The solubility of selenate-AFt (3CaO·Al2O3·3CaSeO4·37.5H2O) and selenate-AFm (3CaO·Al2O3·CaSeO4·xH2O)

Evaluation of ettringite and hydrocalumite formation for heavy metal immobilization: Literature review and experimental study

“…Similarly, Baur and Johnson [31] found in their study of selenate tri-and monophase that the monophase was the stable phase above pH 12.0.…”

“…It is therefore necessary to conduct geochemical modeling in the specific system in order to evaluate the concentration of hazardous oxyanions in the pore solution. Baur and Johnson [31] modeled the solubility of selenate in the presence of monosulfate and selenate triphase, as well as in the presence of monosulfate and selenate monophase against pH. Their model showed that selenate monophase controlled selenate solubility to lower levels than ettringite at high pH values (>11.5).…”

“…M.Chrysochoou, D. Dermatas / Journal of Hazardous Materials 136 (2006) [20][21][22][23][24][25][26][27][28][29][30][31][32][33] …”

Stabilization/solidification of selenium-impacted soils using Portland cement and cement kiln dust

“…The X-ray diffractograms for the K, M and DM soil-cement slurry samples are arranged vertically, top to bottom, in each figure. Based on the work of Baur and coauthors [27][28][29], attempts were made in the Se(IV) and Se(VI) systems to verify the presence of CaSeO 3 , and Se(VI)-substituted ettringite (AFt) and monosulfate (AFm) phases, respectively.…”

“…This is in contrast to Ghosh-Dastidar et al [30] who found that the sorption of SeO 2 (g) on hydrated lime at elevated temperatures resulted in the formation of CaSeO 3 under SO 2 (g) deficient conditions, as confirmed by XRD. Likewise, Baur and Johnson [27,28] generated CaSeO 3 , but used neat aqueous experiments and synthetically generated monosulfate, ettringite and calcium silicate hydrate (CSH) phases. While they explicitly sought CaSeO 3 ·H 2 O in XRD spectra, no agreement could be attained for either the available PDF files with their measured XRD spectra (8 • , 16 • and 24 • 2Â), or the experimentally determined solubility product data, leading Baur and Johnson [27] to ultimately conclude that SeO 3 2− was incorporated into AFm phases at high Se concentrations.…”