INTERACTIONS OF METALS AND PROTONS WITH ALGAE

Proton uptake by intake algal cells was found to consist of two processes: (1) a fast ( less than 4 s) surface reaction and (2) a slow diffusion of protons into cells. A pH titration technique measured only the rapid surface reaction that forms negative sites at higher pH. Adsorption of alkali, alkaline earth, and transition metal ions on algae was quantitatively represented by the Langmuir adsorption isotherm with its two parameters y//m, the maximum amount of metal adsorbed, and K, the equilibrium constant taken as a measure of bond strength. Variations of these parameters with pH and type of metal indicate that metals adsorb to algal surfaces by electrostatic attraction to negative sites, such as carboxylate anions of poly(galaturonic) (pectin), as previously suggested.