Influence of mechanochemical activation on dissolving model corrosion films formed on ion-exchange resins using Trilon B

Inorganic deposits formed during operation and intermediate storage contain radionuclides, whose removal during the chemical decontamination of spent ion-exchange resins used in filters for special water purification at nuclear power plants has proved to be a challenge. In such deposits, radionuclides of the corrosion group (58.60Co, 54Mn, 51Cr) are typically located in the crystal lattice of poorly soluble iron oxides. The present work discusses the possibility of using mechanochemical activation in the decontamination of spent ion-exchange resins polluted with deposits of activated corrosion products from structural materials. Samples of natural and synthesised on the surface of the KU-2-8 cation exchanger in the presence of the 57Co label magnetites were used as model deposits. It was shown that an increase in the duration of mechanochemical activation leads to an increase in the dissolution rate of magnetite in model decontamination solutions based on еthylenediaminetetraacetic acid disodium salt (Trilon B) and nitric acid. It was shown that, when using Trilon B, magnetite dissolves more efficiently, which is explained by the interaction between the oxide surface and organic complexing agents. It can be assumed that solid-phase reactions occur during the mechanochemical activation of magnetite in the presence of dry reagents (Trilon B, oxalic, ascorbic and citric acids). Therefore, a poorly soluble shell formed on the oxide surface hinders the dissolution at a low magnetite/solution ratio. Unlike the reagent-free activation, for magnetite activated in the presence of oxalic acid, an increase in the solution/magnetite ratio promotes the dissolution of iron oxides. Using the example of a model cation exchanger, it was shown that the rate and efficiency of decontamination of spent ion-exchange resins polluted with deposits containing activated corrosion products increase significantly after mechanochemical activation in the presence of oxalic acid.

Oxalic Acid, a Versatile Coformer for Multicomponent Forms with 9-Ethyladenine

Six new multicomponent solids of 9-ethyladenine and oxalic acid have been detected and characterized. The salt screening has been performed by mechanochemical and solvent crystallization processes. Single crystals of the anhydrous salts in 1:1 and 2:1 nucleobase:coformer molar ratio were obtained by solution crystallization and elucidated by single-crystal X-ray analysis. The supramolecular interactions observed in these solids have been studied using density functional theory (DFT) calculations and characterized by the quantum theory of “atoms in molecules” (QTAIM) and the noncovalent interaction plot (NCIPlot) index methods. The energies of the H-bonding networks observed in the solid state of the anhydrous salts in 1:1 and 2:1 nucleobase:coformer are reported, disclosing the strong nature of the charge assisted NH···O hydrogen bonds and also the relative importance of ancillary C–H··O H-bonds.

Solubilization of struvite and biorecovery of cerium by Aspergillus niger

Cerium has many modern applications such as in renewable energies and the biosynthesis of nanomaterials. In this research, natural struvite was solubilized by Aspergillus niger and the biomass-free struvite leachate was investigated for its ability to recover cerium. It was shown that struvite was completed solubilized following 2 weeks of fungal growth, which released inorganic phosphate (Pi) from the mineral by the production of oxalic acid. Scanning electron microscopy (SEM) showed that crystals with distinctive morphologies were formed in the natural struvite leachate after mixing with Ce3+. Energy-dispersive X-ray analysis (EDXA), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) confirmed the formation of cerium phosphate hydrate [Ce(PO4)·H2O] at lower Ce concentrations and a mixture of phosphate and cerium oxalate decahydrate [Ce2(C2O4)3·10H2O] at higher Ce concentrations. The formation of these biogenic Ce minerals leads to the removal of > 99% Ce from solution. Thermal decomposition experiments showed that the biogenic Ce phosphates could be transformed into a mixture of CePO4 and CeO2 (cerianite) after heat treatment at 1000 °C. These results provide a new perspective of the fungal biotransformation of soluble REE species using struvite leachate, and also indicate the potential of using the recovered REE as biomaterial precursors with possible applications in the biosynthesis of novel nanomaterials, elemental recycling and biorecovery. Key points • Cerium was recovered using a struvite leachate produced by A. niger. • Oxalic acid played a major role in struvite solubilization and Ce phosphate biorecovery. • Resulting nanoscale mineral products could serve as a precursor for Ce oxide synthesis.

Effect of Oxalic Acid Treatment on Conductive Coatings Formed by Ni@Ag Core–Shell Nanoparticles

Low-cost metallic nanoink based on nickel–silver core–shell nanoparticles (Ni@Ag NPs) was used for the formation of conductive metallic coatings with low sintering temperature, which can be successfully applied for replacement of currently used silver-based nanoinks in printed electronics. The effect of oxalic acid (OA) on the sintering temperature and conductivity of coatings formed by Ni@Ag NPs was evaluated. It was found that the addition of OA to the ink formulation and post-printing treatment of deposited films with this acid provided a noticeable decrease in the sintering temperature required for obtaining conductive patterns that is especially important for utilizing the polymeric substrates. The obtained resistivity of metallic coatings after sintering at temperature as low as 100 °C was found to be 30 µΩ·cm, only ~4 times higher compared to the resistivity of bulk Ni that is promising for future application of such materials for fabrication of low-cost flexible printed patterns.