The stability of the rare sodium antimonate, brizziite, and it's role in Sb mobility. (28th February 2018)

• Record Type: Journal Article
• Authors: Roper, Adam J.; Leverett, Peter; Murphy, Timothy D.; Williams, Peter A.
• Is Part Of: Mineralogical magazine. Volume 82:Number 1(2018)
• Page Start: 89
• Page End: 93
• Publication Date: 2018-02-28
• Subjects: brizziite, -- antimony, -- solubility, -- stability, -- chemical mineralogy, -- supergene zone; Mineralogy -- Periodicals; Mineralogy -- Great Britain -- Periodicals; 549.05
• DOI: 10.1180/minmag.2017.081.023
• Languages: English
• ISSNs: 0026-461X

Abstract

ABSTRACT: Synthesis and solubility studies of brizziite, NaSbO3, have been undertaken to determine the possible role of this rare secondary phase in the immobilization of Sb under supergene conditions and the conditions responsible for its formation in the supergene zone. Solubility studies were undertaken at T = 298.15 K. A value of ΔGf ө ) (NaSbO3, s, 298.15 K) = –806.66 ± 1.4 kJ mol –1 was derived. Calculations involving tripuhyite, FeSbO4, byströmite, MgSb2 O6, ordoñezite, ZnSb2 O6 and rosiaite, PbSb2 O6, show that brizziite is a thermodynamically stable phase only at negligible activities of Pb 2+ (aq) at high pH and high salinity. Calculations involving mopungite Na[Sb(OH)6 ] combined with reported mineral associations suggest that mopungite is the thermodynamically unstable precursor to brizziite and its presence in natural settings must be due to kinetic stability. This explains why brizziite is such a rare secondary phase and therefore why it cannot exert any significant influence on the dispersion of Sb in the supergene environment.