Search Results (5)

This review examines the impact of various aqueous electrolytes on hydrogen absorption and self-corrosion in magnesium (Mg) anodes. The discussion integrates both historical and recent studies to explore the mechanisms behind self-corrosion and anomalous hydrogen evolution (HE) under conditions of the Negative Difference Effect (NDE) and Positive Difference Effect (PDE). The focus is on the formation and oxidation of magnesium hydride in regions of active dissolution under NDE conditions. In the case of PDE, anodic dissolution occurs through the passive MgO-Mg(OH)₂ film, which shields the metal from aqueous electrolytes, thereby reducing hydrogen absorption and abnormal HE. The NDE conditions showed delayed reduction activity at the surface, attributed to a hydride phase within the corrosion product layer. Hydride ions were quantified through their anodic oxidation in an alkaline electrolyte, measured by the electric charge passed. The review also considers the role of de-passivating halide ions, electrolyte acidity buffering, and the addition of ligands that form stable complexes with Mg²⁺ ions, on the rates of hydride formation, self-corrosion, and anodic dissolution of Mg. The study evaluates species that either inhibit or promote hydrogen absorption and self-corrosion. Full article

The use of large quantities of phosphorus-containing fertilizers has resulted in an increase in phosphorus content in the groundwater system, and phosphorus can be adsorbed on the surface of carbonate rocks, affecting their dissolution process and thus carbon sequestration and sink enhancement in carbonate rocks. Therefore, in this study, limestone was exposed to 2 mg/L and 100 mg/L phosphate solutions for 12 d through static batch adsorption experiments. The hydrochemical results showed that in 100 mg/L phosphate solution, a substitution reaction occurred to produce CaHPO₄ precipitate, while the concentration of each ion in 2 mg/L phosphate solution was relatively stable and in dynamic equilibrium; combined with XRD and XPS analyses, the main mechanism of phosphate adsorption may be chemical precipitation, which is preferentially adsorbed to Ca sites on carbonate rocks, and the surface deposits are mainly CaHPO₄ and a small amount of Mg₂PO₄(OH). The FTIR spectra were obtained in the range of 1040 cm⁻¹–1103 cm⁻¹ for observed phosphate vibrations, and the υ₃ (asymmetric stretching) mode was more significant in the experimental group with a higher phosphate concentration. Raman spectra located near 149 cm⁻¹ and 275 cm⁻¹ involved Ca²⁺ or Mg²⁺ relative translations and vibrations, corroborating the FTIR spectroscopic results; a combination of XRD, XPS, FTIR, and Raman spectra confirmed that phosphate adsorption on limestone may be due to the interaction of electrostatic, chemical precipitation, and ligand exchange mechanisms. In addition, the SEM-EDS results showed that, with the combined effect of the water–rock chemical reaction and physical adsorption, metal–phosphorus phase precipitation was formed on the limestone surface, which promoted the dissolution of limestone and may have an unfavorable effect on the carbon sequestration and sinking of carbonate rocks. Full article

Titanium dioxide nanoparticles (TiO₂-NPs) are increasingly used in consumer products for their particular properties. Even though TiO₂ is considered chemically stable and insoluble, studying their behavior in biological environments is of great importance to figure their potential dissolution and transformation. The interaction between TiO₂-NPs with different sizes and crystallographic forms (anatase and rutile) and the strong chelating enterobactin (ent) siderophore was investigated to look at a possible dissolution. For the first time, direct evidence of anatase TiO₂-NP surface dissolution or solubilization (i.e., the removal of Ti atoms located at the surface) in a biological medium by this siderophore was shown and the progressive formation of a hexacoordinated titanium–enterobactin (Ti–ent) complex observed. This complex was characterized by UV–visible and Fourier transform infrared (FTIR) spectroscopy (both supported by Density Functional Theory calculations) as well as electrospray ionization mass spectrometry (ESI-MS) and X-ray photoelectron spectroscopy (XPS). A maximum of ca. 6.3% of Ti surface atoms were found to be solubilized after 24 h of incubation, releasing Ti–ent complexes in the micromolar range that could then be taken up by bacteria in an iron-depleted medium. From a health and environmental point of view, the effects associated to the solubilization of the E171 TiO₂ food additive in the presence of enterobactin and the entrance of the Ti–enterobactin complex in bacteria were questioned. Full article

The active form of vitamin D, 1α,25-(OH)₂D₃, not only promotes intestinal calcium absorption, but also regulates the formation of osteoclasts (OCs) and their capacity for bone mineral dissolution. Gal-3 is a newly discovered bone metabolic regulator involved in the proliferation, differentiation, and apoptosis of various cells. However, the role of galectin-3 (gal-3) in OC formation and the regulatory effects of 1α,25-(OH)₂D₃ have yet to be explored. To confirm whether gal-3 contributes to the regulatory effects of 1α,25-(OH)₂D₃ on osteoclastogenesis, osteoclast precursors (OCPs) were induced by macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor κB ligand (RANKL). TRAP staining and bone resorption analyses were used to verify the formation and activation of OCs. qPCR, Western blotting, co-immunoprecipitation, and immunofluorescence assays were used to detect gene and protein expression. The regulatory effects of gal-3 in OC formation after treatment with 1α,25-(OH)₂D₃ were evaluated using gal-3 siRNA. The results showed that 1α,25-(OH)₂D₃ significantly increased gal-3 expression and inhibited OC formation and bone resorption. Expression levels of OC-related genes and proteins, matrix metalloproteinase 9 (MMP-9), nuclear factor of activated T cells 1 (NFATc1), and cathepsin K (Ctsk) were also inhibited by 1α,25-(OH)₂D₃. Gal-3 knockdown attenuated the inhibitory effects of 1α,25-(OH)₂D₃ on OC formation, activation, and gene and protein expression. In addition, gal-3 was co-localized with the vitamin D receptor (VDR). These data suggest that gal-3 contributes to the osteoclastogenesis inhibitory effect of lα,25-(OH)₂D₃, which is involved in bone and calcium homeostasis. Full article

The addition of Fe²⁺ is considered an effective method for increasing methane production, but the added Fe²⁺ may not be absorbed by anaerobic microorganisms due to complex chemical reactions. In this study, ethylenediaminetetraacetic acid (EDTA) was used as a ligand of Fe²⁺ (EDTA-Fe) to promote the dissolution of Fe, and the anaerobic performances of kitchen wastes (KWs) in a semi-continuous reactor were studied. The results indicated that the biogas yields and methane contents were enhanced to 594–613 mL·g⁻¹VS_add·d⁻¹ and 63.6–64.4% at an organic loading rate (OLR) of 2.5 gVS_add·L⁻¹·d⁻¹ due to EDTA-Fe addition. Simultaneously, the EDTA-Fe was more effective than Fe²⁺ in preventing the acidification of KWs with a high OLR (5.0 gVS_add·L⁻¹·d⁻¹). In addition, the sequential extraction results showed that the water-soluble fraction of Fe in the R3 (EDTA-Fe addition) was 1.49-fold of that in the R2 with Fe²⁺ addition. The contents of coenzymes F420 and F430 were also improved 1.09 and 1.11 times, respectively. Mechanism analysis confirmed that the EDTA enhanced methane production and operational stability by promoting the dissolution of Fe and maintaining a high content of water-soluble Fe. Full article