Generation of pH Gradient

As soil-fluid-chemical systems must be electrically neutral, charges cannot be added to, formed in, or removed from a system without the simultaneous addition. 

The initial bonding in a group of oriented water moiecules 

Nonetheless, the spatial and temporal changes in soil pH induced by the electrochemical remediation process are evident. As a result, physical and chemical changes of the soil and the contaminants associated with the change in soil pH have to be carefully taken into account to maximize the efficiency of electrochemical remediation of contaminated soil. 

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Airpholine and other similar carrier ampholytes are generally used for the formation of pH gradients. They contain, however, chemically ill-defined components which may contaminate the purified products. The development of other means for the generation of pH gradients would be highly desirable and was a prime objective of much of our theoretical modeling. Three alternatives were pursued ... 

The first practical IEF experiments were carried out with the use of synthetic molecules, called carrier ampholytes, to generate the pH gradients.1,26 Carrier ampholytes are amphoteric electrolytes that carry both current and buffering capacity. Much of the early theoretical activity in electrofocusing dealt with the properties required of carrier ampholytes and is more or less irrelevant to a current discussion.1,3,9 Different varieties of... 

Fig. 2.5. Interaction of Ca transport with the proton circuit, a, Ca uptake alone discharges the membrane potential b, Ca uptake in exchange for protons extruded by the respiratory chain generates a pH gradient c, Ca uptake together with a weak acid such as acetate does not build up a pH gradient d, Ca cycling in heart mitochondria driven by the proton circuit. R, respiratory chain C, calcium uniport NH, sodium/proton antiport NC, sodium/calcium antiport.

In order to optimize productivity and reduce the loss of catalyst or product it is advisable to minimize the effects of reaction-generated dynamic pH-gradients. 

Consequently, electrical neutrality is maintained and no membrane potential is generated. A pH gradient of 3.5 units across the thylakoid membrane corresponds to a proton-motive force of 0.20 V or a AG of —20.0 k] mol (—4.8kcalmol ). 

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