Acidithiobacillus ferrooxidans: performances on the low-grade polymetallic oxidized-manganese and sulfur-nickel ores redox system

A simultaneous bioleaching process to extract nickel, cobalt, copper and manganese from polymetallic nodule and low-grade nickel sulfide ore by using Acidithiobacillus ferrooxidans is proposed in this study. Thermodynamic investigations and potential analysis showed that the selective leaching of Ni, Co, Cu, Mn is feasible. The electrochemical measurements reveal that A. ferrooxidans increases the potential difference between nodule anode and sulfide cathode. A. ferrooxidans leads to the negative shift of corrosion potential and the increment in electron release of the sulfur-containing substance, and accelerates the electron transfer and exchange current density in the nodule digestion. Under the optimal conditions, in the presence of A. ferrooxidans the final pregnant solution contained 0.86 g Ni/L, 56 mg Co/L, 0.62 g Cu/L, and 5.81 g Mn/L with the improvement of 5.1%, 4.1%, 5.9% and 4.9% referring to operation with sterile solution. The leaching rate of Ni, Cu, Co and Mn increases respectively by a factor of 0.17, 0.48, 0.10, and 0.093 in the A. ferrooxidans and Fe(III) medium relative to the Fe(III) alone, with a mean of 0.91, 0.70, 0.34 and 0.45 to the control.

Electron pair escape from fullerene cage via collective modes

Experiment and theory evidence a new pathway for correlated two-electron release from many-body compounds following collective excitation by a single photon. Using nonequilibrium Green’s function approach we trace plasmon oscillations as the key ingredient of the effective electron-electron interaction that governs the correlated pair emission in a dynamic many-body environment. Results from a full ab initio implementation for C60 fullerene are in line with experimental observations. The findings endorse the correlated two-electron photoemission as a powerful tool to access electronic correlation in complex systems.

Electron Release and Proton Acceptance Reactions of (dpp-BIAN)Mg(THF)3

(dpp-BIAN)Mg(THF)3 (1) (dpp-BIAN = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) and (PhCOO)2 react with splitting of the peroxide bridge and formation of the dimeric magnesium benzoate [(dpp-BIAN)MgOCOPh(THF)]2 (2). The reaction of 1 with PhCOOH yields the dimeric magnesium benzoate [(dpp-BIAN)(H)MgOCOPh(THF)]2 (3), whereas 1 and furanyl-2-carboxylic acid react with liberation of hydrogen and formation of (dpp-BIAN)Mg[OCO(2-C4H3O)]2 Mg(dpp-BIAN)(THF) (4). Compounds 2, 3, and 4 have been characterized by elemental analysis, IR spectroscopy, and X-ray structure analysis, compound 3 also by 1H NMR spectroscopy. The eightmembered metallacycles of the centrosymmetric dimers 2 and 3 are almost completely planar. The two magnesium atoms in 4 show different coordination spheres; one is surrounded by its ligands in a trigonal bipyramidal manner, the other one in a tetrahedral fashion. The Mg···Mg separations in 2, 3 and 4 are 4.236, 4.296, and 4.030 Å, respectively

Mechanism of tiron as scavenger of superoxide ions and free electrons

Sodium 4,5-dihydroxybenzene-1,3-disulfonate (tiron) has been reported to be an efficient chelator of certain metal ions, and a substrate in several enzyme reactions. Its small size facilitates cell entry and therefore modulates intracellular electron transfer reactions as an antioxidant by scavenging free radicals. Its reduction by electrochemical and enzymatic methods gives identical products; a semiquinone detectable by EPR spectroscopy. In a test of its use as a spin trap, in comparison with DMPO, tiron does not form a molecular spin-adduct but proves more functional as an electron trap. Electron addition to tiron is more facile than reduction of dioxygen as observed by the non-formation of DMPO-OOH spin-adduct in the system XO/HPX/O2/DMPO/tiron. Rather, it is the tiron semiquinone radical which is formed quantitatively with increasing concentration of hypoxanthine independent of oxygen concentration. These results offer explanation for the action of tiron and its suitability for measuring electron release in hypoxic conditions, and also for mitigating redox-induced toxicity in drug regimes by acting as an electron scavenger.