Effects of Ca-ligand stability constant and chelating agent concentration on the CO2 storage using paper sludge ash and chelating agent

In this paper, we performed an experimental study on how to maximize CO2 storage, produce high purity CaCO3, and control the morphology of CaCO3 in the process of indirect carbonation using paper sludge ash (PSA) and chelating agents as solvents. To this end, the effects of the Ca-Ligand (Ca-L) stability constant and concentration of chelating agents on the Ca extraction efficiency, carbonation efficiency, and the characteristics of CaCO3 produced were investigated. For the study, a total of seven chelating agents (fumarate, adipate, malonate, IDA, citrate, NTA, and EDTA) in a wide range of Ca-L stability constant (Log K) of 2.0-12.4 were adopted, and the concentrations of each chelating agent were adjusted to 0.1 and 0.5 M. According to the experimental results, it was revealed that the storage of CO2 and the yield, purity, and morphology of CaCO3 could be controlled by adjusting the type (or Ca-L stability constant) and concentration of the chelating agent. The higher the Ca-L stability constant and concentration of the chelating agent, the higher the Ca extraction efficiency, but the lower the carbonation efficiency. The highest CO2 storage and CaCO3 production were obtained by using citrate with a Log K value of 4.7.