Quaternary Amine Groups Research Articles

Structure-selectivity relationship of anion exchange resins with different quaternary amine functional groups for highly selective removal of PFAS from chromium-plating wastewater

Anion exchange resin (AER) adsorption is an effective technology for the removal of per- and polyfluoroalkyl substances (PFAS) from wastewater. However, existing AERs with tributylamine functional groups have poor adsorption selectivity for perfluorinated carboxylic acids (PFCAs) and 6:2 fluorotelomer sulfonate (6:2 FTS), and the structure-selectivity relationship is still unclear. In this study, several novel gel AERs with long-chain amine groups were prepared. It was found that their adsorption selectivity for 6:2 FTS was 3.3–5.1 times that of commercial AERs, and the adsorption amount for 6:2 FTS in chromium-plating wastewater was 2.1 times that of the commercial PFA694E. On this basis, we synthesized 16 AERs with different quaternary amine functional groups, and explored the structure-selectivity relationship through the selectivity coefficients and adsorption energies of different AERs for seven typical PFAS. The order of adsorption selectivity of AERs with different quaternary amine groups for PFAS was AER-(12–1-1) > AER-(8–1-1) > AER-(4–4-4) > AER-(4–1-1) ≈ AER-(2–2-2) > AER-(1–1-1), where the three numbers are the carbon-chain lengths of the three alkyl groups attached to the nitrogen atom of the quaternary amine group. Density functional theory (DFT) calculations confirmed the enhanced adsorption selectivity and contribution of both non-electrostatic and electrostatic interactions by the long-chain amine groups, and a quantitative relationship between theoretical calculations and experimental results was established. These results could provide guidance for the development of efficient adsorbents for PFAS removal from wastewater.

Prussian Blue-Assisted NIR Triggered In-Situ Polymerized Nanocomposite Hydrogel for Wound Repair.

Hydrogels are commonly used as wound dressings to help maintain a moist environment around the wound and isolate contaminants, thus promoting healing. For irregular wounds, the slow healing process and even infection may occur due to the inability of dressings to adhere well to the wound. Prussian blue (PB) is a metal-organic framework (MOF) material with excellent photothermal conversion and superior stability. In this paper, a kind of near-infrared (NIR) light triggered in-situ polymerized antimicrobial hydrogel was prepared. The free radical initiator was encapsulated in the hollow PB by a phase change material (PCM) to maintain stability. The raised temperature triggered by NIR induced the release and decomposition of the initiator. The matrix was formed by the cross-linking of double bonds on modified chitosan. The quaternary amine groups of modified chitosan and the photothermal properties of PB enhanced the antimicrobial properties of the hydrogel. High-quality wound healing was demonstrated in the whole skin defect model. This study provides a new reference for the preparation of in-situ polymerized hydrogel dressings for irregular wounds.

Enhanced Nitrate Nitrogen Removal from Wastewater Using Modified Reed Straw: Adsorption Performance and Resource Utilization

This paper presents a study on the efficient removal of nitrate nitrogen from wastewater using modified reed straw (MRS) and its subsequent resource utilization. The modification of the reed straw involved the introduction of branching quaternary amine groups to enhance its adsorption capacity for nitrate nitrogen. Experimental investigations were conducted to analyze the impact of packing height, flow rate, and initial solution concentration on the dynamic adsorption performance of the MRS. The results revealed that the maximum dynamic adsorption capacity of the MRS for nitrate nitrogen reached 14.76 mg/g. Furthermore, valuable nitrate nitrogen nutrient solution was successfully recovered through subsequent desorption experiments for resource recycling. Moreover, the application of the MRS led to notable enhancements in column height, fresh weight, chlorophyll content, and nitrogen content of the treated plants, indicating its efficacy in promoting plant growth. Overall, the findings demonstrate that MRS serves as a versatile adsorbent capable of efficient nitrate nitrogen removal and subsequent resource utilization.

Pilot-scale removal of PFAS from chromium-plating wastewater by anion exchange resin and activated carbon: Adsorption difference between PFOS and 6:2 fluorotelomer sulfonate

Chromium-plating wastewater is an important source of per- and polyfluoroalkyl substances (PFAS) contamination. Currently, adsorption is considered to be one of the main technologies for the removal of PFAS from wastewater. However, no pilot-scale studies have been conducted to investigate its application in chromium-plating wastewater and the adsorption characteristics of 6:2 fluorotelomer sulfonate (6:2 FTS), the alternative to perfluorooctane sulfonate (PFOS). In this study, we evaluated the removal of PFAS from chromium-plating wastewater by granular activated carbon (GAC) and anion exchange resin (AER) at a pilot-scale. The breakthrough curves of PFOS and 6:2 FTS were similar in GAC columns, but significantly different in AER columns, with PFOS and 6:2 FTS reaching 10% breakthrough at about 45,000 BV and 4,000 BV, respectively. The replacement of 6:2 FTS by PFOS and other coexisting organic substances resulted in the concentrations of 6:2 FTS in the AER effluent reaching up to 3.8 times the influent concentrations. Density functional theory (DFT) calculations showed that the adsorption energy of PFOS on the quaternary amine group of AER was more negative than that of 6:2 FTS, and the weak affinity of AER for 6:2 FTS was closely related to the solvent effect. According to the cost analysis, if 6:2 FTS becomes the target PFAS, AER adsorption will no longer have a cost advantage over GAC adsorption. This study can provide technical support for the adsorptive removal of PFAS from electroplating wastewater and guide the development of efficient adsorbents for PFAS alternatives.

Amino-modified hemp stem for high-capacity adsorption of Cr(VI) from aqueous solution

Two novel adsorbents, triethylenetetramine-grafted hemp stems (HS-TETA) and choline chloride-grafted hemp stems (HS-CL), were prepared by using epichlorohydrin as etherifying agent. The obtained adsorbents were comprehensively characterized, and the adsorption capacity for hexavalent chromium (Cr(VI)) was evaluated under various single-factor conditions, including adsorbent dosage, contact time, solution pH, initial hexavalent chromium concentration, and temperature. HS-TETA and HS-CL exhibit excellent adsorption performance, with maximum adsorption capacities of 396.88 and 335.04 mg/g, respectively, outperforming previous relevant studies. The adsorption behavior of Cr(VI) by HS-TETA and HS-CL was investigated using adsorption kinetics, adsorption isotherms, and adsorption thermodynamics. The adsorption process follows the pseudo-second-order kinetic model and the Langmuir isotherm model, suggesting a monolayer adsorption process with chemical adsorption. Thermodynamic analysis reveals that the adsorption of Cr(VI) on two adsorbents is spontaneous and exothermic. Combined with the characterization, it can be speculated that the adsorption of Cr(VI) on two adsorbents involves electrostatic effects, reduction, and complexation processes. HS-TETA and HS-CL exhibit good recyclability. After 5 cycles, HS-TETA and HS-CL maintain over 50% and 85% of their initial adsorption capacity, respectively. The cycling performance of HS-CL containing quaternary ammonium and amine groups is significantly superior to that of HS-TETA containing only an amine group, indicating that the introduction of the quaternary ammonium group enhances the cycling performance of the adsorbent. HS-TETA and HS-CL, as cost-effective and efficient adsorbents, offer a promising solution for the treatment of Cr(VI)-contaminated wastewater and facilitate the recycling of agricultural waste.

Chitosan based Janus cryogel with anisotropic wettability, antibacterial activity, and rapid shape memory for effective hemostasis

Excessive bleeding and bacterial infection leading to death is a major concern worldwide, particularly in cases of deep and narrow noncompressible hemorrhage. Herein, a novel Janus cryogel with anisotropic surface wettability, antibacterial activity, and rapid shape recovery was designed by constructing a hydrophilic porous cryogel using chitosan (CS), acacia gum (AG), and quaternized mesoporous bioglass (QMBG), with subsequent surface hydrophobic modification using octadecanol. The asymmetric hydrophobic surface modification of octadecanal endowed OCAQ with outstanding antiblood and antibacterial permeability, effectively preventing blood outflow and the invasion of bacteria to the wound. The hydrophilic parts with interconnected macroporous structure give the cryogel with ultra-high water uptake (5167 ± 182 %) and rapid water-trigged shape recover ability (≈2.1 s). The presence of active CS, AG, and QMBG in cryogel contributes to its exceptional blood clotting ability. Janus cryogel presents outstanding hemostatic performance (0.14 ± 0.03 g) in rat's liver injury model. Moreover, Janus cryogel exhibits excellent antibacterial properties due to the combination of its hydrophobic surface and antimicrobial quaternary amine groups. Meanwhile, the Janus cryogel has favorable hemocompatibility and biocompatibility. A Therefore, the Janus cryogel will become a candidate with great potential for clinical application of noncompressible wound as a multifunctional dressing.

Removal of diclofenac from aqueous solution by chitosan-encapsulated Aliquat-336 capsules: Optimization of preparation conditions and adsorption mechanism

To enhance the effectiveness of ionic liquids in water treatment, a novel approach was devised involving the encapsulation of ionic liquids within a chitosan shell. This study focuses on the development and application of chitosan-encapsulated Aliquat-336 capsules (CACs) for the removal of diclofenac (DCF) from aqueous solution. The optimal preparation conditions, as determined through response surface methodology, were as follows: (1) Aliquat-336 content = 13.8%, (2) TPP concentration = 6%, and (3) crosslinking time = 0.5 h. CACs exhibited exceptional adsorption capabilities for DCF across a wide pH range, and the maximum adsorption capacity was 387.2 ± 25.6 mg/g at pH 7 according to the adsorption isotherm results. Adsorption kinetic results showed that the overall adsorption rate of DCF was controlled by liquid film diffusion. Furthermore, the slight antagonism of coexisting anions at low concentrations and significant synergy at high concentrations confirmed the practical suitability of CACs. The characterization of CACs before and after adsorption was analyzed by electron microscopy, pHPZC analysis, Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The results demonstrated the successful preparation of CACs and underscored the pivotal role played by the quaternary amine group within Aliquat-336, encapsulated within the CACs, in facilitating the removal of DCF through electrostatic attraction.

Ultrasensitive Flexible Thermal Sensor Arrays based on High-Thermopower Ionic Thermoelectric Hydrogel.

Ionic circuits using ions as charge carriers have demonstrated great potential for flexible and bioinspired electronics. The emerging ionic thermoelectric (iTE) materials can generate a potential difference by virtue of selective thermal diffusion of ions, which provide a new route for thermal sensing with the merits of high flexibility, low cost, and high thermopower. Here, ultrasensitive flexible thermal sensor arrays based on an iTE hydrogel consisting of polyquaternium-10 (PQ-10), a cellulose derivative, as the polymer matrix and sodium hydroxide (NaOH) as the ion source are reported. The developed PQ-10/NaOH iTE hydrogel achieves a thermopower of 24.17mV K-1 , which is among the highest values reported for biopolymer-based iTE materials. The high p-type thermopower can be attributed to thermodiffusion of Na+ ions under a temperature gradient, while the movement of OH- ions is impeded by the strong electrostatic interaction with the positively charged quaternary amine groups of PQ-10. Flexible thermal sensor arrays are developed through patterning the PQ-10/NaOH iTE hydrogel on flexible printed circuit boards, which can perceive spatial thermal signals with high sensitivity. A smart glove integrated with multiple thermal sensor arrays is further demonstrated, which endows a prosthetic hand with thermal sensation for human-machine interaction.

Investigation of the correlation between molecular structures with high-temperature and salt resistance for acrylamides polymer in drilling fluid

Deep oil and gas are essential alternative resources for future energy sources, but the lack of high temperature and high salt resistance mechanisms and agents significantly limits their development. Copolymers of six commonly used high-temperature and salt resistance monomers and acrylamide with similar molecular weights were prepared to improve oil recovery in deep reservoirs. The effects of different functional groups on the high-temperature and salt resistance of polymers were revealed by the drilling fluid and elemental analysis, TOC test, Zeta potential, particle size, and other analytical methods. Experimental results indicate that the pyrrole ring groups, quaternary amine groups, long-chain sulfonate groups, and benzenesulfonic acid groups can effectively improve the high-temperature stability of polymers in an aqueous solution. Quaternary ammonium groups and pyrrole rings can enhance the polymer adsorption with clay under high temperatures and high salinity conditions due to charge attraction. However, these functional groups hinder the clay dispersion and reduce the stability of drilling fluids. Hydration groups, such as sulfonic and carboxylic acid groups, can better maintain the colloidal stability of drilling fluids under high temperatures and high salinity, and benzene sulfonic acid groups are the optimal hydration groups. After the polymer is adsorbed on the clay surface, the benzene sulfonic acid group assists in forming a thicker hydration film on the clay surface, effectively hindering the damage of high temperature and high salinity on the clay. The findings and observations of this study provide theoretical support for the development of high-temperature and salt resistance polymers for water-based drilling fluids of ultra-deep wells.

On-tissue chemical derivatization enables spatiotemporal heterogeneity visualization of oxylipins in esophageal cancer xenograft via ambient mass spectrometry imaging

On-tissue chemical derivatization (OTCD) effectively enhances ionization efficiency of low abundant and poorly ionized functional molecules to improve detection sensitivity and coverage of mass spectrometry imaging (MSI). Combination OTCD and MSI provides a novel strategy for visualizing previously undisclosed metabolic heterogeneity in tumor. Herein, we present a method to visualize heterogeneous metabolism of oxylipins within tumor by coupling OTCD with airflow-assisted desorption electrospray ionization (AFADESI)-MSI. Taking Girard's P as a derivatization reagent, easily ionized hydrazide and quaternary amine groups were introduced into the structure of carbonyl metabolites via condensation reaction. Oxylipins, including 127 fatty aldehydes (FALs) and 71 oxo fatty acids (FAs), were detected and imaged in esophageal cancer xenograft with AFADESI-MSI after OTCD. Then t-distributed stochastic neighbor embedding and random forest were exploited to precisely locate the distribution of oxylipins in heterogeneous tumor tissue. With this method, we surprisingly found almost all FALs and oxo FAs significantly accumulated in the core region of tumor, and exhibited a gradual increase trend in tumor over time. These results reveal spatiotemporal heterogeneity of oxylipins in tumor progression, highlighting the value of OTCD combined with MSI to gain deeper insights into understanding tumor metabolism.

A robust mixed-charge zwitterionic polyurethane coating integrated with antibacterial and anticoagulant functions for interventional blood-contacting devices.

Antifouling coatings based on zwitterionic polymers have been widely applied for surface modification of interventional blood-contacting devices to combat thrombosis and infection. However, the weak adhesion stability of the zwitterionic coating to the device surface is still the key challenge. In this work, biocompatible mixed-charge zwitterionic polyurethane (MPU) polymers, that bear equal amounts of cationic quaternary amine groups and anionic carboxyl groups, were developed and further uniformly dip-coated onto a thermoplastic polyurethane (TPU) substrate with a commercial aliphatic isocyanate cross-linker (AIC). During the curing process, AIC not only crosslinks MPU chains into a polymer network but also reacts with hydroxyl groups of TPU to interlink the polymer network to the substrate, resulting in a cross-linking reinforced MPU coating (CMPU) with excellent mechanical robustness and adhesion strength. Taking advantage of the mixed-charge feature, the final zwitterionic CMPU coating exhibits both excellent antifouling and antibacterial activities against protein adsorption and bacterial growth, respectively, which is beneficial for effectively inhibiting the occurrence of in vivo infection. Moreover, anticoagulation studies show that CMPU-coated TPU catheters can also prevent the formation of blood clots in ex vivo rabbit blood circuits without anticoagulants. Hence, the designed CMPU coating has immense potential to address thrombosis and infection for interventional blood-contacting devices.

Green synthesis of quaternized chitosan nanogel using emulsion-photopolymerization as redox-responsive drug carrier

We report the green synthesis of trimethyl chitosan-functionalized poly(2-hydroxyethyl methacrylate) (PHEMA-TMC) nanogels via surfactant-free emulsion photopolymerization. TMC, a quaternized derivative of chitosan, was synthesized through methylation of chitosan, resulting in quaternary and tertiary amine groups as the main substitution products. TMC tertiary amine moiety and riboflavin (RF) acted as a redox photo-initiating system to generate free radicals for the polymerization under light irradiation. The effects of polymerization parameters such as irradiation time, concentrations of TMC and RF were investigated using MBA as crosslinker. Under the optimal condition of 1 % TMC, 4 % HEMA, 0.8 μM RF, 5 % MBA, and 4 h of polymerization time, the cationic PHEMA-TMC nanogel was synthesized with 76 % monomer conversion and an average diameter of about 106 nm. Moreover, the disulfide-crosslinked PHEMA-TMC nanogel was also synthesized using the disulfide dimethacrylate crosslinker, which exhibited a redox-induced degradation and release of encapsulated melatonin, potentially useful as a redox-responsive drug delivery carrier.

Development of Nanoscale Hydrated Titanium Oxides Support Anion Exchange Resin for Efficient Phosphate Removal from Water

In this work, a macroporous strongly basic anion exchange resin D201 was used as the matrix and loaded with nano hydrated titanium oxide (HTO) to fabricate a novel resin-based nano hydrated titanium oxide adsorbent (HTO-D201), which was characterized by scanning electron microscope-energy dispersion spectroscopy (SEM-EDS), transmission electron microscope (TEM), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analysis. Adsorption isotherm, pH influence competitive adsorption and column adsorption experiments were conducted to investigation the adsorption behavior of HTO-D201 to phosphorus in water. The adsorption effect of adsorbent HTO-D201 on phosphorus in water, and the corresponding adsorption mechanism, are discussed. It was observed that HTO-D201 exhibited spontaneous adsorption behavior with Langmuir fitting maximum adsorption capacity of 34.08 mg∙g−1 under a pH of 6.8 and a temperature of 298 K. Adsorption isotherms confirmed that enhancing temperature could promote the adsorption process. SO42−, NO3− and Cl− were used as competing ions in competitive adsorption, which confirmed better anti-interference ability of HTO-D201 compared with that of unmodified D201. The column adsorption experiment implied that HTO-D201 possessed a stable structure and good dynamic adsorption performance, with effective processing capacity of 420BV, which could be regenerated and recycled. The adsorption mechanism of HTO-D201 to phosphorus in water is discussed, which was ascribed to a quaternary amine group on the resin and a hydroxyl group on the HTO. This work shows that HTO-D201 is a promising adsorbent that a possesses excellent phosphorus-removing capacity from wastewater and the potential for practical application.

Synthesis of alkyl polyamine with different functional groups and its montmorillonite swelling inhibition mechanism: Experiment and density functional theory simulation

In this work, low molecular weight alkyl polyamine (tris(2-methylaminoethyl)amine (TSA), hexamethyltris(2-aminoethyl)amine (TTA), nonamethyltris(2-aminoethyl)amine (TQA)) with different functional groups and the same hydrophobic chain was synthesized using tris(2-aminoethyl)amine (TPA). X-ray diffraction, scanning electron microscopy, X-Photoelectron spectroscopy, transmission electron microscopy, contact angle, and density functional theory simulation were used to investigate the montmorillonite swelling inhibition mechanisms. The results of the experiments showed that a small amount of TPA, TSA, TTA, and TQA can significantly reduce the basal spacing of montmorillonite (Mt). The basal spacing of montmorillonite did not change with increasing the inhibitor concentration. The basal spacing of Mt-TPA, Mt-TSA, and Mt-TTA had some differences in the dry and wet states, but there was no difference in Mt-TQA. This observation indicated that TPA, TSA and TTA exhibited a three-dimensional spatial configuration in the lamellar spacing of montmorillonite, while TQA was inserted into the space of montmorillonite layer in a single flat layer. As more amine groups were substituted by the methyl groups, the spatial configuration of inhibitors changes from a three-dimensional to a two-dimensional planar structure. The higher the number of hydrogen atom substitutions in the primary amine group by methyl groups, the larger the contact angle, and the stronger the hydrophobic capacity except for the quaternary ammonium groups. The simulation results indicated that the higher the number of substitutions, the larger the adsorption energy. Therefore, inhibitors with a quaternary amine group would have better inhibition performance.

Self-Assembly Anchored Cationic Copolymer Interfaces for Applying the Control of Counterion-Induced Bacteria Killing/Release Procedure.

In recent years, daily hygiene and disease control issues have received increasing attention, especially the raging epidemics caused by the spread of deadly viruses. The construction of the interface of new polymer materials is focused on, which can provide a cyclic operation process for the killing and releasing of bacteria, and perform repeated regeneration, which is of great significance for the development of advanced medical biomaterials. In order to explore the basic physical phenomena of bacterial attachment and detachment on the polymer material interface by different amine groups, this study plans to synthesize four different butyl methacrylate (BMA)-based cationic copolymers with primary, ternary, and quaternary amine groups, and compare their effects on bactericidal efficiency. Since BMA can generate strong hydrophobic interactions with the benzene ring structure, this study used a polystyrene substrate to realize a self-assembled cationic copolymer interface for controlling the counterion-induced bacterial killing/release process. Furthermore, negatively charged ions are introduced to induce changes in the hydration capability of water molecules and control the subsequent bacterial detachment function. In this study, possible directions to answer and clarify the above concepts are proposed, and there is a basic reference principle that can lead to research work in macromolecular biosciencefields.

Quaternary amines exert anti-myocardial ischemia effects via regulation of energy metabolism and oxygen free radicals in myocardial cells in acute myocardial infarction rats

Purpose: To investigate the effect of quaternary amines on myocardial cells of a rat model of cardiac arrest, with respect to energy generation potential and oxygen free radicals.
 Methods: Forty-five Sprague-Dawley (SD) rats were assigned to sham, model and quaternary amine groups (each with 15 rats). After their corresponding treatments, lectrocardiogram (ECG) monitoring of the rats in the three groups at various time periods was carried out. Serum levels of myocardial enzymes, thromboxane B2 (TXB2), prostacyclin I2 (PGI2), serum carbon monoxide (CO), and changes in endothelial carbon monoxide synthase (eNOS) and endothelin (ET), were determined.
 Results: The levels of NO and eNOS were significantly reduced in model rats, relative to sham operation rats, while ET was significantly elevated in sham rats (p < 0.05). There were higher levels of NO and eNOS in the quaternary amine group than in model rats, but ET was higher in quaternary amine group than in model rats. Thromboxane B2 (TXB2) concentration was higher in model rats than in sham rats (p < 0.05). While PGI2 was markedly lower in quaternary group than in sham operation rats. TXB2 was lower in the quaternary amine group than in model rats, while PGI2 was significantly higher in quaternary amine group, relative to model rats (p < 0.05).
 Conclusion: Quaternary amines exert anti-myocardial effects by regulating energy metabolism and oxygen free radicals in myocardial cells of congestive heart failure rats, and thus are potentially useful for the management of acute myocardial infarction.
 Keywords: Quaternary amine; Acute myocardial infarction; Electrocardiogram; Serum myocardial enzymes; Myocardial cells

A concise SAR-analysis of antimicrobial cationic amphipathic barbiturates for an improved activity-toxicity profile

An amphipathic barbiturate mimic of the marine eusynstyelamides is reported as a promising class of antimicrobial agents. We hereby report a detailed analysis of the structure-activity relationship for cationic amphipathic N,N′-dialkylated-5,5-disubstituted barbiturates. The influence of various cationic groups, hydrocarbon linkers and lipophilic side chains on the compounds’ antimicrobial potency and haemolytic activity was studied. A comprehensive library of 58 compounds was prepared using a concise synthetic strategy. We found cationic amine and guanidyl groups to yield the highest broad-spectrum activity and cationic trimethylated quaternary amine groups to exert narrow-spectrum activity against Gram-positive bacteria. n-Propyl hydrocarbon linkers proved to be the best compromise between potency and haemolytic activity. The combination of two different lipophilic side chains allowed for further fine-tuning of the biological properties. Using these insights, we were able to prepare both, the potent narrow-spectrum barbiturate 8a and the broad-spectrum barbiturates 11lG, 13jA and 13jG, all having low or no haemolytic activity. The guanidine derivative 11lG demonstrated a strong membrane disrupting effect in luciferase-based assays. We believe that these results may be valuable in further development of antimicrobial lead structures.

Removing miscellaneous heavy metals by all-in-one ion exchange-nanofiltration membrane

The composition of wastewater containing heavy metal mixtures is often complex and poses a serious threat to human and environmental health. Effective removal of a variety of heavy metal ions with a single technology is challenging, and the conventional split integrated technologies require multi-step processing and a massive footprint. For the first time, we achieve hierarchically integrating ion exchange and nanofiltration into all-in-one “iNF” membranes. The iNF membrane has a hierarchical structure with an interfacial polymerization layer and an ion exchange layer, which can achieve highly efficient indiscriminate heavy metal ion removal, overcoming the defect that traditional nanofiltration membranes can only remove single metal cations or oxyanions. The ion exchange layer can remove heavy metal ions through sulfonic acid groups and quaternary amine groups. In addition, the ion exchange layer can be regenerated by electro-deionization, which is meaningful for sustainable membrane usage. This facile, scalable, and compact integrated process shows outstanding potential and universal applicability in complex wastewater treatment.

Development of ionic liquid filled chitosan capsules to remove Cr(VI) from acidic solution: Adsorption properties and mechanism

Cr(VI)-contaminated water poses a serious threat to the environment. In this study, capsule-type biosorbent Aliquat-336-filled chitosan capsules (AFCCs) were prepared by a simple and gentle method for more efficient and eco-friendly removal of Cr(VI). The experimental results show that the uptake of Cr(VI) by AFCCs increased with increasing Aliquat-336 content. The AFCCs show excellent stability under acidic conditions, and the maximum adsorption capacity was reached at a pH of 2. The maximum adsorption capacity of AFCCs for Cr(VI) was 110.94 ± 5.07 mg/g at 20 °C, which was calculated based on the Langmuir model. The kinetic results show that the adsorption rate control process changed from liquid film diffusion to a chemical reaction with increasing shaking rate. In addition, the AFCCs and adsorption-reduction mechanism of Cr(VI) were characterized by digital photography, electron microscope, zeta potential, Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The results indicated that the electrostatic attraction between quaternary amine groups in Aliquat-336 and Cr(VI) anions plays a major role in the removal of Cr(VI). Subsequently, the adsorbed Cr(VI) obtained electrons from CC/CH and NH3+/NH2+ were reduced to Cr(III), while CC/CH and NH3+/NH2+ were oxidized to CO, CO, =NH+, =N and NO, respectively.

Development of sol-gel silica-based mixed-mode zwitterionic sorbents for determining drugs in environmental water samples

Four novel mixed-mode zwitterionic silica-based functionalized with strong moieties sorbents were synthesized and evaluated through solid-phase extraction (SPE) to determine acidic and basic drugs in environmental water samples. All sorbents had the same functionalization: quaternary amine and sulfonic groups and C18 chains so that hydrophobic and strong cationic exchange (SCX) and strong anionic exchange (SAX) interactions could be exploited, in addition, two of them had carbon microparticles embedded.All sorbents retained both acidic and basic compounds in the preliminary assays but only the basic compounds were retained selectively through ionic exchange interactions when a clean-up step was introduced. The SPE method was therefore optimized to promote the selective retention of the basic compounds, initially with the two best-performing sorbents.After optimization of the SPE protocol, these sorbents were evaluated for the analysis of environmental water samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The method with the best-performing sorbent was then validated with 100 mL of river samples and 50 mL of effluent wastewater samples in terms of apparent recoveries (%Rapp) spiking samples at 50 ng/L (river) and 200 ng/L (river and effluent), matrix effect, linear range, method quantification and detection limits, repeatability, and reproducibility. It should be highlighted that %Rapp ranged from 40 to 85% and matrix effects ranged from -17 to -4% for spiked river samples. When the method was applied to river and effluent wastewater samples, most compounds were found in the range from 24 to 1233 ng/L with detection limits from 1 to 5 ng/L.