Parametric study on a new leaching-absorption-mineralization cycled process of CO2 into CaCO3 based on Ca-rich purified dust

Mineralization process between CO2-rich amine solvents and Ca-rich solid wastes would be very potential for obtaining carbon-free and functional CaCO3 product with high purity. This study aimed to grasp the performance of a new leaching-absorption-mineralization (LAM) cycled process, in which amines acted as both absorbent for gas mixture with low CO2 concentration and leaching agent of Ca2+ out from Ca-containing solid wastes. Different parameters affecting this LAM cycled process were investigated and the properties of mineralized products were characterized in detail. The results showed that 3 mol/L TEA exhibited an excellent capability in Ca2+ leaching out from Ca-rich purified dust, and Ca2+ concentration in leachate appeared a positive relationship with TEA concentration, solid-to-liquid ratio and leaching time. With the help of 30 % additives (HCl, NH4Cl and CH3COOH), Ca2+ concentration in 3 mol/L TEA leachate was enhanced by more than double times. The volume ratio of CO2-rich solvent to Ca2+-rich leachate played a significant role in product yields and the size of mineralized crystals. The pure CaCO3 yield was significantly increased at a bigger volume ratio or a higher adding proportion of additive. When 30 % CH3COOH was added into 3 mol/L TEA, most of mineralized product existed as vaterite, and its total yield reached up to be the maximum value of 530.96 g/kg. After completing the fifth cycle, in comparison with fresh TEA, Ca2+ leaching efficiency and CO2 absorption load of recycled 3 mol/L TEA was decreased by about 18.78% and 12.53%, respectively. The regulation in size and morphology of CaCO3 crystal can be achieved by flexibly changing the volume ratio during LAM cycled process.