INTERACTION OF METALS AND PROTONS WITH ALGAE .2. ION-EXCHANGE IN ADSORPTION AND METAL DISPLACEMENT BY PROTONS

Adsorption of Sr on Vaucheria released an equivalent amount of Ca and Mg, indicating that metal adsorption by alkali and alkaline-earth metals is an ion-exchange phenomenon based on electrostatic interactions. Release of protons when Cu was adsorbed demonstrated additional covalent bonding for this transition metal. Protonated ethylenediamine is adsorbed both as a cation similar to metals and as a neutral species, indicating the presence of additional bonding sites. When the pH of an algal suspension is decreased, Ca and Mg are released equivalent to the amount of proton uptake, which occurred in fast (<50 s) and slow (2 h) processes. Kinetic evidence suggests that the slow process represents rate-determining diffusion of Ca through a dense-phase structure of the alga. © 1990, American Chemical Society. All rights reserved.