Denitrification models

Hydrogenation reactions, particularly for the manufacture of fine chemicals, prevail in the research of three-phase processes. Examples are hydrogenation of citral (selectivity > 80% [86-88]) and 2-butyne-l,4-diol (conversion > 80% and selectivity > 97% [89]). Eor Pt/ACE the yield to n-sorbitol in hydrogenation of D-glucose exceeded 99.5% [90]. Water denitrification via hydrogenation of nitrites and nitrates was extensively studied using fiber-based catalysts [91-95]. An attempt to use fiber-structured catalysts for wet air oxidation of organics (4-nitrophenol as a model compound) in water was successful. TOC removal up to 90% was achieved [96]. 

Tolman W.B. (1995) Synthetic Modeling of the Interactions of Nitrogen Oxides with Copper Proteins Copper Nitrosyl Complexes Relevant to Putative Denitrification Intermediates, Adv. Chem. Ser., 246, 195. 

Coelhoso, I., Boaventura, R., and Rodrigues, A., Biofilm Reactors An Experimental and Modeling Study of Wastewater Denitrification in Fluidized-Bed Reactors of Activated Carbon Particles, Biotechnol. Bioeng., 40 625 (1992)... 

Figure 3. The general nitrogen model for illustrating the bio geochemical cycling in Forest ecosystems. Explanations for the fluxes 1, ammonia volatilization 2, forest fertilization 3, N2-fixation 4, denitrification 5, nitrate respiration 6, nitrification 7, immobilization 8, mineralization 9, assimilatory and dissimilatory nitrate reduction to ammonium 10, leaching 11, plant uptake 12, deposition N input 13, residue composition, exudation 14, soil erosion 15, ammonium fixation and release by clay minerals 16, biomass combustion 17, forest harvesting 18, litterfall (Bashkin, 2002).

ASMl- A basic model dealing with nitrification and denitrification in wastewater,... 

Figure 6.19 shows the concentration profiles of O2, Fe +,NH4+ and N03 near a root calculated with this model for realistic flooded soil conditions and realistic rates of O2 release (last section) Figure 6.20 shows the corresponding fluxes of O2 out of the root and NH4+ and NO3 in. The amount of N denitrified in 10 days in the calculations corresponds to about 10% of the NH4+ initially in the volume of soil influenced by the root. This is of the order of maximum rates of denitrification reported in the literature for rice in flooded soil, indicating that the model parameter values are indeed realistic. 

The reaction and separation synthesis approach of Section 5 has been adopted to the problem of activated sludge process design (83). The conventional designs as well as all novel schemes for combined oxidation/denitrification of wastewater are explored. The process is optimized using a novel methodology for optimal reaction/separation network synthesis, supplied with a comprehensive kinetic model (84). The activated sludge process is synthesized using the systematic... 

Denitrification takes place in anoxic environments where nitrate and nitrite act as electron acceptors (oxidizers) and nitrification reactions then reverse NOf => NO2 => NO. The processes of denitrification (H2) on land are important channels for nitrogen to get into the atmosphere. The intensity of these processes depends on temperature, humidity, pollution of soils with poisonous chemicals, and pH. The quantitative and functional characteristics of these dependences have been well studied. The global model need only take into account temperature and humidity ... 

This model assumes irreversible first-order kinetics for nitrification, denitrification, mineralization, immobilization, and plant uptake. It takes the following form, in which sinks and sources are aggregated ... 

Shaffer et al. (1977) Dutt et al. (1972) model extended to tile-drained croplands and incorporated into a large irrigation return flow model to handle nitrogen as well as dissolved mineral constituents. Model allows user to select the degree of sophistication in simulation or to bypass certain subroutines. Zero-order denitrification and transition-state nitrification added. Model verified for salinity but not nitrogen. 

Frissel and van Veen (1981) Revised version of Beek and Frissel (1983) growth of Nitrosomonas and Nitrobacter by Michaelis-Menten kinetics, including considerations of oxygen levels denitrification by a physical-biological model involving oxygen diffusion ... 

Estuaries have been shown to be active sites of N2O production. DIN loading to sediments was positively correlated with N2O fluxes, indicating that eutrophication may be linked with increases in global emissions of N2O. In fact, a model of DIN transport by world rivers and estuaries indicates that 90% of the denitrification in rivers and estuaries occurs in the northern hemisphere. 

Figure 16.2 Model-predicted latitudinal distribution in the North Atlantic Basin (a) estuarine denitrification (b) total nitrogen transport by rivers. (Modified from Seitzinger, 2000.)...

Dettmann, E.H. (2001) Effect of water residence time on annual export and denitrification of nitrogen in estuaries a model analysis. Estuaries 24, 481-490. 

Jensen, K., Sloth, N.P., Rysgaard-Petersen, N., Rysgaard, S., and Revsbech, N.P. (1994) Estimation of nitrification and denitrification from microprofiles of oxygen and nitrate in model sediments. Appl. Environ. Microbiol. 60, 2094—2100. 

Lehmann, M.F., Reichert, P., Bemasconi, S.M., Barbieri, A., and McKenzie, J.A. (2003) Modeling nitrogen and oxygen isotope fractionation during denitrification in a lacustrine redox-transition zone. Geochim. Cosmochim. Acta 67, 2529-2542. 

Denitrification, 340,473 Desorption, 221,362 Diffuse double layer, 141 Model, 142-146 Thickness, 145 Variable-charge surfaces, 146 Constant-charge surfaces, 143-146 Diffusion, 298, 398 Film diffusion, 398 Particle diffusion, 398 Solution diffusion, 398 Dioctahedral silicates, 122 Dispersion, 367... 

This chapter focuses on the chemistry ofbiomimetic copper nitrosyl complexes relevant to the NO-copper interactions in proteins that are central players in dissimilatory nitrogen oxide reduction (denitrification). The current state of knowledge of NO-copper interactions in nitrite reductase, a key denitrifying enzyme, is briefly surveyed the syntheses, structures, and reactivity of copper nitrosyl model complexes prepared to date are presented and the insight these model studies provide into the mechanisms of denitrification and the structures of other copper protein nitrosyl intermediates are discussed. Emphasis is placed on analysis of the geometric features, electronic structures, and biomimetic reactivity with NO or NOf of the only structurally characterized copper nitrosyls, a dicopper(II) complex bridged by NO and a mononuclear tris(pyrazolyl)hydroborate complex having a Cu(I)-NO formulation. 

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