Soluble secondary minerals of antimony in Pezinok and Kremnica (Slovakia) and the question of mobility or immobility of antimony in mine waters

Abstract

Environmental contextAntimony enters the environment from tailings and mines but there are widely divergent statements about its mobility in the environment. This work addresses the question of mobility of Sb by a combination of mineralogical and geochemical studies. AbstractThis work characterises two occurrences with an abundance of the supergene Sb minerals brandholzite [Mg[Sb(OH)6]2·6H2O], klebelsbergite [Sb4O4(OH)2(SO4)] and peretaite [CaSb4O4(OH)2(SO4)2·2H2O]. Brandholzite forms from near-neutral waters, where stibnite (Sb2S3) decomposes in the presence of abundant carbonates. The SbIII sulfates form from acidic waters, where stibnite decomposes in the presence of marcasite or pyrite (FeS2). These initial supergene minerals form rapidly (brandholzite within weeks) and supply Sb into local waters. Calculation of saturation indices from underground water (present study) and many waters discharged from Sb mines (data from the literature) show that brandholzite (and related soluble Sb minerals) are undersaturated. Hence, if they do exist, they should dissolve. Insoluble Sb phases, such as tripuhyite (FeSbO4) are grossly supersaturated, but do not form (or form very slowly). Hence, we conclude that the mobility of antimony observed in geochemical studies is due to the solubility of the initial supergene minerals. The immobility of antimony stated in mineralogical studies is due to the slow but persistent formation of insoluble tripuhyite. When the kinetics of formation of these minerals are taken into account, the widely divergent statements about mobility or immobility of antimony in the environment can be reconciled.

Processes of metastable-mineral formation in oxidation zones and mine waste

“…The aqueous solutions analysed are always supersaturated with respect to tripuhyite, considered to be the ‘ultimate sink’ of Sb in near-surface environments (Leverett et al , 2012). Field observations show that tripuhyite forms only very slowly (Majzlan et al , 2016a) and is preceded by a series of phases with greater solubility and lesser stability (e.g. Borčinová-Radková et al , 2017).…”

The Release of Antimony from Mine Dump Soils in the Presence and Absence of Forest Litter

“…The latter was mobilized from soils, independent of the soils’ properties, after the addition of external organic matter in the form of beech forest litter [49]. Several other authors also wrote that the tendency of Sb to be leached into soil solution or remain sequestered in solid phases, particularly in partly weathered dump material, depends on various factors, including the primary host minerals and the conditions governing precipitation of secondary Sb-hosting phases [57,58,59]. Furthermore, particularly important are the effects of desorption vs. resorption on the components of the soil solid phase, which are strongly related both to pH and redox conditions [1,3].…”

Chapmanite [Fe<sub>2</sub>Sb(Si<sub>2</sub>O<sub>5</sub>)O<sub>3</sub>(OH)]: thermodynamic properties and formation in low-temperature environments

“…There is not even a small window of p conditions under which both competing phases would be undersaturated. It must be pointed out that tripuhyite, and likely also schafarzikite, possess dense structures whose formation from low-temperature fluids is kinetically inhibited (Majzlan et al, 2016). Therefore, rapid transformation of chapmanite to schafarzikite or tripuhyite should not be expected.…”