MICROWAVE PRECIPITATION OF CACO3 FROM HOMOGENEOUS SOLUTIONS

The precipitation of calcium carbonate, calcite, from homogeneous comp lexed solutions formed by Ca-citrate and HCO3-/CO32- has been carried out in batch and MSMPR reactors activated by microwave radiation. In t he batch experiments, monodisperse calcite crystals with ellipsoidal o r peanut-like shapes have been obtained under certain experimental con ditions, while in the continuous precipitation experiments the calcite crystals present ellipsoidal shapes. These morphologies are unusual f or the phase calcite. In the continuous precipitation experiments, the rate of nucleation observed is higher than the one measured in a conv entional MSMPR reactor in equivalent conditions. A possible explanatio n to this fact lies in the specific effect of microwaves in weakening the Ca-H2O bonding of the inner hydration sphere of calcium, thus favo ring its dehydration, which is the rate controlling factor in the prec ipitation of calcium carbonate.