Effect of time on the carbonation reaction of saline aquifers with controlled pH

摘要

This work investigated the effect of time on the carbonation reaction in synthetic saline solution, under mild conditions and with a controlled pH, aiming the mineral trapping of CO_2 on saline aquifers. The experiments were performed in a glass reactor at 40°C, 6 hours and atmospheric pressure. The saline solution and solid phase were characterized by Flame Atomic Absorption Spectroscopy (FAAS), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). This work demonstrated that the saline solution pH lowers to approximately 7-8 in the first hour of reaction (initial pH of approximately 10), remaining constant until the end of the reaction. Through the analysis by AAS, it was found that the concentration of Ca ions in the brine decreases with time. A greatest reduction in the Ca ions concentration occurs within the first two hours of reaction, remaining constant in the others hours. The Mg concentration showed the trend of the final concentration remains close to initial concentration, even with the carbonates precipitation. SEM analysis indicated that the precipitates obtained had morphology similar to that found for various forms of calcium carbonate (i.e. calcite and aragonite). FTIR analysis shows characteristic bands of carbonates, which agrees with the results of the analysis by SEM.