This study aimed to evaluate the quality of water from village boreholes by measuring physicochemical parameters such as nitrates, nitrites, and total organic carbon (TOC). Forty-five (45) village pumps from the South...This study aimed to evaluate the quality of water from village boreholes by measuring physicochemical parameters such as nitrates, nitrites, and total organic carbon (TOC). Forty-five (45) village pumps from the Southern (Basse Côte) and the Northern (Korhogo) region of Cte d’Ivoire (west Africa) were sampled. Physicochemical parameters such as temperature, pH, conductivity at 25˚C, and turbidity were determined in situ, while nitrite and nitrate were analyzed according to ISO 10304-1 (2007) standard and total organic carbon (TOC) by NF EN 1484 (1997) standard. The results showed that the borehole waters of the Basse Côte and Korhogo analyzed are acidic, with an average temperature of 27.51˚C ± 0.16˚C and 29.95˚C ± 0.51˚C respectively for the Basse Côte and Korhogo regions. The borehole waters of the Basse Côtedo not contain nitrites, while those of Korhogo have average nitrite contents of 0.32 mg/l. The average nitrate rate in the waters of the Basse Côte and Korhogo are 12.08 ± 2.11 mg/l and 11.03 ± 3.18 mg/l respectively. The average TOC concentration of the waters of the Basse Côte is 1.28 ± 0.32 mg/l and that of Korhogo is 0.56 ± 0.09 mg/L. The study showed that the borehole waters of the Basse Côte and Korhogo have average temperatures between 27.4˚C and 29.95˚C with a slightly acidic pH value and acceptable salinity. The TOC concentrations obtained at the different sampling points were all below the French standard (2 mg/L) except for certains pumps of the Basse Côte. The water samples from the Basse Côte were devoid of nitrite. On the other hand, those from Korhogo revealed the presence of nitrite. Also, the borehole waters of the regions of the Basse Côte and Korhogo contain relatively high nitrate contents, presumably due to anthropometric activity. Overall, our study on the quality of drinking water showed that the waters analyzed are in compliance with international standards and safe for consumption.展开更多
This paper presents results of nitrites and nitrates determination in two types of baby foods： commercial products in jars and their homemade conventional counterparts. Nitrites levels in all analyzed samples were be...This paper presents results of nitrites and nitrates determination in two types of baby foods： commercial products in jars and their homemade conventional counterparts. Nitrites levels in all analyzed samples were below of the detection limit （〈 0.9 mg/kg） of applied spectrophotometric method with Griess reagent. Nitrates contents in commercial products ranged： 9.1-38.1 mg/kg while in homemade baby foods levels between 26.6 mg/kg and 118.8 mg/kg were obtained. All the contents of nitrates were lower than the EU legislation maximum limit （200 mg/kg）. Comparison of each type of commercial product with its homemade counterpart baby food evidenced significant differences （p 〈 0.05） in average nitrates levels in favor of the first type. Apart from determining and comparing the levels of nitrates in the baby food samples also risk assessment for an average 6-months old infant to nitrates exposure was conducted. The estimated nitrates intake with a typical portion of 200g of baby food ranged between 6% and 25.7% of acceptable daily intake for commercial and from 18.0% to 80.3% for homemade ones.展开更多
The tolerance to ammonia and nitrites in freshwater ciliate Paramecium bursaria was measured in a conventional open system. The ciliate was exposed to different concentrations of ammonia and nitrites for 2h and 12h in...The tolerance to ammonia and nitrites in freshwater ciliate Paramecium bursaria was measured in a conventional open system. The ciliate was exposed to different concentrations of ammonia and nitrites for 2h and 12h in order to determine the lethal concentrations. Linear regression analysis revealed that the 2h-LC50 value for ammonia was 95.94 mg/L and for nitrite 27.35 mg/L using probit scale method (with 95% confidence intervals). There was a linear correlation between the mortality probit scale and logarithmic concentration of ammonia which fit by a regression equation y=7.32x–9.51 (R2=0.98; y, mortality probit scale; x, logarithmic concentration of ammonia), by which 2 h–LC50 value for ammonia was found to be 95.50 mg/L. A linear correla- tion between mortality probit scales and logarithmic concentration of nitrite is also followed the regression equa- tion y=2.86x+0.89 (R2=0.95; y, mortality probit scale; x, logarithmic concentration of nitrite). The regression analysis of toxicity curves showed that the linear correlation between exposed time of ammonia-N LC50 value and ammonia-N LC50 value followed the regression equation y=2 862.85e-0.08x (R2=0.95; y, duration of exposure to LC50 value; x, LC50 value), and that between exposed time of nitrite-N LC50 value and nitrite-N LC50 value followed the regression equation y = 127.15e-0.13x (R2=0.91; y, exposed time of LC50 value; x, LC50 value). The results demonstrate that the tolerance to ammonia in P. bursaria is considerably higher than that of the larvae or juveniles of some metozoa, e.g. cultured prawns and oysters. In addition, ciliates, as bacterial predators, are likely to play a positive role in maintaining and improving water quality in aquatic environments with high-level ammonium, such as sewage treatment systems.展开更多
Temperature is an important physical factor, which strongly influences biomass and metabolic activity. In this study, the effects of temperature on the anoxic metabolism of nitrite （NO2） to nitrous oxide （N2O） by ...Temperature is an important physical factor, which strongly influences biomass and metabolic activity. In this study, the effects of temperature on the anoxic metabolism of nitrite （NO2） to nitrous oxide （N2O） by polyphosphate accumulating organisms, and the process of the accumulation of N2O （during nitrite reduction）, which acts as an electron acceptor, were investigated using 91% ：e 4% Candidatus Accumulibacterphosphatis sludge. The results showed that N2O is accumulated when Accumulibacter first utilize nitrite instead of oxygen as the sole electron acceptor during the denitrifying phosphorus removal process. Properties such as nitrite reduction rate, phosphorus uptake rate, N2O reduction rate, and polyhydroxyalkanoate degradation rate were all influenced by temperature variation （over the range from 10 to 30℃ reaching maximum values at 25℃）. The reduction rate of N2O by N2O reductase was more sensitive to temperature when N2O was utilized as the sole electron acceptor instead of NO2, and the N2O reduction rates, ranging from 0.48 to 3.53 N2O-N/（hr.g VSS）, increased to 1.45 to 8.60 mg N2O-N/（hr·g VSS）. The kinetics processes for temperature variation of 10 to 30℃ were （01 = 1.140-1.216 and θ2 = 1.139-1.167）. In the range of 10℃ to 30℃, almost all of the anoxic stoichiometry was sensitive to temperature changes. In addition, a rise in N2O reduction activity leading to a decrease in N2O accumulation in long term operations at the optimal temperature （27℃ calculated by the Arrhenius model）.展开更多
Mining and tailings deposition can cause serious heavy metal(loids)pollution to the surrounding soil environment.Soil microorganisms adapt their metabolism to such conditions,driving alterations in soil function.This ...Mining and tailings deposition can cause serious heavy metal(loids)pollution to the surrounding soil environment.Soil microorganisms adapt their metabolism to such conditions,driving alterations in soil function.This study aims to elucidate the response patterns of nitrogen-cycling microorganisms under long-term heavy metal(loids)exposure.The results showed that the diversity and abundance of nitrogen-cyclingmicroorganisms showed negative feedback to heavy metal(loids)concentrations.Denitrifying microorganisms were shown to be the dominant microorganisms with over 60%of relative abundance and a complex community structure including 27 phyla.Further,the key bacterial species in the denitrification process were calculated using a random forest model,where the top three key species(Pseudomonas stutzei,Sphingobium japonicum and Leifsonia rubra)were found to play a prominent role in nitrite reduction.Functional gene analysis and qPCR revealed that nirK,which is involved in nitrite reduction,significantly accumulated in the most metal-rich soil with the increase of absolute abundance of 63.86%.The experimental results confirmed that the activity of nitrite reductase(Nir)encoded by nirK in the soil was increased at high concentrations of heavy metal(loids).Partial least squares-path model identified three potential modes of nitrite reduction processes being stimulated by heavy metal(loids),the most prominent of which contributed to enhanced nirK abundance and soil Nir activity through positive stimulation of key species.The results provide new insights and preliminary evidence on the stimulation of nitrite reduction processes by heavy metal(loids).展开更多
The authors regret<an error occurred regarding the spelling of the author’s name in the final published manuscript.The correct spelling is Jingtao Bi,but it was mistakenly published as Jingtai Bi.We hereby request...The authors regret<an error occurred regarding the spelling of the author’s name in the final published manuscript.The correct spelling is Jingtao Bi,but it was mistakenly published as Jingtai Bi.We hereby request to correct the name to Jingtao Bi as originally intended.>.The authors would like to apologize for any inconvenience caused.展开更多
Zirconia nanotube array films(ZNAF)prepared by anodic oxidation method were used as immobilization materials for acridine orange(AO),rhodamine B(RB)and AO-RB systems.A comparative study on their fluorescence emission ...Zirconia nanotube array films(ZNAF)prepared by anodic oxidation method were used as immobilization materials for acridine orange(AO),rhodamine B(RB)and AO-RB systems.A comparative study on their fluorescence emission intensity,fluorescence resonance energy transfer(FRET)and fluorescence detection of nitrite in aqueous solutions and on immobilization films with ZNAF as carriers was carried out.Results demonstrate that the solution pH values and immobilization on ZNAF have a great influence on the per-formance of these fluorescent molecules.Compared with aqueous solutions,the fluorescence emission in-tensity of AO and RB is considerably increased by immobilization,which is 8.0 and 4.2 times higher than the original,respectively.The energy transfer efficiency(E)of the AO-RB system increases from 40.9%to 84.8%by loading it on ZNAF.Moreover,after immobilization onto ZNAF,the fluorescence detection performance of nitrite is also significantly improved.The limit of detection decreases from 0.95 ng/mL to 0.22 ng/mL and the sensitivity increases from 939.18 to 15,031.68 mL/μg through loading AO onto ZNAF.展开更多
The electrochemical conversion of toxic nitrite(NO_(2)-)is a promising approach for the simultaneous removal of nitrogen contaminants and synthesis of ammonia(NH_(3)).In this study,we present the Er-doping-induced ele...The electrochemical conversion of toxic nitrite(NO_(2)-)is a promising approach for the simultaneous removal of nitrogen contaminants and synthesis of ammonia(NH_(3)).In this study,we present the Er-doping-induced electronic modulation of CoP integrated with nitrogen-doped carbon(CN)nanosheets supported on a titanium mesh(Er-CoP@NC/TM)for the electrocatalytic NO_(2)-reduction reaction(eNO_(2)-RR)for NH_(3)synthesis.The catalyst demonstrates a high Faraday efficiency of 97.08±2.22%and a high yield of 2087.60±17.10μmol h^(-1)cm^(-2)for NH_(3)production.Characterization and theoretical calculations revealed that Er-doping facilitated the electronic modulation of CoP in Er-CoP@NC/TM,which regulated the adsorption behaviors of intermediates and was the rate-limiting step for the eNO_(2)-RR,thereby enhancing the electrocatalytic performance.Quenching experiments and electron paramagnetic resonance tests suggest that both direct electrocatalytic reduction by active hydrogen and electron transfer are critical for the eNO_(2)-RR for NH_(3)synthesis.Furthermore,Er-CoP@NC/TM exhibited high performance across a wide range of NO_(2)-concentrations(0.05-0.1 mol L^(-1))and pH values(4-13).In addition,the catalyst demonstrated strong resistance to anions and a long cycle life in simulated wastewater environments.This study offers a powerful approach for the remediation of NO_(2)-wastewater and recovery of valuable inorganic compounds.展开更多
The authors regret that in 1.2.Instruments section of the article,when describing the principle of TiH300,the original content of“Briefly,ambient HONO was first absorbed by deionized water in a two-channel stripping ...The authors regret that in 1.2.Instruments section of the article,when describing the principle of TiH300,the original content of“Briefly,ambient HONO was first absorbed by deionized water in a two-channel stripping coil.The absorbed liquid nitrite was mixed with sulfanilamide,N-(1-naphthyl)-ethylenediamine dihydrochloride,and hydrogen chloride solution to form the azo dye derivative.”展开更多
Electrocatalytic reduction of nitrate pollutants to produce ammonia offers an effective approach to realizing the artificial nitrogen cycle and replacing the energyintensive Haber-Bosch process.Nitrite is an important...Electrocatalytic reduction of nitrate pollutants to produce ammonia offers an effective approach to realizing the artificial nitrogen cycle and replacing the energyintensive Haber-Bosch process.Nitrite is an important intermediate product in the reduction of nitrate to ammonia.Therefore,the mechanism of converting nitrite into ammonia warrants further investigation.Molecular cobalt catalysts are regarded as promising for nitrite reduction reactions(NO_(2)^(−)RR).However,designing and controlling the coordination environment of molecular catalysts is crucial for studying the mechanism of NO_(2)^(−)RR and catalyst design.Herein,we develop a molecular platform of cobalt porphyrin with three coordination microenvironments(Co-N_(3)X_(1),X=N,O,S).Electrochemical experiments demonstrate that cobalt porphyrin with O coordination(CoOTPP)exhibits the lowest onset potential and the highest activity for NO_(2)^(−)RR in ammonia production.Under neutral,nonbuffered conditions over a wide potential range(−1.0 to−1.5 V versus AgCl/Ag),the Faradaic efficiency of nearly 90%for ammonia was achieved and reached 94.5%at−1.4 V versus AgCl/Ag,with an ammonia yield of 6,498μgh^(−1)and a turnover number of 22,869 at−1.5V versus AgCl/Ag.In situ characterization and density functional theory calculations reveal that modulating the coordination environment alters the electron transfer mode of the cobalt active center and the charge redistribution caused by the break of the ligand field.Therefore,this results in enhanced electrochemical activity for NO_(2)^(−)RR in ammonia production.This study provides valuable guidance for designing adjustments to the coordination environment of molecular catalysts to enhance catalytic activity.展开更多
Ammonia(NH_(3))is a fundamental chemical in agriculture and an ideal hydrogen carrier.Consequently,NH_(3)synthesis strategies with high efficiency,energy conservation,environmental friendliness,and sustainability are ...Ammonia(NH_(3))is a fundamental chemical in agriculture and an ideal hydrogen carrier.Consequently,NH_(3)synthesis strategies with high efficiency,energy conservation,environmental friendliness,and sustainability are desired eminently.The nitrite(NO_(2)^(-))reduction reaction(NO_(2-)RR)to NH_(3)offers a feasibly low-energy consumption and continuable approach to replace industrial NH_(3)synthesis.Herein,polyethyleneimine(PEI)modified Au core Rh shell nanodendrites(Au@Rh-NDs)nanohybrid(Au@Rh-NDs/PEI)with branched structure is synthesized,which achieves the high NH_(3)yield(1.68 mg h^(-1)mg_(cat)^(-1))and Faradaic efficiency(FE)of 95.86%for NO_(2)^(-)-RR at-0.39 V potential in neutral electrolyte.Particularly,the introduction of PEI significantly enhances the electroactivity of Au@Rh-NDs at low concentration of 1 mM NaNO_(2),which originates from the enrichment function of PEI for NO_(2)^(-)-ion.In addition,the Au basement permits the sustainable solar power to expedite the NO_(2)^(-)-RR at Au@Rh-NDs/PEI owing to the localized surface plasmon resonance(LSPR)of the Au core substrate.This work may provide an admissible tactic to build excellent catalysts on account of organic molecule-mediated interfacial engineering in a variety of fields of catalysis and electrocatalysis.展开更多
To prevent bacterial growth and ensure food safety,common practice involves the use of nitrite and phosphate salts.Neverthe-less,elevated nitrite levels in the body can contribute to the development of stomach and eso...To prevent bacterial growth and ensure food safety,common practice involves the use of nitrite and phosphate salts.Neverthe-less,elevated nitrite levels in the body can contribute to the development of stomach and esophageal cancers,while excessive phosphate levels may increase the risk of kidney dysfunction and the onset of osteoporosis.Electrochemical sensing has emerged as a reliable tech-nique for detecting nitrites and phosphates.This study specifically focuses on the use of TiO_(2)-based sensing materials for such detection.The synthesis of nanoparticulate TiO_(2) and Ag-doped TiO_(2) was successfully achieved through a solution combustion technique.The com-position of the materials was examined using X-ray diffraction(XRD)and X-ray absorption near-edge structure(XANES)methods,re-vealing a predominant anatase composition.Doping resulted in particle refinement,contributing to an increased specific surface area and enhanced electron transfer efficiency,as indicated in the examination by electrochemical impedance spectroscopy(EIS).Cyclic voltam-metry(CV)assessed the electrochemical behavior,demonstrating that in nitrite detection,a significant oxidation reaction occurred at an applied voltage of approximately 1.372 V,while in phosphate detection,the main reduction peak occurred at a voltage close to-0.48 V.High sensitivity(2μA·μM^(-1)·mm^(-2) for sodium nitrite and 2.1μA·μM^(-1)·mm^(-2) for potassium phosphate)and low limits of detection(0.0052 mM for sodium nitrite and 0.0045 mM for potassium phosphate)were observed.Experimental results support the potential use of Ag-doped TiO_(2) as a sensing device for nitrites and phosphates.展开更多
The electrochemical biomass valorization of industrial by-products or pollutants using renewable electricity offers significant promise for carbon neutrality.However,the huge challenges still exist in the development ...The electrochemical biomass valorization of industrial by-products or pollutants using renewable electricity offers significant promise for carbon neutrality.However,the huge challenges still exist in the development of efficient bifunctional electrocatalysts.Herein,we put forward a high-efficiency coelectrolysis system by coupling the nitrite reduction reaction(NO_(2)RR)and the glycerol oxidation reaction(GOR)over a novel heterogeneous β-Co(OH)_(2)/Cu_(2)(OH)_(3)Cl catalyst.Theβ-Co(OH)_(2)/Cu_(2)(OH)_(3)Cl shows excellent bifunctional performance with high Faradaic efficiencies of formate(90.1%)and NH_(3)(91.9%)at cell voltage of 1.5 V,high yield rate of formate(89.6 mg h^(-1)cm^(-2))and NH_(3)(36.07 mg h^(-1)cm^(-2))at cell voltage of 1.9 V,and superior stability in an anion exchange membrane co-electrolyzer.The in-situ Raman result confirms the unique Co/Cu-based bimetallic synergistic sites of β-Co(OH)_(2)/Cu_(2)(OH)_(3)Cl towards superior GOR performance,while the operando Fourier transform infrared spectroscopy demonstrates the improved protonation kinetics of key intermediates and optimized water dissociation ability ofβ-Co(OH)_(2)/Cu_(2)(OH)_(3)Cl for high NO_(2)RR activity.Our work illuminates alternative avenues to exploit the innovative and energy-saving technology for the co-production of high-added chemicals.展开更多
Sanchuan ham is appreciated in Yunnan Province,China,for its characteristic flavor and taste,while the microbial community structure and biogenic amines content remain unclear during fermentation processes.In this stu...Sanchuan ham is appreciated in Yunnan Province,China,for its characteristic flavor and taste,while the microbial community structure and biogenic amines content remain unclear during fermentation processes.In this study,we explored the physicochemical property,biogenic amines concentration and microbial diversity of external and internal Sanchuan ham by high-throughput sequencing during the processing of Sanchuan ham.Results showed that the nitrite remained at a stable level of 0.15 mg/kg which was significantly lower than the national health standard safety level of 20 mg/kg.In addition,compared with fresh hams,the content of total free amino acids in ripe Sanchuan ham has grown 14 folds;sour and bitter were the main tastes of Sanchuan ham.Notably,the concentration of cadaverine was the highest of all biogenic amines during the entire fermentation period.At the bacterial phyla level,Firmicutes and Actinobacteria were the two main phyla,while at the genus level,Staphylococcus was a significant strain throughout the whole fermentation.Moreover,the dry stage has a great impact on the succession change of microbial community structure.Simultaneously,the change trends and composition of bacteria in the interior have slight discrepancies with those of the exterior of Sanchuan ham.展开更多
This study employed multispectral techniques to evaluate fulvic acid(FA)compositional characteristic and elucidate its biodegradation mechanisms during partial nitritation(PN)process.Results showed that FA removal eff...This study employed multispectral techniques to evaluate fulvic acid(FA)compositional characteristic and elucidate its biodegradation mechanisms during partial nitritation(PN)process.Results showed that FA removal efficiency(FRE)decreased from 90.22 to 23.11%when FA concentrations in the reactor were increased from 0 to 162.30 mg/L,and that molecular size,degree of aromatization and humification of the effluent FA macromolecules all increased after treatment.Microbial population analysis indicated that the proliferation of the Comamonas,OLB12 and Thauera exhibit high FA utilization capacity in lower concentrations(<50.59 mg/L),promoting the degradation and removal of macromolecular FA.In addition,the sustained increase in external FA may decrease the abundance of above functional microorganisms,resulting in a rapid drop in FRE.Furthermore,from the genetic perspective,the elevated FA levels restricted carbohydrate(ko00620,ko00010 and ko00020)and nitrogen(HAO,AMO,NIR and NOR)metabolism-related pathways,thereby impeding FA removal and total nitrogen loss associated with N_(2)O emissions.展开更多
CeO_(2)-based catalysts are widely investigated for selective catalytic reduction(SCR)of NO with NH3.Interaction of NO/O_(2) with CeO_(2) generally produces two surface species,i.e.,nitrates and nitrites.However,the e...CeO_(2)-based catalysts are widely investigated for selective catalytic reduction(SCR)of NO with NH3.Interaction of NO/O_(2) with CeO_(2) generally produces two surface species,i.e.,nitrates and nitrites.However,the explicit quantification of these two species is still unresolved.Herein,we reported that spectrophotometry characterization was effective in determining surface adsorbed NOx species on CeO_(2) by measuring the corresponding ions(NO_(2)-and NO_(3)^(-))dissolved in aqueous solution.Experimental results show that both nitrate(-NO_(3))and nitrite(-NO_(2))species can be quantitatively evaluated and the accuracy is verified by calibrating with NOx-TPD result.Exclusive transfer of adsorbed NOx from catalyst surface to aqueous solution is confirmed and the dissolution process can be accelerated by ultrasonic treatment.Moreover,useful information related to evolution of surface NOx species under various conditions(O_(2) treatment,different adsorption temperature and duration)and over different catalysts(Fe_(2)O_(3),MnO_(2) and MnOx—CeO_(2))are provided.The result of present study demonstrates the potential of spectrophotometry for quantitative discrimination of surface NOx species on CeO_(2) and other oxide-based materials,which is conducive to mechanism analysis of SCR reaction.展开更多
The nitrite(NO_(2)^(−))to ammonia(NH3)electroreduction reaction(NO_(2)^(−)RR)would be impeded by sluggish proton-coupled electron transfer kinetics and competitive hydrogen evolution reaction(HER).A key to improving t...The nitrite(NO_(2)^(−))to ammonia(NH3)electroreduction reaction(NO_(2)^(−)RR)would be impeded by sluggish proton-coupled electron transfer kinetics and competitive hydrogen evolution reaction(HER).A key to improving the NH_(3) selectivity is to facilitate adsorption and activation of NO_(2)^(−),which is generally undesirable in unitary species.In this work,an efficient NO_(2)^(−)RR catalyst is constructed by cooperating Pd with In2O3,in which NO_(2)^(−)could adsorb on interfacial dual-site through“Pd–N–O–In”linkage,leading to strengthened NO_(2)^(−)adsorption and easier N=O bond cleavage than that on unitary Pd or In2O3.Moreover,the Pd/In_(2)O_(3)composite exhibits moderate H^(*)adsorption,which may facilitate protonation kinetics while inhibiting competitive HER.As a result,it exhibits a fairly high NH_(3)yield rate of 622.76 mmol h^(−1)g^(−1)cat with a Faradaic efficiency(FE)of 95.72%,good selectivity of 91.96%,and cycling stability towards the NO_(2)^(−)RR,surpassing unitary In_(2)O_(3)and Pd/C electrocatalysts.Besides,computed results indicate that NH_(3)production on Pd/In_(2)O_(3)follows the deoxidation to hydrogenation pathway.This work highlights the significance of H^(*)and NO_(2)^(−)adsorption modulation and N=O activation in NO_(2)^(−)RR electrochemistry by creating synergy between a mediocre catalyst with an appropriate cooperator.展开更多
Partial nitrification is a key aspect of efficient nitrogen removal,although practically it suf-fers from long start-up cycles and unstable long-term operational performance.To address these drawbacks,this study inves...Partial nitrification is a key aspect of efficient nitrogen removal,although practically it suf-fers from long start-up cycles and unstable long-term operational performance.To address these drawbacks,this study investigated the effect of low intensity ultrasound treatment combined with hydroxylamine(NH2OH)on the performance of partial nitrification.Results showthat compared with the control group,low-intensity ultrasound treatment(0.10W/mL,15 min)combined with NH2OH(5 mg/L)reduced the time required for partial nitrification initiation by 6 days,increasing the nitrite accumulation rate(NAR)and ammonia nitro-gen removal rate(NRR)by 20.4% and 6.7%,respectively,achieving 96.48% NRR.Mechanis-tic analysis showed that NH2OH enhanced ammonia oxidation,inhibited nitrite-oxidizing bacteria(NOB)activity and shortened the time required for partial nitrification initiation.Furthermore,ultrasonication combined with NH2OH dosing stimulated EPS(extracellular polymeric substances)secretion,increased carbonyl,hydroxyl and amine functional group abundances and enhanced mass transfer.In addition,16S rRNA gene sequencing results showed that ultrasonication-sensitive Nitrospira disappeared from the ultrasound+NH_(2)OH system,while Nitrosomonas gradually became the dominant group.Collectively,the results of this study provide valuable insight into the enhancement of partial nitrification start-up during the process of wastewater nitrogen removal.展开更多
Electrochemical nitrite reduction reaction(NO_(2)^(-)RR) is a potential sustainable route for regulating the nitrogen cycle and ambient ammonia(NH_(3)) synthesis.However,it remains a challenge to precisely regulate th...Electrochemical nitrite reduction reaction(NO_(2)^(-)RR) is a potential sustainable route for regulating the nitrogen cycle and ambient ammonia(NH_(3)) synthesis.However,it remains a challenge to precisely regulate the reaction pathways and inhibit competing reactions(e.g.hydrogenolysis) for efficient and selective NH_(3) production in an aqueous solution environment.Here,we utilize the Schottky barrier-induced surface electric field to construct high-density electron-deficient Pd nanoparticles by modulating the N content in the carbon carrier to promote the enrichment and immobilization of NO_(2)^(-)on the electrode surface,which ensures the ultimate selectivity for NH_(3).With these properties,Pd@N_(0.14)C with the highest N content achieved excellent catalytic performance for the reduction of NO_(2)^(-)to NH_(3) with the 100% Faraday efficiency at-0.5 and-0.6 V vs,reversible hydrogen electrode(RHE) for NH_(3) production,which was significantly better than Pd/C and Pd@N_(x)C samples with lower N content.This study opens new avenues for rational construction of efficient electrocatalysts for nitrite removal and NH_(3) electrosynthesis.展开更多
Human saliva is an indispensable fluid that maintains a healthy oral cavity which otherwise can lead to oral diseases(dental caries and periodontitis).In addition,salivary metabolites and microbiome profile provide ea...Human saliva is an indispensable fluid that maintains a healthy oral cavity which otherwise can lead to oral diseases(dental caries and periodontitis).In addition,salivary metabolites and microbiome profile provide early detection of systemic diseases such as cancer and obesity.Salivary diagnostic has gained popularity due to its non-invasive sampling technique.Fasting(abstinence from food or drink or both)research for weight loss and improve health is common,but studies using fasting saliva are scarce.Some metabolites in fasting saliva have been reported with interesting results,which can be enhanced by considering different confounding factors.For example,fasting saliva contains higher salivary nitrite,which is related to nitric oxide(NO).NO is a vasodilator supporting the healthy function of endothelial cells and its deficiency is connected to many diseases.The timely supply of NO through exogenous and endogenous means is highlighted and the potential advantage of fasting salivary composition changes in relation to COVID-19 infection is speculated.This review aims to provide a general discussion on the salivary composition,properties,and functions of the whole saliva,including the health benefits of fasting.展开更多
文摘This study aimed to evaluate the quality of water from village boreholes by measuring physicochemical parameters such as nitrates, nitrites, and total organic carbon (TOC). Forty-five (45) village pumps from the Southern (Basse Côte) and the Northern (Korhogo) region of Cte d’Ivoire (west Africa) were sampled. Physicochemical parameters such as temperature, pH, conductivity at 25˚C, and turbidity were determined in situ, while nitrite and nitrate were analyzed according to ISO 10304-1 (2007) standard and total organic carbon (TOC) by NF EN 1484 (1997) standard. The results showed that the borehole waters of the Basse Côte and Korhogo analyzed are acidic, with an average temperature of 27.51˚C ± 0.16˚C and 29.95˚C ± 0.51˚C respectively for the Basse Côte and Korhogo regions. The borehole waters of the Basse Côtedo not contain nitrites, while those of Korhogo have average nitrite contents of 0.32 mg/l. The average nitrate rate in the waters of the Basse Côte and Korhogo are 12.08 ± 2.11 mg/l and 11.03 ± 3.18 mg/l respectively. The average TOC concentration of the waters of the Basse Côte is 1.28 ± 0.32 mg/l and that of Korhogo is 0.56 ± 0.09 mg/L. The study showed that the borehole waters of the Basse Côte and Korhogo have average temperatures between 27.4˚C and 29.95˚C with a slightly acidic pH value and acceptable salinity. The TOC concentrations obtained at the different sampling points were all below the French standard (2 mg/L) except for certains pumps of the Basse Côte. The water samples from the Basse Côte were devoid of nitrite. On the other hand, those from Korhogo revealed the presence of nitrite. Also, the borehole waters of the regions of the Basse Côte and Korhogo contain relatively high nitrate contents, presumably due to anthropometric activity. Overall, our study on the quality of drinking water showed that the waters analyzed are in compliance with international standards and safe for consumption.
文摘This paper presents results of nitrites and nitrates determination in two types of baby foods： commercial products in jars and their homemade conventional counterparts. Nitrites levels in all analyzed samples were below of the detection limit （〈 0.9 mg/kg） of applied spectrophotometric method with Griess reagent. Nitrates contents in commercial products ranged： 9.1-38.1 mg/kg while in homemade baby foods levels between 26.6 mg/kg and 118.8 mg/kg were obtained. All the contents of nitrates were lower than the EU legislation maximum limit （200 mg/kg）. Comparison of each type of commercial product with its homemade counterpart baby food evidenced significant differences （p 〈 0.05） in average nitrates levels in favor of the first type. Apart from determining and comparing the levels of nitrates in the baby food samples also risk assessment for an average 6-months old infant to nitrates exposure was conducted. The estimated nitrates intake with a typical portion of 200g of baby food ranged between 6% and 25.7% of acceptable daily intake for commercial and from 18.0% to 80.3% for homemade ones.
文摘The tolerance to ammonia and nitrites in freshwater ciliate Paramecium bursaria was measured in a conventional open system. The ciliate was exposed to different concentrations of ammonia and nitrites for 2h and 12h in order to determine the lethal concentrations. Linear regression analysis revealed that the 2h-LC50 value for ammonia was 95.94 mg/L and for nitrite 27.35 mg/L using probit scale method (with 95% confidence intervals). There was a linear correlation between the mortality probit scale and logarithmic concentration of ammonia which fit by a regression equation y=7.32x–9.51 (R2=0.98; y, mortality probit scale; x, logarithmic concentration of ammonia), by which 2 h–LC50 value for ammonia was found to be 95.50 mg/L. A linear correla- tion between mortality probit scales and logarithmic concentration of nitrite is also followed the regression equa- tion y=2.86x+0.89 (R2=0.95; y, mortality probit scale; x, logarithmic concentration of nitrite). The regression analysis of toxicity curves showed that the linear correlation between exposed time of ammonia-N LC50 value and ammonia-N LC50 value followed the regression equation y=2 862.85e-0.08x (R2=0.95; y, duration of exposure to LC50 value; x, LC50 value), and that between exposed time of nitrite-N LC50 value and nitrite-N LC50 value followed the regression equation y = 127.15e-0.13x (R2=0.91; y, exposed time of LC50 value; x, LC50 value). The results demonstrate that the tolerance to ammonia in P. bursaria is considerably higher than that of the larvae or juveniles of some metozoa, e.g. cultured prawns and oysters. In addition, ciliates, as bacterial predators, are likely to play a positive role in maintaining and improving water quality in aquatic environments with high-level ammonium, such as sewage treatment systems.
基金supported by the National High Technology Research and Development Program (863) of China (No. 2012AA063406)the National Natural Science Foundation of China (No. 51008005)
文摘Temperature is an important physical factor, which strongly influences biomass and metabolic activity. In this study, the effects of temperature on the anoxic metabolism of nitrite （NO2） to nitrous oxide （N2O） by polyphosphate accumulating organisms, and the process of the accumulation of N2O （during nitrite reduction）, which acts as an electron acceptor, were investigated using 91% ：e 4% Candidatus Accumulibacterphosphatis sludge. The results showed that N2O is accumulated when Accumulibacter first utilize nitrite instead of oxygen as the sole electron acceptor during the denitrifying phosphorus removal process. Properties such as nitrite reduction rate, phosphorus uptake rate, N2O reduction rate, and polyhydroxyalkanoate degradation rate were all influenced by temperature variation （over the range from 10 to 30℃ reaching maximum values at 25℃）. The reduction rate of N2O by N2O reductase was more sensitive to temperature when N2O was utilized as the sole electron acceptor instead of NO2, and the N2O reduction rates, ranging from 0.48 to 3.53 N2O-N/（hr.g VSS）, increased to 1.45 to 8.60 mg N2O-N/（hr·g VSS）. The kinetics processes for temperature variation of 10 to 30℃ were （01 = 1.140-1.216 and θ2 = 1.139-1.167）. In the range of 10℃ to 30℃, almost all of the anoxic stoichiometry was sensitive to temperature changes. In addition, a rise in N2O reduction activity leading to a decrease in N2O accumulation in long term operations at the optimal temperature （27℃ calculated by the Arrhenius model）.
基金supported by the National Natural Science Foundation of China(No.41977029).
文摘Mining and tailings deposition can cause serious heavy metal(loids)pollution to the surrounding soil environment.Soil microorganisms adapt their metabolism to such conditions,driving alterations in soil function.This study aims to elucidate the response patterns of nitrogen-cycling microorganisms under long-term heavy metal(loids)exposure.The results showed that the diversity and abundance of nitrogen-cyclingmicroorganisms showed negative feedback to heavy metal(loids)concentrations.Denitrifying microorganisms were shown to be the dominant microorganisms with over 60%of relative abundance and a complex community structure including 27 phyla.Further,the key bacterial species in the denitrification process were calculated using a random forest model,where the top three key species(Pseudomonas stutzei,Sphingobium japonicum and Leifsonia rubra)were found to play a prominent role in nitrite reduction.Functional gene analysis and qPCR revealed that nirK,which is involved in nitrite reduction,significantly accumulated in the most metal-rich soil with the increase of absolute abundance of 63.86%.The experimental results confirmed that the activity of nitrite reductase(Nir)encoded by nirK in the soil was increased at high concentrations of heavy metal(loids).Partial least squares-path model identified three potential modes of nitrite reduction processes being stimulated by heavy metal(loids),the most prominent of which contributed to enhanced nirK abundance and soil Nir activity through positive stimulation of key species.The results provide new insights and preliminary evidence on the stimulation of nitrite reduction processes by heavy metal(loids).
文摘The authors regret<an error occurred regarding the spelling of the author’s name in the final published manuscript.The correct spelling is Jingtao Bi,but it was mistakenly published as Jingtai Bi.We hereby request to correct the name to Jingtao Bi as originally intended.>.The authors would like to apologize for any inconvenience caused.
基金supported by the National Natural Science Foundation of China(No.51972095).
文摘Zirconia nanotube array films(ZNAF)prepared by anodic oxidation method were used as immobilization materials for acridine orange(AO),rhodamine B(RB)and AO-RB systems.A comparative study on their fluorescence emission intensity,fluorescence resonance energy transfer(FRET)and fluorescence detection of nitrite in aqueous solutions and on immobilization films with ZNAF as carriers was carried out.Results demonstrate that the solution pH values and immobilization on ZNAF have a great influence on the per-formance of these fluorescent molecules.Compared with aqueous solutions,the fluorescence emission in-tensity of AO and RB is considerably increased by immobilization,which is 8.0 and 4.2 times higher than the original,respectively.The energy transfer efficiency(E)of the AO-RB system increases from 40.9%to 84.8%by loading it on ZNAF.Moreover,after immobilization onto ZNAF,the fluorescence detection performance of nitrite is also significantly improved.The limit of detection decreases from 0.95 ng/mL to 0.22 ng/mL and the sensitivity increases from 939.18 to 15,031.68 mL/μg through loading AO onto ZNAF.
文摘The electrochemical conversion of toxic nitrite(NO_(2)-)is a promising approach for the simultaneous removal of nitrogen contaminants and synthesis of ammonia(NH_(3)).In this study,we present the Er-doping-induced electronic modulation of CoP integrated with nitrogen-doped carbon(CN)nanosheets supported on a titanium mesh(Er-CoP@NC/TM)for the electrocatalytic NO_(2)-reduction reaction(eNO_(2)-RR)for NH_(3)synthesis.The catalyst demonstrates a high Faraday efficiency of 97.08±2.22%and a high yield of 2087.60±17.10μmol h^(-1)cm^(-2)for NH_(3)production.Characterization and theoretical calculations revealed that Er-doping facilitated the electronic modulation of CoP in Er-CoP@NC/TM,which regulated the adsorption behaviors of intermediates and was the rate-limiting step for the eNO_(2)-RR,thereby enhancing the electrocatalytic performance.Quenching experiments and electron paramagnetic resonance tests suggest that both direct electrocatalytic reduction by active hydrogen and electron transfer are critical for the eNO_(2)-RR for NH_(3)synthesis.Furthermore,Er-CoP@NC/TM exhibited high performance across a wide range of NO_(2)-concentrations(0.05-0.1 mol L^(-1))and pH values(4-13).In addition,the catalyst demonstrated strong resistance to anions and a long cycle life in simulated wastewater environments.This study offers a powerful approach for the remediation of NO_(2)-wastewater and recovery of valuable inorganic compounds.
文摘The authors regret that in 1.2.Instruments section of the article,when describing the principle of TiH300,the original content of“Briefly,ambient HONO was first absorbed by deionized water in a two-channel stripping coil.The absorbed liquid nitrite was mixed with sulfanilamide,N-(1-naphthyl)-ethylenediamine dihydrochloride,and hydrogen chloride solution to form the azo dye derivative.”
基金National Key Research and Development Program of China,Grant/Award Number:2022YFC2105800National Natural Science Foundation of China,Grant/Award Numbers:21901084,21905106,22279041+2 种基金Higher Education Discipline Innovation Project,Grant/Award Number:B17020Specific Research Fund of the Innovation Platform for Academicians of Hainan Province,China,Grant/Award Number:YSPTZX202321Natural Science Foundation of Jilin Province,Grant/Award Number:SKL202302017.
文摘Electrocatalytic reduction of nitrate pollutants to produce ammonia offers an effective approach to realizing the artificial nitrogen cycle and replacing the energyintensive Haber-Bosch process.Nitrite is an important intermediate product in the reduction of nitrate to ammonia.Therefore,the mechanism of converting nitrite into ammonia warrants further investigation.Molecular cobalt catalysts are regarded as promising for nitrite reduction reactions(NO_(2)^(−)RR).However,designing and controlling the coordination environment of molecular catalysts is crucial for studying the mechanism of NO_(2)^(−)RR and catalyst design.Herein,we develop a molecular platform of cobalt porphyrin with three coordination microenvironments(Co-N_(3)X_(1),X=N,O,S).Electrochemical experiments demonstrate that cobalt porphyrin with O coordination(CoOTPP)exhibits the lowest onset potential and the highest activity for NO_(2)^(−)RR in ammonia production.Under neutral,nonbuffered conditions over a wide potential range(−1.0 to−1.5 V versus AgCl/Ag),the Faradaic efficiency of nearly 90%for ammonia was achieved and reached 94.5%at−1.4 V versus AgCl/Ag,with an ammonia yield of 6,498μgh^(−1)and a turnover number of 22,869 at−1.5V versus AgCl/Ag.In situ characterization and density functional theory calculations reveal that modulating the coordination environment alters the electron transfer mode of the cobalt active center and the charge redistribution caused by the break of the ligand field.Therefore,this results in enhanced electrochemical activity for NO_(2)^(−)RR in ammonia production.This study provides valuable guidance for designing adjustments to the coordination environment of molecular catalysts to enhance catalytic activity.
基金supported by the National Natural Science Foundation of China(22273056)the National Training Program of Innovation and Entrepreneurship for Undergraduates(202410718010)+2 种基金the Natural Science Basic Research Project of Shaanxi Province(2024JC-YBQN-0092)the Scientific research project of Shaanxi Institute of Basic Sciences(23JHQ003)the Scientific Research Program Funded by Education Department of Shaanxi Provincial Government(23JK0694)。
文摘Ammonia(NH_(3))is a fundamental chemical in agriculture and an ideal hydrogen carrier.Consequently,NH_(3)synthesis strategies with high efficiency,energy conservation,environmental friendliness,and sustainability are desired eminently.The nitrite(NO_(2)^(-))reduction reaction(NO_(2-)RR)to NH_(3)offers a feasibly low-energy consumption and continuable approach to replace industrial NH_(3)synthesis.Herein,polyethyleneimine(PEI)modified Au core Rh shell nanodendrites(Au@Rh-NDs)nanohybrid(Au@Rh-NDs/PEI)with branched structure is synthesized,which achieves the high NH_(3)yield(1.68 mg h^(-1)mg_(cat)^(-1))and Faradaic efficiency(FE)of 95.86%for NO_(2)^(-)-RR at-0.39 V potential in neutral electrolyte.Particularly,the introduction of PEI significantly enhances the electroactivity of Au@Rh-NDs at low concentration of 1 mM NaNO_(2),which originates from the enrichment function of PEI for NO_(2)^(-)-ion.In addition,the Au basement permits the sustainable solar power to expedite the NO_(2)^(-)-RR at Au@Rh-NDs/PEI owing to the localized surface plasmon resonance(LSPR)of the Au core substrate.This work may provide an admissible tactic to build excellent catalysts on account of organic molecule-mediated interfacial engineering in a variety of fields of catalysis and electrocatalysis.
基金Kasetsart University Research and Development Institute(KURDI,Grant No.FF(KU)51.67)ASEAN University Network/Southeast Asia Engineering Education Development Network(AUN/SEED-Net)for financial support+2 种基金financially supported by the Office of the Ministry of Higher Education,Science,Research and Innovationthe Thailand Science Research and Innovation through the Kasetsart University Reinventing University Program 2021support from the Department of Material Engineering,Faculty of Engineering,Kasetsart University is also acknowledged.
文摘To prevent bacterial growth and ensure food safety,common practice involves the use of nitrite and phosphate salts.Neverthe-less,elevated nitrite levels in the body can contribute to the development of stomach and esophageal cancers,while excessive phosphate levels may increase the risk of kidney dysfunction and the onset of osteoporosis.Electrochemical sensing has emerged as a reliable tech-nique for detecting nitrites and phosphates.This study specifically focuses on the use of TiO_(2)-based sensing materials for such detection.The synthesis of nanoparticulate TiO_(2) and Ag-doped TiO_(2) was successfully achieved through a solution combustion technique.The com-position of the materials was examined using X-ray diffraction(XRD)and X-ray absorption near-edge structure(XANES)methods,re-vealing a predominant anatase composition.Doping resulted in particle refinement,contributing to an increased specific surface area and enhanced electron transfer efficiency,as indicated in the examination by electrochemical impedance spectroscopy(EIS).Cyclic voltam-metry(CV)assessed the electrochemical behavior,demonstrating that in nitrite detection,a significant oxidation reaction occurred at an applied voltage of approximately 1.372 V,while in phosphate detection,the main reduction peak occurred at a voltage close to-0.48 V.High sensitivity(2μA·μM^(-1)·mm^(-2) for sodium nitrite and 2.1μA·μM^(-1)·mm^(-2) for potassium phosphate)and low limits of detection(0.0052 mM for sodium nitrite and 0.0045 mM for potassium phosphate)were observed.Experimental results support the potential use of Ag-doped TiO_(2) as a sensing device for nitrites and phosphates.
基金financially supported by the National Natural Science Foundation of China(22205205)the Science Foundation of Zhejiang Sci-Tech University(ZSTU)under Grant No.21062337-Y。
文摘The electrochemical biomass valorization of industrial by-products or pollutants using renewable electricity offers significant promise for carbon neutrality.However,the huge challenges still exist in the development of efficient bifunctional electrocatalysts.Herein,we put forward a high-efficiency coelectrolysis system by coupling the nitrite reduction reaction(NO_(2)RR)and the glycerol oxidation reaction(GOR)over a novel heterogeneous β-Co(OH)_(2)/Cu_(2)(OH)_(3)Cl catalyst.Theβ-Co(OH)_(2)/Cu_(2)(OH)_(3)Cl shows excellent bifunctional performance with high Faradaic efficiencies of formate(90.1%)and NH_(3)(91.9%)at cell voltage of 1.5 V,high yield rate of formate(89.6 mg h^(-1)cm^(-2))and NH_(3)(36.07 mg h^(-1)cm^(-2))at cell voltage of 1.9 V,and superior stability in an anion exchange membrane co-electrolyzer.The in-situ Raman result confirms the unique Co/Cu-based bimetallic synergistic sites of β-Co(OH)_(2)/Cu_(2)(OH)_(3)Cl towards superior GOR performance,while the operando Fourier transform infrared spectroscopy demonstrates the improved protonation kinetics of key intermediates and optimized water dissociation ability ofβ-Co(OH)_(2)/Cu_(2)(OH)_(3)Cl for high NO_(2)RR activity.Our work illuminates alternative avenues to exploit the innovative and energy-saving technology for the co-production of high-added chemicals.
基金funded by National Natural Science Foundation of China(31460445)Science and Technology Talents and Platform Program of Yunnan Province,No.202105AF150049Yunnan University Key Laboratory of Food Microbial Resources and Utilization(Yunjiaofa[2018]No.135)。
文摘Sanchuan ham is appreciated in Yunnan Province,China,for its characteristic flavor and taste,while the microbial community structure and biogenic amines content remain unclear during fermentation processes.In this study,we explored the physicochemical property,biogenic amines concentration and microbial diversity of external and internal Sanchuan ham by high-throughput sequencing during the processing of Sanchuan ham.Results showed that the nitrite remained at a stable level of 0.15 mg/kg which was significantly lower than the national health standard safety level of 20 mg/kg.In addition,compared with fresh hams,the content of total free amino acids in ripe Sanchuan ham has grown 14 folds;sour and bitter were the main tastes of Sanchuan ham.Notably,the concentration of cadaverine was the highest of all biogenic amines during the entire fermentation period.At the bacterial phyla level,Firmicutes and Actinobacteria were the two main phyla,while at the genus level,Staphylococcus was a significant strain throughout the whole fermentation.Moreover,the dry stage has a great impact on the succession change of microbial community structure.Simultaneously,the change trends and composition of bacteria in the interior have slight discrepancies with those of the exterior of Sanchuan ham.
基金supported by the Key Research and Development Project of Shandong (Nos.2021CXGC011202,2020CXGC011404,and 2022CXGC021002)the National Natural Science Foundation of China (No.22276006)。
文摘This study employed multispectral techniques to evaluate fulvic acid(FA)compositional characteristic and elucidate its biodegradation mechanisms during partial nitritation(PN)process.Results showed that FA removal efficiency(FRE)decreased from 90.22 to 23.11%when FA concentrations in the reactor were increased from 0 to 162.30 mg/L,and that molecular size,degree of aromatization and humification of the effluent FA macromolecules all increased after treatment.Microbial population analysis indicated that the proliferation of the Comamonas,OLB12 and Thauera exhibit high FA utilization capacity in lower concentrations(<50.59 mg/L),promoting the degradation and removal of macromolecular FA.In addition,the sustained increase in external FA may decrease the abundance of above functional microorganisms,resulting in a rapid drop in FRE.Furthermore,from the genetic perspective,the elevated FA levels restricted carbohydrate(ko00620,ko00010 and ko00020)and nitrogen(HAO,AMO,NIR and NOR)metabolism-related pathways,thereby impeding FA removal and total nitrogen loss associated with N_(2)O emissions.
基金Project supported by the National Natural Science Foundation of China(22276097,21976081)the Major Scientificand Technological Project of Bingtuan(2018AA002)。
文摘CeO_(2)-based catalysts are widely investigated for selective catalytic reduction(SCR)of NO with NH3.Interaction of NO/O_(2) with CeO_(2) generally produces two surface species,i.e.,nitrates and nitrites.However,the explicit quantification of these two species is still unresolved.Herein,we reported that spectrophotometry characterization was effective in determining surface adsorbed NOx species on CeO_(2) by measuring the corresponding ions(NO_(2)-and NO_(3)^(-))dissolved in aqueous solution.Experimental results show that both nitrate(-NO_(3))and nitrite(-NO_(2))species can be quantitatively evaluated and the accuracy is verified by calibrating with NOx-TPD result.Exclusive transfer of adsorbed NOx from catalyst surface to aqueous solution is confirmed and the dissolution process can be accelerated by ultrasonic treatment.Moreover,useful information related to evolution of surface NOx species under various conditions(O_(2) treatment,different adsorption temperature and duration)and over different catalysts(Fe_(2)O_(3),MnO_(2) and MnOx—CeO_(2))are provided.The result of present study demonstrates the potential of spectrophotometry for quantitative discrimination of surface NOx species on CeO_(2) and other oxide-based materials,which is conducive to mechanism analysis of SCR reaction.
基金supported by the National Key R&D Program of China(Nos.2022YFA1503104 and 2022YFA1503102)the Natural Science Foundation of Shandong Province(No.2022HWYQ-009)+2 种基金the Natural Science Foundation of Jiangsu Province(No.BK20230243)Taishan Scholars Project(No.tspd20230601)Qilu Young Scholars Program of Shandong University.
文摘The nitrite(NO_(2)^(−))to ammonia(NH3)electroreduction reaction(NO_(2)^(−)RR)would be impeded by sluggish proton-coupled electron transfer kinetics and competitive hydrogen evolution reaction(HER).A key to improving the NH_(3) selectivity is to facilitate adsorption and activation of NO_(2)^(−),which is generally undesirable in unitary species.In this work,an efficient NO_(2)^(−)RR catalyst is constructed by cooperating Pd with In2O3,in which NO_(2)^(−)could adsorb on interfacial dual-site through“Pd–N–O–In”linkage,leading to strengthened NO_(2)^(−)adsorption and easier N=O bond cleavage than that on unitary Pd or In2O3.Moreover,the Pd/In_(2)O_(3)composite exhibits moderate H^(*)adsorption,which may facilitate protonation kinetics while inhibiting competitive HER.As a result,it exhibits a fairly high NH_(3)yield rate of 622.76 mmol h^(−1)g^(−1)cat with a Faradaic efficiency(FE)of 95.72%,good selectivity of 91.96%,and cycling stability towards the NO_(2)^(−)RR,surpassing unitary In_(2)O_(3)and Pd/C electrocatalysts.Besides,computed results indicate that NH_(3)production on Pd/In_(2)O_(3)follows the deoxidation to hydrogenation pathway.This work highlights the significance of H^(*)and NO_(2)^(−)adsorption modulation and N=O activation in NO_(2)^(−)RR electrochemistry by creating synergy between a mediocre catalyst with an appropriate cooperator.
文摘Partial nitrification is a key aspect of efficient nitrogen removal,although practically it suf-fers from long start-up cycles and unstable long-term operational performance.To address these drawbacks,this study investigated the effect of low intensity ultrasound treatment combined with hydroxylamine(NH2OH)on the performance of partial nitrification.Results showthat compared with the control group,low-intensity ultrasound treatment(0.10W/mL,15 min)combined with NH2OH(5 mg/L)reduced the time required for partial nitrification initiation by 6 days,increasing the nitrite accumulation rate(NAR)and ammonia nitro-gen removal rate(NRR)by 20.4% and 6.7%,respectively,achieving 96.48% NRR.Mechanis-tic analysis showed that NH2OH enhanced ammonia oxidation,inhibited nitrite-oxidizing bacteria(NOB)activity and shortened the time required for partial nitrification initiation.Furthermore,ultrasonication combined with NH2OH dosing stimulated EPS(extracellular polymeric substances)secretion,increased carbonyl,hydroxyl and amine functional group abundances and enhanced mass transfer.In addition,16S rRNA gene sequencing results showed that ultrasonication-sensitive Nitrospira disappeared from the ultrasound+NH_(2)OH system,while Nitrosomonas gradually became the dominant group.Collectively,the results of this study provide valuable insight into the enhancement of partial nitrification start-up during the process of wastewater nitrogen removal.
文摘Electrochemical nitrite reduction reaction(NO_(2)^(-)RR) is a potential sustainable route for regulating the nitrogen cycle and ambient ammonia(NH_(3)) synthesis.However,it remains a challenge to precisely regulate the reaction pathways and inhibit competing reactions(e.g.hydrogenolysis) for efficient and selective NH_(3) production in an aqueous solution environment.Here,we utilize the Schottky barrier-induced surface electric field to construct high-density electron-deficient Pd nanoparticles by modulating the N content in the carbon carrier to promote the enrichment and immobilization of NO_(2)^(-)on the electrode surface,which ensures the ultimate selectivity for NH_(3).With these properties,Pd@N_(0.14)C with the highest N content achieved excellent catalytic performance for the reduction of NO_(2)^(-)to NH_(3) with the 100% Faraday efficiency at-0.5 and-0.6 V vs,reversible hydrogen electrode(RHE) for NH_(3) production,which was significantly better than Pd/C and Pd@N_(x)C samples with lower N content.This study opens new avenues for rational construction of efficient electrocatalysts for nitrite removal and NH_(3) electrosynthesis.
文摘Human saliva is an indispensable fluid that maintains a healthy oral cavity which otherwise can lead to oral diseases(dental caries and periodontitis).In addition,salivary metabolites and microbiome profile provide early detection of systemic diseases such as cancer and obesity.Salivary diagnostic has gained popularity due to its non-invasive sampling technique.Fasting(abstinence from food or drink or both)research for weight loss and improve health is common,but studies using fasting saliva are scarce.Some metabolites in fasting saliva have been reported with interesting results,which can be enhanced by considering different confounding factors.For example,fasting saliva contains higher salivary nitrite,which is related to nitric oxide(NO).NO is a vasodilator supporting the healthy function of endothelial cells and its deficiency is connected to many diseases.The timely supply of NO through exogenous and endogenous means is highlighted and the potential advantage of fasting salivary composition changes in relation to COVID-19 infection is speculated.This review aims to provide a general discussion on the salivary composition,properties,and functions of the whole saliva,including the health benefits of fasting.
