Power exchange function

When an empirical fit of exchange data can be accomplished with a power exchange function in which n = 1, but 1, the reaction can be termed simple ion exchange. That a sorption reaction obeys simple ion exchange implies that... 

Simple ion exchange describes the competitive adsorption onto clays of most metal cations present in solution at concentrations from about 10 to 10 mol/kg. It has most often been used.to describe the sorption of alkaline earth and alkali metal cations onto clays. In the case of minerals having pH-dependent surface charge (e.g., kaolinite, metal oxyhydroxides) simple ion exchange or the power-exchange function (see below) may also fit the adsorption data mea.sured in systems at constant pH. 

The general power-exchange function applies when n I and 1. The exchange reaction... 

What is the power-exchange function and how is it related to ion exchange and Donnan exchange Give examples of the applicability of each of these approaches to competitive cation adsorption. How are activity coefficients dealt with in ion-exchange reactions ... 

The sorption equilibrium obeys a power-exchange function... 

Langmuir, D. 1981, The power exchange function A general model for metal adsorption onto geological materials. In Adsorption from aqueous solutions, ed D. H, Tewari, pp. 1-17. New York Plenum Press. 

OzsvATH, D. 1979. Modeling heavy metal sorption from subsurface waters with the n-power exchange function. M.S. thesis. The Pennsylvania State Univ, University Park, PA. 

In ion-exchange chromatography (lEC), the mobile phase modulator is typically a salt in aqueous solution, and the stationary phase is an ion-exchanger. For ddnte conditions, the solute retention faclor is commonly found to be a power-law function of the salt uormahty [cf. Eq. (16-27) for ion-exchange equilibrium]. 

Cation Exchange Extractants. This class of extractants includes phenols, branched alkyl carboxylic acids, alkyl phosphoric acids, diketones, and alkyl-aryl sulfonic acids. The last group listed, sulfonic acids, are analogous to sulfonic-acid cation exchange resins and have very little selectivity. Diketones, alkyl phosphoric acids and carboxylic acids can provide both cation exchange functions and coordination functions. This feature has made bis(2-ethylhexyl)phosphoric acid one of the most versatile and powerful extractants of this type. (5) The nation below illustrates simple cation exchange extraction. 

The majority of micro-reactors reported in the literature are stiU dedicated to catalyst evaluation. These reactors are usually monolith-type laboratory devices without heat-exchange functions, which allow for the removal of the microstructured plates after testing [26-35]. These are supplied by electrical power for heating and are StiU far away from a practical appUcation. Therefore, the design of these reactors wiU not be discussed in detail below, bearing in mind that they are useful tools for catalyst screening and characterization. 

Combinatorial. Combinatorial methods express the synthesis problem as a traditional optimization problem which can only be solved using powerful techniques that have been known for some time. These may use total network cost direcdy as an objective function but do not exploit the special characteristics of heat-exchange networks in obtaining a solution. Much of the early work in heat-exchange network synthesis was based on exhaustive search or combinatorial development of networks. This work has not proven useful because for only a typical ten-process-stream example problem the alternative sets of feasible matches are cal.55 x 10 without stream spHtting. 

Operating co.sts. Power requirements for air-cooled heat exchangers can be lower than at the summer design condition provided that an adequate means of air-flow control is used. The annual power requirement for an exchanger is a function of the means of airflow control, the exchanger seiwice, the air-temperature rise, and the approach temperature. 

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