Increased Solubility and Bioavailability of Hydroxy-Cr(III) Precipitates in the Presence of Hydroxamate Siderophores.

Siderophores are a diverse group of low molecular weight biogenic metallophores with a particular affinity for Fe(III) but they also have potential to complex a number of other polyvalent metal cations, including Cr(III). Here we show that two hydroxamate siderophores, desferrioxamine B and rhodotorulic acid, at environmentally relevant concentrations, facilitate the dissolution of hydroxy-Cr(III) precipitates from a common layer silicate. Desferrioxamine B and rhodotorulic acid induced maximum initial Cr dissolution rates of 11.

Dissolution of Al-Substituted Goethite in the Presence of Ferrichrome and Enterobactin at pH 6.5.

Naturally occurring goethites often show Al for Fe substitution approaching 33 mol% Al. This substitution has potential to influence the rate of goethite dissolution and therefore the supply of bioavailable Fe. Siderophores such as ferrichrome and enterobactin have considerable potential to dissolve Fe from Fe rich minerals, including Al-substituted goethites.

Simultaneous release of Fe and As during the reductive dissolution of Pb-As jarosite by Shewanella putrefaciens CN32.

Jarosites are produced during metallurgical processing, on oxidized sulfide deposits, and in acid mine drainage environments. Despite the environmental relevance of jarosites, few studies have examined their biogeochemical stability. This study demonstrates the simultaneous reduction of structural Fe(III) and aqueous As(V) during the dissolution of synthetic Pb-As jarosite (PbFe(3)(SO(4),AsO(4))(2)(OH)(6)) by Shewanella putrefaciens using batch experiments under anaerobic circumneutral conditions.

Reactions of lysine with montmorillonite at 80 degrees C: implications for optical activity, H+ transfer and lysine-montmorillonite binding.

Amino acid-smectite interaction may have catalyzed prebiotic reactions essential for the emergence of life. Lysine solutions (0.05 M) were reacted with Na-smectite in adsorption-desorption experiments.

Investigations into the kinetics and thermodynamics of Sb(III) adsorption on goethite (alpha-FeOOH).

This study reports thermodynamic and kinetic data of Sb(III) adsorption from single metal solutions onto synthetic aqueous goethite (alpha-FeOOH). Batch equilibrium sorption experiments were carried out at 25 degrees C over a Sb:Fe molar range of 0.005-0.

Influence of hydrology on heavy metal speciation and mobility in a Pb-Zn mine tailing.

Among the inorganic toxicants of greatest concern in mine tailings, Pb, Zn, Cu, Cd and As figure prominently due to their abundance and potential toxicity. Here we report on their biolability and solid-phase speciation in two sediment cores subject to variable hydrological regimes at an abandoned pyritic mine tailing. The oxic conditions of well-drained sediments induced pyrite oxidation and the subsequent liberation of H+, SO4(2-) and considerable quantities of Fe(III), which precipitated as goethite.

Copper-glyphosate sorption to microcrystalline gibbsite in the presence of soluble Keggin Al13 polymers.

Among the most reactive yet largely neglected adsorbents of toxicant species occurring in acidic aquatic environments are the epsilon-Keggin Al13 polyoxocations [AlO4Al12(OH)24(H2O)12(7+)], known generally as Al13 polymers. Here, we report on the sorption of Cu(II), a common ingredient of pesticides, and glyphosate {N-[phosphonomethyl]glycine (PMG)}, a widely applied herbicide, to microcrystalline gibbsite [gamma-Al(OH)3] in the presence of soluble Al13 polymers over the pH range 4-7. In the presence of gibbsite and soluble Al13 polymers, dissolved Cu(II) decreased gradually with pH, achieving a minimum at pH 5.

Influence of organic ligands on Cr desorption from hydroxy-Cr intercalated montmorillonite.

Retention of metals as hydroxy precipitates on mineral surfaces is an important process maintaining environmental quality. Hydroxy precipitates of Cr(III) are particularly important because appreciable mobilisation of intercalated, hydrolysed Cr from montmorillonite is currently thought to occur only via oxidative dissolution. The present study examines the potential of oxalate, tartrate, and citrate to desorb Cr from both hydroxy-Cr and hydroxy Al-Cr precipitates sorbed to montmorillonite.