Title page for ETD etd-05072012-224907


Type of Document Master's Thesis
Author Ma, Juan
Author's Email Address mjuan@vt.edu
URN etd-05072012-224907
Title CO2 Mineralization Using Reactive Species
Degree Master of Science
Department Mining and Minerals Engineering
Advisory Committee
Advisor Name Title
Yoon, Roe-Hoan Committee Chair
Adel, Gregory T. Committee Member
Luttrell, Gerald H. Committee Member
Keywords
  • CO2 sequestration by mineralization
  • Magnesium/Calcium ion
  • pH controlling
Date of Defense 2012-04-24
Availability unrestricted
Abstract
To address the environmental changes associated with increasing levels of atmospheric CO2, a possibility of mineralizing CO2 with the species such as Ca2+ and Mg2+ ions that are already present in sea water was studied. A series of experiments conducted at temperatures in the range of 20 to 40oC showed that the activation energy for the formation of nesquehonite (MgCO33H2O) is 64.6 kJ/mol. It was found that the activation energy barrier can be readily overcome by simple agitation and heating at slightly elevated temperatures, e.g., 40oC. The kinetics of mineralization and the %Mg2+ ion utilization varies depending on energy dissipation rate, temperature, pH, and NaCl concentration. The maximum Mg2+ ion utilization achieved was 86%. Thermodynamic calculations were carried out to construct the species distribution diagrams, predict the pH of CO2 mineralization, and to predict %Mg ion utilization (or extraction) from sea water.

To address the issues concerning the acidification of sea water during CO2 mineralization, spent solutions were treated with basic minerals such as limestone and olivine. It was found that in the presence of these minerals the pH rises to the pH of minimum solubility of the buffering mineral. The pH of minimum solubility of limestone is 8.3 and that of olivine is 8.6. Other means of pH neutralization were also discussed.

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