Anion Exchange Resin Research Articles

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.

Anionic N-Heterocyclic Carbenes from Mesoionic Imidazolium-4-pyrrolides: The Influence of Substituents, Solvents, and Charge on their 77Se NMR Chemical Shifts.

Mesoionic compounds are the starting material for the synthesis of unique anionic N-heterocyclic carbenes. Herein, mesoionic imidazolium pyrrolides synthesized from pyrrole-2-carbaldehyde via various N-alkyl-4-pyrroyl-imidazoles are described. These were converted into nine new 4-(pyrrol-2-yl)-substituted imidazolium salts and transformed into the mesoionic title compounds using an anion exchange resin. The DFT-calculated (B3LYP/6-311++G**) CREF values indicate a great potential for the formation of anionic N-heterocyclic carbenes by deprotonation, which were generated and reacted with selenium to obtain selenoureas. The 77Se NMR shifts investigated under systematic variation of conditions are dependent on the substitution pattern (ΔδSe = 133 ppm) and the steric demand of the substituents. Solvent dependencies of the 77Se NMR shifts were investigated applying toluene-d8, THF-d8, CDCl3, CD2Cl2, pyridine-d5, acetone-d6, DMSO-d6, CD3CN, AcOD, and MeOD. The influences of the referencing method on the 77Se shifts using external or internal Me2Se or Ph2Se2 and solvent can add up to ΔδSe = ca. 80 ppm. In addition, we observed a temperature dependence of both the selenoureas and the reference reagent Ph2Se2 as well as a 77Se shift difference of the analyte caused by interaction with internally added Ph2Se2. The negative charge of deprotonated selenoureas shifts the values by an additional -20 ppm.

Fractionation of phenolic aldehydes by liquid–liquid extraction and polymer resin adsorption

ABSTRACT The extraction and adsorption characteristics of three phenolic aldehydes with high physicochemical similarity in lignocellulosic biomass hydrolyzate, which are fermentation inhibitors, were investigated. The extraction process considered both physical extraction with two organic solvents and reactive extraction with five basic extractants. In physical extraction, n-hexane was found to be the most suitable organic solvent for selectively separating 4-hydroxybenzaldehyde from the three phenolic aldehydes, and in reactive extraction, trioctylphosphine oxide was identified as the most suitable basic extractant for the selective separation of syringaldehyde. In the adsorption process, various neutral polymer resins and anion-exchange polymer resins were employed. Among them, the neutral polymer resin XAD16 was found to be the most suitable for selectively separating 4-hydroxybenzaldehyde. To efficiently separate and concentrate the three phenolic aldehydes with equal mass percentages, a proposed five-step fractionation process included the aforementioned extraction and adsorption techniques. By implementing n-hexane-based physical extraction in step 4 and NaOH solution-based back-extraction in step 5 of the fractionation process, the purities of 4-hydroxybenzaldehyde, vanillin, and syringaldehyde in the final solution increased from their initial 33.3% each to 67.6%, 69.8%, and 76.4%, respectively, at a volume ratio of the aqueous phase to the organic phase of 1:15.

Chromatographic separation of Re-188 from reactor produced W-188 using Bio-Rex 5 anion exchange resin

Chromatographic separation of Re-188 from reactor produced W-188 using Bio-Rex 5 anion exchange resin

Control of drinking water disinfection byproducts with a novel bromide-selective anion exchange resin: Design, mechanism, and performance

In regions where drinking water sources containing elevated bromide levels, the formation of brominated disinfection byproducts (Br-DBPs) is enhanced, which may increase risks of cancer and birth defects. Anion exchange resin (AER) adsorption is a promising approach for reducing precursors of Br-DBPs (e.g., bromide and natural organic matter) due to its strong electrostatic force for reversible ion exchange process. However, high bromide water sources typically have high salinities, and the presence of co-existing ions (e.g., sulfate, nitrate, chloride) can significantly diminish the efficiency of conventional AERs, which use polyacrylic or polystyrene skeletons with trimethyl-ammonium functional groups. This study designed a novel AER with the polystyrene skeleton and tripentyl-ammonium functional group for the selective bromide removal, which resisted interferences from co-existing ions based on ion dehydration and ion-pairing electrostatic interactions. Column experiments with continuous high-bromide water flows demonstrated that the novel AER exhibited up to three times the operating capacity of conventional AERs, achieving reductions of 71.2 %, 44.6 %, and 67.7 % in bromide, dissolved organic carbon, and specific UV absorbance, respectively. Competitive experiments showed that the novel AER's strong sulfate interference resistance enhanced its bromide selectivity. The electrostatic interactions between AER fragments and bromide or sulfate particles were quantitatively evaluated using density functional theory calculations. Treatment with the novel AER led to reductions in total organic bromine, aliphatic Br-DBPs, and cyclic Br-DBPs by 76.7 %, 62.5 %, and 90.5 %, respectively. Notably, cytotoxicity assays using Chinese hamster ovary cells indicated a 39.7 % decrease in overall cytotoxicity of chlorinated drinking water following treatment with the novel AER.

Occurrence, toxicity, and control of halogenated aliphatic and phenolic disinfection byproducts in the chlorinated and chloraminated desalinated water

Seawater desalination is widely used to overcome the freshwater shortage worldwide. However, even after three-stage reverse osmosis treatment, the desalinated water still contained 14.6 μg/L of aliphatic disinfection byproducts (DBPs), 384.2 ng/L of bromophenolic DBPs, 3.5 ng/L of iodophenolic DBPs, 1024.7 μg/L of Br-, 2.8 μg/L of I-, and 2.4 mg C/L of dissolved organic carbon (DOC). After the desalinated water was disinfected with chlor(am)ine, the concentrations of halogenated aliphatic and phenolic DBPs further increased, and bromophenolic DBPs were the toxicity forcing agents. When surface water was mixed with desalinated water and then chlorinated, the yield of aliphatic and phenolic DBPs significantly elevated. Separately chlorinating desalinated water and surface water before mixing could mitigate this adverse situation. Chloramine disinfection was more conducive to reducing the total calculated toxicity of disinfected desalinated waters and mixed waters compared to chlorine disinfection. The treatment of desalinated water with granular activated carbon could effectively remove DOC and UV254, leading to a reduction in the content of total organic halogen after chlor(am)ination. Although anion exchange resin could adsorb Br-, it also released the organic precursors of DBPs, ultimately increasing the yield of DBPs. The results of this study can provide a reference for the seawater desalination industry to improve seawater pre-treatment and desalination processes and thus minimize the DBPs.

Micro Scale Chromatography of Human Plasma Proteins for Nano LC-ESI-MS/MS

Organic precipitation of proteins with acetonitrile demonstrated complete protein recovery and improved chromatography of human plasma proteins. The separation of 25 μL of human plasma into 22 fractions on a QA SAX resin facilitated more effective protein discovery despite the limited sample size. Micro chromatography of plasma proteins over quaternary amine (QA) strong anion exchange (SAX) resins performed best, followed by diethylaminoethyl (DEAE), heparin (HEP), carboxymethyl cellulose (CMC), and propyl sulfate (PS) resins. Two independent statistical methods, Monte Carlo comparison with random MS/MS spectra and the rigorous X!TANDEM goodness of fit algorithm protein p-values corrected to false discovery rate q-values (q≤ 0.01) that agreed on at least 12,000 plasma proteins, each represented by at least three fully tryptic corrected peptide observations. There was qualitative agreement on 9,393 protein/gene symbols between the linear quadrupole versus orbital ion trap but also quantitative agreement with a highly significant linear regression relationship between log observation frequency (F value 4,173, p-value 2.2e-16). The use of a QA resin showed nearly perfect replication of all the proteins that were also found using DEAE-, HEP-, CMC-, and PS-based chromatographic methods combined and together estimated the size of the size of the plasma proteome as ≥12,000 gene symbols.

Optical characteristic of dissolved organic matter polar fractions by spectrum technologies and the relationship with indirect photodegradation of ofloxacin

Ofloxacin (OFL) is a commonly used antibiotic and is widely present in various water bodies. Indirect photodegradation is crucial for the transformation and fate of antibiotics in surface water, which largely depends on the structure and composition of dissolved organic matter (DOM). Nevertheless, knowledge about the optical characteristics of diverse DOM polar fractions as well as the relationship with indirect photodegradation of antibiotics is still scarce. In this study, XAD-8 in combination with anion and cation exchange resins was used to separate DOM into six polar fractions: hydrophilic acid (HIA), hydrophilic basic (HIB), hydrophilic neutral (HIN), hydrophobic acid (HOA), hydrophobic basic (HOB) and hydrophobic neutral (HON). UV–vis and fluorescence spectroscopy were applied to analyze DOM polar fractions and explore their impact on OFL indirect photodegradation. The results showed that indirect photodegradation was the primary photodegradation route of OFL when the irradiation wavelength was greater than 320 nm, triple-state excited DOM (3DOM*) was the main reactive intermediates (RIs) that affected the indirect photodegradation of OFL. Excitation-emission matrix spectroscopy combined with parallel factor analysis (EEMs-PARAFAC) and correlation analysis demonstrated that terrestrial humic-like substances could yield generous RIs to facilitate OFL indirect photodegradation. The HIB and HOA fractions of SRNOM contained large aromaticity and humification degree and more terrestrial humic-like substances, thus exhibiting greater OFL indirect photodegradation rates. The HOA and HOB fractions of FA had abundant terrestrial humic-like substances and contributed more to OFL indirect photodegradation. This study helped us understand the effect of DOM structural characteristics on the OFL indirect photodegradation.

Study on the chloride removal performance of porous anion exchange resin models constructed via 3D printing technology

Industrial production produces a large amount of wastewater containing chloride (Cl-) ions, and elevated concentrations of Cl- pose substantial environmental hazards. This study presents a novel approach using ion exchange resin for the removal of chloride, combined with the advantages of controllable and rapid model design afforded by 3D printing technology, to prepare a porous ion exchange model (PIEM). The optimal conditions for pretreatment, chloride removal, and alkaline regeneration of PIEM were systematically explored. Under these optimal conditions, the chloride removal efficiency of a single PIEM in simulated wastewater with a 1000 mg/L Cl- concentration was 67.4 %. Following five cycles, the chloride removal efficiency stabilized at 40 %. When thirty PIEMs assembled into a quartz tube device were used and subjected to six cycles, the total chloride removal efficiencies reached 85.2 % for 2 L of simulated wastewater with a Cl- concentration of 1000 mg/L and 52.6 % for 1 L of actual wastewater with a Cl- concentration of 2915 mg/L. The mechanism of chloride removal by PIEM involves ion exchange and hydrogen bonding adsorption between the ion exchange resin and Cl- in the surrounding wastewater. This study develops a new method of removing chloride by immobilizing ion exchange resin through 3D printing, which prevents the significant loss of ion exchange resin during the chloride removal process and ensures high efficiency in removing chloride, providing new insights for the development of chloride removal technology.

Gel-type resin loaded with nano-hydrated ferric oxide for the removal of anions from papermaking wastewater

The main anions in papermaking wastewater are sulfate and chloride. In this paper, a strongly basic gel-type anion exchange resin (201×7) loaded with 20 ~ 200nm hydrated ferric oxide was prepared by dispersion impregnation with ethanol. The modified resin enhances the ability to remove sulfate by complexation of ligands to cause sulfate to form outer and inner sphere complexes on hydrated ferric oxide. The modified resin was dependent on acidic conditions, and the maximum exchange capacity for sulfate was enhanced by 14.2% under the optimal pH, exchange time, and ion concentration conditions. Competitive exchange experiments showed that the removal effect of the modified resin on chloride was almost unchanged under different chloride, sulfate ratios, and the degree of improvement of the removal effect on sulfate decreased from 9.5 ~ 5.5% with the increase of chloride ratio. The removal of sulfate by the modified resin was consistent with the proposed secondary kinetics and Langmuir adsorption model. In addition, the modified resin maintained 88% reuse after four desorption-adsorption cycles and achieved a regeneration rate of 93.1% after was eluted with HCl and reloaded with hydrated ferric oxide. The expected removal effect was well achieved when the resin was applied to the actual wastewater treatment. The above results indicate that the hydrated ferric oxide modification can improve the ability of the 201×7 resin to remove sulfate from water, and is a promising method for removing anions from papermaking wastewater.

Itching for Answers: A Comprehensive Review of Cholestatic Pruritus Treatments

Cholestasis is a clinical and laboratory syndrome indicating impaired bile production or excretion. One of the hallmark symptoms of cholestasis is pruritus. Itch can be severe and debilitating for patients, impacting their quality of life similarly to pain, and, in some cases, it can be refractory. Current therapies like anion exchange resins and rifampicin, offer partial relief but with side effects. Effective, well-tolerated treatments are urgently needed. This literature review examines existing options (bile acid sequestrants, antihistamines, opioid antagonists, sertraline, and rifampicin) and explores novel therapies (monoclonal antibodies, PPAR agonists, and bile-acid-based therapies). We analyze mechanisms, limitations, and adverse effects to aid clinicians and researchers. Novel approaches include monoclonal antibodies to inhibit bile recirculation and PPAR agonists targeting pruritus signaling. Despite the limited current options, ongoing research promises better treatments for cholestatic pruritus, addressing its distressing impact. In summary, cholestasis-associated pruritus poses a significant challenge with limited treatments. Advancements in understanding its pathophysiology offer hope for more effective therapies in the future.

Regeneration of conventional and emerging PFAS-selective anion exchange resins used to treat PFAS-contaminated waters

Anion exchange resins (AERs) have emerged as a promising separation technology to remediate PFAS-contaminated waters due to their improved selectivities and capacities in comparison to legacy activated carbon adsorbents. Presently, site managers choose between AER systems employing resins defined as being ‘regenerable’ with relatively low PFAS selectivity, and PFAS-selective resins that are marketed as ‘single-use’ media intended for disposal upon PFAS breakthrough. However, the potential for these highly-selective adsorbents to be regenerated and/or reused remains poorly characterized. This study presents a comprehensive evaluation of the efficacy of various regenerant solution constituents, mixtures, and operational considerations on the regenerability of both ‘regenerable’ and ‘PFAS-selective’ AERs that were loaded during a pilot treatment study of PFAS-contaminated groundwater. Batch screening of regenerant solution constituents found that both classes of resins may be effectively regenerated using combinations of salt brine and organic cosolvent, with high cosolvent fractions being necessary for PFAS-selective AERs. While neither brine-only nor solvent-only regenerant solutions led to effective PFAS desorption, the efficacy of regeneration with brine/cosolvent mixtures varied with salt type and cosolvent composition. Chloride salts outperformed sulfate and bicarbonate salts, cosolvent efficacy depended on the volume fraction and type used, and highly non-polar solutions led to optimal PFAS desorption. Continuous-flow regeneration experiments showed near-complete PFAS desorption from regenerable AERs using 10 bed volumes (BVs) of 70 % methanolic brine solutions, whereas PFAS-selective resins required more bed volumes (30) of brines with higher methanol content (90 %) or a more hydrophobic cosolvent (n-propanol); increasing regenerant empty-bed contact time had minimal effect on PFAS desorption. > 90 % methanol recovery from the resulting waste regenerant mixtures was accomplished with negligible PFAS contamination using distillation, leaving a minimal volume of a PFAS-concentrated still bottoms waste that may be further treated for PFAS destruction. Life cycle analyses revealed that groundwater treatment using PFAS-selective AERs operated in a regenerable mode have lower environmental impacts and costs than systems using conventional regenerable AERs, and lower treatment costs than systems operated using PFAS-selective resins in a single-use mode. Although counterintuitive, these findings stem from the fact that higher cosolvent requirements for regeneration of PFAS-selective resins lead to greater internal recycling of regenerant solutions and much lower volumes of residual waste still bottoms that require off-site incineration or disposal.

Degradation of the AMP/PZ-based solvent CESAR1 and effects of solvent management in two longtime pilot plant tests

Two 24/7 longtime testing campaigns at the CO2 capture pilot plant at Niederaussem with an accumulated testing time of more than 40,000 h with the CESAR1 solvent, an aqueous solution of 26.7 wt% 2-amino-2-methylpropan-1-ol (AMP) and 12.9 wt% piperazine (PZ), provide a unique data base for the development of solvent management technologies and the evaluation of hypotheses on amine degradation. In the first campaign with a testing time of 34,000 h without replacement of the solvent inventory, three solvent management strategies with different effect mechanisms were investigated: adsorptive removal of trace elements from the solvent by two kinds of active carbon, removal of ionic contaminants by ion exchange using cation and anion exchange resins, and removal of NO2 from the flue gas by treatment with a thiosulfate/sulfite solution. After replacement of the solvent inventory the second campaign was conducted, in which none of the solvent management technologies mentioned have been applied for 10,000 h. The results of the two campaigns allow a direct comparison of the solvent degradation behavior. It is shown that active carbon does not significantly affect the accumulation rate of degradation products in CESAR1, and that an inappropriate kind of active carbon can cause foaming. Anionic degradation products, metal complexes, trace components and cationic contaminants can be effectively removed from the aged solvent by ion exchange. However, after their removal, accelerated formation of oxidative degradation products by a factor of up to 3 higher than before the anion exchange was observed. Removal of NO2 from the flue gas did not affect the NH3 emissions from the CO2 absorber, but it led to the highest observed increase rate of the accumulation of acidic degradation products for aged CESAR1. The results show that exaggerated efforts for solvent management are contra-productive and that a reassessment of the effect mechanisms of solvent management technologies is necessary.

Separation of recombinant erythropoietin and human serum albumin without the use of sophisticated equipment

A number of drugs based on recombinant erythropoietin contain human serum albumin as an auxiliary component. The presence of this protein hinders the proper control of the drug quality in accordance with the requirements of regulating agencies. We propose the novel method for separation of recombinant erythropoietin (epoetin beta) and human serum albumin. It is based on the subsequent use of hydrophobic sorbent and anion exchange resin placed in gravity flow columns (without the use of spin-columns). The proposed approach makes it possible to concentrate and purify the preparations containing the epoetin beta both at high and at minimal concentrations (the ratio of the amount of albumin and erythropoietin in the used preparations can reach 125:1). The average yield of epoetin beta after the use of hydrophobic sorbent and anion exchange resin was 75 % and 97 %, respectively. It was shown that the determined conditions of sample preparation had no affect on the content of the epoetin beta in the product.

Rapid removal and catalytic decomposition of nitrate in anion-exchange resin containing gold nanoparticles toward purification of groundwater

We investigated the catalytic reduction of NO3– in various single-metal-introduced anion-exchange resins (AERs) in 1 bar H2 and observed that the reaction proceeded successfully. Among the metals considered in this study, Au was optimal in terms of catalytic activity and ease of catalyst preparation, whereas Ru exhibited the highest activity. The AER with Au (Au@AER) containing the optimal amount of Au (0.3mmol/g) decomposed 0.38mmol/g of NO3– primarily into N2O under optimized reaction conditions (80°C and 5 h). The decomposition amount corresponded to 41 % conversion. The incorporation of Au into the AER increased its ion-exchange capacity from 1.18 (pristine AER) to 1.46mmol/g (Au@AER); in contrast, the ion-exchange equilibrium constant decreased from 1.4 to 0.83 L mol−1 owing to the change in the structure of the anion-exchange sites in the AER. Au@AER was reusable for ion-exchange removal and catalytic decomposition of NO3– up to five times without performance degradation.

Preloading Long-Chain Quaternary Ammonium Groups to Synthesize a High-Efficient Anion-Exchange Resin for Eliminating Bacterial Contaminants in Drinking Water.

Bacterial contamination in drinking water is a global health concern, necessitating the development of highly efficient treatment techniques. Anion-exchange resins (AERs) have long been employed for removing anionic contaminants from drinking water, but their performance for bacterial contamination is poor. Here, we develop a novel AER (AER6-1) with exceptional bactericidal effects and ultrafast adsorption rates of extracellular DNA (eDNA) (2.2- and 11.5-fold compared to other AERs) achieved through preloading quaternary ammonium groups (QAGs) with hexyl chain (-C6-N+-) on the resin exterior and successively grafting QAGs with a methyl chain (-C1-N+-) inside a resin pore. The AER6-1 outperforms other commercial AERs and ultraviolet disinfection, exhibiting superior elimination of total bacteria, potential pathogens (Escherichia coli and Pseudomonas aeruginosa), eDNA, and antibiotic resistance genes (mexF, mexB, and bacA) in actual drinking water, while maintaining a comparable anion exchange capacity with other commercial AERs. Theoretical calculations of density functional theory and xDLVO combined with XPS elucidate the crucial roles of hydrogen bonding and hydrophobic force provided by the resin skeleton and -C6-N+- in cleaving the bacterial cell membrane and increasing the adsorption kinetics on eDNA. This study broadens the scope of AERs and highlights an effective way of simultaneously removing bacterial and anionic contaminants from drinking water.

Innovative Determination of Zinc Isotope Ratios in Geological Reference Materials: A Combined Precipitation and Anion Exchange Resin Method by MC-ICP-MS

Innovative Determination of Zinc Isotope Ratios in Geological Reference Materials: A Combined Precipitation and Anion Exchange Resin Method by MC-ICP-MS

Sorption/desorption and degradation of long- and short-chain PFAS by anion exchange resin and UV/sulfite system

A combined sorption/desorption and UV/sulfite degradation process was investigated for achieving efficient elimination of PFAS from water. Two gel-type resins, Purolite A532E and A600, and one macroporous resin, Purolite A860, were firstly tested for the sorption of individual PFPrA, PFHxA, PFOA, PFOS, and GenX at different concentrations. Sorption data and density functional theory (DFT) calculations revealed that electrostatic interactions predominated for short-chain PFAS sorption and hydrophobic interactions played a more significant role for long-chain PFAS than for short-chain PFAS. A600 and A860 were selected for desorption tests with 0.025% NaOH, 5% NaCl, and 5% NH4Cl solution with or without 20% ethanol (EtOH) due to their high sorption capacity for all target PFAS. The mixture of 5% NH4Cl and 20% EtOH as the desorption solution typically showed the highest desorption efficiency. PFOS was the most resistant for desorption but its desorption could be enhanced by stronger mixing conditions (in 5% NaCl + 20% EtOH). Direct degradation of studied PFAS in the desorption solution (0.025% NaOH, 5% NaCl, and 5% NH4Cl) by UV/sulfite achieved 97.6–100% degradation and 46.6–86.1% defluorination. EtOH hindered degradation and thus should be separated from the water before UV/sulfite degradation.

Anion exchange recovery of rhenium from industrial liquors followed by direct synthesis of a rhenium halide salt

In the present study, the sorption of perrhenate ions from sulfuric acid liquors was studied using three types of polymer ion exchange resins. An anion exchange resin type 1 (a copolymer of 2-methyl-5-vinylpyridine with divinylbenzene (VP-DVB)) as well as two polyfunctional resins containing anion and cation exchange functional groups, namely, type 2 (a carboxylated VP-DVB with pyridine-2-carboxylic acid (picolinic acid) functional group) and type 3 (an aminophosphorylated VP-DVB with pyridine-2-[(methylamino)methyl]phosphonic acid functional group), were studied. The resins before and after rhenium sorption were characterized by FT-IR spectroscopy and XPS spectroscopy. The incorporation of additional acidic functional groups into the polymer matrix of the VP-DVB resins led to a slight decrease in the rhenium anion exchange capacity. At the same time, polyfunctional resins make it possible to strip rhenium with hydrochloric acid. A completely new process for the preconcentration of rhenium as a halide compound, which will contribute to the low-cost production of metallic rhenium, can be implemented using these new polyfunctional resins. Column sorption experiments using real uranium leach liquors demonstrated an exchange capacity of 33.2 mg of Re per gram of resin and a concentration factor in the eluate of ∼2500. The possibility of anion exchange recovery of rhenium from uranium leach liquors by Type 3 resin followed by direct precipitation of potassium hexachlororhenate from hydrochloric acid desorption liquor was demonstrated. The present study provided a new resin for rhenium recovery with excellent adsorption and elution characteristics, which is a promising candidate for practical applications.

Gold recovery from chloride leach solution of TCCA using D301 anion exchange resin and elution with thiourea

Trichloroisocyanuric acid (TCCA), which is used for gold leaching, is an alternative to cyanidation due to its lower toxicity and higher efficiency. This study investigated the gold recovery procedures from highly effective chloride leaching solution using the D301 resin. This approach prevented the inhibition of gold adsorption when using activated carbon. Herein, the optimal conditions for gold adsorption were discussed, including establishing adsorption kinetics and isotherms, and calculating adsorption activation energy. Additionally, SEM (Scanning Electron Microscope), FTIR (Fourier Transform Infrared Spectroscopy), and XPS (X-ray Photoelectron Spectroscopy) techniques were used to reveal the mechanism of gold adsorption using D301 resin. Under optimal conditions (pH 4.0, temperature 25 °C, time 120 min), an average adsorption percentage of 99.2% was achieved. Analysis of the adsorption data confirmed that gold adsorption followed the pseudo-second-order kinetic model and Freundlich adsorption isotherm. The calculated activation energy was 9.69 kJ mol−1, indicating a predominance of physical adsorption involving ion exchange reactions with protonated tertiary amine groups in the D301 resin beads. Furthermore, among various eluents tested in desorption experiments, a solution containing a mixture of thiourea and hydrochloric acid with 0.4 mol L−1 and 0.8 mol L−1, respectively, demonstrated superior efficiency, achieving a successful desorption percentage reaching 95.7 ± 0.3% within 80 min. After three cycles of resin regeneration, the regeneration efficiency reached 91.2% while maintaining an average adsorption percentage of 95.3%.