Methodology For CaCO3 Core 
1) MICP (microbially induced calcium carbonate precipitation):  Details to https://www.authorea.com/users/169562/articles/210343-micp
2) Dopamine-Induced Mineralization of CaCO3 Vaterite Microspheres 
3)  Silane coupling agent, N- (trimethoxysilylpropyl) ethylenediaminetriacetate trisodium salt (TES- PEDTA, Gelest, 35% in water), based growth of CaCO3 nanocrystal.
4)  Implement the method of Softening Hard water:  http://www.chemistry.wustl.edu/~edudev/LabTutorials/Water/FreshWater/hardness.html