Nitrogen Elimination Research Articles

Mechanism of Thiol-Induced Nitrogen(II) Oxide Donation by Furoxans: a Quantum-Chemical Study

Quantum-chemical calculations according to DFT with UB3LYP functional in the 6-311++G** basis set, and accounting for solvation effects by the polarized continuum method were used to study the mechanisms of thiol-induced fragmentation of unsubstituted and annulated furoxans with the elimination of nitrogen(II) oxide. A preference for NO formation according to the radical mechanism involving an attack by sulfanyl radical (HS˙) on the carbon atom bonded to the N-oxide group was demonstrated for all systems. Anionic mechanisms involving HS– anions were not feasible in any of the cases due to high endothermic effects.

N‐Imidazolylation of Sulfoximines from N‐Cyano Sulfoximines, 1‐Alkynes, and N‐Sulfonyl Azides

AbstractThe rhodium‐catalyzed N‐imidazolylation of N‐sulfonyl‐1,2,3‐triazoles with a variety of N‐cyano sulfoximines has been developed for the synthesis of N‐imidazolyl sulfoximines via elimination of molecular nitrogen. Copper‐catalyzed [3+2] cycloaddition followed by rhodium‐catalyzed N‐imidazolylation from 1‐alkynes, N‐sulfonyl azides, and N‐cyano sulfoximines is also demonstrated for the synthesis of N‐imidazolyl sulfoximines in a one‐pot procedure.magnified image

Life cycle assessment of cotton textile products in Turkey

Cotton textile and clothing industry is a complex and multi-tiered system that consists of cotton cultivation and harvesting, fiber production, yarn manufacturing, fabric preparation, fabric processing that includes bleaching and dying sub-processes among others and fabrication of the final product. An array of environmental concerns are associated with this sector, the most significant of which are issues related to use of agrochemicals in the cultivation of cotton and water, energy and chemical consumption in the fabric processing stage. Textile industry is a significant contributor to the Turkish economy constituting 18% of total export volume in 2013 according to Turkish Statistical Institute. In the study, environmental impacts of Eco T-shirts produced from organically grown cotton and processed with green dyeing recipe were compared to that of conventional T-shirts, in terms of their contributions to global warming, acidification, aquatic and terrestrial eutrophication and photochemical ozone formation using life cycle assessment methodology. The results reveal that Eco T-shirts have lower impact potentials across all inspected categories, with the most dramatic reduction in aquatic eutrophication potential (up to 97%) due to elimination of nitrogen and phosphorus containing chemical based fertilizers. The results also show that global warming potential is by far the largest environmental impact for both conventional and Eco T-shirts with the main impact coming from use phase, followed by cultivation and harvesting and fabric processing phases. The results of the analysis underline the importance of utilizing sustainable raw materials in all life cycle stages of cotton textile products and the necessity of focusing on the consumer behavior and sustainable practices in the use phase of the products as well.

Electrochemical oxidation of humic acid and sanitary landfill leachate: Influence of anode material, chloride concentration and current density

The influence of applied current density and chloride ion concentration on the ability of Ti/Pt/PbO2 and Ti/Pt/SnO2–Sb2O4 anodes for the electrochemical oxidation of humic acid and sanitary landfill leachate samples was assessed and compared with that of BDD anode. For the experimental conditions used, results show that both organic load and nitrogen removal rates increase with the applied current density and chloride ion concentration, although there is an optimum COD/[Cl−]0 ratio below which there is no further increase in COD removal. Metal oxide anodes present a similar performance to that of BDD, being the results obtained for Ti/Pt/PbO2 slightly better than for Ti/Pt/SnO2–Sb2O4. Contrary to BDD, Ti/Pt/PbO2 promotes lower nitrate formation and is the most suitable material for total nitrogen elimination. The importance of the optimum ratio of Cl−/COD/NH4+ initial concentrations is discussed.

ChemInform Abstract: Thermolysis of 1‐(Thiophen‐2‐yl)‐1H‐tetrazoles: A Route to Thiophene‐Fused Imidazoles and Pyrimidines.

Abstract Thermal reactions of 1-(thiophene-2-yl)-1H-tetrazoles are reported for the first time. The solution thermolysis of 1-(thiophene-2-yl)-1H-tetrazoles under conventional heating and microwave irradiation afforded the unexpected new thieno[2,3-d]pyrimidines incorporating two thiophene rings, which were obtained as major or only product. The synthesis of these heterocycles was rationalized considering the initial nitrogen elimination to generate imidoylnitrene followed by rearrangement to the corresponding carbodiimide and subsequent cyclization triggered by the nucleophilic attack of the in situ generated 2-aminothiophene. The flash vacuum pyrolysis and solution thermolysis of 1-(thiophene-2-yl)-1H-tetrazoles also gave thieno[2,3-d]imidazoles via intramolecular formal insertion into a C–C bond of the corresponding imidoylnitrene intermediate.

Synthesis of 3,3-diphenyl-3H-pyrazoles applying vinyl sulfones as chemical equivalents of acetylenes in reaction of 1,3-dipolar cycloaddition to diphenyldiazomethane

Vinyl phenyl sulfone, methyl (E)-3-(phenylsulfonyl)- and methyl (E)-3-(p-tosyl)acrylates, (E)-3-(phenylsulfonyl)- and (E)-3-(p-tosyl)acrylonitriles react in ethyl ether at 20°C with diphenyldiazomethane leading to the formation of the corresponding 5,5-diphenyl-3-(arylsulfonyl)- Δ2-pyrazolines. Products containing a methoxycarbonyl or cyano group at treating with DBU in dichloromethane at 0°C suffer a dehydrosulfonation and are converted into 4-substituted 3,3-diphenyl-3H-pyrazoles. The oxidation of the mentioned Δ2-pyrazolines with activated manganese dioxide in benzene at 20°C leads to the formation of 4-methoxycarbonyl- and 4-cyano-substituted 5-arylsulfonyl- 3,3-diphenyl-3H-pyrazoles respectively. The reactions of α-bromovinyl phenyl sulfones and a-bromovinyl methyl sulfones with diphenyldiazomethane afforded the corresponding 3-bromo- 5,5-diphenyl-3-sulfonyl-Δ1-pyrazolines. The first among them at 20°C suffered spontaneous elimination of molecular nitrogen and converted into 1-bromo-2,2-diphenyl-1-(phenylsulfonyl)cyclopropane whose structure was established by X-ray diffraction analysis. The action of DBU on another Δ1-pyrazoline resulted in the formation of the product of the Ramberg–Backlund reaction, 5-methylene-3,3-diphenyl-Δ1- pyrazoline together with the product of hydrodebromination–isomerization, 5,5-diphenyl-3-(methylsulfonyl)- Δ2-pyrazoline.

Using the same cut-off for sulfur hexafluoride and nitrogen multiple-breath washout may not be appropriate.

Recent evidence suggests that results from multiple-breath washout (MBW) using nitrogen (N 2 ) as washout gas are different to those obtained by using sulfur hexafluoride (SF 6 ). Explanations were mainly related to different MBW equipment and gas properties. We aim to mention a new aspect, namely using the same cut-off in both techniques to determine lung clearance index (usually 2.5% of initial tracer concentration) irrespective of additional contribution of tissue-nitrogen in N 2 -MBW. In a simple model calculation we subtracted 1% tissue-N 2 from the N 2 -MBW in real washout traces from two children, one with cystic fibrosis (CF) and one healthy. This "SF 6 -washout simulation" decreased LCI differently in the children. In the healthy subject 1/40 th (2.5%) was achieved two breaths earlier compared to the original signal and changed LCI from 6.7 to 5.9 (12%), while in CF 1/40 th was achieved 19 breaths earlier leading to a LCI decrease from 13.7 to 10.0 (27%). It would have been required to wash out SF6 until 1/66 th (1.5%) to be comparable to N 2 washout at 1/40th (2.5%), or to stop N2-MBW already at 3.5% of the starting concentration to make both techniques comparable. We show that a basic physiological-mathematical difference between both techniques additionally accounts for different sensitivities and poor agreement between SF 6 - and N 2 -MBW. The best way of adjusting for the contribution of tissue-N 2 needs to be examined in future studies. Thus, despite increasing use in different disease groups, the books on MBW technology are obviously not closed yet.

The Extended Oxygen Window Concept for Programming Saturation Decompressions Using Air and Nitrox.

Saturation decompression is a physiological process of transition from one steady state, full saturation with inert gas at pressure, to another one: standard conditions at surface. It is defined by the borderline condition for time spent at a particular depth (pressure) and inert gas in the breathing mixture (nitrogen, helium). It is a delicate and long lasting process during which single milliliters of inert gas are eliminated every minute, and any disturbance can lead to the creation of gas bubbles leading to decompression sickness (DCS). Most operational procedures rely on experimentally found parameters describing a continuous slow decompression rate. In Poland, the system for programming of continuous decompression after saturation with compressed air and nitrox has been developed as based on the concept of the Extended Oxygen Window (EOW). EOW mainly depends on the physiology of the metabolic oxygen window—also called inherent unsaturation or partial pressure vacancy—but also on metabolism of carbon dioxide, the existence of water vapor, as well as tissue tension. Initially, ambient pressure can be reduced at a higher rate allowing the elimination of inert gas from faster compartments using the EOW concept, and maximum outflow of nitrogen. Then, keeping a driving force for long decompression not exceeding the EOW allows optimal elimination of nitrogen from the limiting compartment with half-time of 360 min. The model has been theoretically verified through its application for estimation of risk of decompression sickness in published systems of air and nitrox saturation decompressions, where DCS cases were observed. Clear dose-reaction relation exists, and this confirms that any supersaturation over the EOW creates a risk for DCS. Using the concept of the EOW, 76 man-decompressions were conducted after air and nitrox saturations in depth range between 18 and 45 meters with no single case of DCS. In summary, the EOW concept describes physiology of decompression after saturation with nitrogen-based breathing mixtures.

Reactions of octahydroacridine-4-carbonitrile (carboxamide) with electrophilic reagents

Octahydroacridine-4-carbonitrile (carboxamide) was shown to react with aryldiazonium salts and other electrophilic reagents in acidic and neutral media. The reactions occurred at the methine carbon atom, forming the corresponding 4-functionalized derivatives. The obtained azo compounds decomposed at 140–155°С with elimination of nitrogen and gave products formed by the reactions of radical intermediates.

Thermolysis of 1-(thiophen-2-yl)-1H-tetrazoles: a route to thiophene-fused imidazoles and pyrimidines

Thermal reactions of 1-(thiophene-2-yl)-1H-tetrazoles are reported for the first time. The solution thermolysis of 1-(thiophene-2-yl)-1H-tetrazoles under conventional heating and microwave irradiation afforded the unexpected new thieno[2,3-d]pyrimidines incorporating two thiophene rings, which were obtained as major or only product. The synthesis of these heterocycles was rationalized considering the initial nitrogen elimination to generate imidoylnitrene followed by rearrangement to the corresponding carbodiimide and subsequent cyclization triggered by the nucleophilic attack of the in situ generated 2-aminothiophene. The flash vacuum pyrolysis and solution thermolysis of 1-(thiophene-2-yl)-1H-tetrazoles also gave thieno[2,3-d]imidazoles via intramolecular formal insertion into a C–C bond of the corresponding imidoylnitrene intermediate.

Integrated fixed-biofilm activated sludge reactor as a powerful tool to enrich anammox biofilm and granular sludge

A pilot-scale activated sludge bioreactor was filled with immobile carrier to treat high ammonium wastewater. Autotrophic nitrogen elimination occurred rapidly by inoculating nitrifying activated sludge and anammox biofilm. As the ammonium loading rate increased, nitrogen removal rate of 1.2kgNm−3d−1 was obtained with the removal efficiency of 80%. Activated sludge diameter distribution profiles presented two peak values, indicating simultaneous existence of flocculent and granular sludge. Red granular sludge was observed in the reactor. Furthermore, the results of morphological and molecular analysis showed that the characteristics of granular sludge were similar to that of biofilm, while much different from the flocculent sludge. It was assumed granular sludge was formed through the continuous growth and detachment of anammox biofilm. The mechanism of granular sludge formation was discussed and the procedure model was proposed. According to the experimental results, the integrated fixed-biofilm activated sludge reactor provided an alternative to nitrogen removal based on anammox.

SPATIAL AND TEMPORALVARIATION OF DISSOLVED INORGANIC NUTRIENTS, AND CHLOROPHYLL-α IN A TROPICAL ESTUARY IN NORTHEASTERN BRAZIL: DYNAMICS OF NUTRIENT REMOVAL

Monthly sampling campaigns were carried out between February 2010 and January 2011 to evaluate the spatial and temporal distribution of nutrients (ammonium, nitrite, nitrate, dissolved organic nitrogen, phosphate, dissolved organic phosphorus and silicate) and chlorophyll-α along a salinity gradient in the tropical Cachoeira River estuary, subject to the untreated effluents of a sewage treatment plant (STP). During the study period the lowest and highest river discharge occurred in February and April 2010, respectively. High river outflow promoted increased concentrations of inorganic nitrogen and silicate but did not affect the concentration of phosphate. Based on the chlorophyll-α concentration the estuary may be classified as eutrophic / hypereutrophic in its inner portion and mesotrophic in the lower region. The inner portion is more affected by the nutrient load carried out by the river and STP, while dilution by seawater contributed to the reduction of the nutrient concentrations in the lower reaches of the estuary. The results indicate that nutrient uptake by the phytoplankton is the most effective dissolved inorganic nutrient removal processes, especially for phosphate. Mixing diagrams suggest that the coupling of nitrification and denitrification processes is also responsible for the elimination of nitrogen from this ecosystem.

Elimination of Carbon, Nitrogen and Phosphorus in Domestic Wastewater through a Series of Anaerobic and Aerobic Reactors for a Developing Country like Benin

Waste water treatment in order to preserve water resources is one of the major concerns in developing countries. This study aims to test the operating effectiveness of a pilot designed on a basis of several laboratory experiments, which consists of an anaerobic and aerobic pond in series. The test was performed through monitoring global parameters of pollution. The results of the analysis of these parameters indicate an elimination of 91% of suspended solids, 68% of COD, 77% of BOD5, 61% of nitrate and 81% of phosphorus. It was also noticed that the anaerobic pond removes most, carbonaceous organic materials and especially suspended matters; and the aerobic pond most, nitrogen and especially phosphorus. This study reveals the effectiveness of the series connection of an anaerobic and aerobic pond for domestic wastewater treatment.

Elimination of ammoniacal nitrogen existing in wastewater by infiltration percolation process

Cluster development and human activity, be it domestic, industrial or agricultural, is responsible for the production of natural pollution (organic, inorganic,..). The objective of this research is to follow the evolution of ammoniacal nitrogen , nitrites and nitrates in domestic wastewater treated by the process of infiltration-percolation using sand of M'zar (region of Agadir, Morocco) as a filter material. The latter is characterized by the effective diameter (D 10 ) and the coefficient of uniformity (C u ) which is 0.15 and 1.46 respectively. The operating principle is based on an aerobic biological filtration on granular medium (sand). The nitrogen content of treated water varies with the origin of raw sewage and sewage system conditions, the results we found show a 95% removal of this pollutant.

Operational Strategies for Promoting Nitrogen Elimination in Centrate Side Stream Treatment

Operational Strategies for Promoting Nitrogen Elimination in Centrate Side Stream Treatment

The Effect of Influent Characteristics and Operational Conditions over the Performance and Microbial Community Structure of Partial Nitritation Reactors

Nitrogen is a main contaminant of wastewater worldwide. Novel processes for nitrogen removal have been developed over the last several decades. One of these is the partial nitritation process. This process includes the oxidation of ammonium to nitrite without the generation of nitrate. The partial nitritation process has several advantages over traditional nitrification-denitrification processes for nitrogen removal from wastewaters. In addition, partial nitritation is required for anammox elimination of nitrogen from wastewater. Partial nitritation is affected by operational conditions and substances present in the influent, such as quinolone antibiotics. In this review, the impact that several operational conditions, such as temperature, pH, dissolved oxygen concentration, hydraulic retention time and solids retention time, have over the partial nitritation process is covered. The effect of quinolone antibiotics and other emerging contaminants are discussed. Finally, future perspectives for the partial nitritation process are commented upon.

Application of density functional theory to the nitric oxide heterogeneous reduction mechanism in the presence of hydroxyl and carbonyl groups

Comprehensive theoretical calculations are carried out to investigate the nitric oxide (NO) heterogeneous reduction mechanism in the presence of hydroxyl (OH) and carbonyl (>CO) groups. Energetics (activation energy and thermochemistry data) and kinetics (thermal rate constant) for the proposed pathways are provided by density functional theory (DFT) and conventional transition state theory (TST), respectively. The role played by OH and >CO has been clarified. In the presence of OH, four stepwise reactions with the highest energy barrier of 251.7 kJ/mol are found to produce new active sites. Subsequently, a number of elementary reactions with energy barrier below 116.1 kJ/mol take place to reduce NO. The role of > CO is to yield NCO intermediate. The formation of NCO is highly exothermic with 709.4 kJ/mol, which contributes to the elimination of carbon dioxide (CO2) and nitrogen (N2). The discovered mechanism is consistent with previous experimental observation that NO heterogeneous reduction is enhanced due to the presence of oxygen.

Constrained‐Geometry Bisphosphazides Derived from 1,8‐Diazidonaphthalene: Synthesis, Spectroscopic Characteristics, Structural Features, and Theoretical Investigations

Investigations on the Staudinger reaction between 1,8-diazidonaphthalene and phosphorous(III) building blocks, a key step in the synthesis of superbasic bisphosphazene proton sponges, yielded a set of bisphosphazides with a constrained geometry 1,8-disubstituted naphthalene backbone. This compound class has attracted our interest not only due to their surprisingly high stability, but in particular because of their theoretically predicted basicity in the range of their bisphosphazene analogues that can be referred to the constrained geometry interaction of two highly basic nitrogen atoms. Eleven new bisphosphazides bearing simple P-amino groups as well as P-guanidino substituents, azaphosphatrane moieties, P2 building blocks, or chiral P-amino substituents derived from L-proline are presented. They were studied concerning their spectroscopic properties and partly also their chromophoric and structural features. In the case of the pyrrolidino-substituted TPPN(2N2) (TPPN = 1,8-bis(trispyrrolidinophosphazenyl)naphthalene), the stepwise nitrogen elimination is investigated theoretically and experimentally, which led to the isolation and structural characterization of TPPN(1N2) bearing a phosphazide and a phosphazene functionality in one molecule. Attempts to protonate the obtained bisphosphazides and to prove the computationally predicted pKBH(+) values through NMR titration reactions resulted in their decay, which again was rationalized by theoretical calculations. Altogether we present the so far most extensive spectroscopic, structural and theoretical investigation of constrained geometry bisphosphazides and their Brønsted and Lewis basic properties.

Effect of aeration on pollutants removal, biofilm activity and protozoan abundance in conventional and hybrid horizontal subsurface-flow constructed wetlands

The large area demand of constructed wetlands (CWs) is documented as a weak point that can be potentially reduced by applying active aeration. The aim of this study was, therefore, to understand the effects of aeration on the treatment performance, the biofilm activity, the protozoan population size and potential CW footprint reduction of different horizontal flow (HF) CW configurations. Two experimental periods were considered: a first period with low organic loading rate (OLR) and a second period with high OLR. Three HF CW configurations were compared: a conventional (control), an aerated and a hybrid CW (aerated followed by a non-aerated CW). The results obtained reinforced the competence of aerated CW for organic matter removal (81–89% of chemical oxygen demand) while for nitrogen elimination the control (19–24%) and hybrid (8–41%) systems performed better than the aerated system (-6% to 33%). Biofilm activity and protozoa abundance were distinctly higher at the inlet zones when compared with the outlet zones of all CWs, as well as in the aerated systems when compared with the non-aerated CWs. The protozoan abundance increased with an increase in the OLR and ciliates were found to be the dominant group. Overall, the active aeration highlighted the efficiency and stability of the CWs for organic matter removal and thus can be used as a promising tool to enhance microbial activity and grazing by protozoa; eventually reducing solid accumulation in the bed media. These beneficial effects contribute to reduce the CWs’ area requirements.

Metabolic and embryonic responses to terrestrial incubation of Fundulus grandis embryos across a temperature gradient

This study simulated terrestrial incubation and measured rates of embryogenesis, nitrogen elimination, heart rate, lactate production, maximum length of time a hatch could be delayed and developmental responses of terrestrially incubated Gulf killifish Fundulus grandis embryos at temperatures ranging from 20 to 30° C. Temperature had a positive relationship with rate of embryogenesis, but a negative relationship with extent of extended incubation. The 30° C treatment reached embryonic maturity 6 days before the 20° C treatment. Embryos hatched between intervals of 240 and 336, 144 and 288, 96 and 240 and 96 and 192 h after reaching developmental maturity for the 20, 23, 26 and 30° C treatments. Significantly higher concentrations of total nitrogen, in the form of ammonia and urea, were recorded in the 20 and 30° C treatments. While temperature significantly influenced lactate and ATP concentrations, no significant influence of time of incubation was detected. Terrestrial embryos displayed an ability to develop quickly during embryogenesis and prolong incubation for an extended period of time after reaching embryonic maturity. This adaptation may be a life-history trait used to minimize asynchronous hatching, cannibalism and cohort size heterogeneity.