Zwitterionic Compounds Research Articles

Per- and Polyfluoroalkyl Substances in Contaminated Soil and Groundwater at Airports: A Canadian Case Study.

The occurrence of 93 classes of per- and polyfluoroalkyl substances (PFASs) was investigated at aqueous film-forming foam (AFFF)-impacted sites of four Canadian airports. Surface/subsurface soil and groundwater samples were characterized using high-resolution mass spectrometry (HRMS) and an improved total oxidizable precursor (TOP) assay. PFAS profiles, loads, and spatial trends were highly site-specific, influenced by the AFFF use history, variations in sorption, transport, and in situ transformation potential of PFASs. All sites have been impacted by more than one AFFF chemistry, with the active firefighter training area exhibiting a greater PFAS variety and total PFAS burden than decommissioned sites. Zwitterionic and cationic compounds composed a large percentage (34.5-85.5%) of the total PFAS mass in most surface soil samples in the source zone but a relatively low percentage (<20%) in groundwater samples. Background soils surrounding the source zone contained predominantly unidentified precursors attributed to atmospheric deposition, while in AFFF-impacted soils, precursors originating from AFFFs can be largely captured by HRMS using available suspect lists. Horizontal transfer of PFASs in surface soils was limited, but vertical migration down the soil column occurred even in locations of low permeability. This study provides a critical data set to support developing new priority analyte lists and integrating TOP assay for comprehensive PFAS monitoring at AFFF-impacted sites.

Role of lysine amino acid in zinc‐based ionic thermoplastic elastomer: Dosage‐properties correlation study

AbstractIonic thermoplastic elastomer (TPE) materials have substantial scientific and commercial value due to their recyclable nature and wide adaptive applications. This article presents experimental results and analysis on the effects of the addition of “zwitterionic component” on various properties of maleic anhydride–grafted ethylene–propylene (M‐EPM)–based ionic TPEs. For this purpose, L‐lysine amino acid has been used, which contains a zwitterionic group and a primary amine group. The present work aims to understand how zwitterionic compounds can influence the behavior of the typical ionic TPEs. In this work, a reference ionic TPE sample and different test batches were prepared by varying the dosage of lysine amino acid in the rubber compound. Samples were easily prepared by using conventional rubber processing equipment, such as an internal mixer, two‐roll mill, and hydraulic press. Mechanical and other physical properties were investigated to examine the ionic cluster formation assisted by lysine amino acid. Adverse and favorable aspects of using lysine amino acid in zinc‐based M‐EPM ionic TPE have been discussed comprehensively.

Emerging Designs of Aggregation-Induced Emission Agents for Enhanced Phototherapy Applications

Emerging Designs of Aggregation-Induced Emission Agents for Enhanced Phototherapy Applications

Imparting Strong Antifouling Properties to the Transparent PVB Coating through the Zwitterionic Compound Condensation

Fouling is a ubiquitous and longstanding challenge that causes both economic and environmental problems, especially for underwater detection equipment, as fouling directly limits the normal services and functions of such equipment. Therefore, it is necessary to develop coatings with high transparency and good antifouling performance. Herein, a novel zwitterion compound was synthesized, and an antifouling coating with excellent comprehensive properties was prepared by integrating 3-[[3-(triethoxysilyl)-propyl] amino] propane-1-sulfonic acid (TPAPS) into polyvinyl butyral (PVB) polymer, which possesses excellent mechanical properties and transparency. The physical and chemical, mechanical, and antifouling properties, and the light transmittance of the coating were characterized by the SEM, FT-IR, XPS, UV-VIS. The results show that the coating had good mechanical properties and adhesion to the substrate, and the strong hydration ability of TPAPS endowed the coating with excellent resistance to oil stains and biofouling. More importantly, the structure of the coating was homogenous and its surface roughness was very little, which imparted the coating with high transmittance. This research provides a facile approach for synthesizing high-transparency materials with excellent antifouling and mechanical properties.

Convenient synthesis of zwitterionic calcium(II)-carboxylate metal organic frameworks with efficient activities for the treatment of osteoporosis

Calcium supplementation is effective in alleviating the process of osteoporosis and the occurrence of osteoporotic fractures for people with long-term calcium deficiency. Herein, five water-stable calcium carboxylate compounds, that is, mononuclear coordination compound [Ca(Cbdcp)(H2O)6]·0.5H2O (1, H3CbdcpBr = N-(4-carboxybenzyl)-(3,5-dicarboxyl)pyridinium bromide), and metal organic frameworks (MOFs) {[Ca3(Dcbdcp)2(H2O)12]·2H2O}n (2, H4DcbdcpBr = N-(3,5-dicarboxybenzyl)-(3,5-dicarboxyl)pyridinium bromide), {[Ca(Cmdcp)(H2O)4]·3H2O}n (3, H3CmdcpBr = N-carboxymethyl-(3,5-dicarboxyl)pyridinium bromide), {[Ca(Cdcbp)]·2H2O}n (4, H3CdcbpBr = 3-carboxyl-(3,5-dicarboxybenzyl)-pyridinium bromide) and {[Ca0.5(Cmcp)]·2H2O}n (5, H2CmcpBr = N-carboxymethyl-(3-carboxyl)pyridinium bromide), were synthesized from the reaction of CaCl2 with five different kinds of zwitterionic carboxylate ligands in the presence of NaOH, respectively. Compounds 1–5 were characterized by Fourier-transform infrared (FTIR) spectroscopy, elemental analyses, single-crystal X-ray crystallography, and inductively coupled plasma mass spectrometry (ICP-MS). Compound 1 features a mononuclear structure and MOF 2 with a one-dimensional (1D) structure while MOFs 3 and 5 with 2D layer structures and MOF 4 showing a 3D structure. Compounds 1–5 exhibited good water stability and possessed considerable biocompatibility with primary mice osteoblasts. The in vitro ability of compounds 1–5 in regulating osteoblastic differentiation was studied via alkaline phosphatase (ALP) staining, alizarin red S (ARS) staining, and quantitative real-time polymerase chain reaction (qPCR). Among these 5 compounds, MOF 4 showed the overall best in vitro osteogenic effects. Then, we administrated MOF 4 intragastrically to bilaterally ovariectomized mice for 8 weeks and found that bone loss caused by ovariectomy (OVX) was significantly alleviated. Besides, MOF 4 administration showed no toxic effects in the main organs of the mice. Altogether, zwitterionic carboxylate ligands-based calcium compounds provide a new strategy for calcium agents development.

Bis(2-pyridyl)ditellane as a Precursor for [HgTe]-Based Clusters and Zwitterionic Compounds

Bis(2-pyridyl)ditellane as a Precursor for [HgTe]-Based Clusters and Zwitterionic Compounds

Dimethyl Sulfoxide-Free Cryopreservation of Human Umbilical Cord Mesenchymal Stem Cells Based on Zwitterionic Betaine and Electroporation.

The effective cryopreservation of mesenchymal stem cells (MSCs) is indispensable to the operation of basic research and clinical transplantation. The prevalent protocols for MSC cryopreservation utilize dimethyl sulfoxide (DMSO), which is easily permeable and able to protect MSCs from cryo-injuries, as a primary cryoprotectant (CPA). However, its intrinsic toxicity and adverse effects on cell function remain the bottleneck of MSC cryopreservation. In this work, we cryopreserved human umbilical cord mesenchymal stem cells (UCMSCs) using zwitterionic betaine combined with electroporation without any addition of DMSO. Betaine was characterized by excellent compatibility and cryoprotective properties to depress the freezing point of pure water and balance the cellular osmotic stress. Electroporation was introduced to achieve intracellular delivery of betaine, intending to further provide comprehensive cryoprotection on UCMSCs. Compared with DMSO cryopreservation, UCMSCs recovered from the protocol we developed maintained the normal viability and functions and reduced the level of reactive oxygen species (ROS) that are harmful to cell metabolism. Moreover, the in vivo distribution of thawed UCMSCs was consistent with that of fresh cells monitored by a bioluminescence imaging (BLI) system. This work opens a new window of opportunity for DMSO-free MSC cryopreservation using zwitterionic compounds like betaine combined with electroporation.

Cross platform solutions to improve the zebrafish polar metabolome coverage using LC-QTOF MS: Optimization of separation mechanisms, solvent additives, and resuspension solvents

Untargeted metabolomics has been widely used for studies with zebrafish embryos. Until now, the number of analytical approaches to determine metabolites in zebrafish is limited, and there is a lack of consensus on the best platforms for comprehensive metabolomics analysis of zebrafish embryos. In addition, the capacity of these methods to detect metabolites is unsatisfactory and the confidence level for identifying compounds is relatively low. To improve the metabolome coverage, we mainly focused on the optimization of separation mechanisms, mobile phase additives, and resuspension solvents based on liquid chromatography (LC) coupling to high-resolution mass spectrometry (HRMS) techniques. Moreover, the procedures for optimizing methods were assessed when taking metabolite profiles in both positive and negative ionization modes into account. Four LC columns were studied: C18, T3, PFP, and HILIC. In positive ionization mode, it was strongly recommended to employ the HILIC approach operated at the neutral condition, which led to the presence of more than 4700 features and the annotation of 151 metabolites, mainly zwitterionic and basic compounds, in comparison to reverse phase (RP)-based methods with less than 1000 features. In negative ionization mode, the PFP column operated at 0.02% acetic acid showed the best performance in terms of metabolite coverage: 3100 metabolic features were detected and 218 metabolites were annotated in zebrafish embryos. Metabolite profiles mainly contained acidic and zwitterionic compounds. HILIC-based platforms were complementary to RP columns when analyzing highly polar metabolites. Additionally, it was preferable to reconstitute zebrafish extracts in 100% water for analysis of metabolites on RP columns, with a 20–30% increase in the number of identified metabolites compared to a 50% water in methanol solution. However, water/methanol (1:9, v/v), as resuspension solution, was advantageous over water/methanol (1:1, v/v) for HILIC analysis showing an 8–15% increase in detected metabolites. In total 336 polar metabolites were annotated by the combination of the optimized HILIC (positive) and PFP (negative) approaches. The largest metabolome coverage of polar metabolites in zebrafish embryos was obtained when three approaches were combined (negative PFP and HILIC, and HILIC positive) resulting in more than 420 annotated compounds.

Intramolecularly Double-Donor-Stabilized Stannylene and Its Coordination towards Ag(I) and Au(I) Centers.

The intramolecularly double-donor-stabilized stannylene 1 has been synthesized from the salt-metathesis reaction between two equivalents of lithium pyridine ene-amide L1 and SnCl2 . Compound 1 exhibits dipolar behavior when reacted with B(C6 F5 )3 leading to the zwitterionic compound 2. The reaction of 1 with one equivalent and 0.5 equivalent of AgOTf (OTf=trifluoromethane sulfonate) result in the formation of a stannylene-AgOTf complex 3 and a homoleptic distannylene-silver ionic complex 4, respectively. Analogous to complex 4, the gold(I) complex 5 has been synthesized from the reaction between two equivalents of 1 and 0.5 equivalent of AuCl.SMe2 /Me3 SiOTf. Complex 5 is the first example of homoleptic stannylene-Au(I) ionic complex among the very scarce reports on stannylene-gold(I) coordination complexes. All compounds have been structurally characterized using single crystal X-ray crystallography. Solution-state characterization have been performed using multinuclear NMR techniques. Detailed DFT calculations on the optimized geometries 1 o, 3 o-5 o reveal the change in sp- hybridization on the pyramidal Sn(II) center upon metal coordination and their bonding overlaps.

(IMCS Second Place Best Paper Winner) Investigation of Room Temperature Ionic-Liquid (RTIL) Modified Electrode for Decoupling Soil Electrochemistry

Room temperature ionic liquid (RTIL) is a unique zwitter-ionic compound, that possesses excellent physical and chemical properties, which enables electrochemical applications such as to be utilized as a transducer for probing a complex matrix such as soil. The wide electrochemical window and elevated double layer capacitance of RTIL helps to gauge soil parameters which is helpful to understand soil state. In this work we investigate the utility of RTIL modified electrodes as viable sensors for decoupling soil electrochemistry. Soil plays the key role in plant and crop production and is a vital parameter in the ecological structure of the planet and indispensable in the food ecosystem cycle. Soil health monitoring in the near past has been highly qualitative and speculative with more recent advancements still trying to fill the void of a holistic soil profile. In fields and crop-circles, testing methods to perform in-situ profiling however from one lab is likely to vary with another and hence results are not universally compatible. Additionally, these normalized techniques ideally involve empirical approaches, extensive sample preparation which adds on to a temporal factor along with equipment for extraction and subsequently-analysis. This therefore-stimulates the need for a testing methodology that is capable of rapid analysis in an in-situ environment that can be applicable universally.In this paper, we focus on: a rapid electrochemical point probing mechanism that acts as a soil state evaluation platform via a 3-electrode sensor modified by a widely characterized-RTIL [BMIM] [BF4] interfacial transducer medium. The proposed quantitative model –‘DENSE’ probes the soil diffuse double layer (DDL) dielectric to evaluate a thorough chemical profile of the soil matrix. The experimental design was implemented to capture the effect of electroactive species in the soil matrix altered by adding nutritional amendments. Non-faradaic probing was then performed in this design to gauge the inherent capacitive modulations of the soil system as a function its compositional changes. Therefore, by looking at the rate of electrochemical activity and inherent soil dielectric changes driven by an RTIL interfacial layer, it is possible to decouple information on nutrient availability in soils with potential for application towards temporal soil analysis.Figure: (A) Equivalent-circuit (DENSE) model of the soil-water matrix and a schematic representation of the model with respect to the electrode-electrolyte interface (B) Impedance nyquist plot and (C) Bode-phase to denote the pseudo-capacitive dominant nature of the soil matrix (1:1, 1:2) and the comparatively resistive behavior of the baseline and 2:1 mixture Figure 1

Significantly Red-Shifted Emissions of Nonconventional AIE Polymers Containing Zwitterionic Components.

Nonconventional luminescence polymers without any aromatic structures have attracted great interest from researchers due to their special structure and excellent biocompatibility. However, these materials mostly emit in the blue or green region, in which preparation of materials with long-wavelength (especially near-infrared) emission is still a great challenge. In this work, it is found that 2-(dimethyl amino) ethyl methacrylate (DMA) and itaconic anhydride (ITA) undergo a ring-opening reaction at room temperature, and subsequently generate zwitterionic compound (IDMA). Based on the clustering-triggered emission (CTE) mechanism, ionic bond can effectively promote the isolated electron-rich chromophores to form new emissive clusters with extended electron delocalization. Herein, two oligomers (P1 and P2) with different fluorescence emissions by controlling the concentration of zwitterionic monomers before polymerization are synthesized. It is worth noting that the maximum emission wavelength of P2 at high concentration is up to 712 nm, which is very rare in previous reports. In addition, the resulting oligomer (P2) shows typical aggregation-enhanced emission (AEE), excitation-dependent fluorescence, temperature-sensitive emission, and solvatochromism. The cytotoxicity assay demonstrates that P2 was low toxic to Huh7 and LM3 cells, and suitable for cell imaging. This research provides the possibility for rational molecular design and the feasibility of luminescence regulation.

Leflunomide Sustained Skin Delivery Based on Sulfobetaine-Modified Chitosan Nanoparticles Embedded in Biodegradable Polyesters Films.

The aim of the present study was to prepare a leflunomide (LFD) sustained release transdermal delivery system for the treatment of psoriasis. In this context, LFD-loaded nanoparticles (NPs) based on either neat chitosan (CS) or CS modified with [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SDAEM, a sulfobetaine zwitterionic compound) were initially prepared via ionotropic gelation and characterized in terms of in vitro dissolution, physicochemical, and antibacterial properties. Results showed that the use of the SDAEM-modified CS resulted in the formation of LFD-loaded NPs with improved wetting and solubilization properties, better in vitro dissolution profile characteristics (i.e., higher dissolution rate and extent), and improved (enhanced) antibacterial properties. The resultant LFD-loaded NPs were then embedded in suitable thin-film skin patches, prepared via spin-coating, utilizing two different biodegradable polyesters, namely methoxy polyethylene glycol-b-poly(L-lactide) (mPEG-b-PLA, at a ratio of 25/75 mPEG to PLA) and poly(lactic-co-glycolic acid) (PLGA at a ratio of 75/25 DL-lactide/glycolide copolymer). Results showed the formation of polymeric thin-films with no agglomeration (or trapped air) and uniform structure in all cases, while the LFD-loaded NPs were successfully embedded in the polymeric matrix. Analysis of the obtained in vitro dissolution profiles revealed a sustained release profile of the drug for up to approximately twelve days, while between the two proposed systems, the use of CS-SDAEM NPs (independently of the polyester type) was the most promising formulation approach.

Two Faces of Water in the Formation and Stabilization of Multicomponent Crystals of Zwitterionic Drug-Like Compounds

Two new hydrated multicomponent crystals of zwitterionic 2-aminonicotinic acid with maleic and fumaric acids have been obtained and thoroughly characterized by a variety of experimental (X-ray analysis and terahertz Raman spectroscopy) and theoretical periodic density functional theory calculations, followed by Bader analysis of the crystalline electron density) techniques. It has been found that the Raman-active band in the region of 300 cm−1 is due to the vibrations of the intramolecular O-H...O bond in the maleate anion. The energy/enthalpy of the intermolecular hydrogen bonds was estimated by several empirical approaches. An analysis of the interaction networks reflects the structure-directing role of the water molecule in the examined multicomponent crystals. A general scheme has been proposed to explain the proton transfer between the components during the formation of multicomponent crystals in water. Water molecules were found to play the key role in this process, forming a “water wire” between the COOH group of the dicarboxylic acid and the COO– group of the zwitterion and the rendering crystal lattice of the considered multicomponent crystals.

Dual effects of long-chain alcohols in phase change capture of SO2: Increasing mutual solubility and decreasing product viscosity

To realize the goal of energy-saving SO2 capture process, a series of novel SO2 phase change absorbents (SPCAs) composed of 2-[2-(Dimethylamino)ethoxy]ethanol (DMEE)/long-chain alcohols/hexadecane were investigated in this work. The long-chain alcohols had dual effects in SPCAs, i.e., increasing mutual solubility of DMEE and hexadecane, and decreasing viscosity of the absorption products. Three alcohols, including butyl, hexyl and decyl alcohol, could turn the immiscible mixture of DMEE and hexadecane into homogeneous solution to form SPCAs. The decyl alcohol in absorption product could efficiently decrease the viscosity from 2338.1 mPa·s to 362.02 mPa·s, which is beneficial to gas-liquid mass transfer and fluid transport process. Meanwhile, the NMR and FTIR results indicated that DMEE chemically absorbed SO2, forming a zwitterionic alkyl sulfite compound. The long-chain alcohol formed hydrogen bonds with the alkyl sulfite and it didn't change the reaction mechanism. Noteworthy, the SPCA can absorb 0.823 mol SO2/mol DMEE (0.396 g SO2/g DMEE) at 293.15 K and 0.002 atm, which was exceptionally attractive. Furthermore, the absorbed SO2 could be partly released under vacuum at 110 °C and the net cycle capacity can reach 73% ~ 74% of the maximum capacity, which indicated the SPCAs have a promising application prospect.

Synthesis and Structure of Nido-Carboranyl Azide and Its "Click" Reactions.

Novel zwitter-ionic nido-carboranyl azide 9-N3(CH2)3Me2N-nido-7,8-C2B9H11 was prepared by the reaction of 9-Cl(CH2)3Me2N-nido-7,8-C2B9H11 with NaN3. The solid-state molecular structure of nido-carboranyl azide was determined by single-crystal X-ray diffraction. 9-N3(CH2)3Me2N-nido-7,8-C2B9H11 was used for the copper(I)-catalyzed azide-alkyne cycloaddition with phenylacetylene, alkynyl-3β-cholesterol and cobalt/iron bis(dicarbollide) terminal alkynes to form the target 1,2,3-triazoles. The nido-carborane-cholesterol conjugate 9-3β-Chol-O(CH2)C-CH-N3(CH2)3Me2N-nido-7,8-C2B9H11 with charge-compensated group in a linker can be used as a precursor for preparation of liposomes for Boron Neutron Capture Therapy (BNCT). A series of novel zwitter-ionic boron-enriched cluster compounds bearing a 1,2,3-triazol-metallacarborane-carborane conjugated system was synthesized. Prepared conjugates contain a large amount of boron atom in the biomolecule and potentially can be used for BNCT.

Zwitterionic π-coordination compounds of copper(I) with monosubstituted alkynes: synthesis, crystal and electronic structure of two copper(I) halide π-complexes with 4-amino-1-propargylpyridinium

Crystals of two mononuclear π-coordination compounds of copper(I) halide with 4-amino-1-propargylpyridinium cation – [(HC≡CCH2NC5H4NH2)CuBr2] (1) and [(HC≡CCH2NC5H4NH2)CuCl1.61 Br0.39] (2) – were obtained in the CuX–H2O–(HC≡CCH2NC5H4 NH2)Br system (HC≡CCH2N+C5H4NH2 is 4-amino-1-propargylpyridinium cation (app +), X=Cl or Br). The purity and identity of the synthesized compounds were verified by elemental analysis and IR spectroscopy. The compounds were structurally characterized using X-ray single crystal method and are isostructural. Both crystals are built of zwitterionic appCuX 2 units, in which triple C≡C bond is coordinated to only one copper(I) ion. The Cu–m distance (m is the middle of the C≡C bond) is 1.933(5) and 1.917(3) Å for 1 and 2, respectively. The predisposition of copper(I) halides to coordination polymer self-assembly through Cu–X···Cu bridge formation is not realized in 1 and 2. However, the ≡C–H···Х and N–H···Х hydrogen bonds along with π–π stacking of 4-aminopyridinium groups compensate an absence of the structure-forming interaction Cu–X···Cu. DFT calculations of an electron structure of [(app)CuCl2] were carried out (the restricted Hartree–Fock (RHF) method with a 6–31 G* orbital basis set). Calculated values of the charge density distribution on atoms as well as the constructed molecular orbitals (MOs) are in agreement with stereochemical parameters of the (Cu(I)–(C≡C))-core of both coordination compounds.

Zwitterionic compounds are less ecotoxic than their analogous ionic liquids

Zwitterionic compounds are less ecotoxic than their analogous ionic liquids.

Halogen-containing heteroaromatic carbenes of the 1,2,4-triazole series and their transformations.

A series of new stable halogenated carbenes, 1-tert-butyl-3,4-diaryl-1,2,4-triazol-5-ylidenes, has been synthesized. According to quantum chemical calculations, 4-(2,3,4-trifluorophenyl)-substituted 1-tert-butyl-3,4-diaryl-1,2,4-triazol-5-ylidene is the least basic in comparison with the known sterically open stable heteroaromatic carbenes. Upon heating in organic solvents these carbenes undergo a tandem induced reaction thereby forming 5-amidino-1,2,4-triazoles. The interaction of carbenes with benzylidenemalononitrile, propanesultone and phenyl isothiocyanate results in zwitterionic compounds of the 1,2,4-triazole series. The data for X-ray diffraction study of 1-tert-butyl-3-phenyl-4-(2,4-difluorophenyl)-1,2,4-triazol-5-ylidene, its protonated salt, complex with copper(i) iodide, related complex of 1-tert-butyl-3-phenyl-4-(2-trifluoromethylphenyl)-1,2,4-triazol-5-ylidene, and adduct of 1-tert-butyl-3-phenyl-4-(4-bromophenyl)-1,2,4-triazol-5-ylidene and propansultone are given.

Spatial Trends of Anionic, Zwitterionic, and Cationic PFASs at an AFFF-Impacted Site.

Soil and groundwater from an aqueous film-forming foam (AFFF)-impacted site were sampled at high resolution (n = 105 for soil, n = 58 for groundwater) and analyzed for an extensive list of anionic, zwitterionic, and cationic poly- and perfluoroalkyl substances (PFASs). Spatial trends for perfluoroalkyl acids and many precursors enabled a better understanding of PFAS composition, transport, and transformation. All PFASs without analytical standards were semi-quantified. Summed PFAS and individual PFAS concentrations were often higher at depth than near the surface in soil and groundwater. Zwitterionic and cationic compounds composed a majority of the total PFAS mass (up to 97%) in firefighter training area (FTA) soil. Composition of PFAS class, chain length, and structural isomers changed with depth and distance from the FTA, suggesting in situ transformation and differential transport. The percentage of branched perfluorooctane sulfonate increased with depth, consistent with differential isomeric transport. However, linear perfluorooctanoic acid (PFOA) was enriched, suggesting fluorotelomer precursor transformation to linear PFOA. Perfluorohexane sulfonamide, a potential transformation product of sulfonamide-based PFASs, was present at high concentrations (maximum 448 ng/g in soil, 3.4 mg/L in groundwater). Precursor compounds may create long-term sources of perfluoroalkyl acids, although many pathways remain unknown; precursor analysis is critical for PFAS fate and transport understanding.

Magnetic nanocomposite based on montmorillonite, Fe oxides, and hydrothermal carbon: Synthesis, characterization and pollutants adsorption tests

This work presents the synthesis and characterization of montmorillonite-Fe oxides (Mt-Mag) and Mt-Fe oxides-carbon (Mt-Mag-C) systems as adsorbent materials, prepared by efficient and low-cost procedures. Fe oxides were synthesized by alkaline oxidation in the presence of nitrates while carbonization was hydrothermally synthesized. The adsorption capacity of the synthesized materials was tested against different pollutants (norfloxacin, thiabendazole, thiophanate-methyl, oxytetracycline, P4R and Cr(VI)). Fe particles and carbon were not homogeneously distributed while Mt-Mag-C sample presented a lower specific surface area and porosity than Mt-Mag, related to carbon presence, while magnetic nanoparticles seem not to block Mt external pores. Both materials revealed negative surface charge, indicating that is dominated by montmorillonite. Besides, Mt structure seems to be modified by both Fe oxides and carbon synthesis. The magnetic response was higher in Mt-Mag-C than in Mt-Mag, indicating Fe phases modifications during carbonization. The principal identified Fe oxide was magnetite, with minor contributions of paramagnetic Fe3+, goethite, and paramagnetic relaxation, with a significantly increased of the spectral area of the latter in Mt-Mag-C. Fe concentration determined by Mössbauer spectroscopy resulted higher on Mt-Mag-C than Mt-Mag, indicating that Fe atoms located at the interlayer space of montmorillonite, that give not Mössbauer signal, are exposed by sonication and carbon synthesis, and new magnetite particles are formed through the reduction of Fe3+ atoms in dextrose aqueous solution. The paramagnetic relaxation increase is related to new magnetite particles, that, because of carbon presence, cannot be magnetically coupled. A significant sorption capacity was found for cationic and zwitterionic compounds, revealing the relevance of electrostatic interaction. The magnetic response of Mt-Mag-C and the results of sorption tests for cationic and zwitterionic compounds, claims Mt-Mag-C as a promising sorbent material.