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Parameters affecting Mg(OH)2 extraction from serpentinites in lithuania for the purpose of CO2 reduction by mineral carbonation



Mineral sequestration has a great potential for abating CO2 emissions, especially at locations where no opportunities for CO2 geological storage exist. This article focuses on the mineral carbonation of magnesium silicates, that is, serpentinites, which offers an attractive option for CO2 emission mitigation in Lithuania. Mineral CO2 carbonation in a staged gas/solid process route is one of the most prospective approaches. The process was conducted in several steps. Firstly, extraction of the magnesium hydroxide from serpentinite via a solid/solid reaction between serpentinite and ammonium sulfate salt at a temperature interval of 500–540°C was carried out. The maximum Mg extraction (53.70 %) was obtained with the mass ratio of reactants of 2 g serpentinite/3 g ammonium sulfate, reaction temperature, and time of 520°C and 20 min, respectively. Secondly, the process of precipitation of Mg(OH)2 took place. The effect of precipitation of the Fe-containing compounds (first step) and the Mg(OH)2 (second step) was analyzed. At the pH of 8–10 and 10–12, compounds of Fe and Mg precipitated, respectively. The optimal Fe removal and Mg extraction was achieved at the pH of the ∼9.5 for the first step and at the pH of ∼11.50 for the second step. Finally, the carbonation of extracted magnesium hydroxide was accomplished and reached the effectiveness of 65 % after 15 min at 535°C, 51 bar. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 512–518, 2014