Competitive ions

Here, a primary ion P+ formed by the radiation field reacts with a gas molecule M to give an intermediate complex [PM +] which can either dissociate to a secondary species S + and a neutral fragment N or react with another molecule to produce another complex [PM2 + ]. The latter then dissociates into a tertiary ion T+ or propagates the chain by forming a third intermediate [PM3 + ]. A quaternary ion Q+ may result from dissociation of [PM3 + ], or the chain may continue through reaction of [PM3 + ]. Wexler and Jesse (38), on the other hand, have suggested a model which states that reactive intermediate complexes are not involved in the propagation, but rather the polymerization proceeds by chains of simple consecutive and competitive ion-molecule reactions,... 

On the other hand, optionally added co-ions of the eluent may also interfere with the ion-exchange process through competitive ion-pairing equilibria in the mobile phase. The effect of various amines added as co-ions to the polar-organic mobile phase was systematically studied by Xiong et al. [47]. While retention factors of 9-fluorenylmethoxycarbonyl (FMOC)-amino acids were indeed affected by the type of co-ion, enantioselectivities a and resolution values Rs remained nearly constant. For example, retention factors k for FMOC-Met decreased from 17.4 to 9.8 in the order... 

The lonsiv ion exchange resins are extraction technologies used to separate radionuclides from alkaline wastewater in the presence of competing cations. These resins include lonsiv IE-910 and lonsiv IE-911, which are manufactured using a new class of crystalline silicotitanates (CSTs) invented by researchers from Sandia National Laboratory (SNL) and Texas A M University. CSTs demonstrate high distribution coefficients in acidic, neutral, and alkaline solutions with high concentrations of competitive ions such as sodium and potassium. The affinity of CSTs for strontium in neutral or alkaline wastes is also high. 

Figure 8.10a is an example of some data in which the effect of added salt is more than a competitive ion-binding phenomenon. The reaction involved is the decarboxylation of 6-nitrobenzisoxazole-3-carboxylate, catalyzed by hexadecyl trimethyl ammonium bromide micelles ... 

The detection of contamination with mercury is a very serious issue due to the extreme toxicity and ease of reaction of this heavy metal. Mercury is commonly used in many everyday applications, such as thermometry, barometry or scientific apparatus. Therefore, it is important to note the development of a fluorescent IIP membrane for detection of mercury [63], This membrane was based on the combination of two fluorescent functional monomers, namely 4-vinyl pyridine and 9-vinylcarbazole. Binding of Hg2+ was proposed to be based on complexation of the metal ion with lone pairs of both pyridine and carbazole. The IIP membrane was capable of recognizing Hg2+in the linear range of concentrations from 5 x 10 7 to 1 x 10 4 M. Selectivity of the chemosensor was studied for a wide group of possible competitive ions and the chemosensor responded to all of them in the presence of a fixed amount of Hg2+ at 1 x 10 5 M. Nevertheless, the highest influence on recognition properties was observed in the presence of Cu2+ (4.87%) and Pb2+ (4.57%), which are still acceptable values for the successful detection of Hg2+. This progress stimulates further development of the MIP detection of ions. 

K. Bunzl, Competitive ion exchange in mixed cation exchanger systems Kinetics and equilibria, J. Inorg. Nucl. Chem. 39 1049 (1977). See also K. Bunzl, Kinetics of ion exchange in polydisperse systems, Anal. Chem. 50 258 (1978) for an application to a set of exchangers with different specific surface areas. 

Those that use competitive ion-exchange isotherm equations consider a heterogeneous surface characterized by an energy distribution function (Sposito 1981 Kinniburgh 1983 de Wit et al. 1990 Borkovec and Koper 1994). 

Cemik, M., M. Borkovec, and J. C. Westall. 1996. Affinity distribution of competitive ion binding to heterogeneous materials. Langmuir 12 6127-6137. 

Phipps, J.B. Moodie, L.C. Gyory, J.R. Theeuwes, F. Electrotransport System with Ion Exchange Material Competitive Ion Capture. US Patent 6,289,242, September 11, 2001. 

J. P. Chen, M. L. Chua, and B. P. Zhang, Effects of competitive ions, humic acid, and pH on removal of ammonium and phosphorous from the synthetic industrial effluent by ion exchange resins. Waste Management 22, 711-719 (2002). 

Thionyl chloride is the classical reagent for the preparation of alkyl chlorides from alcohols with retention of configuration. This reaction is known to proceed via alkyl chlorosulfinates (7 75) which decompose by an ion pair mechanism, but may be diverted to an SN2 displacement path by addition of pyridine171 Wagner-Meerwein rearrangements have been observed in the course of alkylchlorosulfinate decomposition, e.g. (176) - (777)172). The behavior of the isomeric chlorosulfinates (178) and (179) is consistent with competitive ion pair collapse and 1,2-alkyl shift173. ... 

With secondary competitive ions Form surface complex X X... 

Competitive ion displacement can represent an important means by which arsenic is released to the aqueous phase, where it is subject to transport. Displacement and mobilization of As by phosphates is of particular concern (Manning and Goldberg, 1996 Reynolds et al., 1999 Violante and Pigna, 2002 Dixit and Hering, 2003), and regions where fertilizer or pesticide runoff and leaching... 

Borkovec. M.. Rusch, U., and Westall, J.C.. Modeling of competitive ion binding to heterogeneous materials with affinity distributions, in Adsorption of Metals by Geomedia, Jenne, E., ed.. Academic Press, New York, 1998, p. 467. 

Inorganic Complex cation Counteranion Competing cation [Ni(NH,)6](NO,)2/Si02 nh + + +(-) + Competitive ion exchange(3)... 

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