Influence de gels mineraux et d'argiles sur la cristallogenese du carbonate de calcium a partir des solutions bicarbonatees

Abstract

Summary The precipitation of calcium carbonate is obtained from a bicarbonate solution added with silica gels, silico-mangnesian gels, ferric gels and clay minerals. Two methods have been performed. The first one consists of a quick removal of CO 2 ; the second one refers to settled solutions. Identification of various carbonates is obtained by infra-red spectroscopy. Morphology of crystalline shapes are analysed with scanning electron microscope. It is etablished: (i) silica gels are not good inhibitors of calcite; (ii) silico-magnesian gels reduce the time of precipitation and promote the deposition of “disordered” calcite (intermediate hydrated form between amorphous calcium carbonate and calcite) and (OH) aragonite; (iii) ferric gels inhibit very strongly calcite; then, vaterite and aragonite are deposited; (iv) at the least, the presence of clay minerals promote the stabilization of amorphous calcium carbonate and “disordered” calcite. The gels and the minerals which are here tested and recognized in soils take therefore an active part in the kinetics of precipitation and in the nature of the calcium carbonates.