Weak Base Anion Exchange Research Articles

Sorption Characteristics and Chromatographic Separation of 90Y3+ from 90Sr2+ from Aqueous Media by Chelex-100 (Anion Ion Exchange) Packed Column.

There is growing demand for separation of 90Y carrier free from 90Sr coexisting to produce high purity 90Y essential for radiopharmaceutical uses. Thus, in this context the sorption profiles of Y3+ and Sr2+ from aqueous solutions containing diethylenetriaminepenta acetic acid (DTPA), ethylenediaminetetra-acetic acid (EDTA), acetic acid, citric acid, or NaCl onto Chelex-100 (anion ion exchange) solid sorbent were critically studied for developing an efficient and low-cost methodology for selective separation of Y3+ from Sr2+ ions (1.0 × 10-5 M). Batch experiments displayed relative chemical extraction percentage (98 ± 5.4%) of Y3+ from aqueous acetic acid solution onto Chelex-100 (anion ion exchanger), whereas Sr2+ species showed no sorption. Hence, a selective separation of Y3+ from its parent 90Sr2+ has been established based upon percolation of the aqueous solution of Y3+ and Sr2+ ions containing acetic acid at pH 1-2 through Chelex-100 sorbent packed column at a 2 mL min-1 flow rate. Y3+ species were retained quantitatively while Sr2+ ions were not sorbed and passed through the sorbent packed column without extraction. The sorbed Y3+ species were then recovered from the sorbent packed column with HNO3 (1.0 M) at a 1.0 mL min-1 flow rate. A dual extraction mechanism comprising absorption associated to "weak-base anion exchanger" and "solvent extraction" of Y3+ as (YCl6)3- and an extra part for "surface adsorption" of Y3+ by the sorbent is proposed. The established method was validated by measuring the radiochemical (99.2 ± 2 1%), radionuclide purity and retardation factor (Rf = 10.0 ± 0.1 cm) of 90Y3+ recovered in the eluate. Ultimately, the sorbent packed column also presented high stability for reusing 2-3 cycles without drop in its efficiency (±5%) towards Y3+ uptake and relative chemical recovery. A proposed flow sheet describing the analytical procedures for the separation of 90Y3+ from 90Sr2+ using chelating Chelex 100 (anion exchange) packed column is also included.

Adsorption and Desorption Behavior and Mechanism of Ruthenium in Nitrite-Nitric Acid System.

Ruthenium is required to separate from high-level liquid waste (HLLW) because Ru is a valuable resource and is negatively influential on the vitrification process of HLLW. However, the separation of Ru is very challenging due to its complicated complexation properties. In this study, the adsorption and desorption characteristics of ruthenium on a synthesized SiPyR-N3 (weak-base anion exchange resin with pyridine functional groups) composite were investigated in nitric acid and nitrite-nitric acid systems, respectively, and the adsorption mechanism was explored. The experimental results showed that SiPyR-N3 has a significantly better adsorption effect on Ru in the nitrite-nitric acid system than in the nitric acid system, with an increase in the adsorption capacity of approximately three times. The maximum adsorption capacity of Ru is 45.6 mg/g in the nitrite-nitric acid system. The SiPyR-N3 possesses good adsorption selectivity (SFRu/other metal ions is around 100) in 0.1 M NO2--0.1 M HNO3 solution. The adsorption processes of Ru in the two different systems are fitted with the pseudo-second-order kinetic model and Langmuir model for uptake kinetics and adsorption isotherms, respectively. The results obtained from the FT-IR, XPS, and UV absorption spectrometry indicate that NO2- was involved in the adsorption process either as a complexing species with the metal ions or as free NO2- from the solution. A 0.1 M HNO3 + 1 M thiourea mixed solution shows effective desorption performance, and the desorption efficiency can reach 92% at 328 K.

Innovative Sol-gel functionalized polyurethane foam for sustainable water purification and analytical advances.

Nanomaterial combined polymeric membranes such as polyurethane foams (PUFs) have garnered enormous attention in the field of water purification due to their ease of management and surface modification, cost-effectiveness, and mechanical, chemical, and thermal properties. Thus, this study reports the use of novel Sol-gel impregnated polyurethane foams (Sol-gel/PUFs) as new dispersive solid phase microextractors (d- µ SPME) for the efficient separation and subsequent spectrophotometric detection of Eosin Y (EY) textile dye in an aqueous solution with a pH of 3-3.8. The Sol gel, PUFs, and Sol gel-impregnated PUFs were characterized using scanning electron microscopy (SEM), goniometry measurements, dynamic light scattering (DLS), energy dispersive spectroscopy (EDS), UV-Visible, and FTIR spectra. Batch experiment results displayed a remarkable removal percentage (96% ± 5.4%) of the EY from the aqueous solution, with the total sorption time not exceeding 60min. These data indicate rate-limited sorption via diffusion and/or surface complex ion associate formations after the rapid initial sorption steps. A pseudo-second order kinetic model thoroughly explained the sorption kinetics, providing a sorption capacity (qe) of 37.64mgg-1, a half-life time (t1/2) of 0.8 ± 0.01min, and intrinsic penetration control dye retention. The thermodynamic results revealed a negative value for ΔG⁰ (-78.07kJmol-1 at 293K), clearly signifying that the dye uptake was spontaneous, as well as a negative value for ΔH⁰ (-69.58kJmol-1) and a positive value for ΔS⁰ (147.65Jmol-1 K-1), making clear the exothermic nature of EY adsorption onto the sorbent, with a growth in randomness at the molecular level. A ternary retention mechanism is proposed, involving the "weak base anion exchanger" of {(-CH2-OH+ -CH2-) (Dye anion)-}Sol-gel/PUF and/or {(-NH2 + -COO-) (Dye anion)-}Sol-gel/PUF via solvent extraction and "surface adsorption" of the dye anion on/in the Sol-gel/PUFs membranes in addition to H-bonding, including surface complexation and electrostatic π-π interaction, between the dye and the silicon/zirconium oxide (Si-O-Zr) and siloxane (Si-O-Si) groups on the sorbent. Complete extraction and recovery (93.65 ± 0.2, -102.28 ± 2.01) of EY dye with NaOH (0.5M) as a proper eluting agent was achieved using a sorbent-packed mini column. In addition, the established extractor displayed excellent reusability and does not require organic solvents for EY enrichment in water samples, making it a talented nominee as a novel sorbent for EY sorption from wastewater. This study is of great consequence for expanding the applicatio1n of Sol-gel/PUFs in developing innovative spectrophotometric sensing strategies for dye determination. In view of this, it would also be remarkable to perform future studies to explore the analytical implications of this extractor regarding safety and environmental and public health issues associated to the pollutant.

Effective isolation of succinic acid from aqueous media with the use of anion exchange resins.

The primary objective of this study was to examine the isolation of succinic acid (SA) from aqueous-based solutions through the utilization of adsorption and ion exchange methods. Four kinds of anion exchange resins were employed, two of which were strong basic (Lewatit M-500 and Lewatit M-600), and the other two were weak basic (Lewatit MP-64 and Lewatit MP-62). The impacts of various variables on the efficiency of the process were examined. The aqueous pH strongly influenced the separation yield. Weak basic exchangers achieved the maximum yield at pH 2.1. However, the highest performance with Lewatit M-600 and Lewatit M-500 was obtained at pH 5 and 6, respectively. The SA separation with the tested resins reached equilibrium in about an hour. The recovery data revealed consistency with the Langmuir isotherm and pseudo-second-order kinetics. Efficiency improved with resin dosage and reduced with SA concentration. It was found that weak basic anion exchange resins were more efficient than strong basic exchangers for the recovery process. Among the resins tested, Lewatit MP-62 demonstrated the highest sorption capacity of 321 mg g-1 and 97.5% yield. The performance of the system decreased with temperature for all alternatives tested; however, its impact was not notable. The isolation process had an exergonic, exothermic, and favorable character based on the thermodynamic constants. Acid-loaded resins were successfully regenerated using trimethylamine and HCl for weak and strong anion exchange resins, respectively.

Preparation of exopolysaccharides by heat-resistant Weizmannia coagulans using anion exchange resins

Weizmannia coagulans with high temperature tolerance and stability was selected for the production of exopolysaccharides (EPS) at the fermentation temperature of 52 °C. The weak basic anion exchange resin was employed in the fermentation for the construction of buffer system to neutralize some lactic acid and form intermolecular hydrogen bonds with hydroxyl groups on capsular polysaccharides of bacteria via tertiary amine groups, resulting in the increased growth space for capsular polysaccharides. In addition, the fermentation at relatively high temperature significantly decreased the adsorption of Ca2+ derived from CaO used for pH adjustment to the resin and sustained the ion exchange capability of the resin available for the formation of intermolecular hydrogen bonds with capsular polysaccharides. The concentration of EPS obtained achieved up to 19.8 g/L, which was increased by approximately 20-fold as compared to the concentration of EPS obtained by conventional fermentation. The conversion rate of carbohydrates to EPS reached up to 35.1%. The EPS produced under the optimized fermentation condition included neutral and acidic heteropolysaccharides with a molecular mass of 3.4 × 104–1.5 × 106 Da. The concentration and molecular mass distribution of EPS exhibited good reproducibility. This study provides a novel method for the industrial production of EPS.

Selective Removal of Transient Metal Ions from Acid Mine Drainage and the Possibility of Metallic Copper Recovery with Electrolysis

ABSTRACT The low pH and high salinity of acid mine drainage (AMD) fundamentally complicates the sorption processes. We explored the selective removal of Cu, Ni and Co ions present in AMD from the excess of ferrous ions of using a chelating resins Lewatit® MonoPlus TP 220 and Lewatit® TP 208. Also, the recovery of metal copper from desorption solution using electrolysis was investigated. The results showed that the most effective sorption of metal ions was achieved with chelating sorbent Lewatit® TP 220. The dynamic capacity of the sorbent under the given conditions (pH= 2.5 ± 0.03, presence of Fe(II/III), Zn(II), Mn(II)) decreased in the following order: Cu(II) (43.3 ± 1.4 g/L) > Ni(II) (22.1 ± 2.1 g/L) > Co(II) (3.6 ± 0.4 g/L). Chelating resin Lewatit® TP 208 under the same conditions showed lower efficiency: Cu(II) (30.6 ± 1.3 g/L) > Ni(II) (9.1 ± 0.17 g/L) > Co(II) (1.3 ± 0.08 g/L). The weak base anion exchanger Purolite® A 832 was successfully used to take up Cu(II) from ammonia solution and easily regenerated with sulfuric acid. The sorption capacity for Cu(II) was calculated to be 19.2 ± 0.5 g/L. Electrolysis experiments were performed with a fluidized bed electrolysis reactor where metallic copper was regenerated from desorption solutions and purified sulfuric acid solutions were obtained.

Removal of perfluoroalkyl acids and common drinking water contaminants by weak-base anion exchange resins: Impacts of solution pH and resin properties

The underlying chemistry of weak-base (WB) anion exchange resins (AERs) for contaminant removal from water is not well documented in the literature. To address this, batch adsorption experiments were conducted at pH 4, 7, and 10 using two representative WB-AERs (polyacrylic IRA67 and polystyrene IRA96) and two representative strong-base (SB) AERs (polyacrylic IRA458 and polystyrene A520E), of differing polymer composition, for the removal of nitrate, sulfate, 3-phenylpropionic acid (3-PPA) as surrogate for natural organic matter, and six perfluoroalkyl acids (PFAAs). Under acidic (pH 4) and neutral (pH 7) conditions, the selectivity of AERs for each contaminant was predominantly influenced by polymer composition followed by the size of the resin functional group. This result reflected the WB-AERs being fully protonated and functioning identical to SB-AERs. Isotherm model parameters revealed WB-AER had higher capacity than SB-AER with analogous polymer composition and porosity regardless of resin selectivity for each contaminant. Under basic conditions (≥ pH 10), contaminant removal by WB-AERs declined due to deprotonation of the tertiary amine functional groups. Removal of PFAAs by the more hydrophobic polystyrene WB-AER (IRA96) remained approximately constant with changing pH, which was possibly due to electrostatic interactions with remaining protonated amine functional groups on the resin.

High selectivity of new thiourea-modified resins for gold: Adsorption performance, mechanism, and recovery

A thiourea-modified weak base anion exchange resin, ZGA451 (thiourea@ZGA451), was prepared. Thiourea@ZGA451 exhibited excellent potential for Au(III) adsorption. The maximum adsorption capacity of Au(III) by thiourea@ZGA451 was 995.6 mg/g at 298 K. The adsorption process followed the Freundlich and pseudo-second-order models, which are monolayer and chemisorption adsorption, respectively. The adsorption mechanism of Au(III) on thiourea@ZGA451 involves electrostatic attraction, chelation, and redox. Thermodynamic experiments showed that the reaction exhibited spontaneous endothermic behavior. Thus, thiourea@ZGA451 possesses outstanding Au(III) adsorption properties.

Bio-Inspired phosphate adsorption by Copper-Decorated weak base anion exchanger

Hybrid-based phosphate adsorbents have high adsorption ability but are challenged with regeneration because of strong bonding. Inspired by phosphate-binding proteins (PBPs) which reached a trade-off between high adsorption and regeneration ability by binding phosphate species with multiple hydrogen bonds, a weak-base anion (WBA) exchange resin was decorated with Cu2+ ions to develop an alternative advanced phosphate adsorbent. Different from the role of metal species in the promoted adsorption of existing hybrid-based adsorbents, the Cu2+ ions mainly drove phosphate diffusion from the liquid to the resin and then induced the phosphate species to bond with multiple –NH2+/–NH groups. Such adsorption exhibited a high entropy (ΔS0 = 132.47 J/mol-K) and was highly exergonic (ΔG0 = -16.83 ∼ -20.14 kJ/mol). Moreover, it enhanced the phosphate selectivity because the driving force for the sorption process originated from the complexation. During the regeneration, the Cu2+-to-Cu-O- transformation could occur under weak alkaline conditions and repelled the adsorbed phosphate species to facilitate desorption. Therefore, the Cu-WBA resin not only exhibited high phosphate adsorptions (31.94 to 61.03 mg-P/g) and high competing-anion tolerance but also was successfully recovered with a diluted NaOH solution (0.05 N). Detailed adsorption behaviors under different pHs, temperatures, and interference of competing anions were examined, and the mechanisms were elucidated.

Adsorption of catechol on a weak-base anion exchanger prepared by a novel template-induced method: Batch tests

In this work, a weak-base anion exchanger (TIR) was synthesized through a novel simplified strategy based on the principle of surface imprinting polymer (SIP) to selectively remove the catechol from aqueous solution. The chloromethylated polystyrene beads (CMPS), diethylamine and catechol were employed as the carrier, amination reagent and template respectively in the study. The N2 adsorption-desorption isotherms and Fourier-transform infrared spectroscopy (FT-IR) indicated that the functional group had been successfully grafted onto the CMPS, which directly constructed template-induced adsorption sites in the pore structure. When the solution was neutral, both TIR and CR could reach the maximum adsorption capacity of catechol. Fitting results of adsorption isotherms suggested that catechol adsorption on the TIR surface might occur in a monolayer manner and was endothermic. The maximum adsorption capacity of TIR (1.60 mmol/g) fitted by Langmuir model was almost twice than that of conventional resin (CR), while the kinetic properties of TIR did not decrease significantly. In the salt (NaCl or Na2SO4) concentration range of 20 to 80 g/L, the adsorption capacity of TIR was about 10% to 50% higher than that of CR. For resorcinol and quinol, as two competitors in binary system, the selectivity coefficients (α) of TIR to catechol were 1.49 and 5.83, respectively, which were significantly higher than those of CR (0.72 and 1.58, respectively). Adsorption behaviors in different solvents and FT-IR spectra after adsorption verify that the main interactions between TIR and catechol were electrostatic attraction, hydrogen bonding, hydrophobic interaction and π-π interaction. The regeneration experiment and FT-IR spectrum after desorption showed that the structure of TIR was stable before and after desorption, and the desorption rate could reach more than 90%. This study showed TIR had a superior selective adsorption capacity for catechol and provided a facile strategy to prepare selective adsorbent for the target phenolic pollutant.

Detailed investigation of effective trace Cr(VI) removal mechanism by anion exchange resin with phenol–formaldehyde matrix

Prolonged exposure to trace Cr(VI) concentrations in potable water can cause serious health problems in living beings. A weak base anion exchange resin, Duolite A7, showed a large capacity for trace Cr(VI) removal from a background of competing anions present at much higher concentrations, while conventional ion exchangers and adsorbents become ineffective due to lack of selectivity under similar conditions. The objective of this study was to find out the mechanism behind such significant capacity shown by the resin. Fixed-bed column studies showed that the resin was fully exhausted below 4,000 bed volumes (BVs) for pH 7, whereas no breakthrough was observed for 25,000 and 131,000 BVs at pH 5 and 3, respectively. Extensive characterization studies revealed that redox reactions were also occurring inside the resin in addition to ion exchange, where Cr(VI) oxidized the amine functional groups and phenol–formaldehyde matrix while itself getting reduced to Cr(III). Cr(III) formed was either precipitated inside the resin as Cr(OH)3 or bound with the oxidation products such as carboxylic acid groups. Analysis of treated water showed that formaldehyde, a carcinogen, was formed due to oxidative attack of Cr(VI) on the resin and was released in the effluent at trace concentrations. A detailed understanding of the mechanism would motivate the development of such redox-active sorbents for selective trace Cr(VI) removal from contaminated drinking water.

Optimization of protocatechuic acid adsorption onto weak basic anion exchange resins: kinetic, mass transfer, isotherm, and thermodynamic study

Optimization of protocatechuic acid adsorption onto weak basic anion exchange resins: kinetic, mass transfer, isotherm, and thermodynamic study

Adsorption properties of macroporous exchangers functionalized with various weak-base groups for aromatic acids: Coupling DFT simulation with batch experiments

Anion exchange resin has an excellent effect on the removal of aromatic acids in wastewater, while the adsorption affinities of the resins with different functional groups are various. In this work, six macroporous weak-base anion exchange resins were synthesized, and the adsorption characteristics of the resins for three typical aromatic acids including benzenesulfonic acid (BSA), benzoic acid (BA), phenol (PH) were investigated. The results showed that the adsorption performance for BSA and BA on these resins were more sensitive to pH than that for PH. The adsorption capacities of the secondary amine resins to aromatic acid in salt-rich environment were higher than that of the tertiary amine resins. In the binary system, when the adsorption mechanisms of the two adsorbates are overlapped to some extent, the competition between them on the resins was more significant. Density functional theory (DFT) simulations confirmed that the adsorption of BSA by the resins was mainly due to electrostatic interaction, and the adsorption of PH was attributed to hydrogen bond, while BA adsorption was the synergism of these two interactions. The functional resins with high binding energies and high natural bond orbital (NBO) charge transfer had good salt resistances. Furthermore, NaCl aqueous solution was suitable for desorption of BSA on the resins, while the proper desorbent for BA and PH was ethanol. These results indicated that DFT could guide the selection of the functional groups and provided an effective method for the design of selective separation materials for aromatic acids in wastewater.

Removal of arsenic from aqueous solution containing hexafluoroarsenate

Arsenic removal from aqueous solutions containing hexafluoroarsenate or arsenate by strong and weak base anion exchangers was studied by dynamic column tests that were carried out using solution containing arsenic and accompanying anions (chlorides, sulfates and fluorides). The specific flow rate of solution was 6 BV/h. Desorption of arsenic was carried out by 1 mol/L NaOH or 2 mol/L KSCN. All the studied anion exchangers performed well in the absence of accompanying anions. In the presence of chlorides and sulfates, studied exchangers showed high selectivity towards hexafluoroarsenate.

Trace Cr(VI) Removal: Evidence of Redox-Active Ion Exchange by a Weak-Base Anion Exchanger

The presence of Cr(VI) in water, even in trace concentrations, is toxic to numerous animals, plants, and microorganisms. Remediation efforts require selective removal of trace concentrations of Cr(...

An innovative platform exploiting solid microcrystalline cellulose for selective separation of bromate species in drinking water: Preparation, characterization, kinetics and thermodynamic study

It is a major challenge to synthesis a cost-effective, efficient and reliable solid phase extractor with exceptional selectivity, capacity and reproducibility for removal of disinfection by-products (DBPs) in drinking water. Thus, the current study extends the analytical utility of microcrystalline cellulose (MCC) as a novel solid extractor against the underexplored bromate ions at trace levels as one of DBPs in drinking water. The proposed MCC platform was prepared via acid (HCl) hydrolysis of cellulose that was isolated from date pits (DPs). Fourier-transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopic (TEM) and thermal gravimetric analysis (TGA) were used for characterization of MCC sorbent prepared from DPs (D-MCC). Disappearance of the distinct FTIR peaks of hemicellulose and lignin were observed. The particle size of D-MCC ranged from 2.5 to 4 µm and rougher. SEM micrographs exhibited clear, smooth and stretched polymer structures on the surface and confirmed from the energy dispersive X-ray (EDX) spectra. SEM, TEM images and XRD data also revealed surface agglomeration in microstructures with a satisfactory crystallinity index of 80.81%. High stability of D-MCC was confirmed as compared to raw DPs A dual retention mechanism of bromate involving an ion association interaction of “weak base anion exchanger” and an added component of “surface adsorption” by the available surface area of the D-MCC is proposed. The D-MCC sorbent was successfully used for complete removal of BrO3− ions from environmental water samples. The sorbent presented extraordinary sorption capacity towards bromate ions in comparison to the frequently available extractor counterparts. D MCC can be packed in column for complete separation of trace levels of bromate ions from water from large volumes of water samples without decrease in its performance. Thus, this system can be utilized for ultra-trace determination of bromate in water using the standard addition method. The reusability of MCC towards bromate removal from drinking water is also included.

Peculiarities of sulfur dioxide sorption from air by weak base anion exchangers

Peculiarities of sulfur dioxide sorption from air by weak base anion exchangers

Adsorption studies of fluoride on weak base anion exchangers and surface modified strong acid cation exchangers in aqueous medium

Adsorption studies of fluoride on weak base anion exchangers and surface modified strong acid cation exchangers in aqueous medium

Effect of Functional Group Density of Anion Exchange Resins on Removal of p-Toluene Sulfonic Acid from Aqueous Solution

Adsorption using anion exchange resins is an efficient method for the removal of aromatic sulfonic acids (ASAs) from industrial wastewater. In this study, a series of weak-base anion exchangers (SD1–SD5) were synthesized to investigate the effect of functional group density of resins on the adsorption of ASAs from wastewater containing competitive inorganic anions. p-Toluene sulfonic acid (PTSA) was selected as a target pollutant, and Na2SO4 was chosen as the competitive inorganic salt because of its widespread existence in industrial wastewater. Adsorption performances of these resins were evaluated and compared in terms of selectivity, kinetics, isotherms, regeneration, and dynamic adsorption behavior. Importantly, the PTSA uptake increased with the raising content of functional groups on resins in the absence of Na2SO4; however, in the presence of a high level of Na2SO4 (for example, ≥1%), a decrease in the functional group density could improve the adsorption capacity of resins for PTSA. Moreover, desorption and fixed bed column experiments were conducted in all resins, thereby confirming the effect of functional group density of resins on the PTSA adsorption in actual application. In brief, this research will provide a better understanding for the design and preparation of anion exchangers for the effective removal of ASA from wastewater.

Purification and polymerisation of microbial d-lactic acid from DDGS hydrolysates fermentation

A multi-step process was developed for microbial d-lactic acid purification, followed by poly-d-lactic acid (PDLA) synthesis via azeotropic polycondensation process. Several anion exchange resins were screened for their binding capacity using model lactic acid solutions. Amberlite® IRA67 (weak base anion exchange resin) showed the highest lactic acid adsorption, with maximum adsorption capacity, qmax, of 136.11 mg lactic acid / g of resin, and was further selected to purify D-lactic acid from DDGS hydrolysates through a three-step process; (1) treatment with 7% w/v activated carbon, (2) acidification of fermentation broth (Amberlite® IRA120) and (3) adsorption of lactic acid by anion exchange (Amberlite® IRA67). At the end of the purification process, 80.4% (w/w) D-lactic acid was recovered with 91.8% (w/w) purity, indicating the effectiveness of the developed downstream process. Furthermore, a clear yellowish solid polymer with a molecular weight of 3010 Da was obtained, suitable for applications in biomedical and agricultural sectors.