Search

In this work, the performances of nickel iron layered double hydroxides (LDH) with the nitrate anion at the interlayer (NiFe-NO3) for the manufacture of anodes for lithium-ion batteries have been tested before and after its sintering at different temperatures. After synthesis, the material was thermally analyzed in a range 30–1250 °C, showing a mass loss occurring in three different consecutive steps leading to a total mass decrease of ~30 mass%. Following thermogravimetric analysis (TGA), four samples were prepared by annealing at four different temperatures: one of the four did not undergo a thermal treatment (NiFe-0), while the remaining three were annealed at 250 °C, 360 °C, and 560 °C for 6 h (NiFe-250, NiFe-360, and NiFe-560). All materials where completely characterized via FE-SEM, PXRD, and FT-IR. The pristine LDH material showed some structural and compositional changes for growing temperatures, starting from the typical turbostratic hexagonal structure through a mixture of amorphous metal oxides and finally to the stoichiometric oxides FeNi2O4 and NiO. The as-obtained materials were mixed with carbon black (C65) and sodium alginate and tested as electrodes in Swagelok half cells in LP30 vs. metallic Li to perform CV and GCPL analysis. The electrochemical tests showed that the performances of NiFe-0, both in terms of stability and specific capacity, are not so different from the one of the NiFe-560, even if the Ni mass% in the former is lower than in the NiFe-560. This phenomenon could be explained by assuming a combined mechanism of reaction involving both intercalation and conversion. [ABSTRACT FROM AUTHOR]

Owing to their structure, layered double hydroxides (LDHs) and allophane are nowadays considered as promising materials for application in different fields. The goal of this work is to compare the efficacy of allophane and ZnAl-SO4 LDH to remove, by adsorption, some cationic and anionic pollutants from industrial wastewater. Both compounds were synthesized via the co-precipitation route (direct method) followed by hydrothermal treatment, obtaining nanoscopic crystallites with a partially disordered turbostratic (ZnAl-SO4 LDH) or amorphous (allophane) structure. The characterization of the obtained compounds was performed by means of powder x-ray diffraction (PXRD), thermal gravimetry analysis (TGA), field emission scanning electron microscopy analysis (FESEM), and Fourier-transform infrared spectroscopy (FT-IR). The sorbents were tested using wastewater produced by a real metalworking plant and containing ionic species such as Cu(II), Fe(III) and Cr(VI), whose concentration was measured by means of inductively coupled plasma-optical emission spectrometry (ICP-OES). This investigation represents an alternative procedure with respect to standard protocols based on customarily made and artificially lab-produced wastewaters. Both sorbents and their combination proved to be efficient in Cr(VI) removal, irrespective of the presence of cations like Cu(II) and Fe(III). A synergistic effect was detected for Cu(II) adsorption in a mixed allophane/LDH sorbent, leading to a Cu(II) removal rate of 89.5%. [ABSTRACT FROM AUTHOR]