posted on 2024-02-28, 08:03authored byHang Zhai, Qiyuan Chen, Yan Duan, Bin Liu, Bu Wang
The aqueous carbonation of calcium silicate (CS), a representative
alkaline-earth silicate, has been widely explored in studies of carbon
dioxide (CO2) mineralization. In this context, we conducted
a specific comparison of the carbonation behaviors between the crystalline
calcium silicate (CCS) and amorphous calcium silicate (ACS) across
a pH range from 9.0 to 12.0. Interestingly, we observed opposite pH
dependencies in the carbonation efficiencies (i.e., CaO conversion
into CaCO3 in 1 M Na2CO3/NaHCO3 solution under ambient conditions) of CCS and ACSthe
carbonation efficiency of CCS decreased with increasing the solution
basicity, while that of ACS showed an inverse trend. In-depth insights
were gained through in situ Raman characterizations,
indicating that these differing trends appeared to originate from
the polymerization/depolymerization behaviors of silicates released
from minerals. More specifically, higher pH conditions seemed to favor
the carbonation of minerals containing polymerized silica networks.
These findings may contribute to a better understanding of the fundamental
factors influencing the carbonation behaviors of alkaline earth silicates
through interfacial coupled dissolution and precipitation processes.
Moreover, they offer valuable insights for selecting optimal carbonation
conditions for alkaline-earth silicate minerals.