Synthesis of a Se 0 / calcite composite using hydrothermal 1 carbonation of Ca ( OH ) 2 coupled to a complex

1 2 In this study, the hydrothermal carbonation of calcium hydroxide under high CO 2-Ar pressure 3 (90 bar) and high temperature (90 °C) coupled with a complex selenocystine fragmentation 4 was carried out by using a batch system in order to synthesize an elemental selenium 5 (Se 0)/calcite composite. Under O 2-poor conditions, the composite was mainly characterized 6 by red spherical selenium nanoparticles " non crystalline elemental selenium " (<500nm) 7 deposited on the calcite matrix. In contrast, under O 2-rich conditions, the composite was 8 characterized by grey rods selenium microparticles " crystalline elemental selenium " (<25µm) 9 dispersed in the calcite matrix. The carbonate matrix was constituted by nano-and micro-10 rhombohedral crystals (<2µm) and micrometric agglomerates and/or aggregates (<5µm). 11 The results presented here demonstrate that Se 0 /calcite composite, with spherical or rod 12 morphologies for elemental selenium can be produced, this composite could possibly has a 13 high potential for medical (ex. dietary supplement) or industrial (ex. pigments) applications. 14 In addition, this study may have implications in the field of biomineralization.