Uptake of technetium by freshwater green microalgae

Abstract

Accumulation of [99Tc]pertechnetate ions (99TcO4−) by the freshwater microalgae Chlorella emersonii, Chlamydomonas reinhardtii and Scenedesmus obliquus has been characterized. In all three species, accumulation consisted of a single rapid energy-independent phase (biosorption), and no energy-dependent accumulation was observed. Biosorption of 99TcOinf4sup−by all three species was concentration dependent, followed a Freundlich adsorption isotherm, and was dependent on pH with increased accumulation by cells with decreasing external pH. Elevated external NaCl concentrations also caused increased accumulation of 99TcOinf4sup−by the cells, as did increased external osmotic potential. Concentrations of K+, Mg2+ and Ca2+ increased accumulation of 99TcOinf4sup−, but concentrations of HCOinf3sup−, SOinf4sup2−and COinf3sup2−decreased 99TcOinf4sup−accumulation by the cells. Most of the 99TcOinf4sup−accumulated by all three species was easily desorbed by 10 mm buffers at various pH values, 0.5 m NaCl, 10 mm Na2CO3 or 10 mm Na2SO4. No differences in the amount of desorption were observed between the various desorption agents used.