Particle surface complex

Adsorption of Metal Ions and Ligands. The sohd—solution interface is of greatest importance in regulating the concentration of aquatic solutes and pollutants. Suspended inorganic and organic particles and biomass, sediments, soils, and minerals, eg, in aquifers and infiltration systems, act as adsorbents. The reactions occurring at interfaces can be described with the help of surface-chemical theories (surface complex formation) (25). The adsorption of polar substances, eg, metal cations, M, anions. A, and weak acids, HA, on hydrous oxide, clay, or organically coated surfaces may be described in terms of surface-coordination reactions ... 

Because of the complexities encountered with a rigorous treatment of the hydrodynamics around particles in industri contactors, mass transfer to and from the adsorbent is described in terms of a mass-transfer coefficient kf. The flux at the particle surface is ... 

To measure an individual particle surface interaction and its material removal effects. Because of the complexity of the polishing system, it is highly desirable to characterize the physical and chemical behavior of individual interactions while other components are fixed. AFM technology can be provided to explore slurry particle interactions with different surfaces in different liquid ambient. 

Gunnarsson M, Abbas Z, Ahlberg E, Nordhohn S. 2004. Corrected Debye-Hiickel analysis of surface complexation HI. Spherical particle charging including ion condensation. J Coll Interf Sci 274 563-578. 

Hsi C, Langmuir D (1985) Adsorphon of uranyl onto ferric oxyhydroxides applications of the surface complexation site-binding model. Geochim Cosmochim Acta 49 1931-1941 Ingri J, Widerlund A, Land M, Gustafsson O, Anderson P, Ohlander B (2000) Temporal variation in the fractionation of the rare earth elements in a boreal river the role of colloidal particles. Chem Geol 166 23-45... 

It was shown in the preceding text that even in the simplest systems many different chemisorbed particles originate on the surface during the catalytic reaction. In principle most of them can interact with each other and probably with gaseous reaction components as well. As a consequence, any catalytic reaction represents a system of simultaneous reactions, and the problem is how to influence the course of a particular reaction—in other words, it is essentially the selectivity problem. Thus in catalysis by metals, probably the modification of the surface properties (by forming the alloys, stable surface complexes, or by the addition of promotors, etc.) seems to be the most promising direction of the further fundamental research. 

The data of Loukidou et al. (2004) for the equilibrium biosorption of chromium (VI) by Aeromonas caviae particles were well described by the Langmuir and Freundlich isotherms. Sorption rates estimated from pseudo second-order kinetics were in satisfactory agreement with experimental data. The results of XAFS study on the sorption of Cd by B. subtilis were generally in accord with existing surface complexation models (Boyanov et al. 2003). Intrinsic metal sorption constants were obtained by correcting the apparent sorption constants by the Boltzmann factor. A 1 2 metal-ligand stoichiometry provides the best fit to the experimental data with log K values of 6.0 0.2 for Sr(II) and 6.2 0.2 for Ba(II). 

Burnett PGG, Daughney CJ, Peak D (2006) Cd adsorption onto Anoxybacillus flavithermus Surface complexation modeling and spectroscopic investigations. Geochim Cosmochim Acta 70 5253-5269 Chenu C, Stotzky G (2002) Interactions between microorganisms and soil particles an overview. In Huang PM, Bollag J-M, Senesi N (eds) Interactions... 

The NO + 03 chemiluminescent reaction [Reactions (1-3)] is utilized in two commercially available GC detectors, the TEA detector, manufactured by Thermal Electric Corporation (Saddle Brook, NJ), and two nitrogen-selective detectors, manufactured by Thermal Electric Corporation and Antek Instruments, respectively. The TEA detector provides a highly sensitive and selective means of analyzing samples for A-nitrosamines, many of which are known carcinogens. These compounds can be found in such diverse matrices as foods, cosmetics, tobacco products, and environmental samples of soil and water. The TEA detector can also be used to quantify nitroaromatics. This class of compounds includes many explosives and various reactive intermediates used in the chemical industry [121]. Several nitroaromatics are known carcinogens, and are found as environmental contaminants. They have been repeatedly identified in organic aerosol particles, formed from the reaction of polycyclic aromatic hydrocarbons with atmospheric nitric acid at the particle surface [122-124], The TEA detector is extremely selective, which aids analyses in complex matrices, but also severely limits the number of potential applications for the detector [125-127],... 

A theoretical model for the adsorption of metals on to clay particles (<0.5 pm) of sodium montmorillonite, has been proposed, and experimental data on the adsorption of nickel and zinc have been discussed in terms of fitting the model and comparison with the Gouy-Chapman theory [10]. In clays, two processes occur. The first is a pH-independent process involving cation exchange in the interlayers and electrostatic interactions. The second is a pH-dependent process involving the formation of surface complexes. The data generally fitted the clay model and were seen as an extension to the Gouy-Chapman model from the surface reactivity to the interior of the hydrated clay particle. 

With a chapter on particle-particle interaction (coagulation) the characteristics of particles and colloids as chemical reactants are discussed. Since charge, and in turn the surface potential of the colloids is important in coagulation, it is illustrated how in simple cases the modelling of surface complex formation permits the calculation of surface charge and potential. The role of particle-particle interaction in natural water and soil systems and in water technology (coagulation, filtration, flotation) is exemplified. 

The photocatalytic oxidation of organic and inorganic compounds and the photo-catalytic production of H202 occurs also at the surface of iron(III)(hydr)oxides. It has been proposed (e.g., Hoffmann, 1990 Faust and Hoffmann, 1986) that the oxidation of S(IV) by 02 in atmospheric water is catalyzed by iron(III)(hydr)oxide particles. It is assumed that the reductant (HSO3) is specifically adsorbed at the surface of an iron(III)(hydr)oxide, forming either a monodentate or a bidentate surface complex ... 

In order to evaluate the two important variables which - in addition to pH - affect the residual concentrations of a metal ion, we use a simple equilibrium approach to assess the effect of these two variables. We assume a constant pH and characterize the effect of particle ligands, =L, by the surface complex formation equilibrium. 

It is surprising that data on natural particles can be fitted over a range of concentrations (representative of those encountered in natural waters) on the basis of a "single-site" surface complex formation model. Apparently similar types of binding groups are predominant and of importance in these particles. 

Speciation of Pb(II) in Glatt river. The concentrations given for CO2, Pb(II), Cu(II) and [Ca2+] as well as for the pollutants EDTA and NTA are representative of concentrations encountered in this river, The speciation is calculated from the surface complex formation constants determined with the particles of the river and the stability constants of the hydroxo-, carbonate-, NTA- and EDTA-complexes.The presence of [Ca2+] and [Cu2+] is considered. 

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