Ammonia particle formation

Investigating Atmospheric Sulfuric Acid-Water-Ammonia Particle Formation Using Quantum Chemistry... 

The reaction of ammonia and hydrogen chloride in the gas phase has been the subject of several studies in the last 30 years [56-65], The interest in this system is mainly that it represents a simple model for proton transfer reactions, which are important for many chemical and biological processes. Moreover, in the field of atmospheric sciences, this reaction has been considered as a prototype system for investigation of particle formation from volatile species [66,67], Finally, it is the reaction chosen as a benchmark on the ability, of quantum chemical computer simulations, to realistically simulate a chemical process, its reaction path and, eventually, its kinetics. 

The scope of this paper is to provide an overview of methods used to study properties of electrically neutral molecular clusters initiating particle formation in the troposphere, with focus on quantum chemistry. The review of results is intended to be complete with regard to water-sulfuric acid-ammonia clusters. Concerning studies on clusters including other molecular species, we review representative examples and newest publications. Ionic clusters and clusters involving iodine, related to coastal nucleation, are mentioned in passing. 

Yu, F. (2006). Effect of ammonia on new particle formation A kinetic H2SO4-H2O-NH3 nucleation model constrained by laboratory measurements. J. Geophys Res. 111D01204, doi 01210.01029/ 02005JD005968. 

The few observations of nucleation in the free troposphere are consistent with binary sulfuric acid-water nucleation. In the boundary layer a third nucleating component or a totally different nucleation mechanism is clearly needed. Gaydos et al. (2005) showed that ternary sulfuric acid-ammonia-water nucleation can explain the new particle formation events in the northeastern United States through the year. These authors were able to reproduce the presence or lack of nucleation in practically all the days both during summer and winter that they examined (Figure 11.16). Ion-induced nucleation is expected to make a small contribution to the major nucleation events in the boundary layer because it is probably limited by the availability of ions (Laakso et al. 2002). Homogeneous nucleation of iodine oxide is the most likely explanation for the rapid formation of particles in coastal areas (Hoffmann et al. 2001). It appears that different nucleation processes are responsible for new particle formation in different parts of the atmosphere. Sulfuric acid is a major component of the nucleation growth process in most cases. 

Zirconia has been synthesized by hydrolysis of zirconium tetrabutoxide in the water pools of reverse microemulsions . Kawai et al. investigated the relationship between particle formation and the solubilized states of water in the reaction system. The results indicate that monodisperse, spherical particles are more easily obtained in reverse and swollen micelles than in a w/o microemulsion. Crystalline Zr02 particles were achieved after calcination at 800 °C. The use of zirconium oxynitrate as precursor is also reported in the literature By reacting a microemulsion containing this precursor with a microemulsion containing aqueous ammonia as water phase, the calcination temperature for obtaining crystalline zirconia could be reduced to 362 °C. 

To establish clear relationships between synthesis conditions and the particle formation process, it is necessary to alter the composition variables in a systematic manner. Investigations motivated by this consideration are beginning to appear [74-83]. Using the NP-4/heptane/water/ammonia system, Chang and Fogler [74] studied the effects of the microemulsion environment on the rates of TEOS hydrolysis and silica particle growth. 

In summary, ammonia oxidation is negligible (4%) compared with the main fate of NH3, deposition (40 %) and particle formation (55 %) the numbers in parenthesis provide the percentage of emitted NH3 (Moller 2003). Thus, ammonia remains in its oxidation state -3, is mainly seen as ammonium (NH4) in air and returns to soils and waters as ammonium, where it moves between the amino group (—NH2) in the biomass and nitrate through nitrification and ammonification. 

Copper Hydroxide. Copper(II) hydroxide [20427-59-2] Cu(OH)2, produced by reaction of a copper salt solution and sodium hydroxide, is a blue, gelatinous, voluminous precipitate of limited stabiUty. The thermodynamically unstable copper hydroxide can be kiaetically stabilized by a suitable production method. Usually ammonia or phosphates ate iacorporated iato the hydroxide to produce a color-stable product. The ammonia processed copper hydroxide (16—19) is almost stoichiometric and copper content as high as 64% is not uncommon. The phosphate produced material (20,21) is lower ia copper (57—59%) and has a finer particle size and higher surface area than the ammonia processed hydroxide. Other methods of production generally rely on the formation of an iasoluble copper precursor prior to the formation of the hydroxide (22—26). 

Different reactions pathways on Rh may explain the intermediate formation of ammonia. NH3 can be obtained via successive reaction steps between adsorbed NHX and dissociated hydrogen species [29]. Alternately, the formation of ammonia may occur via the hydrolysis of isocyanic acid (HNCO) [30]. Isocyanate species are formed by reaction between N and COads on metallic particles. Those species can diffuse onto the support leading to spectator species or alternately react with Hads yielding ultimately HNCO. Previous infrared spectroscopic investigations pointed out that isocyanate species predominantly form over rhodium-based catalysts [31]. 

The formation of aerosol particles was observed [60-63] when ammonia is injected, by reactions of HNOx with undissociated NH3 ... 

Europium oxide (EU2O3) nanorods have been prepared by the sonication of an aqueous solution of europium nitrate in the presence of ammonia. In this reaction, ammonium ions adsorbed on the Eu(OH)3 particles (formed due to the collapse of the bubbles) results in the formation of a monolayer which then fuse together by hydrogen bonding leading to the formation of nanorods [28]. 

In the study of effects of ultrasound on the aqueous reactions of nickel, we found some interesting results, for example, the colloidal formation of Ni-DMG complex and degassing of NH3 during different experiments. When 25 ml of 0.001 M NiSC>4 solution was complexed with 5 ml of 1% dimethyl glyoxime (DMG) in faintly alkaline ammonia medium and sonicated for 30 minutes and compared with another set of 25 ml of complexed solution which was stirred mechanically, a colloidal solution of Ni-DMG complex was formed in sonicated condition. Particles of Ni-DMG complex did not settle even after keeping 3 1 h because of their smaller size, in sonicated solution, whereas in the unsonicated condition large particles of Ni-DMG complex settled down immediately. 

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