[en] Rates of proton-promoted dissolution of bunsenite [NiO(s)] are coupled to titrations for adsorbed protons at the dissolving surface. The results confirm the finding of G. Furrer and W. Stumm that the rate order with respect to protons at pH < ZPC is given by the metal valence; rate orders are close to 2 for NiO(s) and BeO(s) dissolution even though these minerals are structurally distinct. The rate-controlling step is hydration and detachment of a surface complex, and in acidic solutions this complex resembles the hydrated metal. The authors extend this model by speculating that the proton stoichiometry reflects the hydrolysis of surface species and varies with solution pH. This hypothesis leads to rate orders with respect to protons that are nonintegers and that decrease with increasing pH to the ZPC. This dissolution behavior will be observed for oxide solids containing metals that hydrolyze at pH values significantly below the ZPC, such as Al₂O₃, and may account for the low rate orders observed for complicated mixed-oxide solids. This model predicts that the reactivities of partly hydrolyzed surface complexes are greater than those of the fully hydrated metals, and therefore establishes close consistency between the processes of metal removal from a dissolving surface and ligand exchange around the corresponding metal in solution. Interest in the movement of mass at the solid-aqueous interface comes from a wide range of disciplines. Chemists and material scientists, for example, are trying to develop biomimetic methods for materials synthesis that do not require toxic solvents or large amounts of energy. Earth scientists are trying to develop predictive models for the sorption of toxicants to minerals in shallow aquifers and chemical engineers are interested in chemical methods of eliminating oxide corrosion products in hazardous settings, such as in the cooling tubes of a nuclear reactor

[en] Systematic in vitro studies on singlet oxygen luminescence kinetics have been carried out reconciling recently published contradictory results reported for sub-cellular singlet oxygen kinetics obtained with two different approaches: single cell - and cell ensemble measurements. The singlet oxygen luminescence kinetics in two cell lines were investigated after incubation with three different photosensitizers. In each case a strong dependency of the singlet oxygen luminescence kinetics from the applied illumination already at very low doses was observed. Analysis of the obtained results allows judging the usability of the two approaches for detailed investigation of sub-cellular singlet oxygen kinetics. Intrinsically existing detection limits as well as local heating during the measurement will be discussed

[en] Highlights: •Flow microcapillary based monitoring of soluble corrosion product formation. •Influence of the buffering system on Mg–Y–RE alloy corrosion mechanisms. •Presence of Ca/P slows Y/Nd intermetallic dissolution and related cathodic reaction. •Presence of carbonates partially counteracts detrimental Tris complexing effect. -- Abstract: The effect of body fluids inorganic species on element-specific dissolution of a Mg–Y–Rare earth elements (RE) alloy was investigated by flow microcapillary plasma mass spectrometry. A new important aspect of this method is the online monitoring of precipitation dynamic in solution. Adding calcium and phosphate to unbuffered NaCl solutions beneficially stabilises the corrosion products formed. But the choice of the buffer is critical for the Mg–Y–RE alloy degradation mechanisms. Tris(hydroxymethyl)aminomethane leads to strong active dissolution because it complexes the ionic species necessary for corrosion product stabilisation whereas a thin partially protective layer can form in borate and carbonate buffered solutions