Parameters expediting the thermal conversion of Ba-exchanged zeolite a to monoclinic celsian

Abstract

Four samples of Ba-exchanged zeolite A, bearing small residual amounts of Na (0.27, 0.43, 0.58, and 0.74meq/g), were thermally treated in the temperature range 200-1500°C for times up to 28 hours. The same samples were pressed at 30 and 60MPa to form cylindrical pellets which were thermally treated at 1300°C for 5 hours. All materials were characterized by room temperature XRD. The sequence of thermal transformations that Ba-exchanged zeolite A undergoes (zeolite → amorphous phase → hexacelsian → monoclinic celsian) and the strong mineralizing action developed by Na are confirmed. Pressing the Ba-exchanged zeolite A powder-like samples to obtain cylindrical pellets is found to expedite the sluggish final phase transition hexacelsian → monoclinic celsian. The optimum residual Na content of Ba-exchanged zeolite A for transformation into monoclinic celsian is assessed to be between 0.27 and 0.43meq/g. Copyright © 2010 A. Marocco et al.