Nitric Oxide Removal Research Articles

Early Changes in S-Nitrosoproteome in Soybean Seedlings Under Flooding Stress

The shift from aerobic to anaerobic respiration is crucial for soybean response to flooding stress; however, the regulatory mechanism in action at the initial stage of flooding stress has not been fully elucidated. To identify this mechanism in soybean, proteomic analysis of S-nitrosylated proteins was performed with emphasis on nitric oxide (NO)-mediated regulation in soybean seedlings. Removal of NO by addition of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) partially restored seedling growth. After 3, 9, and 24 h of flooding stress, the S-nitrosylation status of 364, 188, and 186 proteins was altered relative to the corresponding status before flooding, respectively. Abundance of S-nitrosylated forms of 2, 186, and 162 proteins differed between the untreated control and flooded soybean plants after 3, 9, and 24 h of flooding stress, respectively. After flooding for 3 h, development, stress, and glycolysis/fermentation categories were identified as the top categories including proteins for which abundance of S-nitrosylated forms increased. Visualization of changes in S-nitrosylation profile by pathway mapping indicated a characteristic pattern in glycolysis/fermentation. Western blot analysis confirmed that S-nitrosylated status of alcohol dehydrogenase increased with flooding. These results suggest that S-nitrosylation comprises rapid molecular processes that change the abundance of the active form of alcohol dehydrogenase.

Cross-linked hemoglobin bis-tetramers from bioorthogonal coupling do not induce vasoconstriction in the circulation.

Hemoglobin-based oxygen carriers (HBOCs) are potential alternatives to red blood cells in transfusions. Clinical trials using early versions of HBOCs noted adverse effects that appeared to result from removal of the vasodilator nitric oxide (NO). Previous reports suggest that size-enlarged HBOCs may avoid NO-rich regions along the vasculature and therefore not cause vasoconstriction and hypertension. Hemoglobin (Hb) bis-tetramers (bis-tetramers of hemoglobin that are prepared using CuAAC chemistry [BT-Hb] and bis-tetramers of hemoglobin that are specifically acetylated and prepared using CuAAC chemistry [BT-acHb]) can be reliably produced by a bio-orthogonal cyclo-addition approach. We considered that an HBOC derived from chemical coupling of two Hbs would be sufficiently large to avoid NO scavenging and related side effects. The ability of intravenously infused BT-Hb and BT-acHb to remain in the circulation without causing hypertension were determined in wild-type (WT) and diabetic (db/db) mouse models. In WT mice, the coupled oxygen-carrying proteins retained their function over several hours after administration. No significant changes in systolic blood pressure from baseline were observed after intravenous infusion of BT-Hb or BT-acHb in awake WT and db/db mice. In contrast, infusion of native Hb or cross-linked Hb tetramers in both animal models induced systemic hypertension. The results of this study indicate that bis-tetrameric HBOCs derived from the bio-orthogonal cyclo-addition process are likely to overcome clinical issues that arise from NO scavenging by Hb derivatives.

Integration of 3D macroscopic graphene aerogel with 0D-2D AgVO3-g-C3N4 heterojunction for highly efficient photocatalytic oxidation of nitric oxide

The application of three-dimensional (3D) aerogels for immobilizing powder catalysts can greatly enhance the catalyst cycling stability. In this study, we modify two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets with zero-dimensional (0D) silver metavanadate (AgVO3) quantum dots. The resulting 0D-2D heterojunction facilitates the separation of electron-hole pairs, and exhibits high efficiency for removing nitric oxide (NO) at low concentrations (600 ppb) at room temperature. The removal efficiency is much higher than that of pure g-C3N4. The porous network framework of the 3D AgVO3-g-C3N4-graphene hybrid aerogel is formed by bridging of graphene oxide sheets. This results in the heterojunction further enhancing electron-hole separation. The modification of g-C3N4 promotes the separation of photogenerated carriers in a step by step manner, and enhances their oxidation-reduction ability. The AgVO3-g-C3N4-graphene hybrid aerogel exhibits excellent catalytic activity for NO removal (maximum of 65%). Cycling experiments verify the stability and recyclability of the aerogel.

Removal of NO in simulated flue with aqueous solution of peroxymonosulfate activated by high temperature and Fe(II)

In this article, a novel control strategy on nitric oxide (NO) removal from simulated flue gas by high temperature and transition metal Fe(II) to activate peroxymonosulfate (PMS) to generate sulfate radicals (SO4·-) and hydroxyl radicals (OH) was investigated for the first. The high oxidation capacity of PMS, in combination with the high activation performance of Fe(II) ions, made the processes significantly effective for NO removal, and a removal efficiency of more than 86% was observed after 25 min treatment. Some experiments were optimized to select optimal experimental parameters: the molar ratio of PMS/Fe(II), solution pH value and activation temperature in terms of NO removal efficiency. The effect of free radical quenching, combined with electron spin-resonance (ESR) analysis confirmed that the presence of SO4·- and OH radicals, and verified that SO4·- was the dominated radical during NO removal process and the strategy of heating and Fe(II) had stronger function to activate PMS. The classical steady-state approximation technique was adopted to obtain the kinetic model of the whole reaction, and the result satisfactorily interpreted the experimental data and had the good reliability (0.978) and (0.988). The removal process of NO from simulated flue gas by the PMS–Fe(II) systems was a pseudo-first-order reaction.

Efficient Inhibition of N2O during NO Absorption Process Using a CuO and (NH4)2SO3 Mixed Solution

The discovery of effective methods toward nitric oxide (NO) removal by solution is valuable for the cost-effective flue gas control. In this study, it is first reported that nitrous oxide (N2O) is obviously suppressed by using copper oxide (CuO) combined with (NH4)2SO3 (NS) solution. CuO has been characterized, and the effects of reactants concentration, additives, temperature, pH and powder size on NO absorption process have been evaluated. The selectivity of N2O can drop from 91.30% to 11.25% under the optimum experimental conditions. Furthermore, based on the method of single-factor analysis, the inhibition of N2O is identified as the coeffect of NS/CuO. In addition, the pathways of NO removal are divided into two parts—N2O formation and NO absorption—and its ratio is calculated in the range of 0.29–0.53. Because of the continuous supply of NS from ammonia desulfurization, this study opens the feasibility of simultaneous desulfurization and denitrification.

Promotional Effect of Cerium and/or Zirconium Doping on Cu/ZSM-5 Catalysts for Selective Catalytic Reduction of NO by NH3

The cerium and/or zirconium-doped Cu/ZSM-5 catalysts (CuCexZr1−xOy/ZSM-5) were prepared by ion exchange and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction by hydrogen (H2-TPR). Activities of the catalysts obtained on the selective catalytic reduction (SCR) of nitric oxide (NO) by ammonia were measured using temperature programmed reactions. Among all the catalysts tested, the CuCe0.75Zr0.25Oy/ZSM-5 catalyst presented the highest catalytic activity for the removal of NO, corresponding to the broadest active window of 175–468 °C. The cerium and zirconium addition enhanced the activity of catalysts, and the cerium-rich catalysts exhibited more excellent SCR activities as compared to the zirconium-rich catalysts. XRD and TEM results indicated that zirconium additions improved the copper dispersion and prevented copper crystallization. According to XPS and H2-TPR analysis, copper species were enriched on the ZSM-5 grain surfaces, and part of the copper ions were incorporated into the zirconium and/or cerium lattice. The strong interaction between copper species and cerium/zirconium improved the redox abilities of catalysts. Furthermore, the introduction of zirconium abates N2O formation in the tested temperature range.

Thioredoxin shapes the C. elegans sensory response to Pseudomonas produced nitric oxide

Nitric oxide (NO) is released into the air by NO-producing organisms; however, it is unclear if animals utilize NO as a sensory cue. We show that C. elegans avoids Pseudomonas aeruginosa (PA14) in part by detecting PA14-produced NO. PA14 mutants deficient for NO production fail to elicit avoidance and NO donors repel worms. PA14 and NO avoidance are mediated by a chemosensory neuron (ASJ) and these responses require receptor guanylate cyclases and cyclic nucleotide gated ion channels. ASJ exhibits calcium increases at both the onset and removal of NO. These NO-evoked ON and OFF calcium transients are affected by a redox sensing protein, TRX-1/thioredoxin. TRX-1's trans-nitrosylation activity inhibits the ON transient whereas TRX-1's de-nitrosylation activity promotes the OFF transient. Thus, C. elegans exploits bacterially produced NO as a cue to mediate avoidance and TRX-1 endows ASJ with a bi-phasic response to NO exposure.

Nitric Oxide Is Required for Melatonin-Enhanced Tolerance against Salinity Stress in Rapeseed (Brassica napus L.) Seedlings.

Although melatonin (N-acetyl-5-methoxytryptamine) could alleviate salinity stress in plants, the downstream signaling pathway is still not fully characterized. Here, we report that endogenous melatonin and thereafter nitric oxide (NO) accumulation was successively increased in NaCl-stressed rapeseed (Brassica napus L.) seedling roots. Application of melatonin and NO-releasing compound not only counteracted NaCl-induced seedling growth inhibition, but also reestablished redox and ion homeostasis, the latter of which are confirmed by the alleviation of reactive oxygen species overproduction, the decreases in thiobarbituric acid reactive substances production, and Na+/K+ ratio. Consistently, the related antioxidant defense genes, sodium hydrogen exchanger (NHX1), and salt overly sensitive 2 (SOS2) transcripts are modulated. The involvement S-nitrosylation, a redox-based posttranslational modification triggered by NO, is suggested. Further results show that in response to NaCl stress, the increased NO levels are strengthened by the addition of melatonin in seedling roots. Above responses are abolished by the removal of NO by NO scavenger. We further discover that the removal of NO does not alter endogenous melatonin content in roots supplemented with NaCl alone or together with melatonin, thus excluding the possibility of NO-triggered melatonin production. Genetic evidence reveals that, compared with wild-type Arabidopsis, the hypersensitivity to NaCl in nia1/2 and noa1 mutants (exhibiting null nitrate reductase activity and indirectly reduced endogenous NO level, respectively) cannot be rescued by melatonin supplementation. The reestablishment of redox homeostasis and induction of SOS signaling are not observed. In summary, above pharmacological, molecular, and genetic data conclude that NO operates downstream of melatonin promoting salinity tolerance.

Catalytic conversion of NO assisted by plasma over Mn-Ce/ZSM5-multi-walled carbon nanotubes composites: Investigation of acidity, activity and stability of catalyst in the synergic system

Mn-Ce/ZSM5-MWCNTs (MWCNTs, multi-walled carbon nanotubes) catalysts were synthesized via an impregnation method to study NO conversion and sulfur resistance with the assistance of plasma. The reaction proceeded excellently at ambient temperature by using bimetallic manganese-cerium as active component, exhibited superior nitric oxide removal efficiency (around 90%) and turnover frequency at relatively low input energy; XRD, BET, TPD, XPS and in-situ FTIR investigations showed that the highly oxidizing environment, interaction of physicochemical structure, improvement of both Lewis and Brønsted acid sites as well as acceleration of the Eley-Rideal (E-R) mechanism were responsible for this catalyst enhancement. The comparison of characterizations over fresh and spent MnCe catalyst along with mechanistic analysis revealed that valence variation of Mn and Ce cations not only provide oxygen vacancies, but more importantly, directly affect the formation and consumption of Lewis acid sites in whole reaction process. Subsequently, an increased number of Lewis acid sites coordinate NH3 molecules with Mn and Ce atoms, then contribute to ammonia adsorption and rob electrons directly from gaseous NO or nitrate anions as following Eley-Rideal pathway. At last, oxidizing radicals (O, O3) and cerium modification inhibit further speciation of ammonium and manganese sulfates species on the catalyst surface, thereby promoting low temperature catalytic activity and sulfur durability.

Nitric oxide removal from flue gas with ammonium using AnammoxDeNOx process and its application in municipal sewage treatment

A novel AnammoxDeNOx process was designed to simultaneously remove NOx in flue gas and ammonium wastewater, with the aim of exploring the possibility of using NO as a long-term and stable electron acceptor for anammox bacteria. The performance of the AnammoxDeNOx process indicated a NOx removal efficiency from simulated flue gas (including CO2, SO2, O2 and NO2) of 87–96% using simulated ammonium wastewater. With municipal wastewater, the removal efficiencies for NOx were 70–90%, total nitrogen 40–70%, and COD 80–90% (NO concentration: 100–500 ppm). The anammox genus underwent considerable changes from the dominant Candidatus Kuenenia in the stage of domestication to the predominant Candidatus Brocadia, which then became the dominant species in the simulated flue gas and actual municipal wastewater stages.

A Mass-Transfer Model of Nitric Oxide Removal In a Rotating Drum Biofilter Coupled with FeII(EDTA) Absorption

The biological nitric oxide (NO) reduction rate in a rotating drum biofilter (RDB) mainly depends on the mass transfer between the gas and liquid phase because of the poor solubility of NO. This work, aimed to facilitate the gas–liquid (GL) mass transfer of NO in RDB, the FeII(EDTA) was used to capture NO and porous drum was employed to increase the eddy current effect of the system. The denitrification rate of GL-RDB was stabilized at about 95% during the long-term operation. A dynamic model of GL-RDB was established to optimize the denitrification performance of this innovative RDB. Experimental results revealed that the developed model well described NO removal in GL-RDB. Model analysis also showed that the rotational speed and inlet NO concentration were the critical parameters in determining of the RBD performance. This work may provide fundamental theory for the further study of GL-RDB.

Nitric oxide in frozen-thawed equine sperm: Effects on motility, membrane integrity and sperm capacitation

Nitric oxide (NO) is a reactive nitrogen species (RSN) that, over the years, has been shown to be integrated with biological and physiological events, including reproductive processes. NO can affect the functionality of spermatozoa through free radical scavenging, deactivating and inhibiting the production of superoxide anions (O2.−). However, the role of NO in mammalian spermatozoa physiology seems paradoxical. The aim of this study was to investigate the effects of NO on motility, hyperactivation, membrane integrity, peroxidation, and capacitation in cryopreserved equine sperm. Ejaculates were collected and cryopreserved. After thawing, samples were centrifuged, suspended in an in vitro fertilization (IVF) medium and incubated with the following treatments: 1) C = control (IVF); 2) A = l-arginine (10 mM – In); 3) L = L-NAME (1 mM – Ih); 4) M = methylene blue (100 mM – Re); 5) AL = L-arginine + L-NAME (In + Ih); 6) AM = L-arginine + methylene blue (In + Re). The samples were evaluated for spermatic kinetics by CASA and other analyses [plasma and acrosomal membranes used the propidium iodide (PI) and Pisum sativum agglutinin (PSA), detection of tyrosine residues phosphorylation in the membrane (F0426), nitric oxide (DAF-2/DA), lipid peroxidation (C11-BODIPY581/591)] by flow cytometry. The l-arginine treatments reduced MOT, PROG, RAP and LIN only at time 0 min compared to the control and L-NAME. These treatments (MT and MP, VAP, VSL, LIN, RAP) also reduced the sperm movement characteristics but only at the beginning of the incubation period. After this period of incubation, motility recovered. NO removal by methylene blue almost completely inhibited sperm motility, but these treatments had the highest percentages of intact membranes. l-arginine treatments improved acrosome reactions and differed from M and AM. NO production, tyrosine phosphorylation and lipid peroxidation did not differ among treatments, except for M and AM, where a reduction in these variables was detected. Therefore, equine sperm capacitation and the acrosome reaction are part of an oxidative process that involves the participation of ROS, and NO plays an important role in the maintenance and regulation of motility, hyperactivation, induction of acrosome reaction and possibly in capacitation, which are indispensable processes for the fertility of equine sperm.

Experimental study on reaction characteristics of NO in (NH4)2SO3 solution

The effects of various factors on the NO removal activity in the (NH4)2SO3 solution were investigated to explore more details and characteristics of the related reactions using full infrared sensor flue gas analyzer (FISFGA). It was found that the conversion yield of NO (9.0%–29.0%) was obviously improved with the increase of gas–liquid contact area, NO residence time and (NH4)2SO3 concentration as well as the adding of CuSO4. However, it was mainly limited by gas–liquid mass transfer rate and slightly inhibited by the gas velocity. Moreover, the FISFGA analysis revealed that two nitric oxide (NO) conversion route with different reduction product of N2O and N2 existed simultaneously upon the existence form of SO32−. It was confirmed by the calculations and the experiments of pH factor that the NO reduction steps were based on the following equation: (1) NO+HSO3−⇋N2O+SO42−+H+; (2) NO+SO32−⇋N2+SO42−. In this system, Eq. (1) with N2O product was the major pathway, but the ratio of Eqs. (2) to (1) was intensified in the presence of CuSO4. It is believed that the suitable additives could promote the NO reduction to N2 furtherly.

Compressible and Recyclable Monolithic g-C3N4/Melamine Sponge: A Facile Ultrasonic-Coating Approach and Enhanced Visible-Light Photocatalytic Activity

Powdery photocatalysts seriously restrict their practical application due to the difficult recycle and low photocatalytic activity. In this work, a monolithic g-C3N4/melamine sponge (g-C3N4/MS) was successfully fabricated by a cost-effective ultrasonic-coating route, which is easy to achieve the uniform dispersion and firm loading of g-C3N4 on MS skeleton. The monolithic g-C3N4/MS entirely inherits the porous structure of MS and results in a larger specific surface area (SSA) than its powdery counterpart. Benefit from this monolithic structure, g-C3N4/MS gains more exposed active sites, enhanced visible-light absorption and separation of photogenerated carriers, thus achieving noticeable photocatalytic activity on nitric oxide (NO) removal and CO2 reduction. Specifically, NO removal ratio is as high as 78.6% which is 4.5 times higher than that of the powdery g-C3N4, and yield rate of CO and CH4 attains 7.48 and 3.93 μmol g−1 h−1. Importantly, the features of low-density, high porosity, good elasticity, and firmness, not only endow g-C3N4/MS with flexibility in various environmental applications, but also make it easy to recycle and stable for long-time application. Our work provides a feasible approach to fabricate novel monolithic photocatalysts with large-scale production and application.

Oxidation of NO by in situ Fenton reaction system with dual ions as reagents

Removal of nitrogen oxides (NOx) is very crucial in coal-fired power plants, smelting plants and some other heavy industries. Herein, a new approach, in situ Fenton (IF) system with dual ions as reagents, was reported for the efficient oxidation removal of nitric oxide (NO). It demonstrated that the in situ Fenton (IF) system was more effective than the premixed Fenton (PF) system due to the increase of yield and utilization of (radOH) in the homogeneous reaction systems. The dual ions with Fe2+ and Mn+ (Mn+ = Ce3+, Cu2+, Co2+, Mn2+) as Fenton reagents were found to be more effective in NO oxidation than Fe2+ as single Fenton reagent. The obvious improvements on the oxidation efficiencies of NO were 18.85%, 16.72%, 16.58%, 16.38% in the Fe2+Ce3+/H2O2, Fe2+Cu2+/H2O2, Fe2+Mn2+/H2O2 and Fe2+Co2+/H2O2 when compared with that in Fe2+/H2O2. The corresponding optimal molar ratios of the dual ions solution were 20%:80%, 20%:80%, 50%:50% and 50%:50% for Fe2+Ce3+/H2O2, Fe2+Cu2+/H2O2, Fe2+Mn2+/H2O2 and Fe2+Co2+/H2O2, respectively. Under the optimal conditions, the oxidation efficiencies of NO were more than 85%. The improvement of NO oxidation efficiencies in the dual ionic IF system could be ascribed to the enhancement on the generation and utilization of oxidative species, which resulted from the continuous injection of fresh reagents and the oxidation of Fe2+Mn+ to Fe3+M(n+1)+ and subsequent re-reduction of them.

Experimental investigation of nitric oxide removal from flue gas using hexamminecobalt(II) solution scrubbing in a pilot-scale facility.

An experimental investigation of operational parameters, including liquid/gas ratio (L/G), inlet nitric oxide (NO) concentration, reaction temperature, and pH value of absorbing agent, on NO removal efficiency with hexamminecobalt(II) solution scrubbing was conducted on a pilot-scale facility to search optimal operation conditions. The experimental results show that NO removal efficiency increased with the pH value of hexamminecobalt solution, while the improving rate dropped gradually. When the reaction temperature increased, the NO removal efficiency increased first and then decreased. At the same time, NO removal efficiency increased with the increasing of L/G and hexamminecobalt concentration, while the removal efficiency did not change much at low NO concentration. The pH of 10.4 and L/G of 16 L/m3 were close to the optimal operation conditions, and the scrubbing temperature fell within a reasonable operation temperature. The experimental results can be used as a reference for the design and operation of scaled-up industrial devices.

SnO2/graphene quantum dots composited photocatalyst for efficient nitric oxide oxidation under visible light

In the present work, we have prepared tin oxide (SnO2)/graphene quantum dots (GQDs) composites and applied them for photocatalytic removal of nitric oxide (NO). In contrast to SnO2 alone, SnO2/GQDs composite has exhibited a remarkably enhanced activity under both full spectrum and visible light illumination. The crystal structure, morphology and surface state of the composite were studied by X-ray diffraction, transmission electron microscopy, Fourier-transformed infrared spectroscopy and X-ray photoelectron spectroscopy. Moreover, diffraction and reflectance spectra and photoluminescence spectra together with the photoelectrochemical tests show that the presence of GQDs in the composite could promote the visible light response as well as charge separation efficiency of the system. This makes SnO2/GQDs composite generate more active species (O2− and OH) for NO oxidation, as evidenced from the electron paramagnetic resonance measurements. This study hence could be referenced for future construction of efficient photocatalytic systems with wide bandgap oxides.

3D Aerogel of Graphitic Carbon Nitride Modified with Perylene Imide and Graphene Oxide for Highly Efficient Nitric Oxide Removal under Visible Light.

3D materials are considered promising for photocatalytic applications in air purification because of their large surface areas, controllability, and recyclability. Here, a series of aerogels consisting of graphitic-carbon nitride (g-C3 N4 ) modified with a perylene imide (PI) and graphene oxide (GO) are prepared for nitric oxide (NO) removal under visible-light irradiation. All of the photocatalysts exhibit excellent activity in NO removal because of the strong light absorption and good planarity of PI-g-C3 N4 coupled with the favorable charge transport properties of GO, which slow the recombination of electron-hole pairs. The aerogel containing thiophene displays the most efficient NO removal of the aerogel series, with a removal ratio of up to 66%. Density functional theory calculations are conducted to explain this result and recycling experiments are carried out to verify the stability and recyclability of these photocatalysts.

A study on simultaneous removal of NO and SO 2 by using sodium persulfate aqueous scrubbing

Abstract Nitric oxide (NO) removal and sulfur dioxide (SO2) removal by sodium persulfate (Na2S2O8) were studied in a Bubble Column Reactor. The proposed reaction pathways of NO and SO2 removal are discussed. The effects of temperatures (35–90 °C), Na2S2O8 (0.05–0.5 mol·L− 1), FeSO4 (0.5–5.0 m mol·L− 1) and H2O2 (0.25 mol·L− 1) on NO and SO2 removal were investigated. The results indicated that increased persulfate concentration led to increase in NO removal at various temperatures. SO2 was almost completely removed in the temperature range of 55–85 °C. Fe2 + accelerated persulfate activation and enhanced NO removal efficiency. At 0.2 mol·L− 1 Na2S2O8 and 0.5–1.0 mmol·L− 1 Fe2 +, NO removal of 93.5%–99% was obtained at 75–90 °C, SO2 removal was higher than 99% at all temperatures. The addition of 0.25 mol·L− 1 H2O2 into 0.2 mol·L− 1 Na2S2O8 solution promoted NO removal efficiency apparently until utterly decomposition of H2O2, the SO2 removal was as high as 98.4% separately at 35 °C and 80 °C.

Nitric oxide removal by action of ZnO photocatalyst hydrothermally synthesized in presence of EDTA

ZnO samples with different morphologies were synthesized in presence of ethylenediaminetetraacetic acid disodium salt (EDTA) at 200 °C under hydrothermal treatment. The morphology of the nanostructures obtained was modified by changing the concentration of EDTA and the reaction time. The effect of the reaction conditions on the morphology, crystallization as well as in the optical and textural properties of the ZnO samples was investigated by using scanning electron microscopy (SEM), X-ray powder diffraction (XRD), UV–Vis absorption spectroscopy (DRS) and adsorption-desorption N2 isotherms (BET). The ZnO performance as photocatalyst was evaluated in the oxidation reaction of nitric oxide (NO) under UV irradiation. The study revealed that ZnO samples with morphology of nanoplates showed significantly higher NO removal than other ZnO samples with morphologies of rods and flower-type. The ZnO sample with the highest photocatalytic activity was measurement using different mass and its stability was tested after several photocatalytic cycles. By the use of scavenger species was determined the participation mainly of the superoxide anion (O2.-) and holes (h+) in the photocatalytic oxidation process of NO.