SYNTHESIS OF NANO-SIZED CaCO3 PARTICLES BY SPRAY DRYER
Method for preparing calcium carbonate comprising the steps of mixing an aqueous solution of NaHCO 3 and an aqueous solution of CaCl 2 , then atomizing them in a pre-heated air flow, thereby obtaining calcium carbonate in powder form and sodium chloride. The calcium carbonate obtained comprises nanoparticles smaller than 200 nm.
The spary dryer provides the ability to synthesize nanometer CaCO3 particles without using surfactants or other chemical species that stabilize the reaction mixture.It allows the control of temperature, air humidity and reagent flow. With this instrument the liquid product is “atomized”. The drying air acts on a surface so large as to allow an instantaneous evaporation of the liquid phase with consequent immediate lowering of the air temperature. The starting solutions, NaHCO3 and CaCl2, prepared in a 2: 1 ratio, are mixed by means of a peristaltic pump.
The high temperature allows the evaporation of the water of the reaction mixture, allowing the direct production of calcium carbonate in powder form; the reaction product below, the NaCl, is removed by subsequent washing in water.
- The developed technology allows to synthetize pure CaCO3 nano-particles;
- No need to use surfactants or other chemical species to stabilize the mixture and the reaction product;
- The method is easily usable on large scale and allows to control the shape and the size of obtained nanoparticles.