In this study, three GR/Cu(II) (Green Rust/Cu(II)) composites (GR SO4 /Cu(II), GR CO3 /Cu(II), and GR Cl /Cu(II)) were synthesized and used to activate dioxygen under weakly acidic conditions. The change in the mechanism caused by three interlayer anions, CO 3 2− , SO 4 2− , and Cl − , was discussed for the first time. Both Cu(I) and H 2 O 2 were generated during GR/Cu(II)-induced dioxygen activation, resulting in the rapid degradation of acetaminophen. The inconsistency between the reaction constant rates and oxidation reduction potential (ORP) order revealed the effects of the various types of interlayer ions. To further reveal the effects of the anions, the variations in the morphology and valence states of the composites were examined. To identify the rate-controlling step of dioxygen activation by the three composites, the production of reactive oxygen species (ROS) was investigated and compared. The combination of interlayer anions and metal ions changed the oxide morphology of the solid-phase materials. Furthermore, changes in the content of the reductive species (Fe(II) or Cu(I)) either enhanced or inhibited specific reaction steps. The results from this study could deepen our understanding of the effects of anions on dioxygen activation by transition metals and provide a basis for the study of oxidation reactions and mechanisms in the presence of various anions.
It is of great importance to separate potassium salts from carbonate-based lakes, especially the low-[K+] but high-[Na+] brine which has been discovered around the world. Here the phase diagram of the quaternary system Na+, K+//Cl–, CO32––H2O was experimentally studied at 298.15 K via the method of isothermal evaporation, and the results corrected the previous diagram reported by Blasdale (J. Am. Chem. Soc.1923, 45, 2935–2946). The type of salts appeared and their solubility during the evaporation, and the density vs composition diagram and the pH values were plotted based on the experimental data. It was found that there were six invariant points, seven univariant curves, and five crystallization fields in the equilibrium phase diagram. To extract single-salt of potassium, certain areas in the Na+, K+//Cl–, CO32––H2O diagram were chosen to be acidified by the compressed CO2, and potassium in the form of KHCO3 was precipitated from the mother solution. The compressed CO2 was able to avoid formation of NaKCO3·6H2O during evaporation of the original system Na+, K+//Cl–, CO32––H2O. Based on experiment data, the region area for potassium salt extraction was determined, and this area was suitable for extracting K+ salts from brines with a [Na+/K+] ratio even lower than 0.44. This strategy opened a new way to recovery of potassium with a maximum yield of 59.88% from the carbonate-chloride-based brine.
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