Influences of Particles and Aquatic Colloids on the Oxidation of Sb(III) in Natural Water

Abstract

Antimony (Sb) is a hazardous metalloid that is ubiquitous in the environment. Its toxicity and mobility are strongly influenced by the valence state. Particles and aquatic colloids are abundant in natural water; however, there is little understanding of how Sb­(III) is oxidized by these substances. In this study, cross-flow ultrafiltration is used to separate the substances in natural water samples into macroparticles (>1 μm), microparticles (1–0.1 μm), colloids (<0.1 μm, >1 kDa), and dissolved substances (<1 kDa). The effects of these different components on oxidation of Sb­(III) were comprehensively investigated by kinetic measurements with the aid of quenchers under simulated sunlight irradiation and dark conditions. The results show that 95% of the Sb­(III) oxidation process was done by the particles (macroparticles and microparticles) and aquatic colloids (colloids and dissolved substances). Macroparticles oxidized Sb­(III) via active substances such as natural organic matter (NOM) and iron oxides, while colloids impacted the oxidation process via dissolved organic matter (DOM) with active groups such as amino acid-like organic matter. The dissolved substances oxidized Sb­(III) via iron ions and some micromolecule organic matter. Common free ions in natural water had no effect on the oxidation of Sb­(III). The reactive oxygen species (ROS) and excited triplet states of DOM (3DOM*) produced by oxidants under photoirradiation can accelerate the oxidation of Sb­(III). These results indicate that Sb­(III) can be oxidized to Sb­(V) rapidly with the help of sunlight in the presence of particles and colloids, and this oxidation process will greatly influence the fate of Sb­(III) in natural water.

The efficacy of Pb, As(v) and Sb(iii) removal by biochar is determined by solution chemistry

“…61 Sb(III) oxidation solely by O 2 is slow, 62 but active substances such as Fe(III)-NOM can accelerate Sb(III) oxidation. 63 In this study, SAWC oxidised Sb(III) to the more mobile Sb(V) in all solutions tested, which explains the generally low removal of Sb(III) (2.3 < log K d < 3.3). The BC related oxidation of Sb is illustrated in Fig.…”

Co-transport of ferrihydrite–organic matter colloids with Sb(v) in saturated porous media: implications for antimony mobility

“…Therefore, it is expected that Fe–OM colloids, which are ubiquitous in subsurface environments, play a crucial component in Sb mobility in natural environments. 25…”

“…24 Sb can usually form associations with low-molecular-weight ligands and interact with Fe-OM colloids in aquatic environments. 1,25 For example, low Fe(II) and high HA concentrations suppressed the formation of thermodynamically more stable goethite and hematite, which benefit the formation of substantial amounts of Fe(III)-OM colloids that affect the mobility and speciation of Sb under OM-rich conditions. 26 This is also evidenced by Hockmann et al, 27 who observed that >15% of Sb(V) occurred in the colloidal phase at a molar Fe/Sb ratio of 400.…”

“…Therefore, it is expected that Fe-OM colloids, which are ubiquitous in subsurface environments, play a crucial component in Sb mobility in natural environments. 25 The co-transport behaviors of colloids and multiple contaminants have been systematically investigated by utilizing packed column experiments. [29][30][31][32][33] Depending on the physical and solution chemistry conditions of the column system, colloids can either benefit from or prohibit the transport of pollutants under different experimental conditions.…”