Biological substrates catalyze the nucleation and growth of sparingly soluble salts however, the underlying mechanism is largely unknown. In the present study, the growth of calcium carbonate (CaCO3), on Acutodesmus obliquus (AO) microalgae was investigated. The test microalgae favored the growth of CaCO3 from solutions supersaturated with respect to calcite (7.94 < SRcalcite < 104.71). The precipitation of calcite on AO was not preceded by measurable induction times, and the rates of calcite crystal growth were higher for higher microalgae cell concentrations. The presence of the microalgae cultivation medium and illumination of the supersaturated solutions accelerated the precipitation of CaCO3, increasing the rate by 75% in comparison with the respective value in its absence. AO cultures, air dried at 25 °C yielded higher precipitation rates, in comparison with the respective rates in the presence of active AO cultures. At 70 °C, nucleation and growth were suppressed, due to the destruction of the molecular structure of the microalgae. The CaCO3 precipitation rates on calcite precipitated on air-dried AO culture, were doubled in comparison with the respective rates obtained with the respective quantities of each component of the composite substrate.
Keywords: calcium carbonate; microalgae; mineralization; precipitation; rate of.