Alkali Conditions Research Articles

Influence of curing regimes on strength development of slag-waste glass-based binary geopolymer.

The disposal of waste glass is an environmental concern to municipal solid waste management authorities. An effective approach for reducing the environmental burdened and disposal problems with waste glass is its reuse in the construction industry. Hence, the feasible utilization of glass powder (GP) was assessed by studying the strength properties of the slag-GP binary geopolymers cured at different curing regimens. It includes ambient (30 °C), low (- 15 °C, 0 °C, and 15 °C) and high temperatures (45 °C, 60 °C, 75 °C, and 90 °C) under dry and humid conditions. In addition, the impact of submerged and autoclave curing conditions was assessed. The workability, setting period, and bulk density of the slag-GP mixes were reduced with increased GP content. As per the experimental data, the optimum GP dose was 10% at ambient temperature. However, a higher dose of GP is beneficial for specimens cured at elevated temperatures. No improvement in strength with the curing period was noticed for specimens cured at low temperatures. Under humid curing, slag-GP geopolymers attained dense microstructure, whereas intense micro-cracks were observed in dry environments. Submerged curing conditions achieved better strength gain under alkali conditions compared to normal and saline conditions. Autoclave-curing conditions established rapid strength gain due to geopolymer mechanism advancements. Moreover, the proposed analytical models predict well the CS at different GP contents, curing temperatures, and curing durations.

Egg white-derived nanocomposite microspheres for alveolar bone defects management

In this study, we developed a new class of nanocomposite microspheres comprising of Ca2+ crosslinked chicken egg white (EW) and Zn-doped mesoporous silica nanoparticles (Zn–SiO2), targeting the challenging alveolar defect repair applications. We drew inspiration from the “Chinese century egg” preservation techniques to crosslink the EW protein using Ca2+ ions under alkali conditions and this has led to a novel alkali-ionic (ai) cross-linked EW network with enhanced mechanical stability. Molecular dynamic simulation was deployed to elucidate the protein crosslinking mechanisms within the microspheres. Zn-doped mesoporous silica nanoparticles (Zn–SiO2) were introduced as degradable functional nanofillers. Results show that the unique Zn–SiO2/ai-EW nanocomposite microspheres have enhanced mechanical strength, desirable degradation profile and biomineralization capabilities. In vitro and in vivo studies show that with the gradual released Ca2+ from the EW matrix can promote osteogenic differentiation; Si4+ and Zn2+ can modulate the immune microenvironment and enhanced angiogenesis. The promising results have demonstrated the strong potential of Zn–SiO2/ai-EW composite microspheres for alveolar bone repair applications.

Interfacial lignin glued cellulose/aramid nanofiber membranes: Combing toughness, stability, and dye rejection performances

Nanoscale cellulose-based membranes have been considered as perfect candidates for organic dye separation attributed to their sustainability, high aspect ratio, and nanoscale designation. However, as natural polysaccharide, nanocellulose still suffers from drawbacks like brittleness and vulnerability. In this work, the tough and stable lignocellulose nanofibers (LCNFs) based composite membranes were fabricated by introducing lignin modified aramid nanofibers (DANFs) as reinforcing agents. Being benefit from the interfacial lignin bridging effects, the noncovalent interactions (e.g., H-bond and π-π stacking) between LCNFs and DANFs strengthened, and the resultant composite membranes presented enhanced tensile strength (∼186.9 MPa, 6.3 time higher than LCNFs membranes), toughness (∼9.28 MJ/m3, 105 time higher than LCNFs membranes), Young’s modulus (∼8.43 GPa, 4.6 time higher than LCNFs membranes), as well as the optimized stabilities (in organic, acidic and alkali conditions). Combing all these advantages, the composite membranes demonstrated promising dye rejection performances toward methyl violet (a reject rate of ∼98.54 % and a flux of ∼29.76 L•m−2•h−1•bar−1), and can removal 63.08 % of methyl violet after 10 recycles. Thus, this research paves a simple and efficient way to made strong LCNFs-based separation membranes that are suitable as dye separator in harsh environments.

Multi-Lasso Peptide-Based Synergistic Nanocomposite: A High-Stability, Broad-Spectrum Antimicrobial Agent with Potential for Combined Antibacterial Therapy.

Lasso peptides, natural biological microcins composed of small molecules, have demonstrated efficient bactericidal activity. However, a single lasso peptide is characterized by a narrow and targeted bactericidal spectrum. In this study, a chitosan (CN) derivative-based polymer nanomaterial incorporating three lasso peptides (MccY, MccJ25, and Klebsidin) was designed and synthesized to broaden its antimicrobial spectrum. To enhance resistance to acid and alkali conditions, arginine was appended to the terminus of conjugates, resulting in Chitosan-Lasso-Peptides-Arg (CN-LPs-Arg), and the nanomaterial biocompatibility and bactericidal activity were characterized. Chemical stability test results demonstrate that CN-LPs-Arg effectively buffered the acid-base effect of the compound. Notably, CN-LPs-Arg extended the antimicrobial spectrum of Gram-negative and Gram-positive strains including Klebsiella, Salmonella, and Staphylococcus (MIC = 0.01-1.0 μM). CN-LPs-Arg exerts its destructive effects on bacteria via a series of mechanisms; it adheres to and then penetrates the membrane, causes rupture, and leads to bacterial death. Transcriptomic data revealed that CN-LPs-Arg produced a distinct inhibitory effect on ribosomal protein subunits synthesis pathways and membrane metabolic inhibition. Furthermore, CN-LPs-Arg was nontoxic to cells and exhibited excellent biocompatibility. CN-LPs-Arg reduced bacterial burden in organs and the levels of inflammatory factors IL-6, IL-8, and TNF-α in tissues of mice with acute bacterial infections. Furthermore, it promoted the recovery of Klebsiella-infected C57BL/6 mice, demonstrating a favorable therapeutic effect in vivo. The multilasso peptide-based synergistic nanocomposite of CN-LPs-Arg exhibited high stability as a broad-spectrum antimicrobial agent with potential for combined antibacterial therapy and utilization in the fields of food, biomedicine, and public health.

Assessment of the bioflocculant production and safety properties of Metabacillus hrfriensis sp. nov. based on phenotypic and whole-genome sequencing analysis

Bioflocculant is considered to have broad application prospect in multi fields for the nontoxic and biodegradation properties. Screening new bioflocculant-producing bacteria with high flocculating activity, stress resistance characteristics, and application security is a significant action in the development of the biofloc technique. A novel bioflocculant-producing species, Metabacillus hrfriensis CT-WN-B3, was isolated from alkali-tolerant strains distributing in Daqing, Heilongjiang Province, China. A strong activity flocculant was detected in the extracellular polymeric substance (EPS) of CT-WN-B3, which could form biofloc more effectively under alkali conditions, with a flocculating rate of more than 70 %. The principal component of the bioflocculant was identified as the polysaccharide of extracellular polymeric substance (EPS) because of its 75.183 ± 2.268 % flocculation contribution, which was very significantly higher than that of the protein and the lipid (p < 0.01). Basing on the whole-genome sequencing analysis of CT-WN-B3, none gene encodes a known virulence factor, but two genes correspond to antibiotic resistance. Antibiotic resistance tests showed CT-WN-B3 was resistant to clindamycin. In the assessment of the antimicrobial spectrum, no antibacterial active substance was detected in the supernatant of CT-WN-B3 culture. Totally, the results of the safety assessment had eliminated the doubts about the application risk of CT-WN-B3. These results indicated that CT-WN-B3 is an alkali-suitable flocculant-producing bacterium for application in multiple fields, under alkali conditions especially.

Fine Structural Analysis of Degummed Fibroin Fibers Reveals Its Superior Mechanical Capabilities.

Bombyx mori silk fibroin fibers constitute a class of protein building blocks capable of functionalization and reprocessing into various material formats. The properties of these fibers are typically affected by the intense thermal treatments needed to remove the sericin gum coating layer. Additionally, their mechanical characteristics are often misinterpreted by assuming the asymmetrical cross-sectional area (CSA) as a perfect circle. The thermal treatments impact not only the mechanics of the degummed fibroin fibers, but also the structural configuration of the resolubilized protein, thereby limiting the performance of the resulting silk-based materials. To mitigate these limitations, we explored varying alkali conditions at low temperatures for surface treatment, effectively removing the sericin gum layer while preserving the molecular structure of the fibroin protein, thus, maintaining the hierarchical integrity of the exposed fibroin microfiber core. The precise determination of the initial CSA of the asymmetrical silk fibers led to a comprehensive analysis of their mechanical properties. Our findings indicate that the alkali surface treatment raised the Young's modulus and tensile strength, by increasing the extent of the fibers' crystallinity, by approximately 40 % and 50 %, respectively, without compromising their strain. Furthermore, we have shown that this treatment facilitated further production of high-purity soluble silk protein with rheological and self-assembly characteristics comparable to those of native silk feedstock, initially stored in the animal's silk gland. The developed approaches benefits both the development of silk-based materials with tailored properties and the proper mechanical characterization of asymmetrical fibrous biological materials made of natural building blocks.

New Thermodynamic Models for Anhydrous Alkaline-Silicate Magmatic Systems

Abstract A new thermodynamic model for silicate melt in the Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–TiO2–Fe2O3–Cr2O3 model system is presented, building on the tholeiitic through to granitic melt model of Holland et al. (2018) [Journal of Petrology, 59, 881–900] but extending for the first time into anhydrous alkaline systems. The new melt model is accompanied by new thermodynamic models for nepheline, kalsilite, leucite, melilite and ilmenite. Collectively these models enable pseudosection modelling of alkaline-silicate magmatic systems, providing a new tool for investigating this geologically- and economically-important compositional space. The models are calibrated with respect to experimental data on phase relations among minerals and melt, and the fit is benchmarked here via detailed comparison with seven experimental datasets, which encompass a range of pressure (0–22 kbar), temperature (680–1350°C), oxygen fugacity (log fO2 ΔFMQ-3 to +1), total alkali (3–16 wt %) and silica (37–70 wt %) conditions. The calculated pseudosections successfully reproduce experimental crystallisation sequences and phase compositions, indicating that the thermodynamic models are well calibrated across this spectrum of conditions. Redox buffered experimental conditions are simulated using oxygen buffered pseudosections. Contouring of oxygen buffered pseudosections with XFe3+ (mol. Fe3+/Fetotal), or pseudosections of varying XFe3+ with ΔFMQ, reveals (i) often complex and non-intuitive relationships between these two representations of oxidation state, and (ii) substantial variation in ferric iron over narrow temperature intervals in some oxygen buffered sets of experiments. An implication is that simulating oxygen buffering is vital when benchmarking thermodynamic models using experimental results. Furthermore, because natural igneous systems likely feature a near-constant XFe3+, it is important to assess experimental results in this framework when making inferences about natural systems, recognising that oxygen fugacity is a consequence not a control of phase equilibria in nature. Overall, our new models provide a novel tool to explore the role of variables, such as pressure, fractional crystallisation and crustal assimilation in the petrogenesis of alkaline-silicate magmatic systems and their associated mineralisation.

Studies on Quantitative Determination of Polyphenols in Seven Harvesting Times of Salvia deserta Schang Leaves and its Stability Evaluation

Introduction: Leaves of Salvia deserta Schang at seven harvesting times in the same year were collected as the materials. Method: The polyphenols were determined by the Folin–Ciocaileu method and High-Performance Liquid Chromatography (HPLC) to compare the quality of samples. The stability of polyphenols was studied under different conditions (light, temperature, pH, common additives). Results: The results showed that the established method is fast, simple and reliable, which is fully validated in terms of outstanding validation data. High Performance Liquid Chromatography (HPLC) for the determination of total polyphenol content can be quickly and accurately detected, reducing the error of manual determination of the content. The study of polyphenol stability was carried out using a UV spectrophotometer (UV) in order to explore the potential factors affecting polyphenol stability as much as possible and to make the study as scientific and rigorous as possible. The results of quantitative determination showed that there are obvious differences in the content of polyphenols in seven samples. The contents of total polyphenols, rosmarinic acid (RA) and caffeic acid (CA) in the samples harvested in July reached the highest level of 41.37, 26.73 and 1.05 mg/g. Conclusion: The results of the stability assay found that light could damage the stability of polyphenols in samples, especially UV light. Polyphenols are quite sensitive to high temperatures. While polyphenols are less stable when exposed to high alkali conditions and salt treatment, they are much more stable when subjected to low concentrations of redox agents, carbohydrates, and preservatives. The developed methods and stability evaluation provide valuable basis information for quality evaluation and the following use of polyphenols in S. deserta Schang leaves.

Portable Sensing Probe for Real-Time Quantification of Ammonia in Blood Samples.

The detection of ammonia levels in blood is critical for diagnosing and monitoring various medical conditions, including liver dysfunction and metabolic disorders. However, traditional diagnostic methods are slow and cumbersome, often involving multiple contact-based steps such as ammonia separation in alkali conditions followed by distillation or microdiffusion, leading to delays in diagnosis and treatment. Herein, we developed a colorimetric assay capable of rapid detection of ammonia in whole blood or plasma samples, utilizing 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-oxidized cellulose nanocrystals (TCNC) coupled with gold nanoparticles (AuNPs). The basis of our assay relies on either (i) the interaction between the carboxylate group (-COO) of TEMPO and ammonium ions or (ii) the manipulation of AuNPs surface plasmon resonance (SPR) through the formation of Au(NH3)43+, which displaces a redox mediator, resazurin, resulting in observable multicolor displays at various concentrations of ammonia. The colorimetric assay exhibits a wide linear detection range for dissolved NH4+ (0.1-37 μM) with a low limit of detection (LOD) of 0.1 μM. Additionally, it effectively measures NH3(g) concentrations in the range of 0.5-144 μM. The fabricated electrochemical nose (E-nose) device demonstrates excellent analytical performance for plasma ammonia sensing (0.05-256 μM). Experimental results demonstrate a linear detection range suitable for clinical applications, with excellent correlation to standard laboratory methods, offering a practical solution for point-of-care (PoC) testing. We anticipate that this approach can be applied broadly to improve patient monitoring and treatment by providing immediate and accurate ammonia measurements in a clinical setting.

Germination characteristics associated with nicosulfuron resistance in Amaranthus retroflexus L.

Nicosulfuron-resistant biotype (R) and -sensitive biotype (S) Amaranthus retroflexus L. seeds were subjected to different temperature, light, salt, osmotic potential, pH value and burial depth treatments. The difference in germination response of two populations to the above abiotic environmental factors was used to study the fitness cost of nicosulfuron-resistance evolution in A. retroflexus. The aim is to find a powerful tool for weed control in the presence of evolutionary resistance selection. The results of this experiment showed that the germination rate and germination index in S population were generally higher than that in R population. When the salt stress was 80 mM, the water potential was -0.1 Mpa ~ -0.4 Mpa, and under strong acid and alkali conditions, the germination index in S population was prominently higher than that in R population (p<0.05). The delayed seed germination in R population indicated that its nicosulfuron resistance may be linked to seed biochemical compositions that altered seed germination dynamics. The resistant and sensitive biotype of A. retroflexus had differently favourable adaptability in diverse environments. Salt, osmotic potential and pH value are not the major constraints for A. retroflexus germination, however, A. retroflexus are strongly responsive to temperature, light and burial depth. Considering that seeds of A. retroflexus are unable to reach the soil surface beyond the depth of 6 cm, deep inversion tillage before sowing may be an effective and economical weed management tool for the control of nicosulfuron resistant A. retroflexus.

Discrimination of dislocation in highly doped n-type 4H–SiC by combining electrochemical reaction and molten alkali etching

This work proposes an effective etching method for highly doped n-type 4H–SiC by combining electrochemical reactions and molten alkali etching. By employing our developed method, threading mixed dislocation (TMDs) and threading screw dislocations (TSDs) can be distinctly visualized as hexagonal etching pits of varying sizes. The slightly smaller threading edge dislocations (TEDs) appear as roughly circular etching pits, while basal plane dislocations (BPDs) are revealed as characteristic seashell-shaped pits. Additionally, we provide a reaction equation that elucidates the mechanism of the electrochemical etching process, thus sparking a new investigation into the discrimination of dislocations under molten alkali conditions. By applying a positive voltage to the wafer, we ensure a continuous supply of holes crucial for the reaction, thereby maintaining both the etching rate and the selectivity towards defects. This approach not only enhances the efficiency of the etching process but also provides a more accurate and reliable method for characterizing and understanding the dislocation properties of highly doped n-type 4H–SiC wafers.

Impact of Exposed Crystal Facets on Oxygen Reduction Reaction Activity in Zeolitic Imidazole Frameworks

Oxygen reduction reactions (ORR) are critical reactions for efficient sustainable and renewable energy storage. However, the limitation of ORR is a slow kinetic reaction due to the multi-step transfer mechanism of electrons. Therefore, electrocatalysts with high ORR activity and stability are needed to overcome the reaction limitations. Zeolitic imidazole framework-67 (ZIF-67) has attracted attention in electrochemical applications due to its multiple redox-active sites and high stability in alkali conditions. The Co-doped porous carbon catalysts derived from ZIF-67 have the potential to be used as ORR catalysts with high performance, while pure phase ZIF-67 electrocatalyst for ORR is rarely studied. The work studies the importance of crystal facets on ORR reactivity. The results show that ZIF-67 nanocube exhibits excellent ORR activity with lower half wave-potential and faster kinetics process compared to its bulk structure. It is proposed that ZIF-67 nanocube provides improvement of selectivity for the four-electron pathway, which is a favorable process with higher reaction efficiency. The density functional theory (DFT) calculations suggest unsaturated Co2+ active sites with enriched (100) facets in the cubic crystal. Therefore, the fast diffusion of oxygen molecules to active sites and strong interaction with intermediate are observed in a cubic structure. The correspondence between experiment and calculation offers enhancement of ORR activity and selectivity from control-specific growth of (100) facet with cubic shape. The work introduces a new strategy for designing highly efficient ORR electrocatalysts with facet-controlled, allowing further study in other electrochemical reactions.

Small GTPase PvARFR2 interacts with cytosolic ABA receptor kinase 3 to enhance alkali tolerance in switchgrass.

Soil alkalization has become a serious problem that limits plant growth through osmotic stress, ionic imbalance, and oxidative stress. Understanding how plants resist alkali stress has practical implications for alkaline-land utilization. In this study, we identified a small GTPase, PvARFR2 (ADP ribosylation factors related 2), that positively regulates alkali tolerance in switchgrass (Panicum virgatum) and uncovered its potential mode of action. Overexpressing PvARFR2 in switchgrass and Arabidopsis (Arabidopsis thaliana) conferred transformant tolerance to alkali stress, demonstrated by alleviated leaf wilting, less oxidative injury, and a lower Na+/K+ ratio under alkali conditions. Conversely, switchgrass PvARFR2-RNAi and its homolog mutant atgb1 in Arabidopsis displayed alkali sensitives. Transcriptome sequencing analysis showed that cytosolic abscisic acid (ABA) receptor kinase PvCARK3 transcript levels were higher in PvARFR2 overexpression lines compared to the controls and were strongly induced by alkali treatment in shoots and roots. Phenotyping analysis revealed that PvCARK3-OE × atgb1 lines were sensitive to alkali similar to the Arabidopsis atgb1 mutant, indicating that PvARFR2/AtGB1 functions in the same pathway as PvCARK3 under alkaline stress conditions. Application of ABA on PvARFR2-OE and PvCARK3-OE switchgrass transformants resulted in ABA sensitivity. Moreover, we determined that PvARFR2 physically interacts with PvCARK3 in vitro and in vivo. Our results indicate that a small GTPase, PvARFR2, positively responds to alkali stress by interacting with the cytosolic ABA receptor kinase PvCARK3, connecting the alkaline stress response to ABA signaling.

Salt–Alkali Tolerance Evaluation for Bermudagrass and Critical Indicator Screening at the Seedling Stage

The adaptability of bermudagrass genotypes to high-pH saline–alkali conditions was investigated through a comprehensive evaluation of 38 genotypes during the seedling stage. For this purpose, two distinct treatments were established: exposure to saline–alkali solution composed of 45% NaCl, 5% Na2SO4, 5% NaHCO3, and 45% Na2CO3 (pH 10.0), and exposure to distilled water as control. On 6th day of treatment, eight physiological indicators were measured. Compared with the control, the net photosynthetic rates, leaf water content, and chlorophyll content of the test genotypes decreased under stress. In contrast, the soluble protein content, proline levels, malondialdehyde concentration, and conductivity exhibited an increase. The salt–alkali tolerance coefficients of each indicator ranged from 0.24 to 8.54, and the variable coefficient was from 9.77% to 62.82%. Based on the salt–alkali tolerance coefficients, the comprehensive evaluation value (D) and resistance coefficient (CSAC) for each genotype were calculated. Subsequently, 38 genotypes were classified into three salt–alkali tolerance clusters by hierarchical clustering analysis, with Cluster I consisting of 10 genotypes with the most salt–alkali tolerance, and Cluster II with intermediate tolerance. Cluster III was comprised of 18 genotypes showing the lowest tolerance. The predictive model for assessing salt–alkali tolerance in bermudagrass is (D) = −0.238 + 0.106 × SACChlb + 0.209 × SACRWC + 0.015 × SACPro + 0.284 × SACProtein + 0.051 × SACPn. Notably, Cluster I genotypes were more vigorous and showed lower damage under saline stress compared to Cluster III. Moreover, stepwise regression analysis pinpointed Chlb, RWC, and Pro as crucial indicators for evaluating salt–alkali tolerance in bermudagrass genotypes.

Proinflammatory Effect of Membrane Vesicles Derived from Enterococcus faecalis at Neutral and Alkaline pH

IntroductionThe present study explored the proinflammatory impact of Enterococcus faecalis membrane vesicles (MVs) derived from culture medium at pH levels of 7.4 and 9.0. MethodsE. faecalis MVs were obtained by centrifugation and purified by size-exclusion chromatography. Proteomic analyses were performed on E. faecalis MVs to investigate their components. THP-1 macrophages were exposed to E. faecalis MVs, and the inflammatory cytokines and proteins were evaluated using enzyme-linked immunosorbent assay and immunoblotting. The inflammatory cytokines in the serum of mice with intraperitoneal injection of E. faecalis MVs were evaluated by enzyme-linked immunosorbent assay, and immunophenotyping of spleen cells was investigated with flow cytometry. ResultsProteomic analysis revealed 196 proteins in E. faecalis MVs obtained under neutral and alkali conditions; 110 proteins were up-regulated, and 79 proteins were down-regulated by alkaline pH. E. faecalis MVs induced secretion of inflammatory factors interleukin (IL)-1β, IL-6, and tumor necrosis factor alpha in a concentration-dependent manner. Immunoblotting revealed that E. faecalis MVs increased expression of pro–IL-1β, nuclear factor kappa Bp65, and Toll-like receptor 2. In vivo studies demonstrated that E. faecalis MVs significantly promoted secretion of IL-1β in mouse serum, whereas inflammatory cells were activated in the spleen. E. faecalis MVs obtained at a pH of 9.0 showed stronger proinflammatory effects than those obtained under neutral pH. ConclusionsE. faecalis produces MVs that carry specific proteins associated with virulence factors, and these MVs can promote inflammation in vitro and in vivo. E. faecalis MVs obtained under alkaline conditions have a stronger proinflammatory effect.

Study on the mechanism of different metal ions synergistic with alkali etching treatment in the flotation of lepidolite and feldspar

The two minerals were separated through alkali etching on the surface of lepidolite and feldspar, in conjunction with metal ion activation flotation. The activation of calcium (Ca2+) ion, magnesium (Mg2+) ion, copper (Cu2+) ion, and ferric (Fe3+) ion under alkali and non-alkali corrosion conditions was investigated, respectively. Micro-flotation experiments demonstrate that Ca2+ and Mg2+ can selectively recover lepidolite but not feldspar when the pH is above 6.5 during alkali etching. The activation of Cu2+ and Fe3+ flotation is not selective and can activate lepidolite and feldspar to some extent, irrespective of alkali etching. Through the valence bond theory, the selectivity of lepidolite and feldspar to dissolve and break bonds under alkali etching in a solution system was calculated. The adsorption differences and mechanisms of four types of metal ions were analyzed using solution chemistry, particle size analysis, and X-ray photoelectron spectroscopy (XPS) detections.

Alkali-driven Donnan dialysis for efficient ammonia recovery from wastewater: Performance, mechanism and optimization

Recovery of ammonia from wastewater is of practical importance toward a sustainable society. To this end, concentration-driven Donnan dialysis (DD) is a promising recovery method especially for its simplicity and negligible energy consumption. Upon the traditional salt-driven DD, the conceptive alkali-driven DD significantly enhanced mass transfer and removal efficiency, yet their performance in terms of key process parameter were not deeply understood and further optimization remained unclear. Models for salt (NaCl) and alkali (NaOH)-driven DD processes were thus established and the ammonia transfer was theoretically investigated. The results showed that a fluctuated Donnan equilibrium constant was found responsible for the superior performance of alkali-driven DD (mass transfer accelerated by 90 % than control). Interestingly, there was an optimal ammonia recovery mode via adjusting ratios of alkali/ammonia and cation/ammonia, two key parameters governing the process efficiency, based on which the salt-alkali coupling-driven DD process was further proposed. It was verified that the coupling-driven DD process achieved the ammonia removal kinetic value of 0.1632 h−1 under insufficient alkali conditions (accounting for 50 % ammonia concentration in feed) with lowest CO2 emissions of 3.49 kg CO2/kg NH4+. The descending overall efficiency of ammonia removal, following alkali-driven (0.2943 h−1) > coupling-driven (0.1632 h−1) > salt-driven (0.1228 h−1), was ascribed to the variations in the electrochemical potential of ions involved in the respective processes. In addition, the cost of chemical consumption for a coupling-driven DD process (3.99 $/kg NH4+) was close to that of a salt-driven process, but much lower than that of an alkali-driven process (14.81 $/kg NH4+). These finding insight the low-carbon and efficient recovery of ammonia from wastewater.

Exogenous putrescine plays a switch-like influence on the pH stress adaptability of biofilm-based activated sludge.

Microbial community adaptability to pH stress plays a crucial role in biofilm formation. This study aims to investigate the regulatory mechanisms of exogenous putrescine on pH stress, as well as enhance understanding and application for the technical measures and molecular mechanisms of biofilm regulation. Findings demonstrated that exogenous putrescine acted as a switch-like distributor affecting microorganism pH stress, thus promoting biofilm formation under acid conditions while inhibiting it under alkaline conditions. As pH decreases, the protonation degree of putrescine increases, making putrescine more readily adsorbed. Protonated exogenous putrescine could increase cell membrane permeability, facilitating its entry into the cell. Subsequently, putrescine consumed intracellular H+ by enhancing the glutamate-based acid resistance strategy and the γ-aminobutyric acid metabolic pathway to reduce acid stress on cells. Furthermore, putrescine stimulated ATPase expression, allowing for better utilization of energy in H+ transmembrane transport and enhancing oxidative phosphorylation activity. However, putrescine protonation was limited under alkaline conditions, and the intracellular H+ consumption further exacerbated alkali stress and inhibits cellular metabolic activity. Exogenous putrescine promoted the proportion of fungi and acidophilic bacteria under acidic stress and alkaliphilic bacteria under alkali stress while having a limited impact on fungi in alkaline biofilms. Increasing Bdellovibrio under alkali conditions with putrescine further aggravated the biofilm decomposition. This research shed light on the unclear relationship between exogenous putrescine, environmental pH, and pH stress adaptability of biofilm. By judiciously employing putrescine, biofilm formation could be controlled to meet the needs of engineering applications with different characteristics.IMPORTANCEThe objective of this study is to unravel the regulatory mechanism by which exogenous putrescine influences biofilm pH stress adaptability and understand the role of environmental pH in this intricate process. Our findings revealed that exogenous putrescine functioned as a switch-like distributor affecting the pH stress adaptability of biofilm-based activated sludge, which promoted energy utilization for growth and reproduction processes under acidic conditions while limiting biofilm development to conserve energy under alkaline conditions. This study not only clarified the previously ambiguous relationship between exogenous putrescine, environmental pH, and biofilm pH stress adaptability but also offered fresh insights into enhancing biofilm stability within extreme environments. Through the modulation of energy utilization, exerting control over biofilm growth and achieving more effective engineering goals could be possible.

Pullulan Polysaccharide as an Eco-Friendly Depressant for Flotation Separation of Chalcopyrite and Molybdenite.

It is difficult to separate molybdenite and chalcopyrite by froth flotation due to the good floatability of the two minerals. In this paper, the separation of copper-molybdenum sulfide minerals was realized by using pullulan polysaccharide (PU) as the depressant. The flotation test results showed that the copper concentrate grade increased from 16.24 to 29.86%, and the copper concentrate recovery reached 83.55% under low alkali conditions. The selective separation mechanism of the two minerals by PU was revealed through contact angle measurements, ζ-potential measurements, Fourier transform infrared (FTIR) spectroscopy analyses, and X-ray photoelectron spectroscopy (XPS) analyses. The ζ-potential and contact angle results showed that PU is more easily adsorbed on molybdenite to strengthen the hydrophilicity of molybdenite. The FTIR and XPS results showed that PU is adsorbed on molybdenite by physical interactions, and hydrophobic interactions and hydrogen bonding play a major role.

Degradation of sodium dodecylbenzene sulfonate (SDBS) and high efficiency treatment of real grey water by TiO2-loaded stainless steel mesh under VUV irradiation

Reusing treated greywater indoors in buildings is an advanced strategy to increase the utilization of limited water resources, but currently there is a lack of feasible technologies for efficiently purifying greywater indoors. In this study, we construct the heterogeneous TiO2-stainless steel mesh (SSM) interface with photocatalytic degradation of sodium dodecylbenzene sulfonate (SDBS) by under vacuum ultraviolet (VUV) irradiation. At the initial SDBS of 10 mg/L, the degradation rates of SDBS with UV/TiO2-SSM and VUV/TiO2-SSM process were 53 % and 74 % respectively within 50 min. The results of specific scavengers experiments and EPR analysis revealed that the ·OH, h+ and direct photolysis contributed to SDBS degradation and mineralization. The degradation rate of SDBS in VUV/TiO2-SSM process was higher at weak acid or weak alkali conditions, while the performance of UV/TiO2-SSM process was better at alkaline conditions. Both Cl− and HCO3− could inhibit SDBS degradation, while SO42− slightly promoted the degradation. Active oxygen species mainly degrade SDBS in two ways: by attacking the α carbon, β carbon, or branched chain carbon on the alkane chain; or by attacking the adjacent carbon on the alkane chain, resulting in the formation of three branch forms of products. The toxicity of the intermediate products shows a decreasing or stable trend. The experiment shows that UV or VUV photocatalytic TiO2-SSM has a good prospect of removing anionic surfactant in the real greywater. This study provides strategies for the development and design of indoor water reuse technologies and devices in buildings.