A New Aqueous Mineral Carbonation Process Utilizing Bipolar Membrane Electrodialysis

Monday, November 8, 2010: 4:05 PM
151 F Room (Salt Palace Convention Center)
Yoshinobu Abe1, Hiroki Nagasawa1, Atsushi Iizuka2, Akihiro Yamasaki3 and Yukio Yanagisawa1, (1)Department of Environment Systems, The University of Tokyo, Kashiwa, Chiba, Japan, (2)Research Center for Sustainable Materials & Engineering, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, Japan, (3)Department of Materials and Life Science, Seikei University, Musashino, Japan

A new aqueous mineral carbonation process which utilizes bipolar membrane electrodialysis was proposed. The proposed process consists of four unit operations, (a) acid leaching of alkaline metals (Ca2+ /Mg2+) from mineral compounds, (b) carbonate precipitation by addition of Na2CO3, (c) acid /alkaline regeneration from salt solution with bipolar membrane electrodialysis, and (d) Na2CO3 generation via absorption of CO2 into NaOH. In the acid leaching step, alkaline metals are extracted from mineral compounds such as alkaline rocks, concrete waste, and steel making slag. In this operation, HNO3 solution is adopted as a leaching solution. In the carbonation sedimentation step, by adding Na2CO3 solution into the leaching solution, sediment of carbonate such as CaCO3 or MgCO3 is obtained and NaNO3 solution is remained. In the acid /alkaline regeneration step, HNO3 solution and NaOH solution are regenerated from NaNO3 solution via bipolar membrane electrodialysis treatment. Regenerated HNO3 solution is then recycled to the acid leaching step. In the Na2CO3 generation step, regenerated NaOH solution is contacted with the gaseous CO2 to form Na2CO3 solution. Exhaust gas from power plant can be directly used without compression. Experimental studies were conducted to confirm the technical feasibility of this process. Results demonstrate that the combination of acid leaching and carbonation sedimentation enhances the utilization of alkaline metals in mineral compounds. Also, HNO3 and NaOH were successfully regenerated from NaNO3 solution. This result suggests that acid and alkaline solution can be used cyclically in this process.


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