Reductive adsorption

The effect of the operating conditions (temperature, presence of C02 and water) on both adsorption-reduction phases has been also analysed. 

Minssieux L., "Method for Adsorption Reduction of Mixed Surfactant Systems", Proc. 4th. Eur. EOR Symp., 1987, p. 293. 

A pressure-swing adsorption (PSA) process cycle is one in which desorption takes place at a pressure much lower than adsorption. Reduction of pressure is used to shift the adsorption equilibrium and affect regeneration of the adsorbent. Figure 16-39 depicts a simplified pressure-swing cycle. Feed fluid containing an adsorbate at a molar concentration of y i = pi /Pi is passed through an adsorbent at conditions... 

This chapter presents the theory and application of zero-valent iron and includes the relevant in situ chemical/physical processes. To illustrate these in situ technologies, the basic mechanisms of adsorption reduction and oxidation processes are discussed for in situ treatment of (1) organic pollutants, (2) heavy metals, and (3) mixtures of organic and inorganic pollutants. The history of zero-valent iron, current applications, mechanisms and kinetics of the system, system improvements, and advantages and disadvantages for zero-valent iron are also discussed. 

Sequestration by Fe° occurs mainly by adsorption, reduction, and coprecipitation, although other processes may be involved such as pore diffusion and polymerization. In most cases, adsorption is the initial step and... 

Uludag-Demirer S, Bowers AR. Adsorption/reduction reactions of trichloroethylene by elemental iron in the gas phase the role of water. Environ Sci Technol 2000 34 4407-4412. 

An interesting application of adsorption microcalorimetry was used by these researchers to examine changes in adsorption behavior of graphite-supported iron/rhodium bimetallic catalysts as a function of oxidation and reduction treatments. The differential heat of oxygen adsorption on the bimetallic catalysts after various treatments was compared to the values obtained for the monometallic materials to determine the relative contributions to the total adsorption. Reduction at 673 K produced an alloy whose... 

Goldhaber, M. B., B. S. Hemingway, A. Mohagheghi, R. L. Reynolds, and H. R. Northrop. 1987. Origin of coffinite in sedimentary rocks by a sequential adsorption-reduction mechanism. Bull. Mineral. 110 131-44. 

Figure 5.56 Number of molecules of oxygen accumulated at the surface of zirconia as a function of irradiation time during the (1) photoinduced adsorption (reduction) of oxygen, and (2) the photooxidation of hydrogen. Reprinted with permisison from Emeline et al. (2005a). Copyright (2005) American Chemical Society.

The effect of thermal surface treatment of carbons carried out in various atmospheres on the NO, adsorption-reduction was studied by Xia and coworkers [103]. They found that activated carbon heated at 1200K in hydrogen adsorbed NO without its oxidation to NO,. This happens as a result of a decreased affinity of the hydrogen reduced carbon to chemisorbed oxygen. It is interesting that such effect was not found on carbons treated in nitrogen. 

Oxidative adsorption Reductive dissolution MnOx MnOx, Fe(II), Co(II), Sn(II) 1... 

Due to its high vapor pressure at the operating temperature of the electrolysis, mercury, whose circulating tonnage represents 700 to 2400 kg/t per day of chlorine production capacity, pollutes the different gaseous streams produced (chlorine, hydrogen). Similarly, it contaminates the different liquids produced by the operation (spent brine, caustic soda, etc.). This results in substantial losses, which must be limited for economic as well as environmental reasons. Whereas small. amounts of mercury in the chlorine (0.1 to 0.2 g/t) are not detrimental to its subsequent uses, the same cannot be said of caustic soda, especially for food applications, in which it is removed by filtration (up to 15 ppb), for hydrogen, from which it is removed (up to 3 to 5 ppb) by absorption in sodium hypochlorite, adsorption on activated charcoal etc, and aqueous wastes, from which it is removed (up to 5 to 10 ppb) by precipitation, adsorption, reduction or extraction. The spent brine, which normally contains 1 to 10 ppm mercury and occasionally 1000 ppm, is usually recycled and therefore does not require treatment... 

Surfactant Mixtures. Another promising approach to minimizing surfactant adsorption is through the formulation of surfactant mixtures. The mechanism of adsorption reduction in surfactant mixtures is based on a unique property of surface active substances the formation of micelles (129—134). 

Lysozyme Gelatin and succinylated gelatin Adsorption Reduction of prosthetic valve endocarditis [106]... 

The small difference between the peak potentials of the neopterin adsorption-reduction process (IIIic) and the first one of folic acid makes it impossible to distinguish them when they are in the presence of each other. In this circumstance the second process of folic acid (l2c) is the alternative for its quantitation. In Fig.4 the voltammogram obtained for a mixture (2 1), after preconcentration at —0.300 V for 30 s under stirring is presented. As expected, the first reduction peak of I (Iic)is influenced by the presence of III, but the second one (l2c) is unaltered and shows linearity with respect to the concentration of I. 

Chemical adsorption-reduction reactions also occur on carbon surfaces resulting in uptake of ions (cations) from aqueous solutions. This occurs when the redox potential of metal ions is high compared with that of the carbon, for example for gold, °(AuClJ/Au) = 1.00 V, for silver, "(Ag /Ag) = 0.80 V and for platinum, (PtCl4 /Pt) = 0.755 V. These metal ions are adsorbed as a result of the following type of Reaction 8.1 ... 

Plyuto (1999) CifiTABr Adsorption on calcined film + reduction [Ag(NH3>2]N03 BImodal Ag nanoparticles in channels (3,6-7 nm due to merged channels) Size increosed after successive adsorption/reduction steps... 

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