Ion Exchange Research Articles

Electrophoretic removal of sinapic acid from rapeseed protein extract

Isolation of proteins from oilseeds to supply functional proteins for the food industry is essential but challenging due to the presence of anti-nutrients such as phenolic compounds. To deliver proteins, the removal of phenolic compounds is crucial. Conventionally, this is accomplished by alcohol washing; however, this is resource-intensive, may be unacceptable for some and does not provide proteins with good techno-functional properties since it alters the native protein structure. To overcome such drawbacks, gentle processing methods must be developed. In this work, we investigated the electro-separation of sinapic acid from rapeseed protein extract. A porous medium (ion exchange or ultrafiltration membrane) permitting electromigration of only sinapic acid and retaining the proteins was utilized under two different potential differences. The electro-separation of sinapic acid relied on electrostatic and electrophoretic forces, which cause their adsorption and permeation. Among the treatments, 1.5 V over an anion exchange membrane showed the best performance, providing considerable sinapic acid removal (34.0 ± 4.0 wt%) while maintaining the protein content and pH stability. A larger system with a larger membrane surface area yielded as high as 90.3 ± 3.8 wt% of sinapic acid removal within 240 min while retaining 88.8 ± 7.6 wt% of the proteins.

Surface water removal of Aluminum(III), Iron(III) and Manganese(II) using sustainable natural serpentinite mining tailings, proof of concept

To remediate surface water as the Doce River and spring waters from Minas Gerais, Brazil, this study examined the possibility of natural serpentinite mining tailings as a sustainable alternative for removing aluminum (III), iron (III), and manganese (II). The study used a Box-Behnken experimental design to examine how initial metal concentration, adsorbate dosage, and adsorption time affect metal removal effectiveness. Results demonstrated impressive performance, with removal rates exceeding 80 % for Al(III) and Fe(III) within the initial 5 min, and 60 % for Mn(II) within 30 min. This study delves deeper into the removal mechanisms, kinetics, adsorption isotherms and characterization identify physisorption and chemisorption pathways in which complex formation with released OH− groups and ion exchange with Mg(II) from serpentinite emerged as key contributors to the removal process. Furthermore, ion metal adsorption and regeneration cycles were assessed, exhibit sustained removal efficacy without notable capacity reduction. Each cycle shows an average metal adsorption capacity of 0.32 mg g−1 and an average Mg(II) release capacity of 0.98 mg g−1. Remarkably, the application of serpentinite successfully lowered the metals content of the Doce River and spring water to drinkable standards. A batch and continuous process is proposed for scaling-up serpentinite's metal adsorption. Overall, this study shows serpentinite's potential as a foundation for sustainable and cost-effective methods to treat surface water contamination with Al(III), Fe(III), and Mn(II).

Mechanistic insights into uptake, transfer and exchange of metal ions by the three-metal clusters of a metalloprotein.

Metallothioneins (MTs) are small proteins that coordinate d-block metal ions in sulfur-metal clusters to control metal ion concentrations within the cell. Here we study metal cluster formation in the MT of the periwinkle Littorina littorea (LlMT) by nuclear magnetic resonance (NMR). We demonstrate that the three Cd2+ ions in each domain are taken up highly cooperatively, that is, in an all-or-none fashion, with a four- to six-fold higher affinity for the C-terminal domain. During the transfer of metal ions from Cd2+-loaded MT to apo MT, Cd2+ is most efficiently transferred from the metalated protein to the apo C-terminal domain. This behavior might be connected to unique structural motifs in the C-terminal domain, such as two double-CXC motifs and an increased proportion of positively charged residues. In Cd2+/Zn2+ metal exchange experiments, the N-terminal domain displayed the most efficient inter-molecular metal exchange. Amide hydrogen exchange reveals fewer protected amides for the N-terminal domain, suggesting the structure might more easily "open up" to facilitate metal exchange. Experiments with a physical separation of donor and acceptor species demonstrate that metal exchange and transfer require protein-protein contacts. These findings provide insights into the mechanism of metal uptake and metal transfer, which are important processes during metal detoxification in snail MTs.

3D model of a stable triangle LiF–NaBr–KBr four-component reciprocal system Li+, Na+, K+ || F-, Вr-

A 3D model of the phase equilibrium states of the quasi-three-component system LiF–NaBr–KBr, which is a stable triangle of the four-component reciprocal system Li+, Na+, K+ || F-, Br-, has been constructed. Based on the 3D-model, polythermal, isothermal sections and the polytherm of phase crystallization were constructed for the first time. Two polythermal sections contain wide areas of boundary solid solutions based on sodium and potassium bromide. In an isothermal section at 650 оC, the fields of the liquid phase and the coexisting two and three phases are delimited. The crystallization polytherm is represented by three fields. In the crystallization field of lithium fluoride, the area of separation of two liquids is limited. The direction of the ion exchange reaction 2LiBr + NaF + KF = 2LiF + NaBr + KBr was confirmed by thermodynamic calculations at temperatures of 400, 600, 800, 1000K. The exothermic nature of the exchange reaction is confirmed by taking a DTA heating curve for a mixture of powders from 50% LiBr + 25% NaF + 25% KF, and the phase composition of the reaction products LiF + NaBr(OTR) + KBr(OTR) is confirmed by X-ray phase analysis data, where OTR is limited solid solution.

Occurrence and efficient removal of PFAS from landfill leachates using on-site DTRO systems: A comprehensive analysis across 11 Chinese cities

Per- and polyfluoroalkyl substances (PFAS), known for their persistent toxicity and mobility, pose significant environmental and human health risks. Here we explored the occurrence and efficacy of on-site Double-Pass Reverse Osmosis (DTRO) systems in removing 30 different PFAS from landfill leachates in 11 diverse cities across China. PFAS concentrations in landfill leachate ranged from 938 to 32,491 ng/L, averaging 6,486 ng/L, predominantly comprising short-chain PFAS, notably perfluorobutane sulfonate (PFBS). Notable emerging substitutes like 6:2 fluorotelomer sulfonate, fluorobutane sulfonamide, and 9-chlorohexadecafluoro-3-oxanone sulfonate were also identified. The PFAS levels correlated positively (r2 = 0.79, p < 0.01) with regional economic development, with coastal areas exhibiting higher concentrations than inland regions. The DTRO membrane filtration and ion exchange resin achieved an average removal efficiency of 94 % for ∑30PFAS and even 99.97 % for PFBS (the concentration of PFBS in the raw leachate ranged from 226.36 ng/L to 27,935.61 ng/L, with an average concentration of 4,506.88 ng/L). The Na ion exchange resin had a limited effect on further reducing the PFAS concentration. Our findings not only contribute to the theoretical understanding of PFAS behavior in landfill leachates but also offer a practical engineering applications for global waste management practices.

A low-impedance cation exchange membrane for extending the voltage window of a BiFeO3-based hybrid supercapacitor through the pH-decoupling strategy

Aqueous hybrid supercapacitors usually suffer from narrow voltage window and poor energy density limited by the thermodynamic decomposition of water. Based on necessary ion exchange membranes, the pH-decoupling strategy can be employed to extend the voltage windows of hybrid supercapacitors. We propose a novel low-impedance cation exchange membrane (CEM) with the interpenetrating network structure for the pH-decoupling strategy, which can be served as the separator for a AC//BiFeO3 supercapacitor to enhance its electrochemical performances. Two CEMs (CEM-1 and CEM-2) with different contents of the sulfonic acid (-SO3H) groups, are fabricated through the copolymerization of various monomers according to the predetermined stoichiometric ratios. FTIR, Raman and XPS spectra reflect that the CEM-2 has the higher content of the -SO3H groups than the CEM-1. The membrane parameter measurements confirm that the CEM-2 has the higher water content, lower membrane resistance and smaller membrane thickness than the CEM-1. The AC//BiFeO3 supercapacitor with the CEM-2 separator provides the higher gravimetric specific capacitance of 61 F g−1 at 1 A g−1, better coulombic efficiencies (97 % ∼ 103 %) and lower Rs value (39.74 Ω) than the AC//BiFeO3 supercapacitors with the CEM-1 separator. Moreover, the AC//BiFeO3 supercapacitor with the CEM-2 separator delivers the maximum energy density of 41.0 Wh kg−1 at the power density of 1.1 kW kg−1. The pH-decoupling strategy with this low-impedance CEM, opens up a new avenue for developing high-performance aqueous electrochemical energy storage devices.

Optimization and characterization of alginate/cinnamaldehyde electrosprayed microcapsule and its application to mongolian cheese preservation

alginate is a good candidate for encapsulating bioactive compounds because the Na+ on its carboxyl groups can take part in an ion exchange process with Ca2+ to generate a calcium alginate shell. Electrospraying technology was used to prepare cinnamaldehyde (CA)-loaded alginate microcapsules. The generation of microcapsules with a minimal diameter could improve the mass transfer of encapsulated materials. The electrospraying parameters were optimized using response surface methodology (RSM). The results indicated that lower alginate concentration led to microcapsules with smaller diameters. The interaction between the concentration of alginate and the needle size affecting the microcapsule diameter was more significant than other mutual interactions. The optimum conditions were an alginate concentration of 1.27 % (w/v), needle size of 24.62 G, flow rate of 2.29 mL/h, voltage of 12.98 kV, CaCl2 concentration of 0.30 M, and distance of 11.01 cm. With a minimal diameter (155.34 μm), the obtained microcapsules displayed good encapsulation efficiency (86.00 ± 1.7 %) and loading capacity (45.00 ± 2.6 %), which had better preserving effects for Mongolian cheese. The study provided a reference for the production of the microcapsules with high antimicrobial effectiveness, exploring the new technological developments and applications of alginate.

Comparative study of silica-based porous materials in the purification of radioactive wastewater

A significant challenge in the treatment of low-level radioactive wastewater is the effective purification of low-concentration radionuclides. Silica-based adsorbents are advantageous for the deep-purification of low-concentration metal ions. This study investigates three primary types of silica-based adsorbents: functionalized mesoporous silica, various modified zeolites, and mesoporous calcium silicate hydrate (C-S-H). These adsorbents were synthesized and their deep-purification effects on heavy metals and radionuclides were compared. The results indicated that mesoporous silica showed relatively poor adsorption for most metal ions. Zeolites outperformed mesoporous silica, with Zn framework-modified zeolites showing enhanced adsorption for several metal ions. Notably, C-S-H displayed superior adsorption performance, achieving high adsorption capacities for various metal ions and radionuclides. Specifically, at a dose of 0.5 g/L, the adsorption efficiency of C-S-H for numerous radionuclides in nuclear power plant wastewater exceeded 92–99 %, highlighting its potential for practical applications. An in-depth analysis of the physical and chemical structure and the adsorption mechanisms of C-S-H revealed its large mesoporous structure and electrostatic attraction to cations across a wide pH range. Multivalent cations were removed through exchange with Ca2+ in C-S-H, whereas monovalent cations were removed through exchange with Na+ in C-S-H. The cyclic structure of silica-oxygen tetrahedra in C-S-H, which promotes large pore formation and provides abundant ion exchange sites, underpins its excellent adsorption properties. This study offers valuable insights for the selection and application of silica-based materials in radioactive wastewater treatment.

Scalable membrane-assisted ion exchange (MEM-IE) strategy for organic acid purification in biorefinery process

The transition towards a carbon-neutral society necessitates radical approaches in the bio-refinery pipeline, particularly in the production of organic acids. The current downstream process from a dilute fermentation broth is limited by the extensive use of acids and bases, along with heavy reliance on energy-intensive distillation. In this work, we propose an entirely membrane-based process to purify organic acids (e.g., gluconic acid) from a crude solution of catalytic dehydrogenation of glucose. To facilitate downstream purification, we introduce an innovative membrane-assisted ion exchange (MEM-IE) strategy, which is a scalable process that can protonate ionic compounds entirely in the solution phase. Instead of a solid ion exchange resin, a bulky yet soluble acidification agent is used to protonate the target compound, which can be easily separated via a size exclusion membrane. We selected non-toxic poly (4-styrene sulfonic acid) (H-PSS, 75 kDa) as the acidification agent to selectively protonate gluconate ions and to enable facile fractionation. The proposed MEM-IE strategy can overcome the scale-up limitation of traditional solid ion exchange resins and can be applied to many types of ionic compounds. The versatility of the proposed process was also demonstrated on formate and lactate compounds. A techno-economic evaluation using the Verberne cost model showed that the proposed process achieves an 80 % reduction in energy consumption compared to the fermentation-based process, and the return on investment (ROI) of a 330 ton-per-day plant was less than a year. The proposed membrane-based process for the purification of organic acids, particularly the MEM-IE strategy, offers a sustainable and energy-efficient downstream separation platform.

Conversion of waste polystyrene into porous adsorbents for efficient removal of hazardous pollutants: Adsorption properties and adsorption mechanism

Herein, the porous adsorbent material (PS-SAS) was prepared by introducing a large number of carboxyl groups on the benzene ring of waste polystyrene (WPS) by Friedel-Crafts acylation reaction using succinic anhydride as the modifying group, followed by further alkaline modification, and was used for the removal of hazardous dye and heavy metal ion. The chemical structure and surface morphology of the prepared adsorbent were assessed via Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), optical microscope (OM), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The prepared adsorbent gave highly efficient separation performance towards malachite green (MG) and Cu2+ with corresponding maximum sorption capacities of 2231 mg/g and 156 mg/g at 298 K. The experimental data indicated that the sorption process followed the Langmuir adsorption isotherm and the pseudo-second-order kinetic model. Moreover, thermodynamic studies also demonstrated that the sorption process occurred spontaneously. The adsorption mechanisms of the adsorbent for MG include hydrogen bonding, electrostatic attraction, n-π interactions, and π-π interactions, while for Cu2+ via electrostatic attraction, ion exchange, and complexation. Furthermore, the selective adsorption, regeneration, dynamic sorption, and simulated wastewater experiment demonstrated that the adsorbent is a promising adsorbent. And phytotoxicity test proved that the prepared adsorbent can effectively reduce the toxicity of dye and metal ions. In summary, the transformation of waste polystyrene into an adsorbent represents a promising solution for water purification.

Revealing Anion Exchange in Two-Dimensional Nanocrystals.

Ion exchange is a powerful postsynthesis tool for the design of functional nanomaterials. However, achieving anion exchange while maintaining the original morphology and crystal structure, as well as elucidating the mechanism, remains challenging. Here, we developed an anion-exchange strategy under mild conditions and revealed an unusual ion-exchange mechanism in the semiconductor nanoplatelets. Kinetic studies have demonstrated that the transformation follows first-order kinetics, with the ligand restricting the guest anion from diffusing only in one-dimensional directions. By monitoring the reaction process, we demonstrated that the anion exchange reaction occurs selectively on the polar surface of the NPLs and exhibits asymmetry at the two polar end faces. Theoretical simulations further confirmed that anion exchange began from the chalcogenide-dominated facet. The thermodynamic data suggest that guest ions diffuse into the crystal interior via a direct exchange mechanism. This study provides a pathway for anion exchange and the construction of functional nanocrystals and a platform for studying the optoelectronic behavior of single-sheet heterojunctions.

Patterns of spatiotemporal variations in the hydrochemistry and controlling factors of bedrock aquifers in the northern region of the Linhuan mining area

Systematically studying the hydrochemical evolution of bedrock groundwater in mining areas during mining process is crucial for effective groundwater resource management and coal mine production. The spatiotemporal characteristics and hydrochemical evolution patterns of the Permian fractured sandstone aquifer (PA) and the Carboniferous Taiyuan Formation limestone aquifer (CTA), both of which are directly associated with coal mining in the northern Linhuan mining area, China, were investigated using multivariate statistical analyses, hydrochemical graphical methods, ion ratio analysis, and a conceptual model. 72 groundwater samples, collected before and after mining, were classified into four groups by hierarchical cluster analysis (HCA). Principal component analysis (PCA) and ion ratio analysis indicated that water-rock interactions involve mineral dissolution (carbonates, gypsum, dolomite, silicates), cation exchange, and common ion effects. Hydrochemical evolution is influenced by bedrock paleotopography, aquifer hydraulic conductivity, and mining drainage. Paletopographic differences significantly influence water-rock interactions and spatial variability in hydrochemistry, with ion concentrations in groundwater increasing as paleotopographic elevation decreases. The pattern of hydraulic conductivity reflects the control exerted by variations in aquifer characteristics on mineral dissolution, leading to minor changes in hydrochemical characteristics. Mining activities disrupt the aquifer's reducing environment, resulting in a significant increase in groundwater SO42− concentration. These findings provide insights and a solid theoretical foundation for studying the hydrochemical variations patterns of groundwater and these control mechanisms in the hidden coal fields of North China.

Sorption thermodynamic and kinetic study of Cu(II) onto modified plant stem bark.

In this study, four types of "Juá" stem barks (Ziziphus joazeiro) were investigated for the removal of Cu(II) from aqueous solutions. The tested samples included natural coarse barks, and barks washed with water, ethanol-water, and NaOH solutions. The solvent-modified materials simulated the waste of the industrial extraction of saponins from bark. The valorization of these processing residues as sorbents was evaluated. The NaOH-washed sorbent exhibited the highest sorption capacity for Cu(II) (maximum sorption capacity 32mgg-1). Ion exchange process between copper and exchangeable surface cations and electrostatic attraction of copper with carboxylate and phenolate groups were identified as the primary sorption mechanisms. Desorption tests revealed that a large portion of the metal sorbed (80%) was easily released from the sorbent thus suggesting, in line with the proposed mechanisms, the existence of weak sorbate-sorbent interactions. The sorptive process was found to be exothermic (∆H° = - 48.1 ± 13.5kJ.mol-1) and thermodynamically favorable at lower temperatures.

Recent Progresses and Challenges to Determine Properties of Sulfonated Polyether Ether Ketone Based Electrolytes for Direct Methanol Fuel Cell Applications

AbstractThis review focuses on fillers, modifications, and methods used in the preparation and development of sulfonated poly(ether ether ketone) (sPEEK) membranes, specifically for direct methanol fuel cell (DMFC) applications as proton exchange membranes in recent years. The primary objective is to evaluate recent advancements by emphasizing key characteristics such as water uptake and swelling capacity, ionic conductivity, methanol permeability, and single cell polarization tests. Additionally, the review aims to provide insights for future researchers by discussing the preparation processes of electrolytes. It presents basic characterizations of membrane electrolytes, including evaluations of the sulfonation degree and ion exchange capacities of sPEEK. High performance of membrane electrolytes is essential for commercialization and to compete with established membranes like Nafion®, which has a perfluorosulfonic acid structure. Therefore, the review also covers detailed characterization methods for assessing long‐term stability when available in the related studies. Numerical results and indicators are categorized and tabulated for easy interpretation and comparative analysis.

Iron and Zinc Metallates Supported on Ion Exchange Resins: Synergistic Catalysts for the Solvent‐free Cyclic Carbonate Synthesis from Epoxides and CO2

Despite extensive research into developing efficient and environmentally friendly catalysts for converting CO2 over the last decade, the search for a robust and cost‐effective catalytic system is ongoing. This study describes developing and applying a new catalytic system using inexpensive ferrate and zincate anions immobilized on easily available commercial ion exchange resins (IER) to produce cyclic carbonates from CO2 with high efficiency and low cost. Two polystyrene‐based anion exchange resins, AmberlystTM A26‐Cl (A26‐Cl) and AmberliteTM IRA‐400‐Cl (IRA400‐Cl), were compared. The results demonstrated the catalysts' remarkable activity under mild conditions and demonstrated the synergistic effect between the polystyrene support and the active ammonium metallates, presenting a scalable, eco‐friendly method for cyclic carbonate production using waste CO2. A Design of Experiment approach was implemented to optimize the catalytic cycloaddition of CO2. The reaction scale‐up to produce a 5 g batch of propylene oxide and conducting recycling tests demonstrated that the catalyst retained its activity over four cycles. The research also explored the use of various epoxides and found that terminal epoxides produced very good yields. In summary, this study introduces a cost‐effective, scalable method for converting CO2 into valuable cyclic carbonates, leveraging the synergistic effects of polystyrene supports and active ammonium metallates.

Remediation of heavy metal contaminated soil in mining areas with vaterite-type biological calcium carbonate

In recent years, research on the remediation of heavy metal contaminated soil by microbially induced carbonate precipitation (MICP) technology has yielded significant findings. However, when utilizing MICP for remediation in situ, urea and calcium chloride may produce high concentrations of NH4+ and Cl-, which subsequently cause secondary pollution. If the biological calcium carbonate (Bio-CaCO3) produced by MICP is employed as a highly efficacious adsorbent, secondary pollution can be avoided while remediating heavy metal pollution. In this study, vaterite-type Bio-CaCO3 was prepared under the regulation of sophorolipids, and the remediation effect and mechanisms for heavy metal contaminated soil were investigated. The results demonstrated that sophorolipids facilitate the formation and stabilization of vaterite-type Bio-CaCO3. The addition of vaterite-type Bio-CaCO3 could notably increase the content of soil organic matter, enhance soil urease activity, and reduce soil catalase activity. On the 30th day of remediation with vaterite-type Bio-CaCO3, the active state content of Pb and Cd in the soil exhibited a decrease of 41.23 % and 35.00 %, respectively. Additionally, the exchangeable state content demonstrated a reduction of 6.61 % and 8.48 %, while the carbonate-bound state exhibited an increase of 12.05 % and 13.89 %, respectively. The principal mechanisms for the remediation of heavy metal contaminated soil by vaterite-type Bio-CaCO3 may be attributed to ion exchange, chemical precipitation, physical adsorption, and complexation reactions. The analysis of the microbial community structure demonstrated that vaterite-type Bio-CaCO3 could enhance the abundance of multiple genera with urease-producing genes, including Pseudomonas, Staphylococcus, and Bacillus while maintaining the soil biodiversity. This study provides a new idea for the remediation of heavy metal contaminated soil around the mining area and offers technical support for the construction of green mines.

Geogenic and anthropogenic factors influencing groundwater quality for irrigation purposes from a volcano-sedimentary aquifer in the Puebla State, Mexico.

This study investigates the hydrogeochemical characteristics and water quality of the Puebla Valley aquifer, a volcano-sedimentary system predominantly influenced by water-rock interactions and ion exchange processes. The research assesses the suitability of groundwater for agricultural irrigation by applying various water quality indices, including salinity and sodicity indices and Wilcox diagrams and USSL. Seventy-one water samples were analyzed to determine key physicochemical parameters and dominant ion concentrations, revealing that the primary hydrogeochemical facies are HCO -Mg and HCO -Ca. The results indicate a heightened risk of salinization, particularly in agricultural and urban areas, underscoring the need for ongoing monitoring. Natural processes such as water-rock interaction and ion exchange are the main factors influencing groundwater quality. However, anthropogenic activities, particularly the use of fertilizers and irrigation return flows from the Atoyac River, exacerbate groundwater quality degradation. This study emphasizes the necessity of sustainable water resource management to ensure the long-term viability of the aquifer.

Use of macromolecules lignosulfonate and graphene oxide to prepare non-autoclaved aerated concrete

The development of new structural materials with thermal insulation properties is urgently need in the construction of smart buildings. Besides, there is a need to develop environmentally friendly and sustainable concrete mix designs. Lignosulfonate (LS) macromolecule and graphene oxide (GO) were used to prepare non-autoclaved aerated concrete (NAC). The addition of a complex GO/LS additive of the composition (0.16/0.0002 wt%) increased the compressive strength by 54 %, and bending strength by 45 % at the age of 28 days' strength gain. The addition of an effective complex GO/LS additive to NAC made it possible to achieve a reduction in water absorption by up to 63 % and thermal conductivity by up to 29 % in comparison. The thermal conductivity coefficient of such NAC specimens was 0.092 W/m·K with water absorption of 9 %. The options for the interactions of the GO/LS modifier with calcium hydroaluminates using the type of ion exchange were proposed. Thus, the introduction of GO/LS nano modifier contributed to high-quality filling of free areas of the cement mixture with mineral formations, which helpd to increase the strength of the aerated concrete and its durability.

Selective Sorption of Noble Metals on Polymer Gel Modified with Ionic Liquid.

The solid phase extraction of Au, Ir, Pd, Pt, and Rh on a polymer gel modified with ionic liquid containing methylimidazolium groups (MIA-PG) has been investigated. The positively charged surface of the sorbent is highly suitable for the sorption of stable chlorido complexes of the studied analytes, while the retention of base metals Cu, Fe, Ni, Zn, and Mn is negligible. Optimization experiments performed showed that, at 0.05 M HCl, the degree of sorption of Au, Ir, Pd, and Pt is above 95%, and only for Rh, the maximum degree is 65%; complete elution is achieved in the mixture of thiourea in HCl. The results obtained from the equilibrium adsorption studies are fitted in various adsorption models, such as Langmuir and Freundlich, and the model parameters have been evaluated. The kinetics analysis indicated that the adsorption of Au, Ir, Pd, Pt, and Rh onto the sorbent follows the pseudo-second-order model. Intraparticle diffusion and ion exchange reactions were the rate-limiting steps. Analytical procedures were developed for Pd, Pt, and Rh determination in road dust and soil and for Au determination in copper ore and copper concentrate. The procedures are validated by the analysis of certified reference materials. Analytical figures of merit confirmed their applicability in routine laboratory practice.

A Review of the Physical, Optical and Photoluminescence Properties of Rare Earth Ions Doped Glasses

Doping glasses with rare-earth ions have garnered significant attention among researchers worldwide. This interest stems from the widespread utilization of rare-earth ions to enhance the optical characteristics of host glasses and exploit the unique spectroscopic properties arising from their optical transitions in the intra-4f shell. Thus, this study reviewed the exceptional potential of rare-earth ion-doped glasses (REIs) in various applications such as solid-state lasers, photonic devices, communication optical fibers, and white light emission. Various methods for the fabrication of glass such as direct melt quenching, sol-gel, ion exchange, sputtering and co-doping techniques were reviewed extensively. The Specific focus was on the physical, optical and photoluminescence properties of glasses produced from glass formers co-doped with rare earth ions. The investigation centers on the comprehensive current applicability of REI-doped glasses. The review concludes based on the physical, optical and photoluminescence properties of rare earth ion-doped glasses that they are extremely useful in photonics, lasers, biomedical and optical communication applications.