A Green Approach to Preparing Vaterite CaCO3 for Clean Utilization of Steamed Ammonia Liquid Waste and CO2 Mineralization

Abstract

In the salt lake industry, large amounts of steamed ammonia liquid waste are discharged as byproducts. The conversion of the residues into high value-added vaterite-phase calcium carbonate products for industrial applications is highly desirable. In this research, the feasibility of preparing vaterite-phase CaCO3 in different CaCl2-CO2-MOH-H2O systems using steamed ammonia liquid waste was studied in the absence of additives. The effects of initial CaCl2 concentration, stirring speed and CO2 flow rate on the composition of the CaCO3 crystal phase were investigated. The contents of vaterite were researched by the use of steamed ammonia liquid waste as a calcium source and pure calcium chloride as a contrast. The influence of the concentration of CNH3·H2O/CCa2+ on the carbonation ratio and crystal phase composition was studied. The reaction conditions on the content, particle size and morphology of vaterite influence were discussed. It was observed that single vaterite-phase CaCO3 was favored in the CaCl2-CO2-NH4OH-H2O system. Additionally, the impurity ions in steamed ammonia liquid waste play a key role in the nucleation and crystallization of vaterite, which could affect the formation of single-phase vaterite. The obtained results provided a novel method for the preparation of single vaterite particles with the utilization of CO2 and offered a selective method for the extensive utilization of steamed ammonia liquid waste.

Influence of Na+ on vaterite formation, content and yield using steamed ammonia liquid waste as a calcium source

“…L. Freddy's 46 research indicated that the pH increased when the concentrations of CaCl 2 and NaCO 3 increased, and the pH of the CaCl 2 and NaCO 3 reaction system is higher than that of the CaCl 2 and (NH 4 ) 2 CO 3 reaction system. However, our study is contrary to this result, as our previous research showed 47 that the pH of the steamed ammonia liquid waste is much higher than that of the same CaCl 2 concentration; the pH reached above 11. However, NaCl solution is a kind of salt and the pH is close to neutral, so the pH of the reaction system continues to decrease the higher the concentration of NaCl in the reaction system.…”