Antimony Sorption to Goethite: Effects of Fe(II)-Catalyzed Recrystallization

Abstract

The environmental mobility and bioavailability of antimony (Sb) are strongly influenced by sorption to Fe­(III) oxide minerals, such as goethite (αFeOOH). Exposure to aqueous Fe­(II), as occurs, for example, under reducing conditions in soils and sediments, catalyzes the recrystallization of goethite. Herein, we examine, for the first time, the effect of Fe­(II)-catalyzed goethite recrystallization on the sorption of co-associated Sb­(V). The use of an enriched aqueous 57Fe­(II) tracer provided direct evidence of Fe­(II)-catalyzed goethite recrystallization and revealed lower levels of recrystallization at higher Sb­(V) loadings. Goethite recrystallization caused increases in the total amount of sorbed Sb along with decreases in the percentage of sorbed Sb that was surface-bound (based on PO4 3– extractions). Extended X-ray absorption fine structure (EXAFS) spectroscopy at the Sb K-edge shows that goethite recrystallization led to increases in the coordination number (CN) for both edge-sharing and double-corner-sharing linkages between Sb­(V)–O and Fe­(III)–O octahedra. The CN increases are consistent with partial structural Sb­(V) incorporation into goethite, with the degree of incorporation increasing with the extent of recrystallization. Overall, the results indicate that Fe­(II)-catalyzed recrystallization of goethite caused a shift from Sb­(V) adsorption at the goethite surface to partial Sb­(V) incorporation into the goethite structure [via heterovalent substitution for up to ∼1.4 mol % Fe­(III)]. These results necessitate a re-evaluation of current concepts regarding the sorption of Sb to goethite. In particular, goethite should be considered as a dynamic phase whose solid structure (not just the reactive surface) may be available for Sb­(V) sorption via structural incorporation during Fe­(II)-catalyzed recrystallization.

Antimony (V) Adsorption at the Hematite–Water Interface: A Macroscopic and In Situ ATR-FTIR Study

“…In shooting range soils, EXAFS characterization indicated that Sb (V) was the major species [15]. Macroscopic and spectroscopic characterizations of soils and sediments have suggested that iron oxides, hydroxides, and oxyhydroxides are major sinks for Sb (V) species, and strong associations have been observed [14,16,17]. Consequently, many adsorption studies using pure iron mineral phases have been reported [10][11][12][13][17][18][19][20].…”

“…Macroscopic and spectroscopic characterizations of soils and sediments have suggested that iron oxides, hydroxides, and oxyhydroxides are major sinks for Sb (V) species, and strong associations have been observed [14,16,17]. Consequently, many adsorption studies using pure iron mineral phases have been reported [10][11][12][13][17][18][19][20]. Macroscopic studies coupled with surface complexation modeling using goethite as a mineral indicate that Sb (V) has strong affinity for goethite and the adsorption is pH-dependent, where Sb (V) retention decreased drastically above pH 6 [10].…”

Seasonal Temperature Oscillations Drive Contrasting Arsenic and Antimony Mobilization in a Mining‐Impacted River System

“…The initial component of this trend is consistent with previous work showing that small (<5%) levels of microbial Fe(III) oxide reduction can cause decreased Sb mobility (Burton et al, 2019). This can occur without Sb(III) formation (which appears to require considerably lower Eh than does As(III) formation; e.g., Mitsunobu et al, 2006) via Fe(II)-induced transformation or recrystallization of Sb(V)-bearing Fe (III) oxides, leading to occlusion of Sb(V) within the host Fe(III) oxide structure (Burton et al, 2019(Burton et al, , 2020.…”

“…In addition, microbially mediated reductive dissolution of As‐ or Sb‐bearing host phases (e.g., Fe(III) oxides) can trigger release of As/Sb species into solution (Burton et al, 2008; Fendorf, Nico, et al, 2010; Hockmann, Lenz, et al, 2014; Kocar & Fendorf, 2009; Kocar et al, 2006). While this is a well‐established driver of enhanced As mobility in sediments, recent evidence indicates that partial Fe(III) oxide reductive dissolution can instead cause decreased Sb mobility under reducing conditions (e.g., Burton et al, 2019, 2020). In addition, aqueous thiolated As(III)/(V) and Sb(III)/(V) species have been shown to play increasingly important roles under sulfidic conditions (e.g., Hockmann et al, 2020; Planer‐Friedrich et al, 2010).…”

Antimonate Sequestration from Aqueous Solution Using Zirconium, Iron and Zirconium-iron Modified Biochars

“…Ren et al 28 demonstrated the high removal capacity for As using Fe-Zr binary oxide. Being from the same group (group V), As and Sb share some similar properties, but also show contrasting interactions with Fe and organic moeities 29,30 .…”