Sulfonic Acid Functionality Research Articles

Electrical Conductivity, Thermo-Mechanical Properties, and Cytotoxicity of Poly(3,4-Ethylenedioxythiophene):Poly(Styrene Sulfonate) (PEDOT:PSS)/Sulfonated Polyurethane Blends.

Electrically conductive polymeric materials have recently garnered significant interest from researchers due to their potential applications in the biomedical field, including medical implants, tissue engineering, flexible electronic devices, and biosensors. Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is considered the most successful conducting polymer due to its higher electrical conductivity and chemical stability, but it suffers from limited solubility in common organic solvents, poor mechanical properties, and low biocompatibility. An area of tremendous interest is in combining PEDOT:PSS with another polymer to form a blend or composite material in order to access the beneficial properties of both materials. However, the hydrophilic nature of PEDOT:PSS makes it difficult to produce composites with non-polar polymers. In order to overcome these problems, we have specifically designed and synthesized two new sulfonated polyurethanes (PUS) with high sulfonic acid functionality. The two polyurethanes, one water-soluble (PUS1) and one water-insoluble (PUS2), were used to make blends with two commercially available PEDOT:PSS formulations (CleviosTM FET and PH1000). Solvent cast films on glass substrates were made from water-soluble PEDOT:PSS/PUS1 blends while free-standing films of PEDOT:PSS/PUS2 blends were fabricated by compression-moulding. Ethylene glycol was used as conductivity enhancer, which showed an increase in the conductivity by several orders of magnitude in most of the compositions investigated. The highest conductivity of 438 S cm-1 was achieved for the blend with 80 wt% of PEDOT:PSS (PH1000) in PUS1.

Enhancing nanofiltration membrane selectivity between mineral salts and organic pollutants by sulfonic acid functionalization for drinking water treatment

Efficient removal of natural organic matter (NOM) and organic micropollutants (OMPs) while preserving essential mineral salts is a critical goal of high-quality drinking water production, which has not been satisfyingly achieved by available nanofiltration (NF) membranes. In this study, a facile modification strategy was developed to enhance membrane salt/organics selectivity, purposely utilizing the advantages of sulfonic acid groups including high hydrophilicity, strong acidity and low complexation propensity for divalent cations. The post-treatment using a heated alkaline solution of taurine endowed the membrane with reduced active layer thickness, properly enlarged pore size and more favorable surface characteristics inheriting from grafted sulfonic acid groups. Compared to the control one, the optimal modified membrane exhibited a more than doubled water permeance and significantly reduced rejections of Ca2+ and Mg2+, while maintaining a high removal capacity for OMPs. The membrane superiority in the rejection selectivity between mineral salts and NOM was further demonstrated for natural surface water treatment, which outperformed a variety of commercial NF membranes. Improved dual resistance to Ca2+-involved organic fouling and scaling was also achieved by the sulfonic acid functionalized membrane with a higher passage of Ca2+. This study provides insights on the fit-for-purpose enhancement of membrane performance for more efficient water treatment.

Sulfonic acid (-HSO3) functionalization effect on graphene oxide membrane by (3 mercaptopropyl) trimethoxysilane and their applications in hydrogen membrane fuel cells

Conventional proton exchange membrane fuel cells (PEMFCs) use a perfluorinated ionomer membrane, e.g., Nafion®, which is expensive and subject to a rigorous synthesis process. Graphene oxide membrane (GOM) is acknowledged as a promising alternative electrolyte due to its hydrophilic nature and attractive proton conductivity in wet conditions. However, GOM loses its negative surface functional groups by hydrogen gas at the anode during operation in PEMFCs, resulting in increased electronic conductivity. In addition, two-dimensional graphene oxide (GO) nanosheets exhibited a larger anisotropy difference in proton conductivity compared to Nafion®. In this study, (3-mercaptopropyl)trimethoxysilane (MPTS, HS(CH2)3Si(OCH3)3) was reacted with the surface of GO nanosheet (M-GOM) by vigorous stirring, where unreacted MPTS was partially removed by a rinsing cycle except the M-GOM powder. Reactive MPTS has two essential reactions which were carried out by forming a hydrolysis reaction (Si-OCH3 to Si-OH) and a condensation reaction (Si-OH to Si-O-Si). The thiol groups of MPTS were oxidized to sulfonic acid groups (-HSO3) to provide high proton conducting stations with GO functional groups (M-GOM/oxid) and compared with non-oxidized thiol groups in a GO matrix (M-GOM/unoxid). The superior –HSO3 effect on M-GOM have reported for proton conductivity, physicochemical properties, ion exchange capacity, thermal stability, gas permeability and fuel cell performance. Furthermore, a hydrogen-permeable metal layer was deposited by a DC magnetron sputter to increase mechanical strength and reduce fuel crossover. A dual-layer membrane composed of M-GOM/unoxid or M-GOM/oxid and Pd thin film was analyzed as an electrolyte for a hydrogen membrane fuel cell (HMFC), which simultaneously performs two roles, an anode catalyst and an electrolyte.

Proton Transport Functionality-Enabled Carbon Support for Improved Fuel Cell Performance and Durability.

A novel Monarch carbon material with proton conduction capability due to the presence of sulfone/sulfoxide/sulfonic groups on the surface was evaluated as a potential cathode catalyst support to enable an electrode design with low ionomer content in proton exchange membrane (PEM) fuel cells. X-ray photoelectron spectroscopy of the carbon support confirmed the sulfonic acid functionality, while dynamic vapor sorption measurements proved higher water uptake. Electrochemical impedance spectroscopy of the PtCo/Monarch electrodes showed higher proton conductivity than state-of-the-art PtCo/C with decreasing ionomer to carbon (I/C) content due to the presence of sulfonic acid functional groups on the carbon support surface. Fuel cell performance and durability measurements showed better high-current density performance for PtCo/Monarch with a 75% lower ionomer content in the electrode compared to that of PtCo/C. Our studies indicate that Monarch carbon could be a viable alternative support for PEM fuel cell catalyst applications.

Enhanced Four-Electron Selective Oxygen Reduction Reaction at Carbon Nanotubes-Supported Sulfonic Acid-Functionalized Copper Phthalocyanine.

In the present work, oxygen reduction reaction (ORR) is explored in an acidic medium with two different catalytic supports (multi-walled carbon nanotubes (MWCNTs) and nitrogen-doped multi-walled carbon nanotubes (NMWCNTs)) and two different catalysts (copper phthalocyanine (CuPc) and sulfonic acid functionalized CuPc (CuPc-SO3-)). The composite, NMWCNTs-CuPc-SO3- exhibits high ORR activity (assessed based on the onset potential (0.57 V vs. reversible hydrogen electrode) and Tafel slope) in comparison to the other composites. Rotating ring disc electrode (RRDE) studies demonstrate a highly selective four-electron ORR (less than 2.5% H2O2 formation) at the NMWCNTs-CuPc-SO3-. The synergistic effect of the catalyst support (NMWCNTs) and sulfonic acid functionalization of the catalyst (in CuPc-SO3-) increase the efficiency and selectivity of the ORR at the NMWCNTs-CuPc-SO3-. The catalyst activity of NMWCNTs-CuPc-SO3- has been compared with many reported materials and found to be better than several catalysts. NMWCNTs-CuPc-SO3- shows high tolerance for methanol and very small deviation in the onset potential (10 mV) between the linear sweep voltammetry responses recorded before and after 3000 cyclic voltammetry cycles, demonstrating exceptional durability. The high durability is attributed to the stabilization of CuPc-SO3- by the additional coordination with nitrogen (Cu-Nx) present on the surface of NMWCNTs.

Sulfonated magnetic graphite carbon nitride solid-phase extraction-ultra performance liquid chromatography-tandem mass spectrometry for screening malachite green and leucomalachite green in freshwater fish

Malachite green (MG) and its metabolite, leucomalachite green (LMG), exert toxic effects on the human body. The use of these dyes is illegal, but they are still detected in aquatic products. Freshwater fish are aquatic products with the high non-qualified rates. Therefore, the sensitive screening of MG and LMG in freshwater fish is of great importance to ensure the safety of aquatic products. Owing to the low contents of MG and LMG in fish and the complex matrix of actual samples, sample preparation is required before detection to purify impurities and enrich the target compounds. Graphite carbon nitride (GCN), a polymer material composed of C, N, and H, has good chemical and thermal stability, a large specific surface area, and a large number of active sites. It has a wide range of application prospects in adsorption and can be used in food safety testing when compounded with Fe3O4 to form magnetic graphite carbon nitride (MGCN). In this study, sulfonated magnetic graphite carbon nitride (S-MGCN) was prepared by further functionalizing MGCN with sulfonic acid. After characterization by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and vibrating sample magnetometry (VSM), a magnetic solid-phase extraction (MSPE) method based on S-MGCN was established to extract MG and LMG from freshwater fish. The targets were screened using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Following sulfonic acid functionalization, S-MGCN showed increased electrostatic interactions based on the MGCN adsorption mechanism, which includes hydrogen bonds and π-π interactions; thus, its adsorption efficiency was significantly improved. The matrix effects were -42.21% and -33.77% before functionalization, -11.40% and -7.84% after functionalization, thus confirming that S-MGCN has significant matrix removal ability. Given that S-MGCN demonstrated excellent efficiency as an MSPE adsorbent, the adsorption conditions for S-MGCN were optimized. The optimal conditions were as follows: adsorbent dosage, 15 mg; adsorption time, 2 min; solution pH, 5; and ionic strength, not adjusted. Under these conditions, the adsorption efficiency of S-MGCN could reach 94.2%. Different organic solvents were used to elute adsorbed MG and LMG, and the desorption efficiency peaked when 1%(v/v) ammonia acetonitrile was used as the elution solvent. The elution volume was also optimized, and a maximum desorption efficiency of 93.2% was obtained when 1 mL of 1%(v/v) ammonia acetonitrile was added to S-MGCN. The limits of detection (LODs) and quantification (LOQs) of the two targets were determined at signal-to-noise ratios (S/N) of 3 and 10, respectively. The LODs and LOQs were 0.075 μg/kg and 0.25 μg/kg, respectively. The linear ranges of the two target compounds were 0.25-20.0 μg/kg with correlation coefficients (r) greater than 0.998. To assess accuracy and precision, we prepared spiked samples at three levels (low, medium, and high) with six parallel samples per level (n=6). The recoveries ranged from 88.8% to 105.9%. The intra- and inter-day relative standard deviations were 5.4%-13.7% (n=6) and 3.3%-11.1% (n=3), respectively. Compared with the national standard method, the proposed method features simpler sample pretreatment procedures, less use of organic reagents (5 mL), and a shorter extraction time (2 min); moreover, the method does not require complicated elution steps, and the eluent can be directly analyzed by UPLC-MS/MS. The test results of actual samples were consistent with those obtained via the national standard method, thus confirming the practical feasibility of the developed method. The proposed MSPE method based on S-MGCN is an efficient and environmentally friendly method that could provide a new methodological reference for the sensitive screening of MG and LMG in actual samples.

Design of molecularly imprinted resin material with sulfonic acid functionalization for enantioseparation of (±)-cathine.

In the current work, an enantioselective imprinting technique was used to develop a very selective adsorbent for the (+)-cathine ((+)-Cat) enantiomer. The phenolic sulfonamide produced from 2,4-dihydroxybenzenesulfonic acid (HBS) and (+)-Cat ((+)-Cat-HBS) was initially synthesized by triphenylphosphene activation and subsequently involved in condensation polymerization with resorcinol in the presence of formaldehyde under acidic conditions. Alkaline sulfonamide bond-breaking was subsequently employed to separate the (+)-Cat template from the polymer, and the resulting imprinted resin ((+)-CIP) displayed high selectivity for the (+)-Cat, with a capacity of 225 ± 2mg/g. Studies of selectivity also showed that the (+)-Cat enantiomer was preferred over its counterpart because of the development of configurationally matching receptors. In addition, the produced resin was used for the enantioresolution of (±)-Cat racemate by column method, yielding a loading supernatant solution with an enantiomeric excess of (+)-Cat 50% and a recovery eluant solution with an excess of (-)-Cat 85%.

Effect of copper ions on transformation of organic sulfur in cationic exchange resins in Li2CO3–Na2CO3–K2CO3 molten-salt system

Cationic exchange resins (CERs) were applied for purification and clarifying process of radioactive wastewater in nuclear industry, which was a kind of sulfur-containing organic material. Molten-salt oxidation (MSO) method can be applied for the treatment of spent CERs and the absorption of acid gas (such as SO2). The experiments about the molten salt destruction of the original resin and Cu ions doped resin were conducted. The transformation of organic sulfur in Cu ions doped resin was investigated. Compared with the original resin, the content of tail gas (such as CH4, C2H4, H2S and SO2) released from the decomposition of Cu ions doped resin was relatively high at 323–657 °C. Sulfur elements in the form of sulfates and copper sulfides were fixed in spent salt through XRD analysis. The XPS result revealed that the portion of functional sulfonic acid groups (-SO3H) in Cu ions doped resin was converted into sulfonyl bridges (-SO2-) at 325 °C. With the enhancement of temperature, sulfonyl bridges (-SO2-) were further decomposed to sulfoxides sulfur (-SO-) and organic sulfide sulfur. The destruction of thiophenic sulfur to H2S and CH4 was prompted by copper ions in copper sulfide. Sulfoxide were oxidized to the sulfone sulfur in molten salt. Sulfones sulfur consumed by reduction of Cu ions at 720 °C was more than it produced by oxidation of sulfoxide through XPS analysis, and the relative proportion of sulfone sulfur was 16.51%.

A Metal-Organic Framework Based Quasi-Solid-State Electrolyte Enabling Continuous Ion Transport for High-Safety and High-Energy-Density Lithium Metal Batteries.

Solid-state lithium metal batteries are promising next-generation rechargeable energy storage systems. However, the poor compatibility of the electrode/electrolyte interface and the low lithium ion conductivity of solid-state electrolytes are key issues hindering the practicality of solid-state electrolytes. Herein, rational designed metal-organic frameworks (MOFs) with the incorporation of two types of ionic liquids (ILs) are fabricated as quasi-solid electrolytes. The obtained MOF-IL electrolytes offer continuous ion transport channels with the functional sulfonic acid groups serving as lithium ion hopping sites, which accelerate the Li+ transport both in the bulk and at the interfaces. The quasi-solid MOF-IL electrolytes exhibit competitive ionic conductivities of over 3.0 × 10-4 S cm-1 at room temperature, wide electrochemical windows over 5.2 V, and good interfacial compatibility, together with greatly enhanced Li+ transference numbers compared to the bare IL electrolyte. Consequently, the assembled quasi-solid Li metal batteries show either superior stability at low C rates or improved rate performance, related to the species of ILs. Overall, the quasi-solid MOF-IL electrolytes possess great application potential in high-safety and high-energy-density lithium metal batteries.

Enhanced proton conductivity by incorporating sulfonic acid groups into a zirconium-based metal-organic framework via ligand exchange

Herein, the postsynthetic ligand exchange process was adopted to construct a series of 1,4-naphthalenedicarboxylic acid (H2NDC) and 6-sulfonate-1,4-naphthalenedicarboxylic acid (H3SNDC) based Zr(IV)-MOFs (Zr-(NDC)x (SNDC)1-x). This strategy anchored functional sulfonic acid groups in the pore of the MOFs. Among them, Zr-(NDC)0.3(SNDC)0.7 exhibited outstanding proton conductivity of 3.18 ✕ 10−4 S cm−1 at 90 °C and 98% relative humidity (RH), which was approximately three orders of magnitude greater than that of pristine Zr-NDC. This work demonstrated a facile in situ ligand exchange approach for constructing functional group modified MOFs with high proton conductivity.

Unprecedented C-C Bond Formation via Ipso Nucleophilic Substitution of 2,4-Dinitrobenzene Sulfonic Acid with Active Methylene Compounds.

The sulfonic acid functionalization of sufficiently electron-deficient benzene sulfonic acids undergoes ipso nucleophilic substitution with various active methylene compounds, leading to new C-C bond formation. Good to excellent yields are obtained under mild conditions without transition-metal (Pd or Cu) catalyst, PTC, and ligand. No solid waste is generated. It is a highly effective strategy for incorporating various active methylene compounds into the o-nitro-substituted benzene ring. This method has been applied not only for synthesizing APIs but also in materials chemistry. It shows a novel route for creating heavily crowded all-carbon quaternary centers. Carbon-carbon bond formation by substituting a sulfonic acid group was unknown.

Reversible Discrete-to-Extended Metal-Organic Polyhedra Transformation by Sulfonic Acid Surface Functionalization.

Metal-organic polyhedra (MOPs) are molecular porous units in which desired functionalities can be installed with precise geometrical and compositional control. By combing two complementary chemical moieties, such as sulfonic acid groups and Rh(II)-carboxylate paddlewheel, we synthesized a robust water-soluble cuboctahedral MOP with excellent features in both solution and solid states. Herein, we demonstrate that the superior chemical stability of the Rh2 unit and the elevated number of functional groups on the surface (24 per cage) result in a porous cage with high solubility and stability in water, including acidic, neutral, and basic pH conditions. We also prove that the sulfonic acid-rich form of the cage can be isolated through postsynthetic acid treatment. This transformation involves an improved gas uptake capacity and the capability to reversibly assemble the cages into a three-dimensional (3D) metal-organic framework (MOF) structure. Likewise, this sulfonic acid functionalization provides both MOP and MOF solids with high proton conductivities (>10-3 S cm-1), comparable to previously reported high conducting metal-organic materials. The influence of the MOP-to-MOF processing in the gas adsorption capacity indicates that this structural transformation can provide materials with higher and more controllable porous properties. These results illustrate the high potential of acidic MOPs as more flexible porous building units in terms of processability, structural complexity, and tunability of the properties.

Effective Production of 5-Hydroxymethylfurfural from Fructose over a Highly Active Sulfonic Acid Functionalized SBA-15 Catalyst

Utilizing sugar compounds (such as fructose) as feedstock for conversion to HMF is very appealing, because it makes the production processes sustainable and improves the economic viability of platform molecules derived from biomass. Here, SBA-15 with sulfonic acid functionalization was created as a heterogeneous base catalyst for fructose hydrolysis reactions to create significant platform chemicals. A fructose conversion rate as high as 100%, along with a 78.7% yield of HMF, were obtained in DMSO at 130 °C after 1 h. The excellent catalytic performance of SBA-15-SO3H in fructose hydrolysis reactions was confirmed by the activation energy’s low value (56.99 kJ/mol). The mild conditions, fast rate of reaction, and simple operation are worth mentioning for other catalysts. SBA-15-SO3H has the potential to promote fructose conversion at lower temperatures.

Visible Light Mediated Heck Coupling of Inactivated Aryl Fluoride/Chloride Over a Sulfonic Acid Functionalized, Melamine‐based Metal‐free Porphyrin Photocatalyst

AbstractWe report the synthesis of a new, sulfonic acid functionalized, melamine‐based metal‐free porphyrin photocatalyst (MBMFPc) for the C−C coupling of the most unreactive aryl halides with alkenes under visible light irradiation. The ionic liquid‐based photocatalyst was characterized using various analytical techniques Proton Nuclear Magnetic Resonance (1HNMR) Spectroscopy, Carbon Nuclear Magnetic Resonance (13CNMR) Spectroscopy, Fourier Transformed Infrared Spectroscopy (FT‐IR), Energy‐dispersive X‐ray Spectroscopy (EDAX), Scanning Electron Microscope (SEM), Brunauer‐Emmett‐Teller (B.E.T) and Ultraviolet‐Visible Spectroscopy (UV‐Vis). The MBMFPc photocatalyst with noticeable Hammett acidity (0.56) and optimal bandgap of 1.44 eV was found to as an effective catalyst in the Mizoroki‐Heck coupling of inactivated aryl fluoride/chloride using 5 W LED in a homemade photoreactor under ambient conditions. The protocol comprising metal‐free green photocatalyst tolerated a variety of aliphatic/aromatic alkenes bearing different substituents afforded good to excellent yields. The role of photogenerated excitons was confirmed by scavenger studies with K2S2O8 and EDTA. The leaching test, stability, and reusability of MBMFPc photocatalyst evidenced as a perfect heterogeneous photocatalyst and afford appreciable yield (80 %) after 5 cycles. A plausible mechanism for photocatalytic C−C coupling has been proposed and described. A metal‐free acid‐functionalized ionic liquid‐based MBMFPc photocatalyst with appreciable TON (4,51,948) and TOF (22,597 h−1) could gain significant attraction as a green catalyst in the pharmaceutical industries for the synthesis of intermediates by C−C coupling using commercial aryl chlorides.

Molecular design of an electropolymerized copolymer with carboxylic and sulfonic acid functionalities

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is the most researched conjugated polymer in the field of organic bioelectronics. The conjugated PEDOT backbone features good redox stability in aqueous electrolyte, and low oxidation potential. However, PEDOT:PSS has two major drawbacks. The PEDOT backbone lacks biofunctionality, limiting the fine tuning of its interface with the biological environment. The dopant PSS is insulating, resulting in a decrease in the capacitance of the polymer. Here, we describe the design of a random copolymer, P(EDOTCOOH-co-EDOTS), based on EDOT monomers functionalized with sulfonic and carboxylic acid groups. The copolymer was successfully synthesized by electropolymerization as confirmed by X-ray photoelectron spectroscopy. Contact angle measurements illustrated the high hydrophilicity of the P(EDOTCOOH-co-EDOTS) (28 ± 6º), attributed to the sulfonate group in the side chains. This in turn led to a higher water penetration into the copolymer film, enhancing significantly its volumetric capacitance (69 ± 4 F cm−3), and thereby, its performance when used as an active channel in an organic electrochemical transistor. Of note, we incorporated the sulfonate group in its sodium salt form retaining its highly ionized properties. This is the first instance of utilizing an uncapped, ionized sulfonate group covalently bound to the backbone of a polymer, where the resultant polymer is oxidized at very low potentials, as well as stable and electroactive in aqueous electrolytes. Furthermore, our molecular design to incorporate carboxylic acid groups paves the way for the development of conjugated polymers that can be tailored for bioelectronic applications.

Covalent organic framework with sulfonic acid functional groups for visible light-driven CO2 reduction.

In this study, a covalent organic framework (TpPa–SO3H) photocatalyst with sulfonic acid function groups was synthesized using a solvothermal method. The morphologies and structural properties of the as-prepared composites were characterized by X-ray diffraction, infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, N2 adsorption–desorption measurements, and field emission scanning electron microscopy. An electrochemical workstation was used to test the photoelectric performance of the materials. The results show that TpPa–SO3H has –SO3H functional groups and high photocatalytic performance for CO2 reduction. After 4 h of visible-light irradiation, the amount of CO produced is 416.61 μmol g−1. In addition, the TpPa–SO3H photocatalyst exhibited chemical stability and reusability. After two testing cycles under visible light irradiation, the amount of CO produced decreased slightly to 415.23 and 409.15 μmol g−1. The XRD spectra of TpPa–SO3H were consistent before and after the cycles. Therefore, TpPa–SO3H exhibited good photocatalytic activity. This is because the introduction of –SO3H narrows the bandgap of TpPa–SO3H, which enhances the visible light response range and greatly promotes the separation of photogenerated electrons.

Thermogravimetric Studies for the Incineration of an Anion Exchange Resin Laden with Short- or Long-Chain PFAS Compounds Containing Carboxylic or Sulfonic Acid Functionalities in the Presence or Absence of Calcium Oxide

Thermogravimetric Studies for the Incineration of an Anion Exchange Resin Laden with Short- or Long-Chain PFAS Compounds Containing Carboxylic or Sulfonic Acid Functionalities in the Presence or Absence of Calcium Oxide

Chemical functionalization of chitosan biopolymer and chitosan-magnetite nanocomposite with sulfonic acid for acid-catalyzed reactions

Abstract Chemical functionalization of chitosan biopolymer and chitosan-magnetite nanocomposite was performed with sulfonic acid functional groups to achieve new solid acid materials. The sulfonic acid functional groups were created through the ring opening nucleophilic reaction of amine groups of chitosan with 1,4-butane sultone. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopies (XPS) verified the successful sulfonic acid functionalization of chitosan. The obtained sulfonic acid functionalized chitosan-magnetite nanocomposite showed superparamagnetic properties according to the vibrating sample magnetometry analysis and exhibited magnetic separation feature from dispersed mixtures. Nitrogen adsorption-desorption analysis indicated the increase in surface area after formation of chitosan-magnetite nanocomposite and functionalization with sulfonic acid. Both of the prepared solid acids exhibited high catalytic activities in the acid-catalyzed acetic acid esterification with n-butanol and benzaldehyde acetalization with ethylene glycol as model reactions. Furthermore, they can be reused several times without considerable loss of their activities.

Experimental and theoretical investigation of high- concentration elution bands in ion-pair chromatography

The effective separation of many solutes, including pharmaceuticals, can be performed using an ion-pair reagent (IPR) in the mobile phase. However, chromatographic separation and mathematical modelling are a challenge in ionpair chromatography (IPC), especially in preparative mode, due to the complicated chromatographic process. In this study, we present a retention mechanism and a mathematical model that predict overloaded concentration profiles in IPC using a system with X-Bridge C18 as stationary phase and tetrabutylammonium bromide in the 0 - 15 mM concentration range as the IPR. Two different mobile phases were used: (i) 15/85 [v/v] acetonitrile/water, (ii) 25/75 methanol/water. The model compounds were sodium salts of organic compounds with sulfonic acid functions. The analytical and preparative elution profiles were obtained for specified conditions. The analytical data were utilized to calculate the difference in electrical potential between the surface and bulk solution using firm electrostatic theory. In the preparative mode in a certain range of IPR concentrations, complicated U-shaped overloaded profiles were observed. In the other considered cases, Langmuir overloaded elution profiles were recorded. A multilayer adsorption model was derived, which is consistent with the dynamic ion exchange models. The model assumes that lipophilic IPR adsorbs on the stationary phase, creating charged active sites that serve as exchange sites for the solutes. The molecules of the solute can adsorb on the already formed IPR layer. It was also assumed that a subsequent layer of solute can form on the formed layer of complexes due to interactions between the solute molecules. The model takes into account the electrostatic attraction and repulsion of the molecules, depending on the considered situation. The proposed model allowed prediction of the overloaded concentration profiles with very good agreement for the model solute and followed the progression from Langmuirian, through U-shaped, to again Langmuirian profiles.

Synergistic effects for fast co-pyrolysis of strong-acid cation exchange resin and cellulose using Py-GC/MS

This study aimed to investigate the co-pyrolysis characteristics of strong-acid cation exchange resin (Amberlyst-15, denoted as A15) and cellulose (CE), in which the existing synergistic interaction effects were uncovered. Crucial variables including pyrolytic temperature, A15-to-CE mass ratio and heating rate were taken into consideration. The levoglucosenone (LGO) production from CE and inorganic sulfur-containing species release from functional sulfonic acid groups of A15 were enhanced in a temperature range of below 400 °C. In this regard, the LGO yield achieved approximately 7 wt% at 300 °C with A15-to-CE mass ratio of 1:1. Relatively, elevating the temperature and heating rate accelerated the A15 self-decomposition and small molecule fragments restructuring to give much more monocyclic and polycyclic aromatics. Noticeably, organic sulfur-containing compounds also were produced in an unignorable amount of 8.2% under preset conditions of pyrolytic temperature of 700 °C and heating rate of 20,000 °C/s. The plausible pathway for the co-pyrolysis transformation of A15 and CE was also proposed on the basis of experimental results. The present work will provide a probable and feasible strategy for the high-value utilization of biomass and waste ion-exchange resins, particularly in the aspect of the generation of certain chemicals.