NO Sorption Research Articles

Micro Nanofibrillated Cellulose as Functional Additive Supporting Processability of Surface-Active Mineral Suspensions: Exemplified by Pixel Coating of an NOx-Sorbent Layer

Unlike established coating formulations, functional particulate coatings often demand the omission of polymer dispersant so as to retain surface functionality. This results in heterogeneous complex rheology. We take an example from a novel development for an NOx mitigation surface flow filter system, in which ground calcium carbonate (GCC), applied in a coating, reacts with NO2 releasing CO2. Inclusion of mesoporous ancillary mineral acts to capture the CO2. The coating is applied as droplets to maximize gas-contact dynamic by forming a pixelated 2D array using a coating device consisting of protruding pins, which are loaded by submersion in the aqueous coating color such that the adhering droplets are transferred onto the substrate. The flow is driven by surface meniscus wetting causing lateral spread and bulk pore permeation. Filamentation occurs during the retraction of the pins. Stress-related viscoelastic and induced dilatancy in the suspension containing the ancillary mesoporous mineral disrupts processability. Adopting shear, oscillation and extensional rheometric methods, we show that the inclusion of an ancillary mineral that alone absorbs water, e.g., perlite (a naturally occurring porous volcanic glass), is rheologically preferable to one that in addition to absorbing water also immobilizes it on the mineral surface, e.g., sepiolite. When including micro-nanofibrillated cellulose (MNFC), critical for maintaining moisture to support NO2 sorption, it is observed that it acts also as a flow modifier, enabling uniform coating transfer to be achieved, thus eliminating any possible detrimental effect on mineral surface activity by avoiding the use of soluble polymeric dispersant.

Modification of CaCO3 and CaCO3 pin-coated cellulose paper under supercritical carbon dioxide-ethanol mixture for enhanced NO2 capture.

In this work, we examine two modifications of fine-ground calcium carbonate material (GCC) in order to enhanced sorption of NO2 and subsequent reaction properties toward NO2-/NO3- formation by firstly exposing the GCC to supercritical (sc) CO2 in order to increase particle surface area, a choice specifically made to avoid altering the surface chemistry, and secondly considering the potential advantage of using a surface coupling agent toward NO2. The modification by the coupling agent amino silane (AMEO silane) was applied in a supercritical CO2-ethanol mixture. The samples were characterised before and after modification by field emission scanning electron microscopy (FESEM), specific surface area determination (BET nitrogen adsorption), ATR-FTIR spectroscopy and ion chromatography to reveal the effects of the surface modification(s) on the morphology, surface textural properties and sorption versus reaction properties with NO2. The performance of the treated sorbents for NO2 capture was evaluated at room temperature. Results show that reactivity of NO2 with GCC was observed to increase as a function of increased surface area resulting from scCO2 exposure, but that the presence of AMEO silane on the surface, while enhancing initial adsorption of NO2 was seen subsequently to act to block reactivity. Thus, judicious use of coupling agent can provide desired rapid initial adsorption of the gas, but the goal of long-term CaCO3-consuming reactivity, so as to prolong the uptake of NO2 beyond surface saturation alone, is achieved by increasing surface area while retaining chemical-free exposed CaCO3 surface.

Battling Chemical Weapons with Zirconium Hydroxide Nanoparticle Sorbent: Impact of Environmental Contaminants on Sarin Sequestration and Decomposition.

The promising reactive sorbent zirconium hydroxide (ZH) was challenged with common environmental contaminants (CO2, SO2, and NO2) to determine the impact on chemical warfare agent decomposition. Several environmental adsorbates rapidly formed on the ZH surface through available hydroxyl species and coordinatively unsaturated zirconium sites. ZH decontamination effectiveness was determined using a suite of instrumentation including in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to monitor sarin (GB) decomposition in real time and at ambient pressure. Surface products were characterized by ex situ X-ray photoelectron spectroscopy (XPS). The adsorption enthalpies, entropies, and bond lengths for environmental contaminants and GB decomposition products were estimated using density functional theory (DFT). Consistent with the XPS and DRIFTS results, DFT simulations predicted the relative stabilities of molecular adsorbates and reaction products in the following order: CO2 < NO2 < GB ≈ SO2. Microbreakthrough capacity measurements on ZH showed a 7-fold increase in the sorption of NO2 vs SO2, which indicates differences in the surface reactivity of these species. GB decomposition was rapid on clean and CO2-dosed ZH and showed reduced decomposition on SO2- and NO2-predosed samples. Despite these findings, the total GB sorption capacity of clean and predosed ZH was consistent across all samples. These data provide insight into the real-world use of ZH as a reactive sorbent for chemical decontamination applications.

Influence of moisture content on NO2 sorption ability of cedar wood

This study examined the influence of moisture content (MC) on NO2 sorption ability of cedar (Cryptomeria japonica) wood using the specimens with different MCs. Four MC conditions were applied, namely 0%, 8.6%, 12.7% and 16.5%, based on the differences of bonding condition of water molecule in the wood substances. As a result, the NO2 sorption volume increased drastically due to the presence of water, and as the MC increased, the NO2 sorption volume increased slightly. The NO generation volume and nitric acid concentration in the specimens were evaluated after an aeration test, and it was strongly indicated that the NO2 reacted with water in the specimen, and that the NO generation volume increased as the content of multilayer adsorbed water increased. The nitric acid seemed to be formed by the reaction between NO2 and water, and it was then held in the specimen. Based on the NO2 sorption volume calculated using the NO generation volume, it was shown that the NO2 sorption after 12-h aeration was caused mainly by the reaction between NO2 and water. Furthermore, the presence of both water and extractives contributed to the NO2 sorption in the initial period, and the presence of water contributed greatly to the NO2 sorption over the long term.

Influence of drying temperature on NO2 sorption ability of cedar timber

NO2 sorption ability of cedar (Cryptomeria japonica) timbers was evaluated using a new measuring system that was developed in our previous study. Four drying conditions were applied, namely natural drying and three kinds of kiln-drying at 45, 60, and 105 °C. Aeration experiments were conducted using discoid specimens which had a thickness in the longitudinal direction of 1.5 mm, and a diameter of 10 mm. The moisture content was conditioned to 0 or 9 ± 1.0% in each drying condition. As a result, the NO2 sorption ability declined as the drying temperature increased. Based on the analysis of extractives, it was shown that the extractives content had a high correlation with the contribution ratio of extractives in the NO2 sorption volume of the specimens that were dried below 60 °C. Therefore, it was elucidated that the specimen dried naturally has the greatest NO2 sorption ability. Furthermore, the result of the gas chromatography–mass spectrometry (GC/MS) indicated that abietadiene influenced the NO2 sorption ability. Also, the NO2 sorption volume was high especially at the initial stage, which is higher under the condition with moisture.

Kinetic, isotherm and thermodynamic investigations of nitrite (NO2–) removal from water by anion exchange resins

This study presents the evaluation of a strong base (Purolite A200) and weak base (Purolite PFA847) polymeric anion exchange resins for nitrite removal. The different parameters on the removal of NO2– were investigated in batch sorption mode. Common isotherm models; Langmuir and Freundlich, were used in order to present a description of the equilibrium data. Experimental results showed that the equilibrium data tend to follow Freundlich isotherm model for weak base resin and Langmuir model for strong base resin. The sorption of NO2– on anion exchange resins was found to follow the pseudo-second order kinetic model. The values of thermodynamic parameters proved that ion exchange reaction of NO2– onto such resins are endothermic (ΔH &gt; 0).

Influence of loading QCMs with electrochemically-deposited ZnO on their NO2-sensing properties

This paper reports on ZnO layers’ sensitivity to NO2 exposure. ZnO layers were grown by electrochemical deposition on the surface of quartz crystal microbalances (QCMs) with Au electrodes; the sensitivity was estimated by the frequency-time characteristics (FTCs) of the QCM, namely, its resonance-frequency-shift response. The sorption process was investigated in NO2 test gas. The behavior was studied of three different sensors with ZnO layers deposited for different times – 30, 35 and 60 min. The change in the frequency, ΔF, of the QCM as a function of the loaded mass of NO2 was detected in different NO2 concentrations in the range of 250 – 5000 ppm and the value of the sorbed mass was calculated, together with the rate of the NO2 sorption and desorption. As the time of ZnO layers deposition was increased, the sorbed NO2 mass increased for all concentrations used in the experiment. This can be explained by changes in the ZnO layers’ structure with the time of deposition.

Evaluation of NO2 sorption of cedar wood (Cryptomeria Japonica) with difference of the specimen size and contact condition between NO2 gas and specimen using new test system

We developed a new system for measuring the NO2 sorption ability of Japanese cedar (Cryptomeria japonica) wood by referring to Japanese Industrial Standard for JIS R 1701-1 (Test method for air purification performance of photocatalytic materials, Japanese Standard Association, Tokyo, 2004). Aeration experiments were conducted using plated specimen, particle specimen, discoid specimen and wood powder with consideration of aeration condition and surface area which can contact with NO2 gas. In the plated specimen, the NO2 sorption ability was greatly affected by the thickness of longitudinal direction, and high NO2 sorption ability of the transverse section was observed within a thickness range from the surface to ca. 3 mm. The average NO2 sorption volume for discoid specimen for 5 h was approx. five times larger than that those for the plated and particle specimens, which the thickness of longitudinal direction was 1.5 mm. This means that the NO2 sorption effect was especially high under the condition where the NO2 gas passed through tracheid. Also, it was suggested that the interface area between NO2 gas and specimen influenced to the NO2 sorption ability. Furthermore, it was confirmed that the NO2 sorption volume in discoid specimen and the grain size below 0.25–0.50 mm of wood powder reached the greatest.

Comparative studies of low concentration SO2 and NO2 sorption by activated carbon supported [C2mim][Ac] and KOH sorbents

This work evaluated the ability of 1-ethyl-3-methylimidazolium acetate ionic liquid and potassium hydroxide loaded activated carbon sorbents to remove SO2 and NO2 under simulated atmospheric conditions containing ≤10 ppm of gas contaminants in air at 25 °C and relative humidity of 50%. The studies indicate the 1-ethyl-3-methylimidazolium acetate loaded activated carbon, [C2mim][Ac] sorbent, has superior sorption performance for SO2, with breakthrough times greater than pure activated carbon, pelletized KOH activated carbon and granulated KOH loaded activated carbon. The pelletized KOH loaded activated carbon had lowest performance indicating pelletized sorbents are not ideal for use in high flow rate applications such as fuel cells. The SO2 concentration significantly impacted the breakthrough times of the [C2mim][Ac] sorbent, low SO2 concentration resulted in the longest break through times but lowest sorption capacities. The granulated KOH activated carbon and pure activated carbon had highest NO2 break through times compared to [C2mim][Ac] sorbents. The simultaneous SO2 and NO2 sorption studies indicated that the [C2mim][Ac] sorbent had greater selectivity for SO2 than NO2 compared to the KOH sorbents, as evidenced by high breakthrough times for SO2 compared to NO2. Theoretical studies using DFT-B3LYP were performed to elucidate the favored binding interactions of the [C2mim][Ac] with acidic gas contaminants. Theory indicates acidic gas contaminants preferentially interact strongly with the oxygen atoms of the acetate anion compared to the imidazole cation. The computational work also confirmed experiments showing high selectivity of the 1-ethyl-3-methylimidazolium acetate ionic liquid sorbent for SO2 compared to NO2.

The use of microwave radiation for obtaining activated carbons from sawdust and their potential application in removal of NO2 and H2S

Activated carbons obtained from sawdust pellets from coniferous wood were used as adsorbents of nitrogen dioxide and hydrogen sulphide. The precursor was subjected to pyrolysis at 400°C in nitrogen atmosphere and next to physical activation at 600 and 700°C by CO2. Some part of the precursor was also subjected to direct activation at 600°C by CO2. The effect of activation temperature on the textural parameters, acid–base character of the surface and sorption properties of activated carbons was analysed. The resulting carbons were characterized by low-temperature nitrogen sorption, determination of pH and the number of surface oxygen groups by Boehm method. The adsorption of NO2 and H2S was carried out from dry or moist (70% humidity) air.The results have shown that NO2 and H2S sorption properties of activated carbons depend on the temperature of activation and the conditions of adsorption. The results obtained in our study have proved that a suitable choice of the pyrolysis and activation procedure of sawdust can give adsorbents with high capacity of nitrogen dioxide, reaching to 54.7 and 28.8mgNO2/g in dry and wet conditions, respectively and low capacity of hydrogen sulphide of 4.1 and 6.2mgH2S/g in dry and wet conditions, respectively.

Mayenite based supports for atmospheric NOx sampling

In order to obtain a class of calcium based sorbent materials for the quantification and possibly the removal of NOx from the atmosphere, we synthesized and characterized various CaO/Mayenite (Ca12Al14O33) substrates having different weight ratio (w/w) composition. Their reactivity towards NO and NO2 was evaluated by means of several experimental techniques: FT-IR and XRD were used to characterize the species formed during the sorption process, while IC and TGA analysis provided information about the dynamics of the sorption process itself. The hydration reaction occurring on the substrate before NOx sorption has also been considered in our investigation. We finally tested the performance and the reliability of the CaO/mayenite materials in field measurements by incorporating the substrate in a passive sampler device. The simultaneous sorption of atmospheric NO2 and NO has been investigated and the role of the carbon dioxide in the NOx – CO2 exchange reactions has been assessed. According to the data reported in this paper and thanks to the fairly low cost of production, CaO/Mayenite substrates represent a good class of inorganic alkaline sorbents for NOx suitable for many applications in atmospheric sampling and remediation.

NO2 removal by adsorbents prepared from waste paper sludge

The possibility of changing waste paper sludge into valuable carbonaceous adsorbent was tested. The performance of three types of samples obtained from this waste was studied: chars (PK), activated chars (PKA) and activated initial material (PA). Pyrolysis of the initial material was carried out at 550, 600 and 700°C, while the activation of the initial material and chars obtained with CO2 at 550, 600 and 700°C. The sorption capacity of carbonaceous adsorbents obtained was evaluated on the basis of NO2 adsorption in dry and wet conditions. The NO2 sorption properties of the activates decrease with increasing temperature of activation and the maximum sorption capacity was noted for the samples activated at 550°C. On the basis of measurements in dry and wet conditions, the presence of water was found to increase the NO2 breakthrough capacity. The NO2 sorption capacity of the adsorbents obtained depended on the type and temperature of modification process and acid–base properties of the materials obtained.

Effects of short or long term fumigation with NO2 on plant's factors controlling NO2 sorption rate

Effects of short or long term fumigation with NO2 on plant's factors controlling NO2 sorption rate

Effect of ammoxidation of activated carbons obtained from sub-bituminous coal on their NO2 sorption capacity under dry conditions

The paper presents results of a study on obtaining N-enriched activated carbons from Polish sub-bituminous coal and their effectiveness as adsorbents for removal of pollution from gas phase. The crushed precursor was subjected to pyrolysis at 500, 600 and 700°C followed by activation with KOH at 800°C. The carbonaceous adsorbents were further subjected to the ammoxidation at 350°C, by a mixture of ammonia and air at the ratio of 1:3. Adsorption of NO2 was carried out from dry air. The surface structure and chemistry of the initial and exhausted adsorbents were analysed using the method based on adsorption of nitrogen, Boehm method, elemental analysis. The results have shown that the process of ammoxidation results in the introduction of new nitrogen functional groups in the structure of the activated carbon but also changes the acid–base character of their surface and deteriorates their textural parameters. Introduction of nitrogen into the structure of activated carbons improves their sorption capacity towards NO2 of the majority of the samples. The best sorption capacity in both unmodified and nitrogen-enriched activated carbons obtained from sub-bituminous coal was obtained for the activated carbon pyrolysed at 600°C, with respective values of 33.8 and 66.8mg/g, respectively.

Carbonaceous adsorbents prepared by physical activation of pine sawdust and their application for removal of NO2 in dry and wet conditions

Carbonaceous adsorbents from sawdust pellets from coniferous trees (pines) were obtained by CO2 activation and used as nitrogen dioxide adsorbents. Activation was performed at 800°C for four different periods of time (30, 60, 90 and 120min). The effect of NO2 adsorption in dry and wet conditions on the sorption ability of the activated samples obtained was tested. The results have shown that NO2 sorption properties of the activates increase with increasing time of activation and reach maximum for the samples activated for 90min. On the basis of measurements in dry and wet conditions, the presence of water was found to increase the NO2 breakthrough capacity. The sorption capacity of the adsorbents obtained towards NO2 was proved to be determined by the surface chemistry and the reactions taking place on the surface rather than by the specific surface area development.

Active Carbons Obtained from Bituminous Coal for NO2Removal under Dry and Wet Conditions at Room Temperature

The adsorption of NO2 on active carbons obtained from Polish bituminous coal was studied. Carbonaceous adsorbents were obtained by pyrolysis of coal at 500, 600, and 700 °C followed by activation with KOH at 700 °C. Adsorption of NO2 was carried out from dry and moist (70% humidity) air. The surface structure and chemistry of the initial and exhausted adsorbents were analyzed using adsorption of nitrogen, Boehm method, and elemental and thermal analyses. All adsorbents obtained were found to have acidic surfaces. The best NO2 sorption capacity in both dry and wet conditions was obtained for the active carbon pyrolyzed at 700 °C, with respective values of 25.0 and 43.5 mg/g, respectively. For all materials a considerable amount of NO2 was reduced to NO. Differential thermogravimetry curves of samples after exposure to NO2 showed two new peaks, the first at 90−180 °C, assigned to the removal of physically adsorbed NO2 and NO, and the second at 200−400 °C, assigned to the decomposition of potassium nitrates and nitrites.

Simulation of NO and NO2 sorption–desorption–reduction behaviours on Pt-impregnated HPW supported on TiO2

NO and NO2 (NOx) sorption, desorption and reduction by hydrogen, carbon monoxide and/or propene were investigated on a TiO2-supported heteropolyacid, 12-tungstophosphoric acid hexahydrate (HPW), promoted by platinum. A model taking into account NOx sorption, desorption and reduction was established. Kinetic constants for NOx sorption, desorption and reduction were extracted by modelling for the investigated range of temperature (170–300°C).

Overview of the Fundamental Reactions and Degradation Mechanisms of NOx Storage/Reduction Catalysts

Over the last several years, nitrogen oxide(s) (NOx) storage/reduction (NSR) catalysts, also referred to as NOx adsorbers or lean NOx traps, have been developed as an aftertreatment technology to reduce NOx emissions from lean‐burn power sources. NSR operation is cyclic: during the lean part of the cycle, NOx are trapped on the catalyst; intermittent rich excursions are used to reduce the NOx to N2 and restore the original catalyst surface; and lean operation then resumes. This review will describe the work carried out in characterizing, developing, and understanding this catalyst technology for application in mobile exhaust‐gas aftertreatment. The discussion will first encompass the reaction process fundamentals, which include five general steps involved in NOx reduction to N2 on NSR catalysts; NO oxidation, NO2 and NO sorption leading to nitrite and nitrate species, reductant evolution, NOx release, and finally NOx reduction to N2. Major unresolved issues and questions are listed at the end of each of the reaction process fundamental sections. Degradation mechanisms and their effects on NSR catalyst performance are also described in relation to these generalized reactions. Since at this stage it does not appear possible to arrive at a complete and consistent mechanistic model describing the broad, existing experimental phenomenology for these processes, this review is primarily focused on summarizing and evaluating literature data and reconciling the many differences presented.

Sorption–Desorption of NOxfrom a Lean Gas Mixture on H3PW12O40·6H2O Supported on Carbon Nanotubes

NOx sorption capacities and efficiencies were measured on a new type of sorbent formed by 12-tungstophosphoric acid (HPW) supported on carbon nanotubes. On such a system, the sorption of both NO and NO2 was observed but compared with HPW alone, a complementary sorption of NOx is possible leading to a capacity of 25 mg/gHPW at 300 °C with an efficiency of 50%. The sorption results from the formation of a [H+(NO2−),NO+)]. complex on HPW and an additional mode of adsorption by a free-nitrate which was identified by the bands at 2261, 1384 and 1295 cm−1 using infrared spectroscopy.

Catalytically promoted NOx sorption by ZrO2-based oxides

Metal promoted zirconia-based oxide sorbents, such as Pt–ZrO2/Al2O3 for NO x have been investigated. To clarify the role of the catalyst component, sorption of NO and NO2 was compared using the samples with and without Pt. The catalytic oxidation of NO to NO2 and successively to nitrate ions is an important role for the Pt catalyst. The experimental results indicate that a high-temperature calcination is essential to remove residual Cl from Pt–ZrO2–Al2O3 prepared from H2PtCl6 in order to provide more active NO x sorption sites. Of M–ZrO2–Al2O3 samples investigated, ruthenium as well as Pt demonstrated relatively good performance as a catalyst component in the sorbent. The FT-IR spectra after sorption of NO and NO2 demonstrated a strong band attributed to stored nitrate ions. The Pt catalyst was more resistant to sulfur poisoning than a base metal catalyst. However, the NO x sorptive capacities of the Pt–ZrO2/Al2O3 sorbents were expected to be deteriorated in dilute SO2 as far as observed from FT-IR spectra.