BIOMIMETIC SYNTHESIS OF CALCIUM-CARBONATE PARTICLES IN A PSEUDOVESICULAR DOUBLE EMULSION

A double water-in-oil-in-water emulsion system was used as a biomimeti c environment for the preparation of calcium carbonate particles. Calc ium ions were extracted from an external aqueous phase (calcium nitrat e solution) into the organic membrane phase (kerosene containing Span 83 as a surfactant and bis(2-ethylhexyl)phosphoric acid as an extracta nt) and stripped into the internal aqueous phase (sodium carbonate sol ution), where the precipitation of calcium carbonate occurred. In this pseudovesicular system it has been found that both the physical and p olymorphic forms of the particles could be controlled by change of pH and method of demulsification such that either calcite or vaterite app eared as single crystals or heirarcically ordered aggregates.