Addition Of Hydroxylamine Research Articles

Mechanism insights into activation of hydroxylamines for generation of multiple reactive species in photochemical degradation of bromophenols

Photolysis of bromophenols and nitrogen cycle are two common processes in the natural water bodies. In the study, effect of hydroxylamine (HA), an intermediate of nitrogen cycle, on UV photolysis of bromophenols in the aqueous solution was investigated under different conditions. It was found that HA presence not only changed formation of reactive species, also varied degradation pathways of 2,4,6-tribromophenol (TBP). During photolysis of TBP, carbon-centered radicals (C), H and eaq− were produced, while new radicals of OH, NO2 and NH2 were produced after addition of HA. Moreover, the added HA greatly inhibited hydrolysis of C via the reaction between them, thereby depressing formation of hydroxylated intermediates (e.g., monohydroxylated 2,6-dibromophenol), and improving debromination of TBP in UV/HA/TBP system. It is worth noting that two new nitro/amino byproducts of concern were detected in UV/HA/TBP system. They are proposed to be generated from the combination of C with NO2 and NH2. Furthermore, nitro/amino byproducts were one of the major sink pathways of HA in UV/HA/TBP system. This is the first article to demonstrate the formation of nitro/amino byproducts form photodegradation of phenolic compounds in the presence of HA, and to clarify reaction mechanism for generation of OH, NO2 and NH2 from HA activation during photolysis of bromophenols in the aqueous solution.

Regulation effects of hydrogen sulfide on ascorbate-glutathione cycle in naked oat leaves under saline-alkali stress.

Saline-alkali stress is one of the common abiotic stresses for plants. Hydrogen sulfide (H2S), as a gas signal, plays an important role in driving the responses of plants to saline-alkali stress. To explore the regulating effects of H2S on the ascorbate (AsA)-glutathione (GSH) cycle in naked oat (Avena nude) under saline-alkali stress, we used sodium hydrogen sulfide (NaHS) as donor of exogenous H2S and hydroxylamine (HA) as H2S synthesis inhibitor to examine the effects of H2S on plant growth, leaf reactive oxygen species, membrane lipid peroxidation, and antioxidants and key enzymes in the AsA-GSH cycle in "Dingyou 9" variety of naked oat under saline-alkali mixed stress. Results showed that spraying 50 μmol·L-1 NaHS could alleviate the inhibition of 50 mmol·L-1 saline-alkali mixed stress on the growth of naked oats, reduce the content of superoxide anions, H2O2, malondialdehyde, oxidized ascorbate (DHA), glutathione (GSH), and oxidized glutathione (GSSG) in leaves of naked oat under saline-alkali mixed stress, increase the ratio of AsA/DHA and GSH/GSSG, but did not affect the content of reduced ascorbic acid (AsA). Spraying NaHS significantly increased the activities of key enzymes, L-galactose dehydrogenase (GalDH) and L-galactono-1, 4-lactone dehydrogenase (GalLDH), for AsA synthesis pathways in naked oat leaves under salt-alkali mixed stress, as well as monodehydroascorbate reductase (MDHAR) in the AsA-GSH cycle, and decreased the activities of ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR), but did not affect the activities of ascorbate oxidase (AO) and glutathione reductase (GR). The addition of HA partially or completely relieved those aforementioned effects. Our results indicated that H2S could increase the efficiency of AsA-GSH cycle by promoting the synthesis of AsA and enhancing the activity of MDHAR, and reduce the oxidative damage of saline-alkali stress to naked oats.

Enhancement of the electro-Fenton degradation of organic contaminant by accelerating Fe3+/Fe2+ cycle using hydroxylamine

The Electro-Fenton process can generate reactive oxygen species capable of oxidizing refractory organic contaminants. However, low regeneration efficiency of Fe2+ restricts its application. Herein, hydroxylamine (HA) was added into the Electro-Fenton (HA/Electro-Fenton) process to accelerate the transformation of Fe3+ to Fe2+. Using dimethyl phthalate (DMP) as target contaminant, the HA/Electro-Fenton system alleviated the two-stage reaction process and accelerated the removal of DMP in the pH range of 2.0–6.0. With improving DMP concentration from 5 mg L-1 to 50 mg L-1, their degradation rate increased in the HA/Electro-Fenton system, while decreased in the Electro-Fenton system. The addition of HA had negligible effect on electro-generation of H2O2, but facilitate the redox cycle of Fe3+/Fe2+ and the generation of hydroxyl radicals, thus improving the degradation of DMP. The final transformation products of HA were N2, N2O, and NO3−. The presence of PO43− improved DMP degradation, while Cl− and organic matters inhibited DMP removal in varying degrees. This study provided useful reference to solve the low efficiency of Fe3+/Fe2+ cycle and expand the pH application range in the Electro-Fenton process.

Rapidly achieving and optimizing simultaneous partial nitrification denitrification and anammox integrated process by hydroxylamine addition for advanced nitrogen removal from domestic wastewater

The achievement and stable maintenance of partial nitrification and partial anammox process for municipal sewage is a challenging research topic at present. In this study, a novel strategy of hydroxylamine (NH2OH) addition under low DO condition was adopted for rapidly achieving simultaneous partial nitrification denitrification and anammox process (SPNDA) to deal with domestic wastewater, the nitrite accumulation ratio (NAR) increased from 1% to 82% in the first 4 days. After the addition of NH2OH was stopped, the PN effect of SPNDA process remained relatively stable within 100 days. During the stable operation period with aerobic HRT of 5 h, the nitrogen removal efficiency was 87.9 ± 4.2%. Moreover, the abundance of denitrifying bacteria and Candidatus Brocadia increased from 1.79% and 0.062% to 22.49% and 0.38% respectively, which promoted nitrogen removal effect. Overall, this study provided a quickly way for achieving the cost-effective SPNDA process to enhance nitrogen removal with NH2OH addition.

A one-pot assembly of Δ2-isoxazolines from ketones, aryl acetylenes and hydroxylamine: Revisiting the mechanism in terms of quantum chemistry

A mechanism of the sequential reaction of ketones with arylacetylenes and hydroxylamine in the presence of KOBut/DMSO followed by the treatment of the reaction mixture with H2O and KOH yielding Δ2-isoxazolines is investigated using a DFT approach by the example of the assembly of (4R,5S)-5-benzyl-4-ethyl-3-methyl-4,5-dihydroisoxazole from pentan-2-one, phenylacetylene and NH2OH·HCl. Activation energies were estimated for successive stages of nucleophilic addition of a ketone carbanion to a triple bond (vinylation), addition of hydroxylamine to a carbonyl group and subsequent dehydration of the carbinolamine formed (oximation), base-assisted E/Z-isomerization of the oxime group, probable prototropic rearrangement of the β,γ-unsaturated oxime to the α,β-unsaturated structure and) intramolecular nucleophilic attachment to a double bond of α,β- or β,γ-unsaturated oxime with the formation of a five-membered heterocycle. It was shown that it is not the α,β-unsaturated oxime that participates in the ring closure, as previously assumed, but the β,γ-unsaturated form.

Enhanced removal of As(III) by heterogeneous catalytic oxidation of As(III) on Fe-biochar fibers with H2O2 and hydroxylamine

Iron oxide-modified biochars are increasingly recognized as a promising arsenic adsorbent. However, most of them face serious challenges in the rapid and efficient removal of As(III). Herein, we integrated the iron oxide nanoneedles vertically covered biochar fibers (Fe-BFs) with H2O2 and Hydroxylamine (HA) to construct a heterogeneous catalytic system for the rapid oxidation and deep removal of As(III) from water. The system oxidized the As(III) to As(V) with high efficiency, and then the generated As(V) could be rapidly removed by adsorption onto Fe-BFs. The removal efficiency of As(III) by Fe-BFs/H2O2/HA at 120 min reached up to 98.93%, which is much higher than that of by Fe-BFs (69.20%) and Fe-BFs/H2O2 (92.32%). The system could work reliably in a wide pH range (4–10). Moreover, fixed-bed column experiments demonstrated that the addition of H2O2 and HA could increase the effective treatment volume from ~350 bed volume (BV) to ~700 BV to meet the drinking water standard (<10 μg/L). The introduction of HA induced the reduction of surface Fe(III) of Fe-BFs to surface Fe(II), which reacted with H2O2 to produce OH. The OH played a very important role in promoting the removal of As(III). This study offers a new strategy to enhance the applicability of Fe modified biochar for As(III) removal.

Achieving stable mainstream nitrogen and phosphorus removal assisted by hydroxylamine addition in a continuous partial nitritation/anammox process from real sewage

Hydroxylamine (NH2OH) as the putative intermediate for anammox ensures the robustness of partial nitritation/anammox (PN/A) process; however, the feasible for NH2OH addition to improve the stability of PN/A process under low-strength ammonia (NH4+-N) condition need to be further investigated. In this study, the restoration and steady operation of mainstream PN/A process were investigated to treat real sewage with in situ NH2OH added in a continuous alternating anoxic/aerobic with integrated fixed-film activated sludge (A3-IFAS) reactor. Results showed that the deteriorated PN/A process caused by nitrate (NO3−-N) built-up was rapidly restored with a distinct decrease of the NO3−-Nproduced/NH4+-Nconsumed ratio from 28.7% to <10.0% within 20 days, after 5 mg N/L of NH2OH was added daily into the aerobic zone of A3-IFAS reactor. After 230 days of operation, the average total nitrogen (TN) and phosphate (PO43−–P) removal efficiencies of 80.8% and 91.5%, respectively were stably achieved, with average effluent sCOD, NH4+-N, TN and PO43−–P concentrations reaching 23.1, 2.3, 7.7 and 0.4 mg/L, respectively. Microbial community characterization revealed Candidatus Brocadia (3.60% and 2.92%) and Ignavibacteriae (1.56% and 2.66%) as the dominant anammox bacteria and denitrifying bacteria, respectively, jointly attached in the biofilm_1 and biofilm_2, while Candidatus Microthrix (5.17%) dominant in floc sludge was main responsible for phosphorus removal. This study confirmed that NH2OH addition is an effective strategy for nitrite-oxidizing bacteria suppression, contributing to the in situ restoration of PN/A process and high stable mainstream nitrogen and phosphorus removal in a continuous PN/A process from real sewage.

Novel insights into overcoming nitrite oxidation bacteria acclimatization problem in treatment of high-ammonia wastewater through partial nitrification

A partial nitrification sequencing batch reactor was operated to reveal mechanisms behind nitrite oxidation bacteria (NOB) acclimatization in high-ammonia wastewater treatment. The influent NH4+-N increased stepwise from 499.7 ± 4.2 mg/L to 6994.5 ± 7.5 mg/L with initial free ammonia (FA) concentration rising from 37.9 ± 3.2 mg NH3-N/L to 715.3 ± 47.3 mg NH3-N/L, respectively. NOB acclimatized this FA range with NO3–-N production increasing from 29.2 ± 2.6 mg/L to 144.1 ± 31.0 mg/L in a cycle, which was caused by the shift of dominant NOB genus from Nitrospira to Nitrolencea. Nitrosomonas as ammonia oxidation bacteria, could sustain its activity of 62.1 ± 0.1 mg NH4+-N/(gVSS∙L∙h) under the same condition. Hydroxylamine addition could be implemented as an emergency measure to alleviate NOB acclimatization in short-term operation. The findings expanded knowledge about NOB acclimatization types and provided novel insights for addressing this problem in a targeted way.

Hydroxylamine enhanced treatment of highly salty wastewater in Fe0/H2O2 system: Efficiency and mechanism study

• Fe 0 -HA/H 2 O 2 enhanced 7.9 times for tartrazine removal in salty system than Fe 0 /H 2 O 2 . • Fe 0 -HA/H 2 O 2 could widen the application of pH to neutral pH. • Fe 0 -HA/H 2 O 2 could obtain remarkable performance at wide salt concentration levels. • Fe 0 -HA/H 2 O 2 have good suitability for treatment of various types of salty wastewater. This study demonstrated a fast and efficient treatment of highly salty wastewater in a hydroxylamine (HA) enhanced Fe 0 /H 2 O 2 system. The apparent rate constant ( k ) in Fe 0 -HA/H 2 O 2 system could achieve 7.9 times higher than that in Fe 0 /H 2 O 2 system using tartrazine as the target pollutant and Na 2 SO 4 as the model salt. The value of k for removing tartrazine in the salty system by Fe 0 -HA/H 2 O 2 process even 12.7 times higher than that in the conventional system which was attributed to the faster Fe 0 corrosion rate in the salty system. Meanwhile, Fe 0 -HA/H 2 O 2 process could obtain remarkable performance for highly salty wastewater treatment at wide salt concentration levels (0–0.2 M) and could also widen the application of pH to neutral pH. The characterizations by SEM and XPS, the intensity of DMPO–OH adduct signals and detection of Fe 2+ and Fe 3+ ions in different systems confirmed the good performance was owing to the faster Fe 0 corrosion rate in the salty system and acceleration of Fe 3+ /Fe 2+ recycle owing the addition of HA inducing fast catalysis of H 2 O 2 and generation of hydroxyl radicals. Moreover, the value of k for removing tartrazine in various types of salty system by Fe 0 -HA/H 2 O 2 process was 2.9–30.8 times larger than Fe 0 /H 2 O 2 process demonstrating the good suitability of Fe 0 -HA/H 2 O 2 process at various types of salty system. Therefore, this study will shed lights on the reactivity of the Fe 0 -HA/H 2 O 2 system and provide an alternative pathway for removal of salty wastewater.

Hydroxylamine addition enhances fast recovery of anammox activity suffering Cr(VI) inhibition

Hydroxylamine (NH2OH), one of the most important intermediates of anammox was employed to test the recovery performance because of its stimulation to anammox bacteria. Batch test indicated simultaneous addition of 1.83 ~ 9.17 mg N /L NH2OH relieved Cr(VI) inhibition because of extracellular reduction to Cr(III). The recovery efficiency (RE) was over 166%, with the effluent Cr(VI) and Cr(III) below 0.25 and 0.12 mg/L, respectively. Anammox activity after Cr(VI) inhibition was effectively recovered by 8 mg N/L NH2OH with RE at 218%. The long-term operation showed 1 ~ 2 mg N/L NH2OH accelerated the recover speed of nitrogen removal rate with 2.84 folds, as well as improving NH4+ conversion ratio and reducing NO3− production. After 55 days recovery, extracellular polymeric substance concentration, anammox activity and heme content recovered better with NH2OH addition. This study will provide the theoretical basis for rapid recovery of anammox activity by NH2OH when suffering Cr(VI) inhibition.

Shortcut nitrification–denitrification achieved by hydroxylamine addition in constructed rapid infiltration system

Shortcut nitrification–denitrification achieved by hydroxylamine addition in constructed rapid infiltration system

Enhanced Nitritation through Long-Term Hydroxylamine Addition: Insight into Ammonium Oxidation Activity and Microbial Community

Enhanced Nitritation through Long-Term Hydroxylamine Addition: Insight into Ammonium Oxidation Activity and Microbial Community

A Convenient One-Pot Synthesis of Chalcones and Their Derivatives and Their Antimicrobial Activity

A series of chalcones were synthesized by base-catalyzed Clasien-Schmidt condensation of substituted benzaldehydes and substituted acetophenones at room temperature. The addition of hydrazine hydrate and hydroxylamine hydrochloride across the double bond of the obtained chalcones gave pyrazole and isoxazole derivatives, respectively. All the synthesized compounds were characterized by 1H and 13C NMR and FT-IR spectroscopy and screened for their in vitro antimicrobial activity against two bacterial strains, Pseudomonas aeruginosa and Pseudomonas oryzihabitans using Ciprofloxacin as standard drug. 1-(2-Methoxyphenyl)-3-phenylprop-2-en-1-one and 1-(4-chlorophenyl)-3-phenylprop-2-en-1-one showed significant activity against both bacterial strains and hence proved to be potent antimicrobial agents.

Enhancement of nitrite production via addition of hydroxylamine to partial denitrification (PD) biomass: Functional genes dynamics and enzymatic activities

This study investigated the activity of partial denitrification (PD) biomass/key enzymes, functional gene expressions in response to 0 ~ 50 mg/L hydroxylamine (NH2OH) addition. Results indicated that NH2OH contributed to nitrite (NO2−-N) production, facilitating the maximum increase of nitrate (NO3−-N) to NO2−-N transformation ratio to 80.47 ± 2.82%, leading to 2.56-fold NO2−-N higher than those of control. The observed transient inhibitory effect on NO3−-N reduction process was attributed by high-level NH2OH (35 ~ 50 mg/L). Enzymatic assays revealed the enhanced activity of both NO3−-N and NO2−-N reductase while the former showed obvious superiority which led to high NO2−-N accumulation. These results were further confirmed by the corresponding functional genes (narG, napA, nirS and nirK). Besides, negative influence of NH2OH addition was limited to PD aggregates, due to the increasing secretion of extracellular polymeric substances (EPS) as well as proteins/polysaccharides ratios in tightly-bound structure of EPS.

The role of hydroxylamine in promoting conversion from complete nitrification to partial nitrification: NO toxicity inhibition and its characteristics

This study investigated a strategy for hydroxylamine (NH2OH) addition for promoting the conversion of complete nitrification to partial nitrification in a sequencing batch reactor (SBR). The results showed that continuous dosing of 5 mg-N/L NH2OH into a complete nitrification reactor for 16 days led to an increase in the nitrite accumulation ratio (NAR) from 0.22% to 95.08% and a significant enhancement in the accumulation of NO and N2O in the liquid. The maximum concentration of NO in each cycle rose with the increase of NAR during NH2OH addition. With the stopping of NH2OH addition, the partial nitrification disappeared progressively in 21 days. The analysis for microbial community showed that Nitrospira was the main NOB and its relative abundance decreased with NH2OH addition and recovered after the cessation of NH2OH addition. Accordingly, NH2OH has a significant and reversible inhibition on Nitrospira and its essence might be related to NO toxicity.

Is Anoxic Operation Effective to Control Nitrate Build-Up and Sludge Loss for the Combined Partial Nitritation and Anammox (CPNA) Process?

There were three main issues of long start-up period, nitrate build-up and sludge loss during the operation of combined partial-nitritation anammox (CPNA). To fully start up the CPNA reactor, the fast achievement of partial-nitritation (PN) was the first step. Firstly, the PN process was successfully achieved within 22 days by 2 mg·L−1 hydroxylamine (NH2OH) addition and online intermittent aeration control at 0.2~0.3 mg·L−1 dissolved oxygen (DO). Then, a novel strategy of adding anoxic stirring phase between feeding and aeration period during CPNA operation was applied. It was shown effective to control nitrate build-up since the mole ratio of NO3−-N production and NH4+-N removed (MNRR) was mostly below 15%. Also, the procedure adjustment was proven useful to alleviate sludge loss by sustaining filamentous bacteria that could act as biomass framework and reduce nitrate substrate. The filamentous denitrifying bacteria could cause sludge bulking. The total nitrogen removal rate (TNRR) varied from 0.20 to 0.45 kg·m−3·d−1 during CPNA operation. In Stage III, after adding anoxic stirring phase, the abundance of nitrogen transformation functional microorganism’s nitrite oxidizing bacteria (NOB) was below 1.6%, which was one order of magnitude lower than Anammox and ammonia oxidizing bacteria (AOB).

Ethyl (3S)-3-[(3aR,5R,6S,6aR)-6-hy-droxy-2,2-di-methyl-tetra-hydro-furo[4,5-d][1,3]dioxol-5-yl]-3-{(3S)-3-[(3aR,5R,6S,6aR)-6-hy-droxy-2,2-di-methyl-tetra-hydro-furo[4,5-d][1,3]dioxol-5-yl]-5-oxoisoxazolidin-2-yl}propano-ate chloro-form monosolvate.

The title compound, C22H33NO12·CHCl3, was obtained as a product of a double aza-Michael addition of hydroxyl-amine on a Chiron with a known absolute configuration. The enanti-opure compound crystallized as a chloro-form solvate, in space group P1, and diffraction data were collected at room temperature with Ag Kα radiation. The Flack parameter refined to x = -0.01 (16); however, the Flack and Watkin 2AD plot clearly shows that differences between Friedel opposites (the D component of the plot) do not carry any reliable information about resonant scattering of Cl atoms, and are rather dominated by random and systematic errors. The RD factor calculated using 1941 acentric Friedel pairs is RD = 0.995. On the other hand, the 2A component of the plot, related to average intensities of Friedel pairs, shows that data are of good quality (RA = 0.069). This example illustrates that while using Ag Kα radiation (λ = 0.56083 Å), scatterers heavier than Cl should be present in a chiral crystal in order to determine confidently the absolute structure of the crystal.

A stereoselective construction of a cis-1,2-oxazadecaline skeleton using a substrate-controlled intramolecular oxy-Michael addition of tyrosine-derived hydroxylamines

A method for the stereoselective construction of cis-1,2-oxazadecaline skeletons via a substrate-controlled intramolecular oxy-Michael addition of readily available tyrosine-derived hydroxylamines has been developed. The approach features an eight-step synthesis of the optically active cis-1,2-oxazadecaline enones from tyrosine esters. The described chiral pool synthetic strategy has great potential for the efficient enantioselective synthesis of natural products possessing cis-1,2-oxazadecaline frameworks, such as trichodermamides.

Enhanced transition metal oxide based peroxymonosulfate activation by hydroxylamine for the degradation of sulfamethoxazole

The enhanced peroxomonosulfate (PMS) activation and sulfamethoxazole (SMZ) degradation performances and mechanisms by hydroxylamine (HA) in the presence of three transition metal oxides (MxOy), hematite (α-Fe2O3), cobalt oxide (Co2O3) and copper oxide (CuO) were comprehensive investigated. The results showed that proper addition of hydroxylamine (HA) can greatly promote the degradation of SMZ in the three MxOy/PMS systems. The results of electron paramagnetic resonance (EPR) study and quenching experiment suggested that OH was the dominating reactive oxygen species (ROS) in the α-Fe2O3/HA/PMS and Co2O3/HA/PMS systems, while in CuO/HA/PMS system, the activated-PMS on the surface of CuO was concluded to be responsible for SMZ degradation instead of free radicals. Furthermore, the intermediates of SMZ in the systems were detected by a high performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) and the degradation pathways of SMZ system were inferred, the results indicated that due to the difference of the dominating ROS and the attack order against oxidation sites, SMZ was degraded in different pathways in α-Fe2O3/HA/PMS, Co2O3/HA/PMS and CuO/HA/PMS system. α-Fe2O3, CuO and Co2O3, could maintain stable catalytic activity in the respective reaction systems and could be efficiently recycled.

Nitrite accumulation in comammox-dominated nitrification-denitrification reactors: Effects of DO concentration and hydroxylamine addition

In this study, nitrite accumulation was investigated under different DO conditions and different hydroxylamine addition methods during the domestic wastewater treatment. Two sequencing batch reactors in parallel were operated under cyclic aerobic and anoxic conditions with the DO concentration of 2.0 and 4.0 mg/L in aerobic phase. The nitrite accumulation rate during high DO conditions increased to 44.8 and 66.7% in 20 days. During hydroxylamine addition, the NAR increased over 90% under the continuous and intermittent hydroxylamine addition. Continuous hydroxylamine addition could result in a more efficient and rapid nitrite accumulation. The findings suggested that comammox could be the main reason for the failure of partial nitrification in a low DO environment (< 0.5 mg/L). The nitrogen variation during typical cycles showed that the continuous hydroxylamine addition suppressed the activity of NOB and the ammonia oxidation rate. Further, the qPCR results indicated that the abundance of comammox amoA (ranged from 6.25 × 107 to 4.16 × 108 copies/g VSS) was higher than those of AOB amoA and Nitrobacter in sludge samples. The findings from the current study may enrich our understanding of partial nitrification and its control strategy.