The demineralization behavior of carbon and chemically-modified carbon electrodes

Abstract

The electrically-induced adsorption of ions by commercial carbons and the effect of several carbon treatments and dispersion additives on finished electrode performance have been investigated. When paired with a working Ag. AgCl electrode, the adsorption capacity of a carbon electrode is a function of the applied potential over the range 0.3 to 1.0 v. For a pair of carbon electrodes the capacity increase with applied potential diminishes at approximately 0.6 v. Most commercial carbons are not highly specific to the charge type of ion which can be adsorbed (under the appropriate polarity). Severe oxidation of the carbon yields a large capacity and high selectivity for cations ( > 1 meq/g) whereas high temperature treatment in an ammonia atmosphere reduces the cation capacity of the carbon. The inclusion of an inert polymeric binder during electrode fabrication results in excellent mechanical stability. The relatively low anion capacity of many commercial carbons can be improved by incorporating additives such as a cationic polyelectrolyte, a quaternary ammonium salt or polyethylenimine during dispersion preparation.