous selective separation and enrichment of bromine and cesium ions by electrochemically switched amphoteric ion membrane

A BiOBr film electrode was prepared by electrodeposition method for verifying an electrochemically switched amphoteric ion exchange (ESAIX) mechanism. Physical and electrochemical characterization results reveal that the BiOBr can switch the valence of Bi between Bi3+ and Bi(3-x)+ to selectively insert Cs+ with simultaneously release Br− at a reduction potential, while it can selectively insert Br− with simultaneously release Cs+ at an oxidation potential. The separation factors of BiOBr film electrode for Cs+/K+, Cs+/Na+, Cs+/Li+, and Cs+/Rb+ cations were 3.71, 3.23, 4.94, and 7.46, respectively, and for Br−/F−, Br−/Cl− and Br−/NO3− anions were 2.11, 1.55 and 3.83, respectively, which showed relatively excellent selectivity for Br− and Cs+. Density functional theory (DFT) calculations reveal that the selectivity of BiOBr towards Br− and Cs+ comes from the lower ion migration energy barrier in the BiOBr lattice. Based on the ESAIX mechanism, a novel electrochemically switched amphoteric ion membrane coupling permselective (ESAIM-CP) system was further developed for the simultaneous separation and enrichment of Br− and Cs+, which successfully achieved the enriched CsBr with 2 folds of the original concentration from a mixed solution of Cs2SO4 and KBr.

Recovery of rare earth elements from mine wastewater using alginate microspheres encapsulated with zeolitic imidazolate framework-8

There is increasing demand and interest in efficient methods for the recovery of rare earth elements (REEs) from wastewater because of the growing concerns associated with the negative impacts of REEs-rich waste discharged on pristine ecosystems. Here, we designed a ZIF-8@ALG composite hydrogel by encapsulating zeolitic imidazolate frameworks-8 (ZIF-8) into sodium alginate and poly (vinyl alcohol) double cross-linked networks (ALG) for the recovery of REEs from mine wastewater. ZIF-8@ALG showed exceptional REEs adsorption performance with the most superior separation factor (Ho/Mn) of 597.5. For the REEs considered, the ZIF-8@ALG composite exhibited a preference for heavy REEs with high adsorption efficiencies (65.3 ∼ 97.2%) and distribution coefficients (2045.5 ∼ 28500.0 mL·g−1). Adsorption involved a combination of electrostatic attraction, complexation and ion exchange mechanisms. REEs adsorbed on ZIF-8@ALG could also be desorbed using sodium citrate via ion-exchange and complexation, thus achieving efficient REEs recovery. In addition, ZIF-8@ALG was stable and reusable, maintaining effective adsorption in wastewater over four consecutive cycles, where the optimal adsorption efficiency reached 80.0%. Overall, this study provided an effective and feasible method for the recovery of REEs in mine wastewater, and confirmed that ZIF-8-based materials have significant potential for REEs recovery applications in wastewater engineering treatment.

Construction of a novel Eu-MOF material based on different detection mechanisms and its application in sensing pollutants aniline, F- and Hg2+

Aniline is an organic pollutant with carcinogenicity and teratogenicity, while F- and Hg2+ are toxic ions that are easily soluble in water. When they are released to the environment, they will pose a threat to human health. Designing a material that can simultaneously detect three types of pollutants is of great significance. In this paper, a novel rare earth metal organic framework material (Eu-MOF) with three-dimensional structure based on 1-methylimidazole-4,5-dicarboxylic acid was synthesized for the first time through solvent thermal method. It has excellent luminescent performance and can be used as a multifunctional fluorescent probe to detect aniline, F-, and Hg2+ based on photoinduced electron transfer, energy competitive absorption, and ion exchange mechanisms, with detection limits of 1.79 × 10-8, 8.13 × 10-8, and 8.83 × 10-7 M, respectively. It is worth noting that Eu-MOF can detect F- and Hg2+ in real water samples, such as lake water and green tea water, with favorable recovery rates.

Co-Al layered double oxide activated carbon composite for eliminating lead ions from water

In the current study, preparation of cobalt-aluminum layered double oxide doped activated carbon (Co-Al LDO/AC) was achieved by the co-precipitation technique and utilized for the remediation of lead (Pb2+) from water. Various methods were employed to examine the properties of the composite material, including BET, XRD, FTIR, SEM, and EDS analysis. The material characterization outcomes indicated that the LDO structure was successfully incorporated into the AC matrices with a surface area of 189.4 m2/g. The influence of adsorption parameters including Co-Al LDO/AC dosage, period of contact, initial Pb2+ loading, and initial solution pH were investigated. Moreover, the isotherm and kinetic models were investigated to provide a deeper understanding of the elimination mechanism of Pb2+ ions. The adsorption results illustrated that pH has a substantial influence on Pb2+ removal with a highest removal effectiveness at pH = 6 and a fast adsorption rate within 7 h. The kinetic data were well aligned with the pseudo-second-order model while the isotherm data obeyed the Sips model (R2>0.966). The highest adsorption uptake, estimated by the Sips model was 25.09 mg/g. Considering the modeling and characterization of the spent Co-Al LDO/AC, a chemical interaction process was involved in the elimination process and mainly controlled by ion exchange, electrostatic interactions, and surface complexation mechanisms. Accordingly, the Co-Al LDO/AC could have great potential as a promising hybrid for the purification of toxic Pb2+ ions from contaminated water streams.

Efficient removal of radioactive iodide from contaminated seawater by radiation-resistant Ag+-doping polypropylene nonwoven adsorbents

For the efficient removal of radioactive iodide ions from medium and low radioactive contaminated water, an Ag-doped adsorbent was designed via radiation grafting method and chemical modification and applied based on the solid–liquid adsorption method. The silver loading content in the adsorbents could be flexibly decided by adjusting the sulfhydryl content. SEM/EDS, ATR, XPS, and XRD characterization methods were used to determine the features of the new adsorbents. With the silver content 67.9 mg/g and 125.6 mg/g in the adsorbents PGM25%-Ag+ and PGM220%-Ag+ respectively, the maximum I− adsorption capacities were varied at 29.92 mg/g and 100.82 mg/g. In wide pH conditions (pH7-11), PGM25%-Ag+ was sufficient to achieve 131I removal efficiency of over 92 %, and the removal efficiency was almost unaffected in the coexistence of high concentration (10 mmol/L) of anions and complex real contaminated seawater, highlighting the applicability and selectivity of the adsorbent. The adsorption behavior conformed to the Langmuir isothermal model and pseudo-second-order kinetics model. XPS analysis confirmed that excellent adsorption capacity and selectivity were attributed to the chemical adsorption mechanism of ion exchange and complexation occurs between I− and Ag on the solid–liquid interface, where AgI precipitation formed. In addition, the Ag+-doping adsorbent withstood the harsh conditions of 200 kGy irradiation by observing the ATR structure, thermal stability, and 131I removal property. This study provides a feasible solution for the treatment of low and medium-radioactive contaminated seawater.

Porous durian shell biochar modified by KMnO4 (Mn-DSB) as a highly selective adsorbent for Be(II).

The mining of uranium-beryllium ores has resulted in substantial beryllium (Be) contamination. In this study, agricultural waste durian shells were utilized as raw materials to prepare biochar, which was further modified to enhance its adsorption capacity (Mn-DSB). The results effectively demonstrated Mn loading onto the DSB surface. Batch experiments were conducted to identify the optimal adsorption conditions of Mn-DSB for beryllium. At a temperature of 35 °C and pH 6, beryllium's maximum adsorption capacity (Qe) was 42.08 mg·g-1. The materials' internal structure was analyzed before and after adsorption via multiple techniques. Mn-DSB manifested potent selectivity towards beryllium in multicomponent mixed solutions, binary systems, and uranium-beryllium wastewater, as the beryllium removal rate exceeded 90%. The study investigated the recyclability of Mn-DSB and found that after five reuse cycles, the adsorption and desorption efficiencies were 90% and 85%, respectively. The strong ligand complexation (N-H, CO32-, -OH) and ion exchange mechanisms (with Mn7+ ions) of Mn-DSB explained its high adsorption capacity. Therefore, this study demonstrates the potential of Mn-DSB for treating uranium-beryllium tailing wastewater.

Tuning mono-divalent cation water composition by the capacitive ion-exchange mechanism

Soil salinization poses a significant challenge to agricultural activities. To address this, the agricultural industry seeks an irrigation water solution that reduces both ionic conductivity and sodium adsorption rate (SAR), thereby diminishing the risks of soil sodification and fostering sustainable crop production. Capacitive deionization (CDI) is an attractive electrochemical technology to advance this search. Recently, a one-dimensional transient CDI model unveiled a capacitive ion-exchange mechanism presenting the potential to adjust the treated water composition by modifying monovalent and divalent cation concentrations, thereby influencing the SAR index. This behavior would be achieved by using electrodes rich in surface functional groups able to efficiently capture divalent cations during conditioning and releasing them during charging while capturing monovalent ions. Beyond the theoretical modelling, the current experimental research demonstrates, for the first time, the effectiveness of the capacitive ion-exchange mechanism in a CDI pilot plant using real water samples spiked with solutions containing specific mono and divalent ions. Electrosorption experiments and computational modeling, specifically Density-Functional Theory (DFT), were used along with the analysis of the surface functional groups present in the electrodes to describe the capacitive ion-exchange phenomenon and validate the steps involved on it, highlighting the conditioning as a critical step. Various operational and flow modes confirm the versatility of CDI technology, achieving separation factors (RMg/Na) of 5–6 in batch, raising production from 0.5 to 0.8 L m−2 h−1 (batch) to 8.0–8.1 L m−2 h−1 when using single pass although reducing RMg/Na to 2. The reliability of the CDI technology in reducing SAR was also successfully tested with different influent compositions, including magnesium and calcium. Finally, the robustness of the capacitive ion-exchange mechanism was validated by a second CDI laboratory 9-cell stack cycled over 350 cycles. Our results confirm the reported theoretical model and expands the conclusions through the experiments in a pilot plant showing direct implications for employing CDI in agricultural applications.

Ammonium Removal in Wastewater Treatments by Adsorbent Geopolymer Material with Granite Wastes: Full-Scale Validation

Elevated ammonium (NH4+) concentrations in untreated waterways contribute to eutrophication and dissolved oxygen depletion. Geopolymer (GP) materials are introduced as sustainable, straightforward operation and low-cost option for pollutant adsorption through ion exchange mechanism. In the present study, a porous metakaolin-based geopolymer with granite waste additions was synthetized, characterised and validated as adsorbent material for NH4+ pollution in water. At this point, treatments to reduce GP alkalis leaching were also considered to comply with the water discharge regulations. The adsorption mechanism was analysed by Redlich-Peterson isotherm model concluding that NH4+ was disposed on the GP surface as a monolayer with strong physical-chemical attraction between molecules. Kinetics of the process followed the Weber-Morris rate equation being the intraparticle diffusion the limiting process. Continuous experiments at lab-scale suggested a maximum removal of 97% during the first hours and an adsorption capacity (q) of 25.24 mg/g. Additionally, as a main novelty of the work, the GP was validated in a full-scale pilot plant monitoring pH, electrical conductivity and NH4+ concentration. The obtained data revealed that the GP is high selective in a real wastewater stream and removed 81% of NH4+, higher adsorption values than those reported for natural and some synthetic zeolites.

Characteristics and Influence Factors of Pb(II) Adsorption by Graphene Oxide-Montmorillonite Composite.

This study presents the fabrication of a novel porous composite of graphene oxide-montmorillonite (GO-MMT) through the modification of montmorillonite using the freeze-drying method for the purpose of Pb removal. The characterization of the GO-MMT composite was conducted using scanning electron microscopy, Fourier transform infrared spectrometry, and X-ray diffraction. The results from batch adsorption experiments revealed that the GO-MMT composite exhibited a superior capacity for Pb removal compared to MMT. Furthermore, a single factor experiment confirmed that the dosage of the GO-MMT composite or GO, pH, temperature, and reaction time all significantly influenced the adsorption of Pb by the GO-MMT composite, MMT, or GO. This superiority can be attributed to the presence of oxygen-containing functional groups, the site-blocking effect, and the ion exchange mechanism exhibited by the GO-MMT composite.

Application of phosphonium ionic liquids to separate Ga, Ge and In utilizing solvent extraction: A review

Due to the sudden rise in demand, a shortfall in the supply of critical metals or high technology metals, especially gallium (Ga), germanium (Ge) and indium (In) is experienced throughout the globe. The different primary and secondary resources are being utilized to recover and recycle these metals through the widely accepted technique, solvent extraction (SX). The extraction of metals may be potentially achieved by compounds of negligible volatility, phosphonium ionic liquids (Phos ILs). Ionic liquids (ILs) are potential and useful compounds to separate and recover Ga, Ge and In from synthetic solutions and waste materials due to their tunable nature to achieve higher selectivity, superior physicochemical properties and diverse structural properties. Ion exchange mechanism was mainly found applicable for the extractive separation of such metals through Phos ILs. Based on the efficiency, extraction mechanism and diverse operating conditions of Phos ILs, the present review provides a comprehensive description of separation as well as recovery of Ga, Ge and In from the synthetic solutions as well as waste materials.

Aerobic granular sludge for complex heavy metal-containing wastewater treatment: characterization, performance, and mechanisms analysis.

Complex heavy metal (HM)-containing wastewater discharges pose substantial risks to global water ecosystems and human health. Aerobic granular sludge (AGS) has attracted increased attention as an efficient and low-cost adsorbent in HM-containing wastewater treatment. Therefore, this study systematically evaluates the effect of Cu(II), Ni(II), and Cr(III) addition on the characteristics, performance and mechanism of AGS in complex HM-containing wastewater treatment process by means of fourier transform infrared spectroscopy, inductively coupled plasma spectrocopcy, confocal laser scanning microscopy, extracellular polymeric substances (EPS) fractions detection and scanning electron microscope-energy dispersive X-ray. The results showed that AGS efficiently eliminated Cu(II), Ni(II), and Cr(III) by the orchestrated mechanisms of ion exchange, three-layer EPS adsorption [soluble microbial products EPS (SMP-EPS), loosely bound EPS (LB-EPS), tightly bound EPS (TB-EPS)], and inner-sphere adsorption; notably, almost 100% of Ni(II) was removed. Three-layer EPS adsorption was the dominant mechanism through which the HM were removed, followed by ion exchange and inner-sphere adsorption. SMP-EPS and TB-EPS were identified as the key EPS fractions for adsorbing Cr(III) and Cu(II), respectively, while Ni(II) was adsorbed evenly on SMP-EPS, TB-EPS, and LB-EPS. Moreover, the rates at which the complex HM penetrated into the granule interior and their affinity for EPS followed the order Cu(II) > Ni(II) > Cr(III). Ultimately, addition of complex HM stimulated microorganisms to excrete massive phosphodiesterases (PDEs), leading to a pronounced decrease in cyclic diguanylate (c-di-GMP) levels, which subsequently suppressed EPS secretion due to the direct linkage between c-di-GMP and EPS. This study unveils the adaptability and removal mechanism of AGS in the treatment of complex HM-containing wastewater, which is expected to provide novel insights for addressing the challenges posed by intricate real wastewater scenarios.

Revealing proton-coupled exchange mechanism in aqueous ion-exchange synthesis of nickel-rich layered cathodes for lithium-ion batteries

Ion exchange is a promising synthetic method for alleviating severe cation mixing in traditional layered oxide materials for lithium-ion batteries, leading to enhanced structural stability. However, the underlying mechanisms of ion exchange are still not fully understood. Such a fundamental study of the ion-exchange mechanism is needed for achieving the controllable synthesis of layered oxides with a stable structure. Herein, we thoroughly unearth the underlying mechanism that triggers the ion exchange of Ni-rich materials in aqueous solutions by examining time-resolved structural evolution combined with theoretical calculations. Our results reveal that the reaction pathway of ion exchange can be divided into two steps: protonation and lithiation. The proton is the key to achieving charge balance in the ion exchange process, as revealed by X-ray adsorption spectroscopy and inductive coupled plasma analysis. In addition, the intermediate product shows high lattice distortion during ion exchange, but it ends up with a most stable product with high lattice energy. Such apparent discrepancies in lattice energy between materials before and after ion exchange emphasize the importance of synthetic design in structural stability. This work provides new insights into the ion-exchange synthesis of Ni-rich oxide materials, which advances the development of cathode materials for high-performance lithium-ion batteries.

Activation of Fe3O4/bentonite through anchoring of highly dispersed and photo-reduced Cu ions for higher pH fenton-like degradation and effective adsorption of Congo red dye

Recently, highly dispersed metal catalysts have gained considerable attention due to active catalytic sites' enhanced exposure for efficient metal-based heterogeneous catalysis. Herein, we report the synthesis of highly dispersed photo-reduced Cu(I) clusters on Fe3O4/bentonite (FB) and amine-modified FB (-N-FB) for efficient Fenton-like catalysis. For that, Cu(II) ions were first chelated by surface heteroatoms of FB (in addition to the ion exchange mechanism), followed by photoinduced reduction to Cu(I). Both products (Cu1-FB and Cu1-N-FB) efficiently degrade Congo red dye while exhibiting high kinetic constants of 0.027 and 0.059 m−1 for Cu1-FB and Cu1-N-FB, respectively. In addition, the investigation of the dye adsorbing capability of the products demonstrated the maximum adsorption capacity of 600 and 610 mg/g for Cu1-FB and Cu1-N-FB, respectively. Results suggested that adsorption followed the Langmuir isotherm model, which operated spontaneously through physical interactions. Both adsorption and degradation reactions were repeated to demonstrate the reusability of the products, which yielded promising results, and the adsorption and degradation mechanisms were proposed with the help of Fourier transform infrared spectroscopy (FTIR) and high-resolution mass spectrometry (HRMS).

Synthesis of magnetic-responsive imidazole-based poly (ionic liquid)s as a recycle adsorbent for simultaneously removing iodine molecules and iodide ions

Nuclear waste management and nuclear energy generation require the proper disposal of 129I and 131I, which are radioactive isotopes of iodine. For recognition of different types’ iodine, a magnetic poly (ionic liquid)s (Fe3O4@SiO2-MPS-PILs) was formed by the selected imidazole ionic liquid monomer and core–shell Fe3O4@SiO2-MPS via free radical polymerization. The resulting adsorbent containing plenty of imidazole N-heterocycle units, benzene rings, and ionic bonds in the backbones was suitable for simultaneously adsorbing iodine molecules and iodide ions. The adsorption mechanisms for iodine in cyclohexane and iodide ions from aqueous solution were based on charge transfer and ion exchange mechanisms, respectively. The adsorption equilibrium for iodine in cyclohexane was attained at 12 h, and the kinetics of iodine adsorption closely followed the pseudo-second-order model. Iodine adsorption on Fe3O4@SiO2-MPS-PILs was best described by Langmuir model with a maximum iodine adsorption capacity of approximately 714.29 mg g−1. Iodide ions adsorption was best explained with Freundlich model and a maximum adsorption capacity of 335.80 mg g−1 was achieved in an iodide solution with a 500 mg L–1 concentration. Notably, Fe3O4@SiO2-MPS-PILs retained over 90 % of its original adsorption performance after the 5th cycle. This work proves that the adsorbent Fe3O4@SiO2-MPS-PILs was efficient and recyclable, and has good application prospects in the practical treatment of iodine and iodide.

Chimie Douce Derived K-Based P2-Type Transition Metal(s) Layered Oxides for Secondary K-Ion Batteries

Owing to great societal and technological benefits, there has been a remarkable growth in the industrial demand for enhanced energy storage for many target applications including electric vehicles, aerospace applications, and portable electronics. Secondary K-ion batteries (KIBs) are among the potentially inexpensive candidates for energy storage systems beyond state-of-the-art Li-ion batteries (LIBs). Electrochemical cells based on mobile carrier K+ can provide efficient energy storage because of comparative ionic diffusion in bulk and swift charge transfer at the interface due to weak Lewis’s acidity.1,2 Despite various advantages over LIBs and NIBs, the roadblock of practical KIB implementation lies in identifying suitable cathodes that reversibly (de)intercalate K+ at optimum voltage, swift rate, and with prolonged cycle life.Despite constant efforts to develop new cathodes for K+ -ion batteries, several challenges such as low concentrations of K-ions due to strong electrostatic repulsions between the K+ - K+ ions and difficulty in preparation from direct synthesis routes3 limit its practical application. In this scenario, we have adopted the chimie douce (soft chemistry) method to design the novel layered transition metal oxide cathode from the parent P2 type Na-based system. In addition, we have probed the ion exchange mechanism using X-ray diffraction and transmission electron microscopy (TEM) techniques. Rietveld analysis confirmed the structure having a P2-type stacking sequence with hexagonal symmetry and P6/3mmc space group. Further, we have successfully examined the chemical ion-exchanged novel layered P2- K2/3Co1/3Mn2/3O2 as a cathode for KIB at ambient and high temperatures. It delivered a good capacity (~70 mAh/g) with an average redox potential of 3.0 V along with good cycling stability and coulombic efficiency (CE) in temperature ranging from 25-50 ºC. Ex-situ X-ray diffraction analysis and potentio/galvanostatic titration techniques were used to analyse the K+ insertion mechanism. This study can assist in developing new insertion K+ host materials for viable and reliable practical applications.