The mechanism of the sodalite-to-cancrinite phase transformation in synthetic spent Bayer liquor

Abstract The precipitation of zeolite, sodalite and cancrinite and subsequent phase transformations were investigated under a variety of conditions in sodium aluminate liquor. At sufficiently high SiO 2 relative supersaturation, amorphous sodium aluminosilicate and zeolite precipitated at temperatures as high as 160°C. They subsequently transformed to sodalite and finally to cancrinite. Thus the sequence of the transformation of phases is: [Aluminosilicate species]→Amorphous phase→Zeolite (Linde A)→Sodalite→Cancrinite. It was found that sodalite did not transform to cancrinite in the absence of a liquid medium. The transformation of sodalite to cancrinite was demonstrated to involve a solution-mediated mechanism with sodalite dissolution and subsequent cancrinite precipitation. Neither the amorphous phase nor the zeolite phase precipitates at typical spent Bayer liquor SiO 2 supersaturation.

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