Alkaline digestion of dunite for Mg(OH)_2 production: An investigation for indirect CO_2 sequestration

摘要

The sequestration of CO_2 by carbonating natural minerals has a great potential for secure reduction of net CO_2 emissions. Feedstock Mg-silicate minerals are usually converted into Mg rich solutions or Mg(OH)_2 before the carbonation process, due to the slow reaction kinetic of direct carbonation. The present work studied the alkaline digestion of Mg-silicate minerals into Mg(OH)_2 for CO_2 sequestration. Powdered dunite containing ~73 + 2 wt% of forsterite (Mg_2SiO_4) was dissolved using highly concentrated NaOH aqueous systems at 90 and 180 °C with varied NaOH concentration and duration of reaction. Thermal analysis and Rietveld Refinement Quantitative Phase Analysis (QPA) confirmed that an effective digestion of dunite was possible at 180 °C achieving 80 wt% of Mg(OH)_2. It was found that NaOH concentration in solution, temperature and duration of reaction significantly influence the progress of digestion.