Ion Exchange Resin Research Articles

Managing PFAS exhausted Ion-exchange resins through effective regeneration/electrochemical process

This study proposes an integrated approach that combines ion-exchange (IX) and electrochemical technologies to tackle problems associated with PFAS contamination. Our investigation centers on evaluating the recovery and efficiency of IX/electrochemical systems in the presence of five different salts, spanning dosages from 0.1 % to 8 %. The outcomes reveal a slight superiority for NaCl within the regeneration system, with sulfate and bicarbonate also showing comparable efficacy. Notably, the introduction of chloride ion (Cl−) into the electrochemical system results in substantial generation of undesirable chlorate (ClO3−) and perchlorate (ClO4−) by-products, accounting for ∼18 % and ∼81 % of the consumed Cl−, respectively. Several agents, including H2O2, KI, and Na2S2O3, exhibited effective mitigation of ClO3− and ClO4− formation. However, only H2O2 demonstrated a favorable influence on the degradation and defluorination of PFOA. The addition of 0.8 M H2O2 resulted in the near-complete removal of ClO3− and ClO4−, accompanied by 1.3 and 2.2-fold enhancements in the degradation and defluorination of PFOA, respectively. Furthermore, a comparative analysis of different salts in the electrochemical system reveals that Cl− and OH− ions exhibit slower performance, possibly due to competitive interactions with PFOA on the anode's reactive sites. In contrast, sulfate and bicarbonate salts consistently demonstrate robust decomposition efficiencies. Despite the notable enhancement in IX regeneration efficacy facilitated by the presence of methanol, particularly for PFAS-specific resins, this enhancement comes at the cost of reduced electrochemical decomposition of all PFAS. The average decay rate ratio of all PFAS in the presence of 50 % methanol, compared to its absence, falls within the range of 0.11–0.39. In conclusion, the use of 1 % Na2SO4 salt stands out as a favorable option for the integrated IX/electrochemical process. This choice not only eliminates the need to introduce an additional chemical (e.g., H2O2) into the wastewater stream, but also ensures both satisfactory regeneration recovery and efficiency in the decomposition process through electrochemical treatment.

A review of current practices on lead ions removal from different aqueous streams

Toxic heavy metals like Lead are destructive to humans and the environment when existing above their threshold limits. Several conventional lead abatement methods are used in wastewater treatment plants to restore the ecology, food supply, and human and animal health. Many tactics are used to remove harmful Pb metals, like ion exchange, chemical precipitation, membrane filtration, and coagulation. These have a few principal approaches for removing metal ions from used water. Rapid developments in tailor-made materials science have proved to remove Lead metal using ion exchange resins, zeolite, polymeric membranes, and ionic liquids due to their low cost, surface accessibility, and unique benefits. This review paper has studied the detailed benefits and shortcomings of removing lead ions from wastewater using numerous materials, processes of production, possibly destructive properties on public health, and potential hybrid routes. In addition, this work observes the present advancements and developments in lead mitigation tools using different techniques for the past five years. Furthermore, this research review opens up to study of other materials' diverse applications in removal processes.

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.

Cementation of spent radioactive ion-exchange resin ashes using alkali-activated cements: Physicochemical and structural changes

Spent ion-exchange resins (IERs) constitute the major volume of solid radioactive wastes generated by the nuclear industry and Portland cement wasteforms exhibit limitations for their conditioning and storage. In this paper, an alternative approach is conducted involving the solidification of IER ashes (IERAs) through the use of “one-part” alkali-activated cements (AACs). Systems with different chemistry based on blast furnace slag (BFS) and metakaolin (MK) were formulated and the physicochemical and structural changes of the gel products after incorporating IERAS were investigated. The incorporation of the IERAs reduced the amount of C-A-S-H and (N,C)-A-S-H products while changing the pore structure and microstructure, reducing the mechanical strengths of the cement matrices; these effects were more remarkable in the high BFS systems. New insights are elucidated on the microstructural changes of the gel phases and suggest that AACs with BFS/MK ratios of 25/75 and 50/50 are promising candidates for conditioning IERA wastes.

Samarium(III) Removal by Weak Acid Exchanger Amberlite IRC-50 in (H+) and (Na+) Forms

Adsorption of samarium(III) on a weakly macroporous cation exchanger Amberlite IRC-50 (H+) and (Na+) forms is studied as a function of the initial pH of the aqueous solution, time and temperature, initial samarium(III) ion concentration, and the amount of resin at a fixed temperature (20 ± 1 °C). The concentration range was between 0.1–5 mmol/L, the pH range was between 1.8 and 10.5; the stirring time was between 2 and 60 min; and the amount of resin was between 0.025 and 0.15 g. Both the film and particle diffusion equations are applied to explain the kinetic data. The rate constant values for samarium(III) adsorption were calculated for both film and particle diffusion processes. It is observed to follow the order (Na+) > (H+). Temperature is found to have an insignificant effect on both diffusional processes. Various thermodynamic parameters (ΔH°, ΔS°, and ΔG°) from samarium(III) exchange on the resin were calculated. The optimum conditions were found to be a concentration of 1 mmol/L, pH of 9.3, stirring time of 20 and 5 min for Amberlite IRC-50 (H+) and (Na+) forms, respectively, and 0.15 g of resin. The equilibrium extraction of samarium was 22.2 mg/g for Amberlite IRC-50 (H+) and 21.9 mg/g for Amberlite IRC-50 (Na+) at an initial concentration of 1 mmol/L. The results obtained show that the Amberlite IRC-50 weak cationexchange resin performed well for the removal and recovery of samarium(III). The optimization procedure provides access to industrial-scale Sm(III) removal processing.

Sequestration of CO2 using emulsion phase structure

This study proposes a cost-effective method for creating an emulsion structure to capture 100 % of the CO2 released during chemical reactions. The emulsion, composed of water, kerosene, sodium lauryl sulfate (SLS), sodium hydroxide (NaOH), triethylamine (TEA), and amine-functional ion exchange resin (IER), demonstrates high CO2 capture efficiency. Results indicate that a 10 mL emulsion sample could capture 12.72 g of CO2, representing 95.4 % of the total CO2 produced during the chemical reaction between acetic acid and sodium carbonate. In contrast, an ion exchange resin granule captures only 0.01 g of CO2. Consequently, 10 mL of emulsion sample containing 60 units of IER is necessary to achieve 100 % CO2 capture.

Spent ion-exchange resin as a new aggregate to enhance specific heat capacity of composite building materials: A case study on gypsum plaster

Spent ion exchange resin (SIER) is a by-product derived from drinking water treatment plants, possessing intriguing physicochemical properties that render it a promising ingredient for composite building materials. Surprisingly, there has been a luck of research investigating its impact on the performance of such materials. This study addresses this gap by characterizing unfired and fired gypsum-based composites with varying SIER weight ratios (10–50 wt%) and firing temperatures (300, 600, and 900°C). X-ray diffraction, scanning electron microscopy, and the hot disk method were employed to explore the effects of SIER on the composites’ thermal-mechanical features. The results revealed the significance of SIER as a promising waste-based aggregate to enhance the specific heat capacity (cp) of gypsum-based composites. With increasing SIER content and firing temperature, the composites demonstrate improved cp, reduced thermal conductivity, and decreased compressive strength. Both unfired and fired composites exhibited an increase in cp, up to 74.4% and 331.8%, respectively. The composite material achieved a noteworthy reduction in thermal conductivity, reaching 0.132 W/m.K, and a specific heat capacity increase to 4491.35 J/kg.K, which surpasses that of the control sample by more than four times (1040 J/kg.K). These newly developed composites hold significant promise as thermal energy storage materials for low-temperature building applications.

Influence of ionic radius on the degree of extraction of rare earth metals during sorption by the interpolymer system AMBERLITE IR-120 –AВ-17-8

Studies have been carried out on the sorption of rare earth metal ions in solution using the interpolymer system Amberlite IR-120:AB-17-8. The purpose of the work is to search for conditions for maximum sorption of rare earth elements (Dy, Tb, Gd, Eu and Sm) from aqueous solutions using the effect of remote interaction of ion exchange resins. Methodology. The residual concentrations of rare earth ions were determined using an Optima 8300DV Duo inductively coupled plasma spectrometer. Results. The best sorption characteristics were determined by the interpolymer system at a ratio of 3:3. The residual concentration of rare earth elements in the solution was: Dy – 4.64 mg/l, Tb – 4.16 mg/l, Gd – 4.21 mg/l, Eu – 4.16 mg/l, Sm – 4.56 mg/l. The variations in the ionic radius of the ions chosen for the study are Dy3+<Tb3+<Gd3+<Eu3+<Sm3+. The degree of sorption of interpolymer system increased with increasing ionic radius of the metals. For dysprosium with the smallest ionic radius, the degree of sorption was η – 52%, and for terbium, gadolinium and europium it increased to η – 58%. For individual Amberlite IR-120 (6:0), the degree of sorption of terbium ions was 47%. Conclusion. The results of the study showed that the interpolymer system with a ratio of 3:3 has the best sorption activity. It has been established that the degree of sorption of interpolymer pairs increases with increasing order of the ionic radius of metals (Tb3+< Gd3+< Eu3+).

Investigation of phenolic compounds recovery from brewery wastewater with coupled membrane and adsorption process

Recovery of phenolic compounds from food-processing by-products represents an interest for various industrial sectors. The potential of a coupled ultrafiltration and adsorption or ion exchange resin process was analyzed to recover phenolic compounds from a brewery liquid residue. Ultrafiltration yielded a 95% removal of turbidity-causing compounds without significant modification of the chemical composition of brewery by-products. After a pH optimization step, ten different macroporous resins, including MN202, SP700, HP2MGL, LXA8302, LWT510, XAD16N, FPX66, WA20, WA30 and SCAV4, were screened for phenolic compounds sorption. Resins were selected through a multi-step batch test procedure according to their performance in phenolic compounds adsorption capacity, phenolic compounds selectivity compared to carbohydrates and price. The strong base resin SCAV4 with OH- counter ion showed the highest adsorption capacity, 35.4 ± 0.8 mg·gdryresin−1, with selective sorption of phenolic compounds. Higher temperatures of 48 °C improved the adsorption and desorption performances of LXA8302 and SCAV4 resins, compared to 25 °C. Up to 70% of phenolic compounds were desorbed from adsorption resin with adequate solvent.

Decontamination of spent ion-exchange resins from the nuclear fuel cycle using chemical decontamination and direct current

The study presents the results of deep decontamination of the spent ion-exchange resin from the Kursk NPP, where the task of processing and conditioning of the resin is still not solved. The article shows that decontamination of the resin under dynamic conditions with a solution of the composition NaOH – 0.75 mol L−1, NaNO3 – 2.25 mol L−1 reduces its activity by 1 order of magnitude due to removal of Cs-137 (by washing). The subsequent washing of the resin with a solution of H2SO4 – 1.0 mol L−1, FeSO4 – 0.5 mol L−1 results in a decrease of its activity by another 1 order of magnitude due to removal of Eu-152-154 (100%) and partial removal of Co-60 (90%) and Am-241 (92%).It was found that further attempts to reduce the activity of the resin were ineffective due to the presence of insoluble precipitates, whose activity was mainly (more than 98%) accounted for by Co-60 (30.2%) and Nb-94 (68.1%) radionuclides. To remove these poorly soluble precipitates, we suggested decontamination by direct current through placing the resin between an anode and a cathode. A solution of H2SO4 of a concentration of 0.1 mol L−1 was used as an electrolyte. It has been found that an addition of FeSO4 (0.009 mol L−1) increases the rate of precipitate removal more than 1.5-fold. During the treatment by electric current, particles are mechanically removed, whereas insignificant amounts of Cs-137 and Co-60 (no more than 2.6%) enter the electrolyte. After the treatment and washing the resin with a NaNO3 solution, its activity decreases by another three orders of magnitude. The resulting activity of the resin was 350 Bq kg−1, which made it possible to classify it as industrial waste.

Precise Measurement of Magnesium Isotopes in Fe‐Mg Minerals Using a Multi‐collector SHRIMP Ion Microprobe

The distribution of Mg isotopes in minerals is becoming increasingly relevant in Earth science. Usually, they are determined by dissolving mineral concentrates and, after purifying Mg with ion exchange resins, analysing the resulting solutions by TIMS or, most often, MC‐ICP‐MS. When applied to individual minerals, these methods are slow and prone to contamination from impurities in the concentrates, inconveniences that may be avoided using spot analysis techniques such as LA‐MC‐ICP‐MS or SIMS, albeit at the price of a large instrumental mass fractionation (IMF) and isobaric interferences, most prominent in the former. Here, we studied the potential of the multi‐collector SHRIMP II ion microprobe for measuring Mg isotopes in Fe‐Mg silicates and oxides. We found that, when corrected for the divergence of the Mg ion paths within the sample chamber caused by the Earth's magnetic field, the SHRIMP's IMF overwhelmingly depends on the mineral species, and the effects of variable chemical composition are negligible. We propose that the IMF is caused by the force constant difference, ∆F, between "hard" and "soft" bonds linking the ions of the studied element to the mineral lattice. Given that ∆F is a constant for each mineral species, we calculated IMF‐correction factors for the most common Mg‐bearing minerals. The thus‐calculated correction factors permit the analysis in the same session, and with reasonable accuracy (within ~ 0.3‰ of the δ26Mg determined by SN‐MC‐ICP‐MS analyses of concentrates), of samples from different mineral species, facilitating the application of Mg isotopes to terrestrial studies.

Removal of Ni(II) ions from wastewater by ion exchange resin: Process optimization using response surface methodology and ensemble machine learning techniques

This study investigates the removal of nickel ions from aqueous solutions using Amberlite IR120 Na resin. Response surface methodology (RSM) and Ensemble machine learning models were employed to predict and evaluate the adsorption capacity of the resin. The effects of the initial concentration of nickel ions (10–90 mg/L), resin dose (0.1–0.7 g/L), initial pH (3−9), and temperature (10–40 ºC) were analyzed as independent variables. In order to assess the efficiency of Ensemble models, five methods, including random forest, extra tree, AdaBoost, gradient boosting, and XGboost models, were employed. The results demonstrated that the XGboost model predicts the adsorption capacity of the resin for Ni(II) with very high accuracy in the training phase (R2 = 1) and the test phase (R2 =0.96). The maximum adsorption capacity of the resin in the optimization step was achieved for CCD (initial Ni(II) concentration of 45.69 mg/L, resin dose of 0.1 g/L, pH of 6.64, and temperature of 39.68 ºC) and Bayesian optimization (initial Ni(II) concentration of 54.78 mg/L, resin dose of 0.11 g/L, pH of 4.72, and temperature of 39.02 ºC) techniques by 142.67 mg/g and 139.60 mg/g, respectively. Moreover, the Bayesian optimization method resulted in a lower error (0.63 mg/g) than the CCD model (1.53 mg/g). Based on statistical measures, it can be concluded that XGBoost outperforms CCD.

Boric acid recovery from wastewater by chromatographic separation and mathematical modeling

The new approaches in industrial wastewater management underscores the importance of reclaiming valuable materials. Within the boron industry, the generation of substantial wastewater containing preliminary boron species is a significant concern. This study focuses on recovering boric acid from boron production wastewater, addressing the challenge of separating impurities like sulfate, calcium, and magnesium. The methodology adopts chromatographic separation using a cation exchange resin in two forms: (1) Finex CS10GC cation exchanger in Na+ form and (2) Finex CS10GC cation exchanger in Ca2+/Mg2+ form. Notably, the Finex CS10GC ion exchanger in Na+ form achieves a separation efficiency of 95.5 % at a flow rate of 5 mL/min with a 0.20 bed volume (BV) loading. In contrast, the Ca2+/Mg2+ loaded resin achieves a separation efficiency of 23.3 % at the same flow rate. As the boron loading rate decreases to 10 %, the separation efficiency increases to 42.6 %. The flow rate also plays a crucial role, as an increase corresponds to a decrease in separation efficiency. Notably, the Finex CS10GC ion exchanger in Na+ form consistently exhibits superior separation efficiency and band resolution. A mathematical model is introduced to simulate the effective separation of boric acid from other impurities. The quality of the recovered boric acid conforms to the standard grade (Merck KGaA), exhibiting a purity level within the range of 99.5–100 %, suggesting substantial economic value. The proposed recovery process contributes significantly to environmental preservation by mitigating waste discharge, exemplifying a noteworthy commitment to resource conservation.

Sustainability Evaluation of the Al-Qasab Playa by Integrating Hydrogeochemical and Graphical, ArcGIS Watershed, and Thermodynamic Geochemical Modeling Approaches

Drawing development plans requires evaluating the available resources and assessing their sustainable and subsequent utilization-driven environmental impacts. The current work is concerned with evaluating the sustainability of the halite harvesting process from Al-Qasab Playa, Shaqra, Central Saudi Arabia. The authors integrated, conceptually and quantitatively, ArcGIS-processed SRTM-DEM (Shuttle Radar Topography Mission-Digital Elevation Model) data, hydrogeochemical and thermodynamic-based geochemical modelling, and graphical approaches to achieve the ultimate aims of the study. The watershed is identified as a nonmarine closed basin with a drainage area of 1290 km2, with the slope controlling recharge to the Playa. The Chadha plot including the rainwater exhibits linear regression, with an R2 value of 0.9947, confirming the rainwater origin of the Playa water. The hardness-forming ions are primarily removed in pond 3, eliminating the need for costly and power-consuming steps of softening with ion exchange resins or nanofiltration as it can be used directly as a readily available feed for the chlor-alkali process for producing NaOH, Cl2, and H2 gases through electrolysis. XRD (X-ray diffraction) analysis and the SEM-EDS (Scanning electron microscopy-energy dispersive X-ray spectroscopy) of the harvested halite confirmed its purity. An improved design of the current folkloric harvesting process has been proposed based on the saturation indices calculated thermodynamically to provide a readily available feed intake for the electrolysis chlor-alkali process with or without minimal pretreatment to produce higher value chemicals. The methodological aspects presented here are deemed robust and valid for applications in other study areas, including the assessment of the exploitation of the rejected brine from the desalination plants to achieve the zero liquid discharge approach, as well as other types of sabkhas, regardless of their geographical location.

Adsorption of Toxic Metals Using Hydrous Ferric Oxide Nanoparticles Embedded in Hybrid Ion-Exchange Resins.

Acid mine drainage (AMD) is a major environmental problem caused by the release of acidic, toxic, and sulfate-rich water from mining sites. This study aimed to develop novel adsorbents for the removal of chromium (Cr(VI)), cadmium (Cd(II)), and lead (Pb(II)) from simulated and actual AMD using hybrid ion-exchange resins embedded with hydrous ferric oxide (HFO). Two types of resins were synthesized: anionic exchange resin (HAIX-HFO) for Cr(VI) removal and cationic exchange resin (HCIX-HFO) for Cd(II) and Pb(II) removal. The resins were characterized using scanning electron microscopy and Raman spectroscopy, which confirmed the presence of HFO particles. Batch adsorption experiments were conducted under acidic and sulfate-enhanced conditions to evaluate the adsorption capacity and kinetics of the resins. It was found that both resins exhibited high adsorption efficiencies and fast adsorption rates for their respective metal ions. To explore the potential adsorption on actual AMD, HCIX-HFO demonstrated significant removal of some metal ions. The saturated HCIX-HFO resin was regenerated using NaCl, and a high amount of the adsorbed Cd(II) and Pb(II) was recovered. This study demonstrates that HFO-embedded hybrid ion-exchange resins are promising adsorbents for treating AMD contaminated with heavy metals.

Selective recovery of copper from copper tailings and wastewater using chelating resins with bis-picolylamine functional groups

Industrial and mining wastewater, along with copper tailings, are typically highly acidic and contain copper and other heavy metals, which may contaminate and damage the environment. Copper (Cu) is, however, a valuable metal, making its removal and recovery from such wastewater and tailings environmentally and economically advantageous. Chelating ion exchange resins featuring bis-picolylamine functional groups are especially suitable for application requiring selective recovery of Cu(II) from highly acidic media. In this study, and for the first time, the kinetics, binding capacity and selectivity of Lewatit MDS TP 220 chelating resin towards Cu(II) are reported. The resin was characterized by Zeta potential, scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Factors including pH, initial concentration, contact time, temperature, and selectivity were investigated to assess the adsorption performance of the chelating resin. The adsorption kinetics tests revealed fast adsorption within the first 5–30 min and fitted the pseudo-second-order model, signifying chemisorption process. The adsorption isotherm followed the Langmuir model, implying monolayer adsorption process. The maximum adsorption capacity (qm) for Cu(II) determined by the Langmuir model was 103.9 mg/g. The adsorption thermodynamics showed an endothermic and spontaneous adsorption. FTIR and XPS studies suggested coordination or chelation as the possible adsorption mechanism. Lewatit MDS TP 220 exhibited excellent Cu(II) adsorption, desorption with 2 M ammonium hydroxide (NH4OH), and selectivity in multi-metal ions solution. Additionally, the resin demonstrated excellent reusability after five regeneration steps. This chelating resin is a potential adsorbent for effective and recurrent recovery of Cu(II) from copper tailings and wastewater, thereby contributing to environmental remediation.

Alkaline Cleaning of Ion-Exchange Resins

Alkaline Cleaning of Ion-Exchange Resins

Rapid room temperature synthesis of Mn-doped perovskite quantum dots for white-light-emitting diodes

All-inorganic perovskite quantum dots (PQDs) have excellent photoelectric performance, such as high photoluminescence quantum yield (PLQY), narrow full width at half-maximum (FWHM), and emission spectra covering the visible light wavelength. The emission color can be tuned over the full visible spectral region making them promising for white-light-emitting diodes (WLEDs). Further control over the optical and magnetic properties of PQDs can be achieved through doping of transition metal ions such as Mn2+ ions. In this paper, a rapid doping method is employed at room temperature by using strong-acid cation-exchange resin during the metal ions doping process, which shortens the doping time, and Mn:CsPb(Cl/Br)3 QDs were obtained. By controlling the reaction time between strong-acid cation-exchange resin and PQDs, we achieve different levels of manganese doping, resulting in a new, to the best of our knowledge, fluorescence peak at 600 nm. The introduction of strong-acid cation-exchange resin preserves the integrity of the PQD structure, while completing the doping within 30 min. Due to the low cost and mild reaction conditions of resin, it is expected that the Mn:CsPb(Cl/Br)3 QDs can be mass-produced in large quantities. In addition, in order to provide high-quality white light emission, and prevent anion exchange reactions when mixed with CsPbBr3 QDs, the CsPbBr3 QDs are coated with silicon. Finally, by combining ultraviolet-light-emitting diodes (UVLEDs) with the aforementioned PQD mixture, this paper successfully fabricates WLEDs and demonstrates its excellent photoelectric performance. The constructed WLEDs produce warm white light with a high color rendering index (CRI) of 91 and a high correlated color temperature (CCT) of 5966 K, and the luminous efficacy (LE) of WLEDs is 41lmW−1.

Understanding electrostatic interaction on strong cation-exchanger via co-ion valency effects

Empirical adsorption models have been extensively used to design and optimize ion exchange chromatography (IEC) processes for proteins. The equations go 40 years back to the qualitative findings about the electrical double layer (EDL) in ion exchangers and form the basis of the stoichiometric displacement (SD) model widely used in preparative chromatography. While the SD model reduces the experimental effort to find salt-eluting conditions for the separation, knowledge transfer is restricted from one system to another. However, this limitation can be overcome by understanding the physicochemical interaction mechanism between the solid adsorbent and the electrolyte. Via a theoretical and experimental approach, we investigated the physicochemical adsorption mechanism in IEC and developed a methodology to determine it quantitatively by measuring the effective EDL thickness. We performed negative adsorption experiments in high-performance liquid chromatography to measure the excluded volume of co-ions, citrate, or oxalate on strong cation exchange resin. Together with the physical specifications of the column and the deployment of a modified nonlinear Poisson-Boltzmann equation, we identified the effects of the electrolyte composition on the size of the EDL. While it depends on the concentration, valency, and size of the counterion, we derived that the expansion of the EDL is indicated by different valencies of the carboxylate co-ions in trace amounts. Our findings provide a self-consistent theory of the transport phenomena in a solid/fluid system with all parameters specified with the physical properties of the chromatographic process. Further, optimizing the resin design or improving the adsorption and desorption conditions for biomolecules may be facilitated. Altogether, our work may improve material designing and process development and, thereby, help to overcome the concurrent technological and economic bottlenecks of the well-deployed purification step of IEC.

Removal of Heavy Metals from Contaminated Aquatic Streams Using a Resin Supported Green nZVI

This study addresses the escalating demand for clean water resources driven by population growth and water quality deterioration. The research focuses on evaluating the efficacy of a nanocomposite material, incorporating zero valent iron nanoparticles into a chelating cation exchange resin matrix, for selectively removing heavy metals from polluted aquatic environments. The selected resin, featuring iminodiacetic acid functional groups, demonstrates notable selectivity for heavy metal cations over alkali earth metals. Column experiments were conducted to assess the nanocomposite’s performance, utilizing a feed solution spiked with heavy metals at concentrations ten times higher than Greek legislation limits for wastewater effluent recycling. The nanocomposite exhibited significant effectiveness for Cu, Cr(VI), and Pb, consistently maintaining Cu levels below detection limits and demonstrating limited breakthrough of Cr(VI) and Pb depending on experimental conditions. However, the removal efficiency was lower for Ni and insufficient for Cd, Zn, and As in this complex multicomponent solution. This research contributes valuable insights into the potential application of the developed nanocomposite for targeted removal of specific heavy metals in contaminated water sources, providing a foundation for further exploration and application in water remediation technologies.