Ammonia Dosage Research Articles

Tailored Synthesis of Porous TiO₂ Nanocubes and Nanoparallelepipeds with Exposed {111} Facets and Mesoscopic Void Space: A Superior Candidate for Efficient Dye-Sensitized Solar Cells.

Anatase TiO2 nanocubes and nanoparallelepipeds, with highly reactive {111} facets exposed, were developed for the first time through a modified one pot hydrothermal method, through the hydrolysis of tetrabutyltitanate in the presence of oleylamine as the morphology-controlling capping-agent and using ammonia/hydrofluoric acid for stabilizing the {111} faceted surfaces. These nanocubes/nanoparallelepipeds were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and high angle annular dark-field scanning TEM (HAADF-STEM). Accordingly, a possible growth mechanism for the nanostructures is elucidated. The morphology, surface area and the pore size distribution of the TiO2 nanostructures can be tuned simply by altering the HF and ammonia dosage in the precursor solution. More importantly, optimization of the reaction system leads to the assembly of highly crystalline, high surface area, {111} faceted anatase TiO2 nanocubes/nanoparallelepipeds to form uniform mesoscopic void space. We report the development of a novel double layered photoanode for dye sensitized solar cells (DSSCs) made of highly crystalline, self-assembled faceted TiO2 nanocrystals as upper layer and commercial titania nanoparticles paste as under layer. The bilayered DSSC made from TiO2 nanostructures with exposed {111} facets as upper layer shows a much higher power conversion efficiency (9.60%), than DSSCs fabricated with commercial (P25) titania powder (4.67%) or with anatase TiO2 nanostructures having exposed {101} facets (7.59%) as the upper layer. The improved performance in bilayered DSSC made from TiO2 nanostructures with exposed {111} facets as the upper layer is attributed to high dye adsorption and fast electron transport dynamics owing to the unique structural features of the {111} facets in TiO2. Electrochemical impedance spectroscopy (EIS) measurements conducted on the cells supported these conclusions, which showed that the bilayered DSSC made from TiO2 nanostructures with exposed {111} facets as the upper layer possessed lower charge transfer resistance, higher electron recombination resistance, longer electron lifetime and higher collector efficiency characteristics, compared to DSSCs fabricated with commercial (P25) titania powder or with anatase TiO2 nanostructures having exposed {101} facets as the upper layer.

Improving Capacitance by Introducing Nitrogen Species and Defects into Graphene

AbstractNitrogen‐doped graphene (NG) materials were prepared with different levels of ammonia modification and their capacitive performances were compared. The surface structure, nitrogen species and contents, as well as the defects and disorders of the as‐prepared NG materials were investigated. Electrochemical measurements showed that the capacitance of the NG materials is significantly higher than that of pristine graphene and varies with the ammonia dosage. Graphene modified with 20 mL of ammonia possesses the highest capacitance among all of the materials studied. Further investigation showed that nitrogen species and defects in NG perform pivotal functions in improving capacitance; by contrast, the surface morphology had little influence on the capacitance of the as‐prepared NG materials. Results suggested that adjusting the N1 pyridinic N content is an efficient method for elevating the capacitive performance of NG materials.

Facile fabrication of spherical architecture of Ni/Al layered double hydroxide based on in situ transformation mechanism

Spherical architectures of nickel–aluminum layered double hydroxide (NiAl‐LDH) with hydrotalcite‐like nanoflakes as building blocks were facilely fabricated by precipitation reaction in aqueous solution without any surfactants and organic solvents. Growth of such unique structure undergoes preorganization of primary nanospheres of colloidal amorphous aluminum hydroxide (AAH) in solution, followed by nucleation and crystallizaion of LDH from exterior to interior of AAH spheres by an in situ transformation mechanism. The structure and morphology of LDH spheres depend on both starting raw materials and synthetic parameters including reaction time, reaction temperature, and aqueous ammonia dosage. NiAl‐LDH sphere as positive electrode material delivers improved rechargeable and discharge capacity, with the highest discharge capacity of 173 mAh g−1 at a current density of 30 mA g−1 within a potential range from −0.1 to 0.45 V in 10 mol L−1 KOH solution, due to the faster diffusion processes in the spherical architecture than the powder sample. © 2014 American Institute of Chemical Engineers AIChE J 60: 4027–4036, 2014

Research on the Sol-Gel Method of Preparing Ternary Nano SiO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub>-TiO<sub>2</sub> Materials

Tetraethyl orthosilicate (TEOS), butyl titanate [Ti (OBu)4] and aluminium isopropoxide were used as molecular precursor of ternary nanoSiO2-Al2O3-TiO2 materials. The influences of temperature and the dosage of compounds on the characteristic of ternary nanomaterials were investigated. Transmission electron microscopy (TEM), x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were employed to investigate the characteristics of the nanomaterials synthesized by the sol-gel method. In addition, the adsorption of nanomaterials for different kinds of surfactants was also studied. Results revealed that the influences of temperature, compounds dosages and water on the size of ternary nanomaterials had a significant impact. With the increase of ammonia dosage, the concentration of the OH- ion became higer, and system showed a faster reaction rate. The higer temperature of the system was, the larger size of the ternary nanomaterials was. Moreover, the higer tempreature woule also lead to divide into layer and precipitate. Optimal parameters can be chosen to prepare monodispersed ternary nanoSiO2-Al2O3-TiO2 materials. Results also showed that the surface characteristic of ternary nanoSiO2-Al2O3-TiO2 particles differed from nanosilica, which manifested in forms of the adsorption dosage of surfactants.

Dilute ammonia pretreatment of sugarcane bagasse followed by enzymatic hydrolysis to sugars

In this work, dilute ammonia pretreatment was performed to break the intricate structure of sugarcane bagasse, which resists the enzyme accessibility to cellulose. The effects of pretreatment temperatures (140–180 °C), times (20–100 min) and ammonia dosage (5–25 wt%) on the recoveries of glucan, xylan, and acid in-soluble lignin were evaluated. The pretreatment performed at 170 °C, 60 min and 15 wt% ammonia resulted in delignification of 36.9 % and retaining 94.7 % of glucan and 63.1 % of xylan in the raw material. Then the enzymatic digestibilities of pretreated samples were investigated, 34.2 g glucose and 13.2 g xylose based on 100 g raw material could be obtained after that pretreatment condition, representing 82.7 % glucose and 47.3 % xylose in sugarcane bagasse. The enhanced digestibilities of dilute ammonia pretreated sugarcane bagasse were due to delignification and the removal of proportion of hemicellulose, which were confirmed by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis.

Interpretation of the Oscillating Signals of the Smart NO<sub>x</sub> Sensors Used in Urea Selective Catalyst Reduction Systems via Spectral Analysis

The oscillating signals of NOx sensor observed in urea selective catalytic reduction (SCR) tests are explained via spectral analysis. The NOx sensor built by NGK / Continental requires decoding following the SAE J1939 protocol and thus higher harmonic induced by the discretization is observed in the spectral analysis. The reciprocating motion of the urea pump induces fluctuation of the ammonia dosage, which combined with the nonlinear characteristic from ammonia dosage to NOx downstream SCR result in oscillating NOx sensor readings with different amplitude. The cross-sensitivity of the NOx sensor to ammonia concentration for higher-than-stoichiometric ammonia dosage also results in oscillating NOx sensor signal at lower frequencies.

Monodisperse TiO2 hierarchical hollow spheres assembled by nanospindles for dye-sensitized solar cells

Monodisperse TiO2 hollow spheres assembled by nanospindles were prepared via the facile hydrothermal reaction of peroxotitanium complex precursors. Time dependent trails revealed that the shape evolution involved a one-step chemical conversion from amorphous Ti complex microspheres to anatase TiO2 hierarchical hollow spheres. Meanwhile, the sizes of the spheres could be tuned in a region of 400–1000 nm by simply adjusting the ammonia dosage of the precursor solution. Furthermore, these as-prepared hollow spheres were deposited as a scattering layer on top of the TiO2 nanocrystalline film, and a high energy conversion efficiency of 8.10% was demonstrated based on the bilayer photoanode, in contrast to a 7.29% conversion efficiency for the cell with a pure nanocrystalline photoanode.

Cycling batch vs continuous enrichment of endogenous nitrifiers in membrane bioreactors treating petrochemical wastewater

Petrochemical wastewater treatment is a new sector for the possible widespread application of membrane bioreactor technology. In this field, hard to degrade compounds such as amines and nitrogen residuals were generally the major issues. In addition, over the last years the irregular operation of the manufacturing plants involved drastic variability of the wastewater’s loadings and characteristics, so as to call for more flexible schemes of the treatment plants. This paper compares two different schemes of a continuously fed membrane bioreactor to adequate the nitrification potential to the influent loadings. These are: a) controlled and continuous external ammonia dosage; b) sequencing batch nitrifier enrichment. On the basis of lab and pilot-scale treatment of real petrochemical wastewater, the cyclic batch enrichment process proved to be reliable, cost-effective, and easy to control, being more flexible with respect to changeable influent loadings.

Formation and minimization of bromate ions within non-thermal-plasma advanced oxidation

The formation and minimization of bromate ions as a by-product of the operation of a non-thermal plasma reactor for the removal of refractory organic species from drinking water was investigated. BrO 3 − formation kinetics was found to be 1st order with respect to the Br − concentration. BrO 3 − formation increased when the organic pollutant concentration fell below a threshold value, intrinsic to each organic species. Formation also increased when dissolved ozone concentration was elevated by injection of O 3-rich air, generated inside the reactor, back to the water, although measured O 3 concentrations were low (~0.1 mg/l). BrO 3 − formation significantly decreased at high temperatures (>35 °C) and low pH (~pH6.0) values and was found insensitive to the carbonate alkalinity concentration. Dosage of hypochlorite followed by ammonia to the inlet water was found to be more effective in minimizing bromate formation than ammonia dosage alone. A general method was developed for assessing the relative importance of the various possible bromate formation pathways within plasma reactors, and a probable dominant BrO 3 − formation reaction sequence was suggested for the particular conditions prevailing in non-thermal plasma systems.

SiO 2 nanospheres with tailorable interiors by directly controlling Zn 2+ and NH 3·H 2O species in an emulsion process

SiO 2 nanospheres with tailorable interiors were synthesized by a facile one-spot microemulsion process using TEOS as silica source, wherein cyclohexane including triton X-100 and n-octanol as oil phase and Zn 2+ or NH 3·H 2O aqueous solution as dispersive phase, respectively. The products were characterized by Scanning Electron Microscopy, Transmission Electron Microscopy and X-ray Powder Diffraction. It was suggested that the as-synthesized silica nanospheres possessed grape-stone-like porous or single hollow interior, and also found that the ammonia dosage and aging time played key roles in controlling the size and structure of silica nanospheres. Furthermore, the comparative results confirmed that in-situ zinc species [ZnO/Zn(OH) 2] acted as the temporary templates to construct grape-stone-like interior, and a simultaneously competing etching process occurred owing to the soluble Zn(NH 3) 4 2+ complex formation while the additional excessive ammonia was introduced. With the aging time being extended, the in-situ nanocrystals tended to grow into bigger ones by Ostwald Ripening, producing single hollow interior.

Life cycle assessment of selective non-catalytic reduction (SNCR) of nitrous oxides in a full-scale municipal solid waste incinerator

Selective non-catalytic reduction (SNCR) of nitrous oxides in a full-scale municipal solid waste incinerator was investigated using LCA. The relationship between NO x -cleaning and ammonia dosage was measured at the plant. Un-reacted ammonia – the ammonia slip – leaving the flue-gas cleaning system adsorbed to fly-ash or in the effluent of the acidic scrubber was quantified from the stoichiometric reaction of NO x and ammonia assuming no other reaction products was formed. Of the ammonia slip, 37% was associated with the fly-ash and 63% was in the effluent of the acidic scrubber. Based on NO x -cleaning efficiency, the fate of the ammonia slip as well as the environmental impact from ammonia production, the potential acidification and nutrient enrichment from NO x -cleaning was calculated as a function of ammonia dosage. Since the exact fate of the ammonia slip could not be measured directly, a number of scenarios were set up ranging from “best case” with no ammonia from the slip ending up in the environment to “worst case” where all the ammonia slip eventually ended up in the environment and contributed to environmental pollution. In the “best case” scenario the highest ammonia dosage was most beneficial demonstrating that the environmental load associated with ammonia production is of minor importance. In contrast, in a “worst case” scenario” NO x -cleaning using SNCR is not recommendable at all, since the impacts from the ammonia slip exceed the saved impacts from the NO x removal. Increased dosage of ammonia for removal of NO x is recommendable as long as less than 10–20% of the ammonia slip to the effluent of the acidic scrubber ends up in the environment and less than 40% of the slip to the fly-ash ends up in the environment. The study suggests that the actual fate of the ammonia slip is crucial, but since the release of the ammonia may take place during transport and at the facilities that treat the wastewater and treat the fly-ash this factor depends strongly on local conditions and may be hard to determine. Thus, LCA-modeling proved useful in assessing the balance between ammonia dosage and NO x -removal in flue-gas cleaning from waste incineration.

Model Electrochemical Interfaces in Ultrahigh Vacuum: Solvent Effects upon Coverage-Dependent Infrared Spectra of Carbon Monoxide on Platinum(111)

The influences of the solvating medium on a model electrochemical chemisorbate system-carbon monoxide on Pt(111)-have been explored by means of the infrared spectral responses in the C-O stretching (ν CO ) region to the dosage of various solvents onto CO adsorbed on Pt(111) in ultrahigh vacuum at 100 K. Measurements were made for a range of preadsorbed CO coverages (θ CO ) as a function of the solvent dosage. The molecules selected-methanol, acetonitrile, acetone, benzene, and ammonia-span a range of solvating and dielectric properties. At low CO coverages (θ CO ≤ 0.25), even submonolayer solvent dosages induced in most cases a near-complete shift in the CO binding geometry from atop to doubly bridging coordination, as seen from a displacement of the sharp vco band at 2090-2095 cm -1 by a markedly weaker feature at ca. 1790-1820 cm -1 . Additional (multilayer) solvent dosing yielded essentially no further spectral changes, other than small additional frequency downshifts. Submonolayer ammonia dosage triggered more substantial frequency decreases, yielding vco bands at ca. 1640 and 1530-1565 cm -1 . At saturated (or near-saturated) CO coverages (θ CO ∼ 0.65), solvent dosages yield only milder (≤50 cm -1 ) frequency downshifts in the atop and bridging ν CO features that are present in the absence of solvent. The marked ν CO spectral changes occurring at low (and intermediate) Oco values are interpreted in terms of CO-solvent coadsorption, involving short-range dipolar interactions and through-metal charge polarization. The marked solvent-induced attenuation in the ν CO band intensities seen at low (θ CO ) are discussed in terms of dielectric screening. The conventional dipole-coupling treatment is able to describe approximately the nature and solvent-dependent magnitude of the effect, including the severe intensity attenuation observed with the polarizable solvent benzene. The milder ν CO frequency downshifts observed at higher solvent dosages, as well as for high CO coverages, are consistent with Stark-tuning effects exerted by overlayer (rather than coadsorbed) solvent. Comparisons are made with in-situ infrared spectra for corresponding electrochemical interfaces. Attention is called to the value of this infrared-based UHV electrochemical modeling approach for elucidating interfacial solvation effects.

Ammonia Dosage in Ammonia‐Chlorine Treatment of Water

prominent place among the various modern methods of water sterilization. Ammoniation produces a certain influence on the various processes of chlorination and renders it preferable to ordinary chlorine-treatment in many respects. In previous study we experimentally ascertained the positive qualities of this method, described by several authors (McAmis, Gerstein, Baker and Schmelkes, Cox, Hinman and Beeson, Goehring, Lawrence, Ellms, Spaulding, Green, Braidech, Harold, Ruth, Enslow, A. Matheson, De Laporte, Dodd, Weir Smith, Ely, Amsbary, Caughey, Ehrhardt, Mustard, Capen, Keit, Hough, Irwin, Olszewski). In perfect agreement with other investigators we succeeded in preventing chlorophenol tastes and in increasing the bactericidal action of chlorine by means of ammonia compounds. We noticed that the effect of ammoniation changes according to the conditions in which chlorine-treatment is performed. Having systematically studied the influence of temperature and natural light on this process we proved that the chlorine absorption power increases with their rise and that the resulting changes are not only quantitative, but qualitative as well. We studied also the importance of pH for water ammoniation and demonstrated the fact that the effect of ammonia compounds added to the water is best with pH approaching 7.0 or even with a higher pH value. The ammonia-chlorine process is accompanied by a decrease in the chlorine absorption power in the presence of ammonia or ammoniacompounds. We could prove that the decrease in the chlorine absorption power of the water varies in accordance various admixtures. When vegetable matter (hayor peat-moss decoction) is contained in the water the chlorine absorption power is greatly diminished by the addition of ammonia (becoming 2 or 3 times smaller) ; an even