Effect of Oxalic Acid on Heat Pretreatment for Serpentine Carbonation

A novel pretreatment method for the mineral serpentine was proposed to develop an effective carbonation process for CO2 sequestration. Basically, the method involved preheating a mixture of oxalic acid and serpentine and the subsequent aqueous carbonation. The addition of oxalic acid was found to stimulate the decomposition of serpentine during heat treatment. X-ray diffraction analysis revealed that serpentine is transformed into magnesium oxalate and magnesium oxide by heat treatments at 200°C and 500°C, respectively. The addition of oxalic acid was found to enhance the overall carbonation reaction owing to the formation of magnesium oxide during heat treatment. Thermogravimetric analysis showed that approximately 70% of the Mg2+ was transformed into magnesium oxide. Using this method, a carbonation rate as high as 72% could be obtained by aqueous carbonation at 100°C under 4 MPa. This novel method can potentially reduce the high energy cost and unavoidable use of expensive chemicals for pH control.

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