Protonated Amino Groups Research Articles

A High-capacity Benzoquinone Derivative Anode for All-organic Long-cycle Aqueous Proton Batteries.

Quinone compounds, with the ability to uptake protons, are promising electrodes for aqueous batteries. However, their application is limited by the mediocre working potential range and inferior rate performance. Herein, we examined quinones bearing different substituents, and for the first time introduce tetraamino-1,4-benzoquinone (TABQ) as anode material for proton batteries. The strong electron-donating amino groups can effectively narrow the band gap and negatively shift the redox potentials of quinone material. The protonation of amino groups and the amorphization of structure result in the formation of an intermolecular hydrogen-bond network, supporting Grotthuss-type proton conduction in the electrode with a low activation energy of 192.7 meV. The energy storage mechanism revealed by operando FT-IR and ex-situ XPS features a reversible quinone-hydroquinone conversion during cycling. TABQ demonstrates a remarkable specific capacity of 307 mAh g-1 at 1 A g-1, which is the highest among organic proton electrodes. An all-organic proton battery of TABQ//TCBQ has also been developed, achieving exceptional stability of 3500 cycles at room temperature and excellent performance at sub-zero temperatures.

Hydrochar produced from mixed feedstocks as efficient adsorbent for selenium and chromium removal from acidic wastewater

Selenium (Se) and chromium (Cr) in water might be harmful because of their high toxicity in the aquatic environment. Efficient removal of their hexavalent forms (Se(VI) and Cr(VI)) from extreme acidic wastewater is still challenging. Therefore, several new hydrochars suited for efficient removal of trace Se(VI) and Cr(VI) from acidic wastewater were fabricated from biomass through a hydrothermal method. Most functional groups were retained in the hydrochar, which gave it an excellent adsorption capacity (43.2 mg·g−1 and 132 mg·g−1 for Se(VI) and Cr(VI), respectively). After one batch treatment at exceptionally low pH and a hydrochar dose of 0.2 g·L−1, Se(VI) and Cr(VI) could be removed from 1 mg·L−1 to 6 μg·L−1 and 15 μg·L−1, respectively. The mechanism of adsorption at various pH was elucidated by Scanning Electron Microscopy, Thermogravimetry, Fourier Transform Infrared Spectrometer, X-Ray Photoelectron Spectroscopy and density functional theory (DFT) calculation. The adsorption mechanism for Se(VI) in acidic solution involved the binding of SeO42− with protonated amino groups (−NH3+) of Mix hydrochar. In the pH range of 6.5 to 7, Cr(VI) combined with −NH3+ functional groups primarily in the form of CrO42−. When the pH fell below 6.5, Cr(VI) bound with both −NH3+ and carbonyl groups (−C=O) in the form of HCrO4−. Fast kinetics were observed during the removal process of Se(VI) and Cr(VI). The hydrochar adsorbent showed good stability under acidic environments and during long-term adsorption cycles. These findings may provide theoretical basis for design of adsorption materials for acidic wastewater treatment.

PH-induced morphological reversible transition from microparticles to vesicles for effective bacteria entrapment

Polymer particles with stimuli-responsive properties offer promising applications in healthcare, chemical reactors, development of artificial cells and organelles, as well as in the entrapment of bacteria. In this study, a novel biocompatible, biodegradable, and pH-responsive diblock copolymer based on polylactide (PLA) and poly(2-(diisopropylamino)ethyl methacrylate) (PDPA) was synthesized via a metal-free one-pot/simultaneous ring-opening polymerization (ROP) and reversible addition-fragmentation chain transfer (RAFT) approach (ROP/RAFT). This copolymer was then employed to produce highly monodisperse microparticles using microfluidics droplet generation technique. Utilizing confocal microscopy imaging, a reversible pH-induced morphological transition from microparticles to vesicle-like structures was observed at pH 5.1. The reversible shift in morphology from microparticles to giant vesicles (Vs) in acidic environments is triggered by the protonation of amino groups of the PDPA block, rendering vesicle surfaces positively charged − an advantageous feature for attracting and engulfing negatively charged bacteria. Initial validation involved electrostatic interactions with negatively charged latex resin beads followed by assessing interaction capabilities with gram-negative bacteria, Escherichia coli (E. coli). Additionally, the reversible morphological transition of microparticles-to-vesicles was employed to study drug release at different pHs. This approach proven to be a promising strategy for targeted drug delivery and bacteria entrapment using smart pH-responsive microparticles.

Tunable supramolecular self-assemblies based on cyclodextrin polymer as a loading platform for water-soluble drugs

Drug loading capacity is a crucial character of nano-scaled drug carriers to achieve high quality pharmaceutical preparations. However, efficient encapsulation of water-soluble small molecular drugs still faces large obstacles in many cases. Herein, we designed a novel supramolecular delivery system constructed by poly(β-cyclodextrin) containing benzoic acid groups (PCD-PA) and adamantyl terminated poly(ethylene glycol) (PEG-AD) to provide multiple intermolecular interactions for competent loading of water-soluble small-molecular drugs. PCD-PA had multiple host molecules, and PEG-AD could be inserted via host-guest interaction in different proportion to adjust the composition of supramolecular carrier. Meanwhile, π-π stacking and electrostatic interaction furnished by benzoic acid groups served as binding force for drug entrapment, which led to considerable loading capacity for several water-soluble drugs. Among the drugs with different chemical structures, mitoxantrone hydrochloride and doxorubicin hydrochloride bearing anthraquinone rings and several protonable amino groups acquired the highest loading content as about 14 % in PCD-PA3/PEG-AD supramolecular self-assemblies. Further computational simulations investigated the mechanism of drug loading based on the interactions between the carrier materials and the payloads. In addition, the weakly acidic environment obviously accelerated the release of certain drugs. All in all, this self-assembled supramolecular nano-system displayed great potentials as a delivery platform for diverse water-soluble drugs.

Multifunctional coating with hydrophobicity, antibacterial and flame-retardant properties on cotton fabrics by layer-by-layer self-assembly curing of phytic acid and a tyrosine-derived hyperbranched benzoxazine

The inherent hydrophilicity and biocompatibility of cotton fabrics facilitated bacterial proliferation and safety concerns, limiting their applications. To address these issues, tyrosine-derived polyetherimide, bis(3-aminopropyl)-terminated poly(dimethylsiloxane), and paraformaldehyde were used to synthesize hyperbranched benzoxazine THB-BOZs-PDMS with potent antibacterial and antibiofilm activity. The protonated amino groups of benzoxazine facilitated electrostatic interactions with negatively charged bacteria, and hydrophobic interactions disrupted the cell membrane, leading to bacteria death. Notably, phytic acid interacts with benzoxazines through intermolecular forces, with its phosphoric acid groups facilitating the curing of benzoxazines, thereby imparting flame-retardant properties to the material. Consequently, a multifunctional coating was developed via LBL self-assembly and in-situ curing of benzoxazines and phytic acid on the fabric surfaces. The successful deposition of the coating was confirmed through compositional analysis and morphological characterization. After 4 cycles of LBL modification, the fabrics TBP + PA-CF-4 displayed outstanding antibacterial efficacy, bacterial anti-adhesion properties, and heat resistance. Furthermore, TBP + PA-CF-4 exhibited notable washing and mechanical durability, attributed to the stability conferred by in-situ cured of layers. Compared with other reported modified fabrics, TBP + PA-CF-4 displayed more comprehensive overall performances. These multifunctional fabrics provided a sustainable approach for advancing personal protective materials and public decoration, particularly suited for use in high-humidity environments or military settings.

EDAC-modified chitosan/imidazolium-polysulfone composite beads for removal of Cr(VI) from aqueous solution

To enhance the stability and adsorption performance of chitosan in Cr(VI)-contaminated acidic wastewater, a novel EDAC-modified-EDTA-crosslinked chitosan derivative (CSEC) was synthesized via a one-pot method with chitosan, 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC), and Na2EDTA as raw materials. To further improve the mechanical strength and separation performance of CSEC, a novel composite bead (CSEP) of CSEC and imidazolium-functionalized polysulfone (IMPSF) was prepared through a phase inversion method. The chemical composition and microstructure of CSEC and CSEP were characterized by FESEM, FTIR, NMR and XPS techniques. The maximum adsorption capacities of CSEC and CSEP for Cr(VI) were 145.96 and 135.82 mg g−1 at pH 3, respectively, and the equilibrium time for Cr(VI) adsorption by CSEC and CSEP was 5 min and 8 h, respectively. The adsorption process of Cr(VI) by both CSEC and CSEP was exothermic and spontaneous. Compared to CSEC, CSEP has significantly enhanced resistance to interference from coexisting anions. The removal mechanism of Cr(VI) by CSEP might involve redox reaction as well as electrostatic attraction between Cr(VI) oxyanions and various nitrogen cations, including protonated amino groups, guanidinium groups, protonated tertiary amine groups, and imidazolium cations. The CSEP beads have potential application value in the treatment of acidic wastewater containing Cr(VI).

Preparation of chitosan resin by two-step crosslinking method and its adsorption for palladium in wastewater

To preserve the activity of amine groups on chitosan, chitosan resin (CR) was synthesized using the reversed-phase suspension two-step crosslinking method for the adsorption of palladium from wastewater. The effects of varying the amounts of chitosan, liquid paraffin, ethyl acetate, formaldehyde solution, and epichlorohydrin on the adsorption capacity of CR were investigated using both single-factor experiments and response surface methodology. The preparation conditions for the chitosan resin were optimized, and its adsorption properties were systematically evaluated. The results indicated that CR exhibited a high saturated adsorption capacity for palladium, reaching 195.22 mg·g−1. The adsorption kinetics followed the pseudo-second-order model, while the adsorption isotherms were well described by the Sips model. Thermodynamic analysis demonstrated that the adsorption process was spontaneous and endothermic. Furthermore, CR maintained exceptional stability, with a palladium removal efficiency exceeding 99.8 % even after eight adsorption-desorption cycles. The primary adsorption mechanism is attributed to the interaction between palladium ions and the protonated amino groups of the chitosan resin.

Metal-Free, PPA-Mediated Fisher Indole Synthesis via Tandem Hydroamination-Cyclization Reaction between Simple Alkynes and Arylhydrazines.

A new variant of Fisher indole synthesis involving Bronsted acid-catalyzed hydrohydrazination of unactivated terminal and internal acetylenes with arylhydrazines is reported. The use of polyphosphoric acid alone either as the reaction medium or in the presence of a co-solvent appears to provide the required balance for activating the C-C triple bond towards the nucleophilic attack of the hydrazine moiety without unrepairable reactivity loss of the latter due to competing amino group protonation. Additionally, the formal hydration of acetylenes to the corresponding ketones occurs under the same conditions, making it an alternative approach for generating carbonyl groups from alkynes.

Development of hydrogels from cell wall of Aspergillus oryzae containing chitin-glucan and wet spinning to monofilaments

Fungal mycelium is emerging as a source for sustainable bio-based materials. Fungal biomass of Aspergillus oryzae was prepared by cultivation on bread waste hydrolysate to valorize this abundant food waste. Chitin-glucan-rich alkali-insoluble material (AIM) was isolated from fungal biomass, formed into hydrogels, and wet spun into monofilaments. AIM in the form of fungal microfibers containing 0.09 g polymer of glucosamine (GlcN)/g AIM was subjected to freeze–thaw and deacetylation treatments to increase the amount of GlcN. The GlcN fraction was 0.19 and 0.34 g polymer of GlcN/g AIM, for AIM subjected to deacetylation (AIM-DAC) and freeze–thaw cycles and deacetylation (AIM-FRTH-DAC), respectively. The increased GlcN fraction enabled the formation of hydrogels via the protonation of amino groups after the addition of lactic acid. Morphological differences in the hydrogels included aggregation of the fungal microfibers in the AIM-DAC hydrogel, whereas the microfibers in the AIM-FRTH-DAC hydrogel had a porous and interconnected network. Rheological assessment revealed shear thinning behavior and gel properties of the produced hydrogels. Wet spinning of the hydrogels resulted in monofilaments with tensile strengths of up to 70 MPa and 12 % elongation at break. This demonstrates promising avenues for biomaterial development from fungal cell walls containing chitin-glucan via food waste valorization.

Superior comprehensive performance of modified activated carbon as a hexavalent chromium adsorbent

The presence of hexavalent chromium species (CrVI) in wastewater from manufacturing industries such as electroplating and leather production can pose serious health hazards. To address these concerns, this study developed a novel adsorbent based on activated carbon as the primary material to attract CrVI. Activated carbon has been modified with several other components to improve its comprehensive performance, including adsorption capacity, chemical stability, collectability, and reusability. Specifically, decoration with magnetite nanoparticles made it possible to collect the adsorbent magnetically and reuse it several times. On the one hand, the addition of chitosan not only increased the chemical stability of activated carbon, especially under acidic conditions, but also enhanced the Cr adsorption capacity at pH higher than 4, where adsorption of only activated carbon was significantly decreased, probably because the protonated amino groups attracted chromate anions. In addition, the co-existence of tannic acid did not increase the adsorption capacity significantly but appeared to promote the reductive adsorption of CrVI, where the reduction of CrVI means lowering the toxicity of Cr species. It was demonstrated that activated carbon modified with magnetite, chitosan, and tannic acid exhibited superior comprehensive performance that could be repeatedly used over a wide pH range as compared to the parent activated carbon.

Preparation of oil-in-water type Pickering emulsions stabilized by partially deacetylated nanochitin and pH-triggered drug release

Partially deacetylated nanochitin (DAcNC) exhibits amphiphilicity owing to the hydrophilic protonated amino groups and hydrophobic surface planes of DAcNC. Although DAcNCs possess emulsifying abilities, their role and versatility as emulsifiers remain unclear. In this study, we investigated oil-in-water (O/W) type Pickering emulsions stabilized with DAcNCs. Stable emulsions were formed using a variety of oils such as vegetable oils, decane, and ether oils. Measurements of the interfacial tension and adsorption of DAcNC showed that formation of tolerant interfacial films stabilized the emulsions. Furthermore, the pH-triggered release of ibuprofen, an antipyretic drug, was demonstrated using the emulsion. Enhanced ibuprofen release was observed upon increasing the pH from 2.0 to 6.0. This phenomenon can be attributed to the deprotonation of ammonium moieties on the DAcNC, which induced the desorption of DAcNC from oil/water interfaces. The DAcNC emulsion can be useful for the oral administration of ibuprofen as an antipyretic agent, facilitating intestinal release.

Grafting of Polyethyleneimines on Porous Silica Beads and Their Use for Adsorptive Removal of Cr(VI) from Aqueous Medium

Porous silica-based adsorbents for hexavalent chromium (Cr(VI)) ion removal were prepared by the combined use of functionalization with (3-glycidyloxypropyl)trimethoxysilane and the grafting of branched and linear polyethyleneimine (BPEI and LPEI). LPEI was prepared from polyethyloxazolin by hydrolysis with HCl. The preparation of LPEI was identified by NMR measurements and the grafting of BPEI and LPEI on the silica beads was confirmed by an XPS analysis. The Cr(VI) ion adsorption of the obtained BPEI-grafted silica beads (BPEI–silica beads) was investigated as a function of the pH value, the content of amino groups, the temperature, the Cr(VI) ion concentration, and the molecular mass of the grafted BPEI chains. The Cr(VI) ion adsorption at pH 3.0 increased with an increase in the content of amino groups, and the maximum adsorption capacity of 1.06 mmol/g was obtained when the content of amino groups was at 2.17 mmol/g. This value corresponds to 589 mg/g−1.8KPEI, and the adsorption ratio of about 0.5 is a noteworthy result. The data fit to the pseudo-second-order kinetic model, and the suitability of this fitting was supported by the results that the adsorption capacity and initial rate of adsorption increased with the temperature. In addition, the equilibrium data followed the Langmuir isotherm model. These results clearly demonstrate that the Cr(VI) adsorption occurred chemically, or through the electrostatic interaction of protonated amino groups on the grafted BPEI chains with hydrochromate (HCrO4−) ions. A higher adsorption capacity was obtained for the silica beads grafted with shorter BPEI chains, and the adsorption capacity of BPEI–silica beads is a little higher than that of linear PEI-grafted silica beads, suggesting that the Cr(VI) ion adsorption is affected by the chain isomerism of PEI (linear and branched) as well as the molecular mass of the grafted PEI chains, in addition to the content of amino groups. The experimental and analytical results derived from this study emphasize that the BPEI–silica beads can be used as an adsorbent for the removal of Cr(VI) ions from an aqueous medium.

Bubble-induced self-assembly synthesis of defective hierarchical boehmite with ultra-high removal efficiency towards Congo red: Preparation and adsorption mechanism

To cope with the increasingly urgent environmental issue and provide promising alternative adsorbents, the synergistic preparation route of dissolution and bubble-induced self-assembly was firstly exploited to guide the reconstruction process of a defective hierarchical porous boehmite-microspheres (BMS) adsorbent in a favorable direction to improve the CR adsorption capacity using aluminium hydroxide industrial waste as raw materials. Multiple non-in-situ physicochemical characterization instruments demonstrate that BMS-4 adsorbent possesses abundant coordinatively unsaturated Al–species, large specific surface area, high porosity, oxygen vacancies and oxygen-containing groups, which promote the maximum adsorption capacities for CR up to 6805.08 ± 5.4 mg g−1. Moreover, the Pseudo-second order model and the Langmuir model are more suitable for describing the behavior of CR adsorption, which proves it is more inclined to be monolayer adsorption and there is no chemical reaction between CR and adsorbent. More importantly, it can be practiced in eight cycles of adsorption tests, achieving ultra-high stability for over 94.46 % of the original adsorption capacity. Combined with density-functional theory (DFT) calculations and experimental results, it is illustrated that the amino protonation is responsible for the additional enhancement of CR adsorption, in addition, oxygen vacancy capture and BMS-4/CR–SO3+–NH3 mechanism for enhanced adsorption of dyes is proposed, both of which show that bubble-induced self-assembly provides a promising route for the preparation of high-performance adsorbents.

A novel ion-responsive hydrogel based on quaternized chitosan and hydroxyethyl cellulose for high efficient chloride ion adsorption

Chloride removal is crucial for industrial wastewater discharge, seawater purification and concrete structure durability. In this study, a novel hydrogel with excellent chloride adsorption property was prepared and the adsorption capacity in relation to external pH and other ions was evaluated. The hydrogel was synthesized using a one-pot method with quaternized chitosan (HACC), hydroxyethyl cellulose (HEC), and carboxymethyl chitosan (CMC) as monomers. By adjusting the material compositions, we effectively modulated the microstructure and charge characteristics of hydrogel, achieving a balanced swelling ratio and optimal adsorption performance. The optimal process conditions were identified as 25 °C and a chloride ion concentration of 40 mmol L−1, achieving a maximum adsorption capacity of 1080 mg g−1. Isotherm modeling showed that the adsorption fits well with the Freundlich isotherm, suggesting multilayer adsorption. The quaternary ammonium groups serve as fixed positive charge sites or active adsorption sites, enabling the hydrogel to efficiently adsorb anions through the synergistic effects of electrostatic interactions, physical adsorption, and amino protonation. The varied adsorption capacities of quaternary ammonium groups for different anions give rise to competitive adsorption phenomena among them. The incorporation of silver ions into the hydrogel greatly enhances its selective adsorption of chloride ions through chemical combination. This work presents a comprehensive strategy for designing a novel hydrogel with exceptional adsorption properties specifically tailored for chloride ions.

Tranexamic acid-loaded catechol-modified hyaluronic acid/carboxymethyl chitosan double cross-linked porous gel micropowders for rapid hemostasis and wound healing

Acquiring rapid and effective hemostasis remains a critical clinical challenge. Current researches focus on concentrating blood components to speed up the hemostatic while ignore the effect of anti-fibrinolysis in promoting blood coagulation. Herein, we designed a novel tranexamic acid (TA)-loaded physicochemical double cross-linked multifunctional catechol-modified hyaluronic acid-dopamine/carboxymethyl chitosan porous gel micropowders (TA&Fe3+@HA-DA/CMCS PGMs) for rapid hemostasis and wound healing. TA&Fe3+@HA-DA/CMCS PGMs exhibited high water absorption rate (505.9 ± 62.1 %) and rapid hemostasis (79 ± 4 s) in vivo. Catechol groups, Fe3+ and the protonated amino groups of CMCS induced bacterial death. Moreover, TA&Fe3+@HA-DA/CMCS PGMs displayed sufficient adhesion to a variety of wet rat tissues. TA&Fe3+@HA-DA/CMCS PGMs on various bleeding wounds, including rat liver injury and tail severed models showed excellent hemostasis performance. The TA&Fe3+@HA-DA/CMCS PGMs could promote the healing of full-thickness skin wounds on the backs of rats. The advantages of TA&Fe3+@HA-DA/CMCS PGMs including rapid hemostasis, effective wound healing, good tissue adhesion, antibacterial properties and ease of use make it potentially valuable in clinical application.

Oligopeptide‐Induced Multifunctional Interface Layer with Protonated Hydrophobic Behavior and Strong Affinity for Highly Stable Zinc Anode

AbstractZinc‐ion batteries (ZIBs) have attracted wide attention due to their low redox potential, high capacity, and intrinsic safety. However, key issues such as zinc dendrite growth, corrosion, and passivation on zinc anode detrimentally affect the electrochemical performance. Herein, as proof of a concept of oligopeptide, glutathione with functional groups including –NH2 and −SH is introduced as an electrolyte additive to construct a multifunctional electrode–electrolyte interface layer on the zinc anode. A protonated amino group (NH3+) is formed, which prevents the adsorption of water molecules on the Zn anode, building a hydrophobic interface layer and thus attenuating corrosion. Moreover, the strong interaction between the −SH and the zinc allows glutathione molecules to be tightly anchored to the electrode surface, constructing a robust interface layer. Consequently, a long cycling life of nearly 3000 h at 1 mA cm−2 for the Zn||Zn symmetric battery is achieved, and a stable cycling life of 1600 h is demonstrated at 3 mA cm−2. Furthermore, Zn||activated carbon (AC) hybrid capacitor with the glutathione‐containing electrolyte runs stably for nearly 28 000 cycles at 5 A g−1, among the best results of reported Zn hybrid capacitors.

THE DEPENDENCE OF ACID-BASE EQUILBRIA AND ACIDITY CONSTANTS OF CONGO RED IN BUFFER SOLUTIONS ON THE IONIC STRENGTH

In this study, the spectrophotometric studies of aqueous ethanol solution of Congo red in various buffers solutions at room temperature 25oC and at different ionic strength of 0.05, 0.1, 0.3, and 0.5 KCl mol L-1 were investigated. The acidity constants of Congo red were estimated by three different methods. The two protonation stages were observed in pH range 2 - 4 and 4 - 6 as result as protonation of amino group and azo groups. The dependence of absorption spectra of Congo red on the ionic strength of solutions which exhibited blue shift with increases ionic strength in addition the shape and intensity were varied. Therefore, the acid-base equilibria shifted toward the higher pHs with the rise in ionic strength. Also, the acidity constants were affected by the ionic strength which the acidity constants decrease with increasing ionic strength of solution because the electrostatic interaction force increased.

Preparation of nano-silver containing black phosphorus based on quaternized chitosan hydrogel and evaluating its effect on skin wound healing

Hydrogels with favorable biocompatibility and antibacterial properties are essential in postoperative wound hemorrhage care, facilitating rapid wound healing. The present investigation employed electrostatic adsorption of black phosphorus nanosheets (BPNPs) and nano‑silver (AgNPs) to cross-link the protonated amino group NH3+ of quaternized chitosan (QCS) with the hydroxyl group of hyaluronic acid (HA). The electrostatic interaction between the two groups resulted in the formation of a three-dimensional gel network structure. Additionally, the hydrogel containing AgNPs deposited onto BPNPs was assessed for its antibacterial properties and effects on wound healing. Hydrogel demonstrated an outstanding drug-loading capacity and could be employed for wound closure. AgNPs loaded on the BPNPs released silver ions and exhibited potent antibacterial properties when exposed to 808 nm near-infrared (NIR) radiation. The ability of the hydrogel to promote wound healing in an acute wound model was further evaluated. The BPNPs were combined with HA and QCS in the aforementioned hydrogel system to improve adhesion, combine the photothermal and antibacterial properties of the BPNPs, and promote wound healing. Therefore, the reported hydrogels displayed excellent biocompatibility and hold significant potential for application in the field of tissue engineering for skin wound treatment.

Nitrate Uptake from Water Using Amine‐Functionalized Meso‐ and Macroporous Carbons

AbstractMeso‐ and macroporous carbon materials modified with protonated amino groups (−NH3+Cl−) for aqueous nitrate (NO3−) uptake were prepared by surface functionalization with aminopropylsilane. Although the silane coupling treatment decreased the specific surface area of the carbons, surface modification with the −NH3+Cl− group improved the NO3− uptake capacity of both meso‐ and macroporous carbons. The amount of NO3− adsorbed depends on the specific surface area of the adsorbent; an adsorbent with a larger specific surface area exhibits a larger uptake capacity. Enhanced NO3− adsorption onto the NH3+Cl−‐modified surface occurred through an ion‐exchange mechanism. Changes in the pH of the sample solutions before and after NO3− uptake revealed the competitive exchange of NO3− and OH−. NO3− uptake is inhibited by the coexistence of anions other than NO3− (excess Cl−, SO42−, CO32− and HCO3−) and/or OH− at high pH. In particular, the influence of excess Cl− reveals that NO3− uptake through ion exchange is not irreversible, and the adsorption capacity is determined based on the ion exchange equilibrium.

Preparation and release of antibacterial Na-mica-4/chlorhexidine nanocomposites

High charge swelling micas are layered silicates used in adsorption of several inorganic and organic species. In this study, we evaluated the adsorption of chlorhexidine digluconate on highly charge mica Na-mica-4. Drug release and antibacterial action against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) using the direct contact test for mica/chlorhexidine hybrids were evaluated. The hybrids were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, zeta potential measurements, CHN elemental analysis, and scanning electron microscopy. Chlorhexidine interacts successfully with the mica surface. The maximum amount of chlorhexidine incorporated was 583 mg g−1, and the characterizations indicated that electrostatic attraction between the protonated amino group of the drug and the negative surface of clay was predominant in the formation of hybrids. Release kinetics study indicated that 80% of the drug release occurred in the first 12 h. The antibacterial test proved to be dependent on the time of chlorhexidine release, reaching 100% inhibition against S. aureus and E. coli after 0.5 h and 6 h, respectively.