Investigating the Effect of Leucine on Calcium Carbonate Nucleation Mechanisms in the View of a Circular Economy

The study of calcium carbonate crystallization with differentconcentrationsof leucine has been performed, with a supersaturation ratio spanningfrom 2 to 180, at a temperature ranging from 15 to 35 & DEG;C. Indetail, the crystallization experiments were performed at the temperaturesof 15 & DEG;C without leucine and at 15 and 35 & DEG;C with leucineat the same concentrations previously used (0.520 x 10(-3) and 1.041 x 10(-3) mol/L), at the temperatureof 25 & DEG;C. A comparison among results is carried out, and fromthe measured induction time values, it appears that leucine acts asa promoter for carbonate crystallization, enhancing this behaviorwhen raising its concentration. Interfacial surface tension has beenevaluated, showing values falling in the range 69-117 mJ/m(2). SEM pictures indicate that the crystal structure is a mixbetween calcite and vaterite: initially born as amorphous calciumcarbonate crystals, under the effect of leucine, they change theirhabit into vaterite crystals, without completely turning out in themore stable form of calcite.Promoting CaCO3 precipitation with leucine canplay a role in CO2 capture and sequestration processesin the carbonation/calcination cycle.