Impregnation counterion

By electropolymerization of pyrrole in solvents containing polyelectrolytes such as potassium polyvinylsulfate, it is possible to prepare films of polypyrrole with polymeric counterions which have good conductivity (1-10 S cm-1) and strength (49 MPa) 303 304,305). Such a material could be used reversibly to absorb cations in an ion exchange system. Pyrrole has also been electrochemically polymerized in microporous polytetrafluoroethylene membranes (Gore-tex), impregnated with a perfluorosulphonate ionomer 3061. 

Remarkably, the electrocatalytic process is modulated by electrolyte counterions. This can be seen in Figure 5.18, which displays CVs at (m-MOF-modi Tied paraffin-impregnated graphite electrodes immersed into 1.0 mM H O plus Oj-saturatcd (a) 0.10 M Et4NC104/MeCN and (b) 0.10 M LiClO4/MeCN solutions. In the presence of size-hindered Et4N+ ions, only the oxygen-localized reversible reduction process at a midpoint potential of ca. -0.80 V is observed. In the presence of Li+ ions, however, two reduction waves at ca. -0.60 and -1.20 V are recorded, followed, in the subsequent anodic scan, by anodic peaks at -0.85, -0.45, -1-0.40, -1-0.90, and -1-1.40 V. 

In the case of CoMo/A, which presents the same molybdate entities as in the non-promoted sample, their behaviour upon calcination is identical, and AlMoa evolves into an aluminium molybdate phase, and re-appears upon transfer to air. In the case of CoMo/Z, the calcination generally performed at 500°C to eliminate the ammonium counterions induces a decomposition of the cobaltomolybdate entity. Upon rehydration, the so freed molybdenum atoms associate with aluminium as in the impregnation of AHM to give AlMoe. Thus, the calcination-rehydration steps have a levelling effect on the structure of the promoted catalyst the same entities are finally identified whatever the support or the synthesis route. 

Immobilized Liquid Membranes. Facilitated transport liquid membranes for gas separations can be prepared In several configurations. The complexatlon agent solution can be held between two nonporous polymer films (2j1), Impregnated Into the pore structure of a micro-porous polymer film (25), or the carrier can be exchanged for the counterion In an Ion exchange membrane (it). 

The third subregion, called diffuse part of the interface, is charged because in this region the counterions are accumulated. The size of the diffuse part depends strongly on the ionic strength of the impregnating solution. Assuming a planar sohd/water interface, its thickness (L) may be approximately estimated by the formula... 

The impregnation solution contains several chemical species the metal precursor of the active phase, its counterions, coimpregnants precursors are also selected according to their physicochemical properties and cost. 

Due to the low volume of solution used in incipient wetness impregnation, the concentration of the precursor in water is often high and sometimes close to the limit of solubility (which depends much on the counterion chosen and on the presence of ligands surrounding the metal ion). 

The precursor salt introduced by impregnation should be (i) soluble and (ii) easily transformed into an oxidic or metallic phase upon heating. The choice of the counterions balancing the charge of the precursor complexes is steered by these two criteria. 

Also, D-(—)-tartaric acid has been used as a CMPA for the separation of ( )-metoprolol tartarate on silica gel plates preimpregnated with the mobile phase (ethanobwater, 70 30, v/v) containing D-(-)-tartaric acid as a chiral selector. The results of experiments performed with different concentrations of D-(-)-tartaric acid (5.8,11.6, and 23 mmol/1) revealed that the best resolution of the metoprolol tartarate enantiomers was achieved with 11.6 mmol/1 d-(-(-tartaric acid in both the mobile phase and the impregnation solution at 25 2" C. It has been assumed that tartaric acid (p Tai 2.93) dissolved in excess of ethanol could react with ethanol forming monoethyltartrate, which might play a role of a real chiral selector in this separation system [43]. The structures of CSA, ZGP, and monoethyltartrate as counterions are presented in Figure 6.3. 

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