In the part,synthesis of CaCO3 was followed by two basic synthetic routes: (1) the solution route, through a double decomposition reaction, where in aqueous CaCl2 and Na2CO3 or CaCl2 and (NH4)2CO3, or Ca(NO3)2 and Na2CO3 are combined in an equal molar ratio; and (2) the carbonation method, in which CO2 gas is bubbled through an aqueous slurry of Ca(OH)2 [3,4].