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 SO3 addition (in the form of BaSO4, 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% SO3 possess the amorphous structure. Barite phase appears when the addition SO3 content increases to 5 wt%, and the amount of barite crystals increases with further increasing SO3 content. Furthermore, BaSO4 in borosilicate glass melts is more stable than that of Na2SO4. The sample S4 possesses SiO2 and BaSO4 phases in temperature range of 800–1150 °C. The SO3 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 SO3 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 SO42− (∼1.28 × 10−2 g m−2 d−1) after 28 days.