Microstructure, sulfate retention, and aqueous stability of barite-borosilicate glass-ceramics

Abstract In order to increase the solubility of sulfate in glass matrix, barite−borosilicate glass-ceramics were proposed and prepared by melt quenching method. The effects of SO 3 addition (in the form of BaSO 4 , 0–8 wt%, abbreviated as S0 S8) on microstructure, phase structure, and aqueous stability of barite–borosilicate glass-ceramics were studied. The sulfate retention of the glass-ceramics was evaluated. The results show that the samples with addition of 0–4 wt% SO 3 possess the amorphous structure. Barite phase appears when the addition SO 3 content increases to 5 wt%, and the amount of barite crystals increases with further increasing SO 3 content. Furthermore, BaSO 4 in borosilicate glass melts is more stable than that of Na 2 SO 4 . The sample S4 possesses SiO 2 and BaSO 4 phases in temperature range of 800–1150 °C. The SO 3 content in the sample S4 remains almost unchanged when the temperature increases from 800 to 1050 °C, and decreases rapidly with further increasing temperature. About 2.17 wt% of SO 3 can be retained in the sample S6 after melting at 1200 °C. Moreover, the normalized leaching rates of Na and B of the samples S4, S6, and S8 after 28 days are one order of magnitude higher than that of the sample S0. The sample S6 has a lower normalized leaching rate of SO 4 2− (∼1.28 × 10 −2  g m −2  d −1 ) after 28 days.