Antimony

About: Antimony is a research topic. Over the lifetime, 11450 publications have been published within this topic receiving 155660 citations. The topic is also known as: Sb & element 51.

Antimony and arsenic biogeochemistry in the western Atlantic Ocean

Abstract: The subtropical to equatorial Atlantic Ocean provides a unique regime in which one can examine the biogeochemical cycles of antimony and arsenic. In particular, this region is strongly affected by inputs from the Amazon River and dust from North Africa at the surface, and horizontal transport at depth from highlatitude northern (e.g., North Atlantic Deep Water) and southern waters (e.g., Antarctic Bottom and Intermediate Waters). As a part of the 1996 Intergovernmental Oceanographic Commission’s Contaminant Baseline Survey, data for dissolved As(III+V), As(III), mono- and dimethyl arsenic, Sb(III+V), Sb(III), and monomethyl antimony were obtained at six vertical profile stations and 44 sites alongthe 11,000 km transect from Montevideo, Uruguay, to Bridgetown, Barbados. The arsenic results were similar to those in other oceans, with moderate surface depletion, deep-water enrichment, a predominance of arsenate (>85% As(V)), and methylated arsenic species and As(III) in surface waters that are likely a result of phytoplankton conversions to mitigate arsenate ‘‘stress’’ (toxicity). Perhaps the most significant discovery in the arsenic results was the extremely low concentrations in the Amazon Plume (as low as 9.8 nmol/l) that appear to extend for considerable distances offshore in the equatorial region. The very low concentration of inorganic arsenic in the Amazon River (2.8 nmol/l; about half those in most rivers) is probably the result of intense iron oxyhydroxide scavenging. Dissolved antimony was also primarily in the pentavalent state (>95% antimonate), but Sb(III) and monomethyl antimony were only detected in surface waters and displayed no correlations with biotic tracers such as nutrients and chlorophyll a. Unlike As(III+V)’s nutrient-type vertical profiles, Sb(III+V) displayed surface maxima and decreased into the deep waters, exhibitingthe behavior of a scavenged element with a strongatmospheric input. While surface water Sb had a slight correlation with dissolved Al, it is likely that atmospheric Sb is delivered with combustion byproducts and not from mineral aerosols. In the Amazon Plume, antimony concentrations dropped substantially, and an Amazon River sample had a concentration (0.25 nmol/l) that was less than one-fourth those found in other major rivers. Usingthese river data, and estimates of atmospheric fluxes based on

Hydrothermal-synthesized SrTiO3 photocatalyst codoped with rhodium and antimony with visible-light response for sacrificial H2 and O2 evolution and application to overall water splitting

Abstract: The codoping effect of antimony on the photocatalytic activity of visible-light-driven SrTiO 3 doped with rhodium (SrTiO 3 :Rh) was investigated. SrTiO 3 doped with rhodium and antimony (SrTiO 3 :Rh/Sb) prepared by a hydrothermal method was found to be active for photocatalytic H 2 evolution from an aqueous methanol solution and O 2 evolution from an aqueous silver nitrate solution under visible light irradiation, although SrTiO 3 doped with rhodium and no antimony was active only for the H 2 evolution. Photocatalytic activities of SrTiO 3 :Rh/Sb were strongly dependent on the ratio of codopant to dopant (Sb/Rh). Diffuse reflection spectroscopy (DRS), electron spin resonance (ESR), Raman, and action spectrum analyses revealed the contribution of rhodium and antimony to visible-light response of SrTiO 3 :Rh/Sb. Unstable and reversible Rh 3+ ions in oxidation state were the superior species for the H 2 evolution. On the other hand, Rh 3+ ions stabilized by codoping of antimony without the formation of Rh 4+ ions and oxygen defects which would work as undesirable recombination sites between photogenerated electrons and holes played an important role in the O 2 evolution. Moreover, when an IrO X cocatalyst was loaded on the surface of the SrTiO 3 :Rh/Sb photocatalyst, the photocatalytic activity of the O 2 evolution drastically increased. The apparent quantum yield for the H 2 evolution over Pt(0.3 wt%)/SrTiO 3 :Rh(1%)/Sb(1%) and the O 2 evolution over IrO X (3.0 wt%)/SrTiO 3 :Rh(1%)/Sb(1%) at 420 nm were 0.8% and 4.5%, respectively. The Z -scheme system composed of Ru(1.0 wt%)/SrTiO 3 :Rh(2%) as a H 2 -evolving photocatalyst, IrO X (3.0 wt%)/SrTiO 3 :Rh(1%)/Sb(1%) as an O 2 -evolving photocatalyst, and an Fe 3+ /Fe 2+ redox couple as an electron mediator showed photocatalytic activity for overall water splitting under visible light irradiation.