Anion Exchange Mechanism Research Articles

Role of macrocyclic effect in complex formation of palladium(II) with ligands anchored on a solid support

The method for grafting dithiacrown ether and its linear analogue to the silica surface using preliminary prepared organosilicon derivative is developed. The importance of the acylation step in the process of grafting is underlined. The acylation is required to prevent sorption of platinum metals complex anions by the anion exchange mechanism, the probability of which increases due to protonation of the spacer in an acidic medium. The interaction of palladium(II) with anchored ligands in hydrochloric acid media was studied in details. The comparative study of two sorbents revealed that the macrocyclic effect plays a negligible role in binding of palladi um(II) ions. Therefore, linear ligands are preferred for the development of sorbents for molecular recognition of platinum metals ions.

Controlled release of organic-inorganic nanohybrid:cefadroxil intercalated Zn-Al-layered double hydroxide.

BackgroundThe intercalation of an antibiotic drug, cefadroxil (CD), into the inter-gallery of Zn, Al nitrate-layered double hydroxide (LDH) was accomplished using a co-precipitation method. This formed a nanostructured organic–inorganic hybrid material that can be exploited for the preparation of a controlled release formulation.Materials and methodsThe drug–LDH nanohybrid was characterized by using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) thermogravimetric (TG) analysis, X-ray powder diffraction (XRD) and UV–visible (UV–vis) absorption spectroscopy, which confirmed the intercalation process. Release tests of nanohybrid in the presence or absence of NaCl or poly-acrylamide (PAM) were performed in vitro in gastric (pH 1.2), lysosomal (pH 4.0), intestinal (pH 6.8) and blood (pH 7.4) simulated fluid using UV–vis spectroscopy.ResultsAt pH 1.2, LDH was dissolved and intercalated antibiotic released from ZnAl-CD in a molecular form, which led to a significant increase in the antibiotic’s solubility. Results showed that the release of drug from nanohybrid at pH 4.0, 6.8 and 7.4 was a sustained process.ConclusionThis material might reduce side effects by the release of the drug in a controlled manner. However, it was found that the presence of Cl or PAM species in the release media has a negative impact on the release behavior. The weathering mechanism is responsible for the release of CD from the nanocomposite at pH 1.2, while the mechanism of anion exchange may be responsible for the release behavior at pH 4.0, 6.8 and 7.4. A number of kinetic models were chosen to gain more insights into the mechanisms of drug release. At pH 1.2, the zero-order model most satisfactorily explained the release kinetics of CD, while the release data of CD at pH 4.0, 6.8 and 7.4 were governed by Bhaskar kinetics.

Automated solid-phase extraction of phenolic acids using layered double hydroxide-alumina-polymer disks.

The application of layered double hydroxide-Al2 O3 -polymer mixed-matrix disks for solid-phase extraction is reported for the first time. Al2 O3 is embedded in a polymer matrix followed by an in situ metal-exchange process to obtain a layered double hydroxide-Al2 O3 -polymer mixed-matrix disk with excellent flow-through properties. The extraction performance of the prepared disks is evaluated as a proof of concept for the automated extraction using sequential injection analysis of organic acids (p-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid, gallic acid) following an anion-exchange mechanism. After the solid-phase extraction, phenolic acids were quantified by reversed-phase high-performance liquid chromatography with diode-array detection using a core-shell silica-C18 stationary phase and isocratic elution (acetonitrile/0.5% acetic acid in pure water, 5:95, v/v). High sensitivity and reproducibility were obtained with limits of detection in the range of 0.12-0.25μg/L (sample volume, 4mL), and relative standard deviations between 2.9 and 3.4% (10μg/L, n=6). Enrichment factors of 34-39 were obtained. Layered double hydroxide-Al2 O3 -polymer mixed-matrix disks had an average lifetime of 50 extractions. Analyte recoveries ranged from 93 to 96% for grape juice and nonalcoholic beer samples.

Removal of Lead from Water by Liquid-Liquid Extraction using trihexyltetradecylphosphonium Chloride in Different Diluents

The feasibility of ionic liquid trihexyltetradecylphosphonium chloride [THTDP][Cl] as extractant in different diluents for the removal of lead (Pb) from water was investigated using laboratory scale liquid-liquid extraction. The tests were conducted using an extraction mixture which consisted of 5% (v/v) [THTDP][Cl] in different diluents, namely toluene and corn oil. In general, the extraction followed anion exchange mechanism and equilibrium extraction can be achieved at extraction time of 5-10 minutes. In addition, the extraction efficiency was found to decrease when the HCl concentration in Pb solution was increased from 1 M to 3 M for both types of diluents, as a result of competition between excessive Cl- and PbCl42- to form complex with [THTDP] cation. The extraction ability of Pb for [THTDP][Cl] was highly dependent on the types of diluents used where corn oil based extraction mixture showed lower extraction efficiency in comparison to toluene based extraction mixture, as a result of its higher viscosity.

The biosorption potential of modified bottle gourd shell for phosphate: Equilibrium, kinetic and thermodynamic studies

In order to preserve the environment and prevent the occurrence of eutrophication, a new quaternary ammonium biosorbent based on the bottle gourd (Lagenaria vulgaris) shell (QALVS) was prepared and characterized in the present study. The results of FTIR and elemental analyses confirmed the successful modification of the lignocellulosic biomass and showed that 15.68 mg N g-1 was incorporated as cationic ?N+R3 group. The biosorbent was tested to remove phosphate from aqueous solution in batch mode. Kinetic studies indicated that the biosorption of phosphate onto QALVS can be fitted by a non-linear pseudo nth-order model (n ? 1) very well. The Freundlich model provided the best description of the biosorption process. The maximum phosphate biosorption capacity was 16.69 mg P g-1 for QALVS at 20?C and pH 6. Thermodynamic parameters indicate that the biosorption of phosphate by QALVS is exothermic. The anion exchange mechanism was the dominant process, in addition to physisorption. Coexisting ions exhibited a distinct effect on phosphate biosorption with the order of NO3 - > SO4 2- > Cl-. The QALVS biosorbent could be repeatedly used in phosphate biosorption with slight losses in initial biosorption capacities

Facet- and structure-dependent catalytic activity of cuprous oxide/polypyrrole particles towards the efficient reduction of carbon dioxide to methanol

The preparation of cost-effective, stable catalysts for the selective reduction of carbon dioxide (CO2) to C1 products such as methanol is extremely important because methanol can be used directly as a fuel or it can be converted into other value-added products. However, the catalysts currently used for the reduction of CO2 to methanol exhibit poor selectivity, poor stability and very low faradaic efficiency. Herein, we used low-cost, stable cuprous oxide/polypyrrole (Cu2O/Ppy) particles having structures of octahedra and icosahedra (microflowers) that were prepared on linen texture (LT) papers for the selective reduction of CO2 to form a value-added single C1 product, methanol. The Cu2O/Ppy particles possessing both octahedral and microflower shapes with exposed low-index (111) facets and high-index (311) and (211) facets are denoted as Cu2O(OL-MH)/Ppy particles. The as-prepared Cu2O(OL-MH)/Ppy particles exhibited high catalytic activity and selectivity towards the electrochemical reduction of CO2 at -0.85 V vs. RHE to form methanol, with a faradaic efficiency of 93 ± 1.2% and an average methanol formation rate of 1.61 ± 0.02 μmol m-2 s-1. The X-ray photoelectron spectroscopy (XPS) analysis revealed that the pyrrolic nitrogen atoms present in the Ppy shell played a dominant role as active sites for CO2 molecules. The Raman bands of Ppy and Cu2O did not shift even after being subjected to electrolysis for several hours, suggesting superior stability of the Cu2O(OL-MH)/Ppy particles. The high resolution microscopic, spectroscopic, diffraction and electrochemical analysis results clearly revealed that the Ppy shell protected the Cu2O particles and avoided corrosion, dissolution, and structural and crystal facet changes, leading to greater stability. The low-cost, durable, flexible, and catalytically active Cu2O(OL-MH)/Ppy LT paper holds great potential for catalytic, photocatalytic and energy storage applications.

Short-Chain Fatty Acid Transporters: Role in Colonic Homeostasis.

Short-chain fatty acids (SCFA; acetate, propionate, and butyrate) are generated in colon by bacterial fermentation of dietary fiber. Though diffusion in protonated form is a significant route, carrier-mediated mechanisms constitute the major route for the entry of SCFA in their anionic form into colonic epithelium. Several transport systems operate in cellular uptake of SCFA. MCT1 (SLC16A1) and MCT4 (SLC16A3) are H+-coupled and mediate electroneutral transport of SCFA (H+: SCFA stoichiometry; 1:1). MCT1 is expressed both in the apical membrane and basolateral membrane of colonic epithelium whereas MCT4 specifically in the basolateral membrane. SMCT1 (SLC5A8) and SMCT2 (SLC5A12) are Na+-coupled; SMCT1-mediated transport is electrogenic (Na+: SCFA stoichiometry; 2:1) whereas SMCT2-mediated transport is electroneutral (Na+: SCFA stoichiometry; 1:1). SMCT1 and SMCT2 are expressed exclusively in the apical membrane. An anion-exchange mechanism also operates in the apical membrane in which SCFA entry in anionic form is coupled to bicarbonate efflux; the molecular identity of this exchanger however remains unknown. All these transporters are subject to regulation, notably by their substrates themselves; this process involves cell-surface receptors with SCFA as signaling molecules. There are significant alterations in the expression of these transporters in ulcerative colitis and colon cancer. The tumor-associated changes occur via transcriptional regulation by p53 and HIF1α and by promoter methylation. As SCFA are obligatory for optimal colonic health, the transporters responsible for the entry and transcellular transfer of these bacterial products in colonic epithelium are critical determinants of colonic function under physiological conditions and in disease states. © 2018 American Physiological Society. Compr Physiol 8:299-314, 2018.

Screening of Zirconium-Based Metal–Organic Frameworks for Efficient Simultaneous Removal of Antimonite (Sb(III)) and Antimonate (Sb(V)) from Aqueous Solution

Seven kinds of zirconium-based metal–organic frameworks (Zr-MOFs) with different aperture size and organic linkers functionalized with different functional groups (−NH2, −OH, and −SO3H) were screened for their ability to remove antimonite (Sb(III)) and antimonate (Sb(V)) anions from water. Zr-bound hydroxides in Zr-MOFs can simultaneously remove both Sb(III) and Sb(V) via a mechanism of anion exchange. For antimony removal by UiO-66-NH2, the anion exchange seemed to be strengthened due to the Lewis acid–base interactions between the −NH2 groups on the BDC ligand and the antimony oxyanions. Among seven kinds of Zr-MOFs selected here, NU-1000 exhibited fast adsorption kinetics and high removal capacity for both Sb(III) (136.97 mg/g) and Sb(V) (287.88 mg/g), which was much higher than many antimony adsorbents described to date. Uptake of antimony at low concentrations of 100 μg/L (with a remaining antimony concentration of only ∼2 μg/L in 10 min) disclosed that current U.S. Environmental Protection Agency st...

Extraction and separation of multiple platinum group metals from hydrochloric acid solution with sole 1-hexyl-3-methylimidazole-2-thione using microextraction method

In this study, palladium (II), platinum (IV), rhodium (III) and iridium (IV) were sequentially separated with 1-hexyl-3-methylimidazole-2-thione (HMImT) from aqueous hydrochloric acid media by adjustment of hydrochloric acid concentration or in the presence of tin (II) chloride using environmental-friendly microextraction method. It is the first time to use sole extractant to selectively separate four platinum group metals from aqueous solution. Through condition optimization, HMImT shows outstanding extraction capacity (Pd 0.54mmol/g, Pt 0.14mmol/g, Rh 0.82mmol/g) and high extraction percentage to palladium (99.4%), platinum (99.8%), rhodium (99.6%) respectively. The separation coefficient exceeds 10,000 and obtained metals purity reaches 99%. Based on Job's method, FT-IR spectra, UV–vis spectra, 1H NMR spectra and theoretical natural population analysis (NPA), the anion exchange mechanism of HMImT on Pt (IV) extraction was confirmed. By precipitating-calcining method palladium (II), platinum (IV) and rhodium (III) could be recycled in the form of Rh2O3, Pd and Pt2O.

Highly efficient mixed Li+ transport in ion gel polycationic electrolytes

Outstanding Li+ conductivity and diffusivity have been achieved in free-standing ion gel electrolytes synthesized by in-situ photopolymerization of 1-(2-methacryloyloxy)ethyl-3-butylimidazolium bis(trifluoromethane sulfonyl)imide (IMMA) and/or poly(ethylene glycol) methacrylate (EGMA), in the presence of the room temperature ionic liquids 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIFSI), 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide (BMPFSI) and bis(trifluoromethane)sulfonimide lithium salt (LiTFSI). The membranes are easy to handle and thermally stable up to 200ºC. Those containing IMMA in the polymer chain present liquid-like ionic conductivities (up to 10 mS cm−1 at 25ºC), and liquid-like Li+ diffusivities and conductivities (DLi≈4 × 10−11 m2 s−1, σLi≈1.4 mS cm−1 at 25ºC) unreported so far in a solid electrolyte. DLi is not only very high but significantly higher than its counteranions’ diffusivity, DFSI or DTFSI, a very rare behavior in electrolytes where transport is, in principle, ruled by viscosity. It is proposed that in these polycationic electrolytes the motion of Li+ occurs via two different transport mechanisms, the well-known viscosity-governed transport and an additional anion-exchange mechanism that enables very fast Li+ diffusion. This combination has high practical relevance for Li+ batteries as it implies a high contribution of σLi to the overall electrolyte’s conductivity, and it constitutes a breakthrough in the design of polymer-based solid electrolytes for Li.

Selective extraction of vanadium(V) from sulfate solutions into a polymer inclusion membrane composed of poly(vinylidenefluoride-co-hexafluoropropylene) and Cyphos® IL 101

A poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP)-based PIM containing trihexyltetradecylphosphonium chloride (Cyphos® IL 101) as its carrier was developed for the selective extraction of V(V) from sulfate solutions. Various plasticizers/modifiers were tested and best results in terms of rate of extraction and amount extracted were obtained with 2-nitrophenyloctyl ether (NPOE). The optimal PIM composition, with respect to the same criteria was determined to be 35wt% Cyphos® IL 101, 55wt% PVDF-HFP and 10wt% NPOE. Back-extraction of V(V) was achieved using 6molL−1 H2SO4. An anion exchange mechanism is proposed for the extraction of V(V) involving the formation of the complex anion VO2SO4-. The selectivity of the PIM towards V(V) was tested in the presence of Mo(VI), Al(III), Co(II), Cu(II), Fe(III), Mn(II), and Ni(II). Only Mo(VI) was co-extracted with V(V) at pH 2.3. The Mo(VI) interference was eliminated by a two-step separation procedure in which Mo(VI) was extracted at pH 1.1 which was followed by the selective extraction of V(V) at pH 2.3. The PIM was found to be stable over five extraction/back-extraction cycles.

A new Co(III) complex of Schiff base derivative for electrochemical recognition of nitrite anion

The synthesis and characterization of a new Co(III) complex of a salphen-type Schiff base ligand, (E)-2-{[(2-aminopyridin-3-yl)imino]methyl}-4,6-di-tert-butylphenol (HL), are reported. The characterization has been carried out using X-ray single crystallographic, thermogravimetric, and spectroscopic techniques. The complex has been combined with polyvinyl chloride (PVC) membrane of various compositions and tested as an electrochemical electrode towards recognition of several anions. The electrode exhibits exceptional electrochemical recognition for the nitrite $$(\hbox {NO}_{2}^{-})$$ anion in aqueous media. The electrode exhibited a linear response to $$\hbox {NO}_{2}^{-}$$ with a detection limit of $$5.76\,{\upmu }\hbox {M}$$ and displayed a linear Nernstian slope over the nitrite concentration range of $$1.0 \times 10^{-5}$$ – $$1.0\times 10^{-1}\,\hbox {M}$$ in the pH range of 3–7 and a fast response time of less than 10 seconds. Theoretical calculations showed that the sensing could be via anion exchange in the Co(III) complex. SYNOPSIS An octahedral Co(III) complex of the salphen-type Schiff base, (E)-2-{[(2-aminopyridin-3-yl)imino]methyl}-4,6-di-tert-butylphenol, was synthesized, characterized and analyzed for its electrochemical anion recognition property through reversible anion exchange mechanism.

Removal of pertechnetate from aqueous solution using activated pyrolytic rubber char

Low-cost adsorbents, synthesized by pyrolysis of waste rubber (CR) and activated with KOH (CRA), have shown the high removal ability of $${}^{{99{\text{m}}}}{\text{TcO}}_{4}^{ - }$$ from aqueous solutions in wide range of pHs (2–10) with fast adsorption rate. The Langmuir and Freundlich models suggests monolayer and multilayer adsorption of $${}^{{99{\text{m}}}}{\text{TcO}}_{4}^{ - }$$ onto CR and CRA surface, respectively. The removal mechanism of $${}^{{99{\text{m}}}}{\text{TcO}}_{4}^{ - }$$ from solution occurs by replacement with OH− from surface groups (phenolic and/or accompanying carboxylic) of CR and CRA indicating anion exchange mechanism.

Integrated adsorption-membrane filtration process for antibiotic removal from aqueous solution

This study investigated the removal of two widely used antibiotics, norfloxacin (NOR) and ofloxacin (OFL) from aqueous solution by employing a novel integrated adsorption cum membrane filtration process. The application potential of the adsorbent was investigated by evaluating the effect of different process parameters; including solution pH, initial antibiotic concentration and adsorbent dosage. Among these parameters, solution pH significantly affected the removal of antibiotics due to its strong effect on the charges of the adsorbent and the adsorbate. The removal efficiency decreased with an increase in the initial antibiotics concentration and increased with an increase in the adsorbent amount. A maximum removal of 98.7% for NOR and 94.61% for OFL was achieved with 10mg/L initial concentration and at a solution pH of 7. A high removal of NOR as compared with that of OFL was attributed to a high steric hindrance of OFL due to its bulky structure. The adsorption kinetic data for both the antibiotics followed the pseudo second order kinetics, and the sorption isotherm data was best described by the Langmuir model. Further, adsorption of the two antibiotics involved a combination of electrostatic interaction, anion exchange and hydrophobic interaction mechanisms. The FTIR spectrum of the modified LDH obtained before and after adsorption confirmed the adsorbate-adsorbent interaction. Finally, the microfiltration technique using a ceramic membrane was effectively employed to separate the loaded adsorbent from solution to recover and reuse the adsorbent with an aim to reduce the overall cost of the adsorption process.

Selenium Sequestration in a Cationic Layered Rare Earth Hydroxide: A Combined Batch Experiments and EXAFS Investigation.

Selenium is of great concern owing to its acutely toxic characteristic at elevated dosage and the long-term radiotoxicity of 79Se. The contents of selenium in industrial wastewater, agricultural runoff, and drinking water have to be constrained to a value of 50 μg/L as the maximum concentration limit. We reported here the selenium uptake using a structurally well-defined cationic layered rare earth hydroxide, Y2(OH)5Cl·1.5H2O. The sorption kinetics, isotherms, selectivity, and desorption of selenite and selenate on Y2(OH)5Cl·1.5H2O at pH 7 and 8.5 were systematically investigated using a batch method. The maximum sorption capacities of selenite and selenate are 207 and 124 mg/g, respectively, both representing the new records among those of inorganic sorbents. In the low concentration region, Y2(OH)5Cl·1.5H2O is able to almost completely remove selenium from aqueous solution even in the presence of competitive anions such as NO3-, Cl-, CO32-, SO42-, and HPO42-. The resulting concentration of selenium is below 10 μg/L, well meeting the strictest criterion for the drinking water. The selenate on loaded samples could be desorbed by rinsing with concentrated noncomplexing NaCl solutions whereas complexing ligands have to be employed to elute selenite for the material regeneration. After desorption, Y2(OH)5Cl·1.5H2O could be reused to remove selenate and selenite. In addition, the sorption mechanism was unraveled by the combination of EDS, FT-IR, Raman, PXRD, and EXAFS techniques. Specifically, the selenate ions were exchanged with chloride ions in the interlayer space, forming outer-sphere complexes. In comparison, besides anion exchange mechanism, the selenite ions were directly bound to the Y3+ center in the positively charged layer of [Y2(OH)5(H2O)]+ through strong bidentate binuclear inner-sphere complexation, consistent with the observation of the higher uptake of selenite over selenate. The results presented in this work confirm that the cationic layered rare earth hydroxide is an emerging and promising material for efficient removal of selenite and selenate as well as other anionic environmental pollutants.

Two-Dimensional Coordination Polymers with “X”-Shaped Cavities as Adsorbents of Oxoanion Pollutants and Toxic Dyes

The role of cationic and neutral two-dimensional (2D) coordination polymers (CPs) in the efficient capture of inorganic pollutants (chromate and dichromate) and toxic dyes has been explored. Two cationic CPs with Ag(I) salts of BF4– and ClO4– anions and one neutral CP with Cd(NO3)2 of bis(pyridylcarboxamide) ligands have been structurally characterized, and it was found that all of them have isostructural 2D CPs. The sorption of chromate/dichromate by CPs via anion exchange mechanism was shown to depend not only on the nature of the network but also on the nature of the anion present in the as-synthesized host. Among three CPs, the BF4– containing Ag(I) CP exhibited a better ability of sorbing chromate and dichromate from very dilute solution of sorbates (10–4 M). On the other hand, neutral Cd(II) CP containing NO3– ion were found to have a better ability to sorb chromate/dichromate from somewhat concentrated (10–1 M) solutions. Further, BF4– and NO3– containing CPs exhibit selective sorption of chromate ...

Evidence of Multiple Sorption Modes in Layered Double Hydroxides Using Mo As Structural Probe.

Layered double hydroxides (LDHs) have been considered as effective phases for the remediation of aquatic environments, to remove anionic contaminants mainly through anion exchange mechanisms. Here, a combination of batch isotherm experiments and X-ray techniques was used to examine molybdate (MoO42-) sorption mechanisms on CaAl LDHs with increasing loadings of molybdate. Advanced modeling of aqueous data shows that the sorption isotherm can be interpreted by three retention mechanisms, including two types of edge sites complexes, interlayer anion exchange, and CaMoO4 precipitation. Meanwhile, Mo geometry evolves from tetrahedral to octahedral on the edge, and back to tetrahedral coordination at higher Mo loadings, indicated by Mo K-edge X-ray absorption spectra. Moreover, an anion exchange process on both CaAl LDHs was followed by in situ time-resolved synchrotron-based X-ray diffraction, remarkably agreeing with the sorption isotherm. This detailed molecular view shows that different uptake mechanisms-edge sorption, interfacial dissolution-reprecipitation-are at play and control anion uptake under environmentally relevant conditions, which is contrast to the classical view of anion exchange as the primary retention mechanism. This work puts all these mechanisms in perspective, offering a new insight into the complex interplay of anion uptake mechanisms by LDH phases, by using changes in Mo geometry as powerful molecular-scale probe.

Activated carbon-mediated base hydrolysis of alkyl bromides

Activated carbon (AC) is widely used as an adsorbent in water and air purification, but recent studies show that AC can also mediate chemical reactions at ambient temperature, including electron-transfer, redox, free radical, and dehydrohalogenation. Here, we expand the repertoire of such reactions to SN2 base hydrolysis of alkyl bromides. Detailed studies were carried out on the quarantine and pre-shipment fumigant, methyl bromide (MeBr), whose removal from fumigation vent streams is sought due to its ozone-depleting potential. Mixed with a 1M solution of NaOH, ACs are effective adsorbents, but also participate in hydrolysis of MeBr to bromide, methanol, and dimethyl ether. MeBr decay is first order in MeBr and obeys a two-term rate law corresponding to aqueous- and adsorbed-state reactions. The adsorbed-state reaction is, i) unassisted by surface groups, as shown by cycling experiments; ii) 0.83 order in aqueous hydroxide concentration suggesting participation of adsorbed hydroxide; iii) accelerated by pre-adsorption of quaternary ammonium surfactants, which also shift the zeta potential into the positive region; and iv) inhibited by competing inert anions in the order of their chromatographic retention time on ion-exchange resins: Br−<NO3−<ClO4−. The results support an anion exchange mechanism in which hydroxide is attracted to positive sites on the carbon. Normalized to aqueous-phase rate constants, adsorbed-state rate constants for RBr followed the order, R=methyl>ethyl>propyl.

Tracking the Superefficient Anion Exchange of a Dynamic Porous Material Constructed by Ag(I) Nitrate and Tripyridyltriazole via Multistep Single-Crystal to Single-Crystal Transformations.

To avoid the instability and inefficiency for anion-exchange resins and layered double-hydroxides materials, we present herein a flexible coordination network [Ag(L243)](NO3)(H2O)(CH3CN) (L243 = 3-(2-pyridyl)-4-(4-pyridyl)-5-(3-pyridyl)-1,2,4-triazole) with superefficient trapping capacity for permanganate, as a group-7 oxoanion model for radiotoxic pertechnetate pollutant. Furthermore, a high-throughput screening strategy has been developed based on concentration-gradient design principle to ascertain the process and mechanism for anion exchange. Significantly, a series of intermediates can be successfully isolated as the qualified crystals for single-crystal X-ray diffraction. The result evidently indicates that such a dynamic material will show remarkable breathing effect of the three-dimensional host framework upon anion exchange, which mostly facilitates the anion trapping process. This established methodology will provide a general strategy to discover the internal secrets of complicated solid-state reactions in crystals at the molecular level.

Adsorption performance of salicylic acid on a novel resin with distinctive double pore structure

Two approaches were used to synthesize two resins with different pore structures. In one way, the CH2Cl groups in macroporous chloromethylated polystyrene resin were transformed to methylene bridges, and achieved a hypercrosslinked resin with plentiful micropores (denoted GQ-06). In the other way, 50% of the CH2Cl groups in chloromethylated polystyrene resin was used to produce micropores, while the residual 50% of the CH2Cl groups was reacted with 2-aminopyridine, and prepared another resin with double pore structure of hypercrosslinked resin and macroporous resin (denoted GQ-11). The adsorption of salicylic acid (SA) on GQ-11 was investigated using GQ-06 as the reference adsorbent. The effect of pH on the adsorption of SA on GQ-06 was consistent with the dissociation curve of SA. The maximum adsorption capacity of SA on GQ-11 was observed at the solution pH of 2.64. The greater adsorption rate of SA on GQ-11 than that of GQ-06 was attributed to its double pore structure. The multifunctional adsorption mechanism of anion exchange and hydrophobic interaction resulted in the larger equilibrium capacity of SA on GQ-11 than that of GQ-06. GQ-06 and GQ-11 could be regenerated by absolute alcohol and 80% of alcohol −0.5mol/L of sodium hydroxide aqueous solution, respectively.