Ammonium Research Articles

Schistosomiasis transmission: A machine learning analysis reveals the importance of agrochemicals on snail abundance in Rwanda.

Schistosomiasis is an important snail-borne parasitic disease whose transmission is exacerbated by water resource management activities. In Rwanda, meeting the growing population's demand for food has led to wetlands reclamation for cultivation and increased agrochemical enrichment for crop production. However, the ecological consequences of agrochemical enrichment on schistosomiasis transmission remain unexplored. A malacological survey was conducted in 71 villages selected from 15 schistosomiasis endemic districts. Snail sampling was done in wetlands used for agriculture, along lake Kivu and at constructed multipurpose water dams. Water physico-chemical parameters were collected at all snail sampling sites. Analysis of collected data was performed using Xgboost (gain) and Random Forest (mean decrease in accuracy), machine learning techniques, to construct models that evaluate and categorize the importance of all physico-chemical properties on the presence and abundance of intermediate host snails (IHS). Different sets of parameters were relevant for the presence and abundance of Biomphalaria spp. and/or Bulinus spp. snails. Electrical conductivity, elevation, magnesium and lead content were deemed to shape the presence and abundance of Bulinus spp. snails. The impact of phosphate ion concentration, ammonia ions, total nitrogen and total organic carbon levels mirrored their importance towards the presence and abundance of Biomphalaria spp. Factors such as pH, electric conductivity, total nitrogen content and total organic carbon influenced the coexistence of both species. Our study highlights the value of integrating a wide range of predictor variables, enabling effective variable selection to uncover important predictors of snail distribution. The results suggest that agrochemical compounds can enhance the abundance of IHS leading to an increased risk of Schistosoma transmission. Snail surveillance could therefore be integrated into agricultural expansion projects in our match towards schistosomiasis elimination. Recognizing the impact of agrochemicals on IHS is crucial for minimizing schistosomiasis transmission among those working in wetlands while meeting the growing need for food.

Enhanced Efficiency and Stability of Triple-Cation Perovskite Solar Cells through Engineering of the Cell Interface with Phenylethylammonium Thiocyanate.

It is reported that the tricationic mixed halide perovskite Csx(FAyMA1-y)1-xPb(IzBr1-z)3 (CsFAMA) possesses a stable crystal structure and outstanding bandgap tunability, rendering it one of the most competitive candidates for commercial perovskite solar cells (PSCs). Nevertheless, the numerous defects at the interface of the tricationic perovskite give rise to a significant constraint on the light capture performance of the device. Simultaneously, water molecules form intermediate compounds with the perovskite at the interface via hydrogen bonds, accelerating the degradation of the perovskite. This study reports the introduction of two-dimensional (2D) phenylethylthiocyanate (PEASCN) at the interface of three-dimensional (3D) perovskite. This approach significantly passivates the surface defects of the perovskite. Concurrently, due to the propensity of the organic ammonium cation PEA+ to interact with the FA+ base within the perovskite, SCN- is exposed outward to form a small-molecule hydrophobic layer. This method markedly reduces the loss of charge recombination and significantly enhances the device stability. The results indicate that the efficiency of the conventional device treated solely with PEASCN is as high as 23.94%. The unsealed device retains 85.12% of its initial efficiency after being placed in a conventional environment for 500 h. Furthermore, this surface passivation and hydrophobic strategy can be universally applicable to perovskite types with a high FA+ content.

Supramolecular Gels Derived from Primary Ammonium salts of Naproxen and its Amino Acid Derivatives: Design, Synthesis, Structures and its Application as Anti-cancer Agent Against Melanoma Cell B16-F10.

Supramolecular synthon approach was employed to develop a self-drug-delivery system based on organic salt based supramolecular gelators. One such key gelator NAP-PHE∙PEA derived from naproxen-phenylalanine conjugate and phenethylamine showed ability to gel both water and organic solvents. Supramolecular interactions such as π-π and C-H…π were probed by variable-temperature 1H-NMR spectroscopy in the hydrogelation process of NAP-PHE∙PEA. Single crystal structures of nine out of twelve salts were determined and the supramolecular synthon present therein was carefully analyzed. Intriguing insights of the gel-network structure was also investigated by structure-property correlation based on single-crystal and powder X-ray diffraction analysis of gelator/nongelator salts. The gelator salt NAP-PHE∙PEA displayed significant anti-cancer property against cancer cells (B16-F10. HeLa and A375); it was found non-cytotoxic against normal cell lines (E.derm and HEK-293) at comparable concentrations as revealed by MTT assays. The gelator salt NAP-PHE∙PEA also displayed significant anti-cancer behaviour against B16-F10 (scratch assay) and HeLa (multi-cellular tumour spheroid). The methyl salicylate gel of NAP-PHE∙PEA displayed shape-sustaining, load-bearing, self-healing properties along with rheoreversibility, which are considered important for topical applications.

Additives Capable of Stably Supplying Anions/Cations for Homogeneous Lithium Deposition/Stripping.

One of the important factors leading to lithium dendrites is a slow lithium-ion mass transport and imbalanced distribution of the Li+ concentration and nuclei sites on the anode surface. To achieve uniform lithium deposition during the charge and discharge process, we introduce a homemade new copolymer (with the quaternary ammonium group N3R+I- on its side chain as the main functional group), named P35, as a functional electrolyte additive to regulate the lithium deposition. Theoretical calculations show that under the strong coordinating interaction between I- and N3R+, P35 preferentially adsorbs onto the lithium foil surface, effectively countering the adsorption of lithium salt anions such as PF6-. Moreover, the positive charge carried by the quaternary ammonium salt group of P35 could interact with PF6- to limit their mobility. Consequently, the dipole interaction on lithium ions is diminished, leading to an enhancement in the transport rate and a decrease in the concentration gradient of lithium ions. Furthermore, a more efficient SEI was formed due to the dual charges electrostatic shield formed by N3R+I-. Li-Li symmetric cells and Li-LiFePO4 full cells assembled with electrolytes with P35 exhibit better rate performance, smaller polarization, and smoother deposition morphology in comparison to the cells without the P35 additive.

Toward the Electrostatic Catalysis of Nucleophilic Substitutions: A Surface Chemistry Study of the Menshutkin Reaction.

The catalysis of nonredox reactions by external electric fields is one of the most rapidly expanding areas of chemistry. The Menshutkin reaction, a classic example of bimolecular nucleophilic substitution (SN2), involves the conversion of a tertiary amine to a quaternary ammonium salt by coupling it with an alkyl halide. The reaction barrier of the Menshutkin reaction is theoretically predicted to be highly sensitive to the magnitude and direction of an external electric field experienced by the transition state. In this study, we investigate how near-surface electric fields can drive this prototypical nucleophilic substitution by examining the coupling of a diffusive redox-tagged tertiary amine with an electrode-tethered alkyl bromide under a variable external bias. Our findings reveal a competition between electrostatically assisted reactions, solvent effects, and electrochemically triggered side reactions involving radical intermediates. We estimate that only about 5% of the coupling events are attributable to the external field, while the majority of the reaction products originate from electrochemically generated radical intermediates.

Nature-inspired Novel Quaternary Ammonium Compounds: Synthesis, Antibacterial and Antibiofilm Activity.

Inspired by marine compounds isolated from sponges and the increased need for new effective antimicrobials, novel quaternary ammonium compounds with long alkyl chains (C8-C12) were designed and synthesized. Antibacterial and antibiofilm activity of new compounds was evaluated against six microbial strains (S. aureus, E. coli, and P. aeruginosa). All synthesized ammonium salts displayed antibacterial activity with MIC values ranging from 5.0 to 25.0 μg/mL. In addition, most compounds showed strong inhibition of biofilm formation of S. aureus ATCC 25923, P. aeruginosa PA01, and colistin-resistant P. aeruginosa (CRPA) at a concentration of 5.0 μg/mL. Ammonium salt 3 showed 100 % inhibitory activity against all tested bacterial biofilms except that of colistin-resistant S. aureus (CRSA).

Performance evaluation of resin wafer electrodeionization for enhanced nitrogen recovery from ammonium-containing water environment

Ammonium ion (NH4+) is a common pollutant from various sources like human and animal waste, industrial effluents, agricultural runoff, and commercial products, with traditional treatment methods often generating secondary contaminants, such as nitrite and nitrate. In this study, an energy-efficient resin-wafer electrodeionization (RW-EDI) process was employed for nitrogen recovery from ammonium-rich water. The system was operated in a continuous mode, with voltage-current curve measurements identifying a limiting current density of 2.2 A cm−2. With the NH4+ concentration of 1 g/L and a flow rate of 2.4 mL min−1, the system was tested at various cell voltages (1.2–7.2 V). The system could achieve 80 % NH4+ removal efficiency at a cell voltage of 3 V, current density of 2.2 A cm−2, influent NH4+ level of 3 g/L, and flow rate of 6.4 mL min−1. The observed current efficiency and the calculated power consumption were 41 % and 0.78 kWh m−3, respectively. Finally, a mass balance model was developed to predict the number of RW-EDI stacks for complete removal of NH4+ from the feed. Overall, the result from this study demonstrates that the RW-EDI-based system could be a promising technology for recovering nitrogen from wastewater.

Poly(isatin biphenylene) anion exchange membranes based on functionalization of long side chain N-spirocyclic

N-spirocyclic cations have high alkali resistance stability, but their poor mobility hinders the aggregation of cationic groups, which makes it difficult to form a good microphase-separated structure for OH− ion transport. In this work, two kinds of bicationic N-spirocyclic cations containing spacer side chains (BM-DSU and BM-DSD) were designed and synthesized, and a series of poly(isatin biphenylene) anion exchange membranes containing bicationic N-spirocyclic side chains were prepared by grafting different ratios of N-spirocyclic cations onto the poly(isatin biphenylene) polymer backbone. The bicationic N-spirocyclic quaternary ammonium salts containing spacer side chains increased the migration rate of the cationic groups and constructed a more continuous ion transport channel. The OH− ionic conductivities of BM-DSD-PIB-40 and BM-DSU-PIB-40 were 67.8 mS cm−1 and 63.4 mS cm−1 at 80 °C. After soaking at 80 °C in 1 M NaOH for 730 h, the residual conductivities of BM-DSD-PIB-30 and BM-DSU-PIB-30 were 73.19 % and 78.02 %, respectively.

Efficient one-pot tandem C-C formation reaction catalyzed by a multi-functionalized polyacrylonitrile fiber catalyst

A simple and straightforward method has been proposed in this work to construct a multi-functionalized polyacrylonitrile fiber catalyst containing carboxylic acid, tertiary amine, and quaternary ammonium salt to enable series one-pot C-C bond formation in water. The fiber catalyst was prepared from polyacrylonitrile fiber using a two-step method and characterized using various detection techniques. Furthermore, the activity of multi-functional synergistic catalysts can be controlled by adjusting the ratio of acid and base. It is noteworthy that the polyacrylonitrile fiber catalyst with an acid-base ratio of 3:1 (PANF-ABNCl3/1) exhibited superior catalytic activity and high yield in a variety of C-C generation reactions. Additionally, the PANF-ABNCl3/1 catalyst demonstrated exceptional recyclability (at least 10 times) and performed well in scale-up (7.4g, 96%) and continuous flow experiments (can be used continuously for 7 × 24h) using kettle and tubular fixed bed reactor respectively. These findings suggest that the PANF-ABNCl3/1 catalyst holds promise for industrialization.

Encapsulation of Antarctic krill peptide by polysaccharide-based nanoparticles: Preparation, characterization, evaluation of stability and hypoglycemic activity

The aim of this study was to construct a chitosan quaternary ammonium salt (HTCC)/sodium alginate (SA) nanoparticle delivery system for the encapsulation of Antarctic krill peptide (AKP), with the goal of enhancing its stability and post-digestive hypoglycemic activity. Additionally, the effect of the content and encapsulation sequence of HTCC/SA on the structure and properties of AKP-loaded nanoparticles (AKP-loaded NPs) was investigated. As the content of the outermost wall material (HTCC) increased, the particle size of nanoparticles initially increased and then decreased. Concurrently, the zeta potential showed a trend of increase, ranging from -38.77 to 46.07 mV. When SA was used as the outermost wall material, the nanoparticles exhibited a smaller particle size (240.1 nm) and better dispersibility. Electrostatic interaction and hydrogen bonding were the major forces involved in the formation of AKP-loaded NPs. X-ray diffraction revealed that AKP was successfully encapsulated in an amorphous state. Scanning electron microscopy showed that AKP-loaded NPs had an elliptical or blocky appearance. Moreover, AKP-loaded NPs demonstrated good storage and temperature stability, while nanoparticles with HTCC in the outermost layer (HTCC:SA=2:1) showed good pH and ionic stability. During simulated digestion, AKP-loaded NPs inhibited the release of AKP in gastric fluid. Consequently, the hypoglycemic activity of digested AKP-loaded NPs was remarkably higher than unencapsulated AKP. Notably, the nanoparticles with HTCC in the outermost layer provided superior hypoglycemic activity. In summary, the polysaccharide-based delivery system exhibited great potential to improve the stability and post-digestive hypoglycemic activity of AKP, broadening its applications in the food and pharmaceutical industries.

Synchronization of extraction and chromatographic conditions of diverse physicochemical behavior of pseudoephedrine, loratadine and desloratadine for their simultaneous determination in human plasma: Application to pharmacokinetic study

A selective, sensitive, and rapid LC-MS/MS method has been developed, optimized, and validated for the simultaneous determination of pseudoephedrine (PSE), loratadine (LOR), and LOR active metabolite, desloratadine (DES) in K3EDTA human plasma. A simple liquid–liquid extraction method was adopted for extraction of the 3 analytes and their internal standards; chlorpheniramine (CLP), loratadine D4 (LOR-D4), and desloratadine D4 (DES-D4), respectively, giving consistent recovery results (78.38––88.23 %) using diethyl ether: dichloromethane (80:20, v/v) as the extraction solvent. The chromatographic separation was challenging due to the polarity differences between PES, which is more polar, and LOR and DES, which are less polar that affected their physicochemical properties including the retention of the drugs on C18 column. The separation was achieved using of isocratic elution of 20 mM ammonium formate and 2 mM trifluoracetic acid ammonium salt: acetonitrile containing 0.15 % formic acid (12:88, v/v) as a mobile phase pumped onto a Supelco Discovery® C18 (4.6 mm x 100 mm, 5 µm) at 35 °C with a flow rate of 0.8 mL/min. The use of trifluoracetic acid ammonium salt as an ion pair reagent in the selected mobile phase allowed good retention of the polar PSE on the used C18 column with a reasonable retention time. Positive Electrospray ionization was employed followed by detection using a tandem mass spectrometer in multiple reactions monitoring (MRM) mode. The sample analysis of this study was conducted in compliance with ICH guideline M10 on bioanalytical method validation and study sample analysis. The method was linear over the concentration range of (4–1200) ng/mL for PSE, (50–15000) pg/mL for both LOR, and DES. The developed method was accurate (91.14–110.30 %), precise (0.53–7.86 %), and was applied to study the pharmacokinetic profile of the cited drugs in the plasma of healthy human volunteers after single oral administration of the fixed-dose combination Claritin D® tablet, (240/10 mg) of PSE, and LOR, respectively.

Antibacterial activity of polyethylene film by hyperthermal hydrogen induced cross-linking with chitosan quaternary ammonium salt

In this study, hyperthermal hydrogen-induced cross-linking (HHIC) technology was applied to construct a dense cross-linking layer of antibacterial chitosan quaternary ammonium salt (HTCC) to PE surface through the selective cleavage of CH bonds and subsequent cross-linking of the resulting carbon radicals. Before HHIC treatment, UV-Ozone was used to activate PE surface to facilitate HTCC adsorption. FT-IR and XPS analyses proved the successful cross-linking between PE and HTCC. From AFM analysis, the prepared PE cross-linked HTCC film (PE-c-HTCC) showed the rougher surface with average roughness (Ra) of 9.16 nm. The water vapor permeability (WVP) and oxygen permeability (OP) values of the film were decreased by about 83 % and 97 %, respectively. Additionally, the film exhibited strong antibacterial properties against E. coli and S. aureus. In terms of these properties, the shelf life of fresh beef could be extended for 2 days after packing with the PE-c-HTCC film.

Monomer in situ polymerization as topological sutures to achieve strong interfacial adhesion and long-term anti-mold of renewable adhesive

Integrated long-term anti-mold and high bonding capacity properties into renewable biomass adhesives hold significant importance for promoting the green and sustainable development of the wood industry, yet it remains an immense challenge. Drawing inspiration from the design of molecular suture materials, we successfully developed a series of innovative quaternary ammonium salt monomers (APM12) that polymerize in situ with glycidyl methacrylate (GMA) at the interface of bonded adherents. This process constructed molecular sutures on the molecular scale, forming a robust topological entanglement network between the adhesive and the wood substrate. Such a rational structure design allowed the modified soybean meal (SM) adhesive to present a boosted bonding strength and water resistance (2.08 and 1.05MPa). The stably riveting high-effect anti-germ platform imparted the protein adhesive with ultra-long mildew resistance of 150 days for liquid SM@GMA-APM12 adhesives, outperforming all the previously reported protein-based bio-adhesives. The implementation of the suture strategy through an in situ sutural interspersed crosslinking network provided a straightforward approach and offered a novel solution for creating renewable adhesives with multiple desirable properties. Moreover, this suture strategy can be applied to other interface strong adhesion and anti-bacterial materials comprised of polymer structure, such as hydrogel, organic coatings, and membrane, broadening its scope of applications.

Adsorption characteristics and mechanism of novel ink melanin composite modified chitosan for Cd(II) in water

In this study, chitosan (CS), carboxymethyl chitosan (CMCS), and chitosan quaternary ammonium salt (HACC) were successfully loaded with ink melanin (ME) as efficient adsorbents for Cd(II) removal. The results of batch adsorption experiments and structural characterization showed that the modified CS loaded with ME improved the adsorption capacity of the composites for Cd(II). The pseudo-second-order kinetic and Langmuir equations were better suited to describe the batch adsorption experiments. The adsorption of Cd(II) was chemisorption with desirable adsorption effect when the concentration of the three composites was 0.5 mg/mL and the pH value was neutral. Among them, HACC-ME demonstrated remarkable Cd(II) adsorption performance (107.18 mg/g) and sustained an 85 % efficiency in Cd(II) removal over five adsorption-desorption cycles. Ion exchange, complexation, electrostatic attraction, and hydrophobic interaction were the primary mechanisms for Cd(II) removal. Overall, HACC-ME could be employed as a low-cost and highly efficient new natural adsorbent material for the removal of Cd(II) ions from wastewater. These findings illuminate pathways for the development of efficient and novel natural adsorbent materials for environmental cleanup purposes.

One-step condensation synthesis of di-tertiary ammonium salt protic ionic liquid for efficiently catalytic CO2 cycloaddition reaction under cocatalyst- and solvent-free conditions

A novel protic ionic liquid di-tertiary ammonium bromide ionic liquid (DTAB-IL) was synthesized by one-step condensation at 0 ℃ with 85 % yield. DTAB-IL also exhibited effective catalytic activity for CO2 cycloaddition without cocatalyst and solvent. The catalytic reaction conditions were optimized to 90 ℃, 4 h, 1 MPa, and the yield of propylene carbonate was obtained 96 % with high selectivity 99 %. Under the optimal conditions, DTAB-IL catalyst exhibited good recyclability and universality to various epoxides. Furthermore, temperature influence and kinetic investigation for propylene carbonate synthesis were studied. The activation energy for DTAB-IL catalyzing CO2 cycloaddition reaction was 43.93 kJ/mol, and the reaction was found to follow first-order for propylene oxide. Efficient cycloaddition reaction of CO2 and epoxide was attributed to the activation of epoxide and CO2 by di-tertiary ammonium and epoxide ring-opening by bromide anion in DTAB-IL.

Balancing hydrophobicity and surface potential in bio-based bisfuran-containing polyamide coatings for enhanced long-term antibacterial efficacy and endotoxin adsorption

To develop antimicrobial protective materials based on renewable polymers, we synthesized a series of bio-based bisfuran-based polyamide (bFPA) polymers with various functional groups, including allyl quaternary ammonium cations, decyl quaternary ammonium cations, and sulfonate betaine. These bFPA-based coating materials, featuring excellent thermal stability (>230 °C) and biocompatibility, were facilely fabricated on polyurethane (PU) substrates by blending and crosslinking with unsaturated aliphatic PU resin. By altering the combination of different functional groups in bFPA polymers, we controlled the hydrophilicity/hydrophobicity and surface charge properties of the bio-based coating. Compared to pure PU coatings, the bFPA-based coatings with moderate hydrophilicity/hydrophobicity and surface potential significantly reduced the adhesion of model protein and bacteria by approximately 70 % and >99 %, respectively, demonstrating outstanding anti-protein and anti-bacterial adhesion properties. Even after seven cycles of use, the coatings maintained the ability to kill ∼80 % and >99 % of Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria, respectively, indicating long-lasting antibacterial activity. Additionally, the optimized bFPA-based coatings effectively adsorbed ∼80 % of endotoxins from damaged Gram-negative bacteria through electrostatic interactions, thereby reducing the risk of inflammation and sepsis. The development of bio-based polyamide coatings with long-term antibacterial and endotoxin adsorption properties significantly advances their safe and reliable application of in the field of biomedical devices.

Ionic quaternary ammonium-triazole polymers as efficient single-component catalysts for CO2 conversion

Ionic organic polymers with halide counterions have been investigated as effective and reusable single-component, heterogeneous catalysts for the cycloaddition of CO₂ and epoxides to form cyclic carbonates. In this study, we synthesized three new ionic polymers featuring quaternary ammonium-triazole functional groups with iodide counterions. Copper-catalyzed azide-alkyne cycloaddition (CuAAC) between tetrapropargylammonium bromide and various diazide compounds (N3–Ar–N3), where Ar represents 1,4-xylene, 1,5-naphthalene, and 4,4′-phenylbenzamide followed by halide exchange, afforded the organic polymers QAP1–3, respectively. The formation of triazole moieties and the disappearance of azide functional groups were confirmed by 13C CP/MAS NMR and FT-IR spectroscopy, respectively. CO2 sorption studies showed reduced adsorption capacities compared to neutral amine analogs. The xylene-linked polymer (QAP1) exhibited the highest catalytic efficiency for CO2/epoxide cycloaddition, achieving high conversion and selectivity under 10 atm CO2 at 120 °C. Reusability study showed that QAP1 could be reused for four cycles with minimal loss in activity, though some thermal decomposition of quaternary ammonium groups was observed in solution.

Antibacterial carboxymethyl chitosan hydrogel loaded with antioxidant cascade enzymatic system for immunoregulating the diabetic wound microenvironment

Diabetic wound healing faces several complex challenges, such as hypoxia, oxidative stress, and bacterial infections, which severely inhibit the wound-healing process. Herein, a quaternary ammonium salt-crosslinked carboxymethyl chitosan hydrogel (TPC) with excellent antioxidant and antibacterial properties was developed to immunoregulate the diabetic wound microenvironment. The TPC hydrogel was prepared by first mixing carboxymethyl chitosan (CMCS) and protocatechualdehyde (PA), followed by the addition of a quaternary ammonium cross-linker (TSPBA) and a superoxide dismutase (SOD)–catalase (CAT) cascade system. The immobilized SOD and CAT retained their activity, continuously converting endogenous ·O2− and H2O2 to O2 and H2O. PA also provided the TPC hydrogel excellent oxygen and nitrogen radical scavenging capacity. The quaternary ammonium groups in TSPBA significantly enhanced the inherent antibacterial ability of CMCS-based hydrogels. In diabetic wound-healing experiments, this porous and adhesive TPC hydrogel effectively closed wounds and regenerated skin tissue, resulting in shorter wound edges, thicker granulation, and higher collagen deposition levels compared with other groups. The TPC hydrogel also promoted macrophage polarization toward the M2 phenotype, accelerating wound healing by upregulating IL-10 expression, downregulating IL-6 expression, and enhancing angiogenesis. These results demonstrate the great potential of TPC hydrogel as a promising therapeutic dressing for treating diabetic wounds.

Innovative ammonia harvesting from wastewater: A controlled closed-loop process at high pH for enhanced nutrient recovery

This study presents a new, sustainable, high-pH recirculating batch process for the regeneration of NH4+-laden cation exchange resins, while recovering the ammonia as a pure, reusable, solid salt (NH4Cl). The process efficiently recycles a minimal volume of regeneration solution while reducing NaCl consumption between cycles. The regeneration solution, containing a high concentration of NaCl maintained at high pH (pH > 11) allows Na+ to replace the desorbed NH4+, which, due to the high pH, completely transforms into NH3. Real time pH monitoring of the regeneration solution and the column effluent provided accurate tracking of the regeneration rate and allowed concise endpoint determination. Ammonia was recovered by evaporation of the exhausted regeneration solution followed by sublimation (and thereafter deposition) of NH3 and HCl, which produced pure NH4Cl salt.The optimal working conditions for the cation exchange regeneration were identified as 1 M NaCl, pH 12.0, and regeneration solution volume of 1 bed volume. Single-column application of six adsorption-regeneration cycles (no zeolite replacement) showed that the process conditions do not degrade the resin’s adsorption performance. Cost assessment of two possible ammonia recovery options indicated that while stripping NH3 from the regeneration solution and reabsorbing it in an acidic solution is operationally easier, the sublimation-based approach yields a more valuable product. For an optimized sublimation approach, a low regeneration solution volume, combined with a high resin capacity for NH4+, are essential.This process demonstrates a sustainable solution for ammonia salt recovery from wastewater, offering a circular approach that does not only add an important control to the regeneration step, but also harvests ammonia as a reusable product.

Duckweed (Lemna minor L.) as a natural-based solution completely offsets the increase in ammonia volatilization induced by soil drying and wetting cycles in irrigated paddies

One of the primary pathways of nitrogen loss in rice fields, ammonia (NH3) volatilization resulting in low nitrogen use efficiency and contributes significantly to near-surface atmospheric pollution. Duckweed (Lemna minor L.), a common small floating plant in rice fields, often completely covers the water surface. However, the extent to which this biotic cover affects ammonia flux remains unclear. A three-year field experiment was conducted to investigate the effects of duckweed cover on NH3 volatilization in rice fields under two different irrigation management practices (Flooding irrigation vs. alternate wetting and drying irrigation). In the duckweed-free paddies, alternate wetting and drying irrigation significantly increased the cumulative ammonia emissions over the full observation period by 16.6 %, 22.5 % and 7.8 % in 2020, 2021, and 2022, respectively, compared to flooding irrigation. Compared to the duckweed-free paddies, the presence of duckweed significantly mitigated cumulative NH3 volatilization in rice fields, regardless of the irrigation regimes. Under flooding irrigation, the reduction in NH3 volatilization with duckweed cover reached 6.3 %, 33.2 % and 37.6 % over three consecutive years. The reduction was 23.3 %, 48.2 % and 41.8 % under alternate wetting and drying irrigation, demonstrating that duckweed achieved greater reductions in NH3 volatilization under alternate wetting and drying irrigation than flooding irrigation. An independent incubation experiment revealed that physical coverage, ammonium ion absorption and surface water temperature reduction were primary factors contributing to duckweed-induced NH3 emission mitigation, accounting for 50.9 %, 28.4 %, and 20.7 %, respectively. The present study indicates that duckweed might prove a promising nature-based solution for mitigating the potential environmental risks of excessive reactive nitrogen outputs from rice paddies, and for promoting the broader application of alternating wet and dry irrigation.