Multiple stages of aqueous alteration along fractures in mudstone and sandstone strata in Gale Crater, Mars

The effect of pH and hydrogen bond donor on the dissolution of metal oxides in deep eutectic solvents

Atmospheric acid leaching mechanisms and kinetics and rheological studies of a low grade saprolitic nickel laterite ore

Despite stated in some highly cited articles, magnetite is devoided of peroxidase activity In fact, this very stable mixed valence FeII O⋅FeIII 2 O3 complex is not catalytically competent to oxidize standard peroxidase substrates, especially at the biologically relevant pH value of 74 In addition, magnetite whose deleterious redox activity has been suspected in Alzheimer's disease brain damages, does not significantly interact with amyloid peptide Aβ in vitro, and is not able to induce, either in the presence or absence of Aβ, the reductive activation of dioxygen, the first step of an oxidative stress In fact, this highly insoluble mineral iron derivative is probably not involved in the oxidative damage of brain neurons of patients with AD

Magnetite Fe3O4 Has no Intrinsic Peroxidase Activity, and Is Probably not Involved in Alzheimer's Oxidative Stress

Fungal assisted bioleaching process optimization and kinetics: Scenario for Ni and Co recovery from a lateritic chromite overburden

Magnetite (Fe3O4) is a key economically valuable component in iron ore and is extracted by dissolution processes, but among the Fe (oxyhydr)oxides its solubility behavior is one of the least understood. The objective of this study was to improve understanding of magnetite dissolution mechanisms leading to thermodynamic equilibrium by comparing the dissolution of two solid samples, one synthetic and one industrial, using oxalic, sulfuric, and nitric acids at varying concentrations and temperatures. Of the three solid-liquid systems investigated, only the system consisting of magnetite and oxalic acid reached an equilibrium state within the duration of an individual experiment (6 h). In this system, increasing the acid concentration resulted in a significant increase in the equilibrium concentration of dissolved Fe. When dissolving synthetic and industrial magnetite, increasing the temperature not only increased the rate of reaction but also affected the concentration of dissolved Fe. Significant effects were observed when increasing the temperature from 15 to 35°C, but only slight differences were seen on further increases in temperature. Observations regarding the equilibrium state of the sulfuric and nitric acid systems could not be made because equilibrium was not reached. The most important individual observation regarding the equilibrium state of the nitric- and sulfuric-acid systems seems to be that in future studies a much longer reaction time is necessary, due to slow kinetics of the dissolution mechanism. A proton-based mechanism has been hypothesized as the one governing the dissolution of magnetite by these two acids, but only the dissolution of the industrial sample yielded results that were similar for these two acids and consistent with that hypothesis.

Acidic dissolution of magnetite: experimental study on the effects of acid concentration and temperature

Acidic dissolution of hematite: Kinetic and thermodynamic investigations with oxalic acid

Influence of Water Quality on Corrosion of Multi-Oxide Engineering Ceramics

The object of the research was to compare the corrosion resistance of three types of multioxide technical ceramics in hydrofluoric acid containing aqueous media according to a full factorial experimental plan with pH and fluoride ion concentration as variables. The samples were a silicon carbide doped aluminum silicate material, and two membrane coated aluminum silicates with one containing a membrane on both sides of the ceramic plate. The substrates contained more additives on alumina, while the membrane coats were of higher grade aluminum oxide. The samples were shaken in containers for up to two weeks, and their remaining hardness and weight losses were measured. Daily samples drawn from the liquid phase were analyzed for dissolved components. With respect to all measured properties, fluoride concentration affected the materials more detrimentally than alterations in pH.

Marju Mannila

Papers

Acidic dissolution of magnetite: experimental study on the effects of acid concentration and temperature

Acidic dissolution of hematite: Kinetic and thermodynamic investigations with oxalic acid

Influence of Water Quality on Corrosion of Multi-Oxide Engineering Ceramics

Influence of Hydrofluoric Acid Concentration and pH on Corrosion of Porous Multi-Oxide Engineering Ceramics