NO Sorption Research Articles

Effect of O3 on NO2 Sorption from Gas over H-Y Zeolite: Supposition on the Nitrate Anion Formation with NO2 and O3 as Coreactants

The effect of O3 presence on NO2 sorption over Y-type zeolite ion exchanged with H+ was studied. The experiments with a gas-flow system have been performed where the profiles of NO2 sorption and temperature-programmed desorption were registered. Nitrogen dioxide was removed from a stream of humid air with dew point 0 °C by the sorbent saturated with moisture. The distinct influence of ozone presence on the characteristics of NO2 sorption/desorption has been observed. Significant enhancement of NO2 uptake has been obtained by the injection of O3, which has brought about, as it seems, the formation of stable nitrate anions within the sorbent. Also, the probability of the practical application of the observed effect has been considered.

Sorption and Reduction of NO2 on Microporous Ammonium 12-Tungstophosphate

The sorption and reduction of NO2 have been studied on ammonium 12-tungstophosphate, a microporous derivative of 12-tungstophosphoric acid. NO2 penetrates into the bulk structure, where reduction by NH4+ occurs. Nitrogen, oxygen, and nitrous oxide are produced. Nitrogen is desorbed into the gas phase while oxygen apparently participates in a surface oxidation process. Since N2O is produced at higher temperatures, it appears to result from the decomposition of ammonium nitrate formed during the aforementioned processes.

In situ ESR of CrH-ZSM-5 up to 500�C in flowing gas containing O2, H2O, CCl4, NO, NO2, and C3H6

A flow cell was used for the in situ ESR monitoring of the state and reactivity of chromium ions in Cr-ZSM-5. Calcination of Cr(NO3)3/NH4-ZSM-5 in air at 500°C is accompanied by migration of chromium ions inside the zeolitic channels and stabilization ofisolated Cr5+ cations near lattice A13+ ions. Calcination of Cr-ZSM-5 at 750°C leads to a gradual disappearance of the isolated Cr5+ cations and formation of α-Cr2O3 microcrystals. All the Cr5+ cations are accessible to gas-phase molecules: O2 strongly broadens the dipole-dipole signal; H2O sorption increases the local crystal field symmetry; admission of CCl4 results in a small change of the Cr5+ local coordination; strongly stabilized complexes on Cr-ZSM-5 are observed upon sorption of either NO or NO2. The sorption of C2H6 on Cr-ZSM-5 at 20°C is accompanied by a gradual reduction of the Cr5+ sites. At 500°C in [C3H6 + O2 + He] flow, even at a large excess of oxidant, the reduction of a noticeable part of Cr5+ ions takes place. At 400°C, in the same gas mixtures, a deeper reduction of Cr5+ occurs. Closer to stoichiometric conditions, in a [C3H6 + NO + He] flow with 120% excess of oxidant the Cr5+ is completely reduced at 500°C. The oxidation of propene is accompanied by coke deposition on the surface of the catalyst. The implications of the results are discussed.

Acid inputs from the atmosphere in the United Kingdom

Abstract. Inputs of acidity to the ground arise through two distinct routes: wet deposition which includes all acidity deposited in rain and snow and dry deposition, the direct sorption of SO2, NO2 or HNO3 gases by vegetation or soil surfaces. The acidity from dry deposition of SO2 and NO2 is created during the oxidation of deposited SO2 and NO2 to SO24 and NO3− respectively. The areas of Britain experiencing the largest wet deposition of acidity are the high rainfall areas of the west and north, in particular the west central highlands of Scotland, Galloway and Cumbria where inputs exceed 1 kp H+ ha−1 annually. Wet deposited acidity in the east coast regions of Britain is in the range 0.3–0.6 kg H+ ha−1 a−1. Monitoring data for rainfall acidity at rural sites throughout northern Britain show a decline in deposited acidity of about 50% during the last six years. Dry deposition is largest in the industrial midlands and southeast England and in the central lowlands of Scotland, where concentrations of SO2 are largest. In these regions the dry deposition of SO2 following oxidation may lead to acid inputs approaching 3 kg H+ ha−1 a−1 and greatly exceeding wet deposition.

Sorption of NO2 to Interior Materials and the Possibility of Its Removal by Biological Denitrification

Sorption of NO2 to Interior Materials and the Possibility of Its Removal by Biological Denitrification

A quantitative analysis of the relationships between SO2 or NO2 sorption and their acute effects on plant leaves using image instrumentation.

We have reported on a method for evaluating the distributions of stomatal resistance to water vapor diffusion and SO2or NO2sorption on a leaf, using a thermal infrared image instrumentation system. In the present paper, we examined quantitatively the relation-ships between the acute effects, such as stomatal response and visible injury, of SO2or NO2on a leaf and gas sorption, using the image instrumentation method. The results obtained were as follows.1) There was a tendency for stomata to close during SO2or NO2exposure. However, the behavior varied randomly at different sites on a leaf. The differences in stomatal response at local sites were not dependent on those in integrated SO2or NO2sorption for 60 minutes exposure. These results suggest that there are differences in the stomatal sensitivity to SO2or NO2at local sites on a leaf.2) There was a tendency for visible injury to occur at sites where the integrated SO2or NO2sorption was over a threshold value. Injured leaves were generally separated into two areas, a healthy area and an injured one. It was seen that the characteristic visible injuries were caused by differences in boundary layer and stomatal resistances at local sites governing the gas sorption.

A Method for Simultaneous Measurement of NO2 and O3 Sorptions by Plants in Environmental Control Chamber

A method for simultaneous measurement of NO2 and O3 sorption rates of plants in an environmental control chamber was examined. Namely, NO2 and O3 reactions in the chamber were identified and an equation for calculation of the sorption rates, which took the reactions of gases into consideration, was examined. The results obtained were as follows.(1) NO2 reaction rate RNO2 and O3 reaction rate RO3 in the chamber were given byRNO2=kNO2·CdNO2·CdO3, andRO3=kO3·CdNO2·CdO3, where kNO2 is the rate constant of the NO2 reaction, kO3 is the rate constant of the O3 reaction, CdNO2 is the NO2 concentration and CdO3 is the O3 concentration. The value of kNO2 was about 17.5m6·g-1·s-1 and kO3 was about 9.5m6⋅g-1⋅s-1, and these values were slightly influenced by the air conditioning system. The results were nearly equal to the rate constants of the reactions of NO2+O3→NO3+O2 and NO3+NO2+H2O→2HNO3.(2) An equation for the calculation of gas sorption rates in NO2+O3 was given byPh=A⋅xh+B⋅xh+C⋅zh, where, Ph=[ΔPhNO2ΔPhO3], xh=[ΔCdhNO2ΔCdhO3], zh=[ΔCdhNO2-ΔChd-1NO2ΔCdhO3-ΔCdh-1O3]A=[-F 0 0 -F], B=[-kNO2⋅CdO3 -kNO2⋅CdNO2 -kO3⋅CdO3 -kO3⋅CdNO2], C=[-V/τ 0 0 -V/τ], andΔCdh={(2Tc-τ)/(2Tc+τ)⋅ΔCdh-1+{τ/(2Tc+τ)}⋅(ΔCdh+ΔCdh-1)}, and where ΔPhNO2 is the NO2 sorption rate, ΔPhO3 is the O3 sorption rate, F is the ventilation flow rate, V is the volume in the chamber, τ is a sampling time, ΔCdNO2 is the change in NO2 concentration from the initial condition and ΔCdO3 is the change in O3 concentration. The suffix h denotes the values at time h·τ and S denotes the values in the steady-state before plants are placed in the chamber. The reaction term B·xh and the differential term C·zh in the equation are correction terms to obtain the exact sorption rates. The B·xh term corrects the static characteristics, and the C·zh term corrects the dynamic characteristics. As an example, the effect of B·xh on static characteristics was examined.

Studies of Air Pollutant Sorption by Plants

In order to investigate NO2 and O3 sorption by plants during exposure to NO2, O3 and NO2+O3 which are the principal gaseous pollutants, sunflower plants were fumigated with the pollutants in an environmental control chamber. The time courses of sorption rate, transpiration rate and leaf temperature were measured during fumigation, and the sorption processes were discussed by the use of a simplified model. The results obtained are as follows.(1) The stomatal closure and the appearance of visible leaf injury by fumigation with a single gas (NO2 or O3) and a mixed gas (NO2+O3) were observed. The degrees of the appearance of these phenomena were related to the gas concentration, and the degree of injury increased with increasing gas concentration. The degree of injury is also related to the kind of pollutant. In the case of fumigation with NO2 or O3, the NO2 concentration at which the phenomena began to appear was about ten times higher than that for O3. In the case of fumigation with NO2+O3, the phenomena appeared at the concentrations of NO2 and O3 below which the phenomena did not appear during exposure to a single gas (NO2 or O3). The results obtained here may indicate one of the synergistic effects of air pollutaons. The degree of injury for NO2 and O3 on the stomatal closure and the appearance of leaf injury, was distinctly in the order of O3>SO2>NO2.(2) The relations between Q/w′ and Pa during fumigation with a single (NO2 or O3) or a mixed gas (NO2+O3) were expressed by equations of QNO2/w′≅1.4×10-3·PaNO2, and QO3/w′≅.5×10-3·PaO3, where QNO2 and QO3 are sorption rates of NO2 and O3, w′ transpiration rate divided by the water vapor pressure differences between gas-liquid interface in the leaf and the atmosphere, and PaNO2 and PaO3 gas concentration of NO2 and O3 in the atmosphere. These relations were independent of the gas components used for fumigation and the appearance of visible leaf injury. These empirical equations corresponded to those which were derived by using a simplified model, Q/w′=(kw/kg·kr)·(Pa-Pl) at Pl=0 volppm, where Pl is gas concentration at gas-liquid interface in the leaf, kr the ratio of gas diffusive resistance to that for water vapor, kw a constant; 1.05×106 mmHg·cm3·g-1, and kg a constant; 5.40×108 (NO2) or 5.18×108 (O3) volppm·cm3·g-1. The calculated values of kw/kg·kr were coincident with the coefficients of Q/w′ and Pa From the results mentioned above, it was concluded that the NO2 and O3 concentrations at the gas-liquid interface in the leaf are considered to be zero, and the NO2 and O3 sorption rates can be explained by factors such as boundary layer and stomatal resistances, which are related to gaseous diffusion.

Sorption of Nitrogen Dioxide by Calcareous Soils

AbstractThe NO2 sorption capacity and rate of calcareous soils, a calcic soil, and a granular limestone were measured at room temperature by passing air or nitrogen gas containing NO2 through them. In dry air (humidity < 5%), NO2 sorption reached an equilibrium value within 2.5 min. In moist air (humidity > 95%), NO2 sorption increased to as much as 10‐fold that in dry air and approximately equaled the acid‐titratable basicity of calcareous soils. The sorption rate was proportional to the unreacted fraction of the capacity with sorption rate constants ranging from 0.015 to 0.03 min‐1 at a NO2 concentration of 0.5% volume. At a concentration of 0.1%, the sorption rate was slower but the capacity remained unchanged. Sorption of NO2 was similar when either air or a nitrogen carrier was used.

The Effect of Sorption on the Structure of Surfaces of Solids. II. Sorption of NO2—N2O4 on Rutile1

The Effect of Sorption on the Structure of Surfaces of Solids. II. Sorption of NO₂—N₂O₄ on Rutile¹