| Abstract
| - The surfaces of two algae species (Cyclotellacryptica,diatom; Chlamydomonas reinhardtii, green alga) werecharacterized with regard to their interactions with copper.Chemical and spectroscopic methods (FT-IR, continuous-wave EPR, and two-pulse ESEEM) gave information aboutthe kinds of functional groups (-NH2, R-COOH, R-OH, andSi-OH) on the surfaces of the algae. Maximum protonbindingcapacities of 9.7 × 10-4 and 9.1 ×10-4 mol/g algae (dryweight) were determined for C. cryptica and C.reinhardtii,respectively. The maximum Cu(II) binding capacity was7.6× 10-7 mol/g for the diatom and 6.2 ×10-6 mol/g for thegreen alga with [Cu2+] =10-13−10-11 insolution (at pH6.9). Less than 1% of the total proton binding sites areoccupiedby copper under these conditions. The highconditionalstability constants (log K = 11.9 for C.cryptica and log K =11.3 for C. reinhardtii, at pH 6.9) demonstrate thestrongbinding of copper to the algae surfaces. These resultsareconfirmed by the CW-EPR and two-pulse ESEEM spectroscopy, which indicate binding to N-ligands, withhistidinebeing one of the possible ligands for copper. Thebindingsites on algae surfaces represent a buffer capacity forCu2+ in natural waters.
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