Magnetic iron oxides were prepared by precipitation of Fe(II) hydroxide using different precipitation agents: ammonia, benzylamine and sodium hydroxide, followed by oxidation with the oxygen dissolved in water. Thermal analysis, coupled with FTIR spectroscopy, has evidenced the formation of a mixture of magnetite and maghemite, with a higher content of magnetite in case of the powder synthesized with benzylamine. The stability of magnetite at oxidation by air during storage at room temperature and 60 °C was investigated by means of TG/DSC simultaneous thermal analysis, FTIR spectroscopy and X-ray diffractometry. Thermal analysis evidenced an exothermic process with mass gain in temperature range 100–190 °C, corresponding to magnetite oxidation process, but due to the superposition of other processes it could not offer quantitative information. FTIR spectroscopy has provided, especially through the first and second derivatives of FTIR spectra, the most valuable information regarding the evolution of magnetite to maghemite, due to their different characteristic bands. XRD technique has evidenced a slight shift of the main diffraction peaks at higher 2-theta values during the evolution of magnetite to maghemite. According to thermal analysis data, the powder synthesized with ammonia was completely oxidized after 15 days, while the other two powders, synthesized with benzylamine and sodium hydroxide, were completely oxidized after 110 days of keeping in air at room temperature. For a temperature of 60 °C, the oxidation was much faster; the oxidation process of the powder synthesized with benzylamine disappeared from TG/DSC curves after 1 day. All final powders were formed from nanoparticles with diameters up to 25 nm, with magnetic properties characteristic to nanometric maghemite.

Investigation of magnetite nanoparticles stability in air by thermal analysis and FTIR spectroscopy

Recent advances in the methanol carbonylation reaction into acetic acid

The disposal of hazardous waste of any form has become a great concern for the industrial sector due to increased environmental awareness. The increase in usage of hydroprocessing catalysts by petrochemical industries and lithium-ion batteries (LIBs) in portable electronics and electric vehicles will soon generate a large amount of scrap and create significant environmental problems. Like general electronic wastes, spent catalysts and LIBs are currently discarded in municipal solid waste and disposed of in landfills in the absence of policy and feasible technology to drive alternatives. Such inactive catalyst materials and spent LIBs not only contain not only hazardous heavy metals but also toxic and carcinogenic chemicals. Besides polluting the environment, these systems (spent catalysts and LIBs) contain valuable metals such as Ni, Mo, Co, Li, Mn, Rh, Pt, and Pd. Therefore, the extraction and recovery of these valuable metals has significant importance. In this Review, we have summarized the strategies used to recover valuable (expensive) as well as cheap metals from secondary resources-especially spent catalysts and LIBs. The first section contains the background and sources of LIBs and catalyst scraps with their current recycling status, followed by a brief explanation of metal recovery methods such as pyrometallurgy, hydrometallurgy, and biometallurgy. The recent advances achieved in these methods are critically summarized. Thus, the Review provides a guide for the selection of adequate methods for metal recovery and future opportunities for the repurposing of recovered materials.

/pdf/recycle-recover-and-repurpose-strategy-of-spent-li-ion-22ggr5h40r.pdf

Recycle, Recover and Repurpose Strategy of Spent Li-ion Batteries and Catalysts: Current Status and Future Opportunities

Three different novel chitosan derivatives for medical or biotechnological applications have been successfully obtained by chemical modification of reactive amino and hydroxyl groups in chitosan chain. The modification has led to incorporation of different amount (one to three) of long-distanced amino and imine groups into each repeating unit. These highly functionalized chitosan derivatives were used as a matrix for magnetite nanoparticles. The thermal stability of all obtained chitosan materials has been determined using thermogravimetric analysis in oxidative and inert atmosphere. Chitosan containing two side substituents behaves differently from the other two, which is caused by the significant water uptake. Magnetite causes decrease in thermal stability of studied chitosan derivatives. The highest stability is observed for the nanocomposite obtained from chitosan with three side groups. The changes in the structure of the magnetite core have been observed above 600 °C in nitrogen. Due to the different competitive reactions occurring in the modified chitosan, the proposed mechanism of thermal degradation is very complex.

/pdf/effect-of-side-substituents-on-thermal-stability-of-the-m8sak5xvap.pdf

Effect of side substituents on thermal stability of the modified chitosan and its nanocomposites with magnetite

Structural and magnetic
studies of monophasic maghemite (γ-Fe2O3)
magnetic nanocrystallites (MNCs) synthesized by the co-precipitation chemical
route are reported in this paper. For the synthesis, a starting precursor of
magnetite (Fe3O4)
in basic medium was oxidized at room temperature by adjusting the pH = 3.5
at 80°C in an acidic medium without surfactants. X-ray diffraction (XRD)
pattern shows widened peaks indicating nanometric size and Rietveld Refinement confirms
only one single-phase assigned to γ-Fe2O3 MNCs. High Resolution Transmission Electron Microscopy (HR-TEM) demonstrates
the formation of nanoparticles with diameter around D ≈ 6.8 ± 0.1 nm which is in good agreement with Rietveld Refinement
(6.4 ± 1 nm). A selected area electron diffraction pattern was carried out to
complement the study of the crystalline structure of the γ-Fe2O3 MNCs. M(H) measurements taken
at different temperatures show almost zero coercivity and remanence indicating
superparamagnetic domain and high magnetic saturation.

/pdf/structural-and-magnetic-properties-of-monophasic-maghemite-g-45vzab9tfd.pdf

Structural and Magnetic Properties of Monophasic Maghemite (γ-Fe2O3) Nanocrystalline Powder

A recycle process of NCA cathode scrap from lithium-ion batteries has been carried out. Nitric acid (HNO3) and hydrogen peroxide (H2O2) were used as leaching agents and reducing agents, respectively. The leaching process was carried out with a 1.5 M nitric acid (HNO3) solution, a solid to liquid ratio (S / L) of 100 g / L and a temperature of 80°C. The reducing agent concentration and the effect of the leaching time were investigated. Sol-gel and sintering processes were aimed to recover NCA material and reuse it for manufacturing lithium-ion batteries. The results showed that the highest leaching efficiency was at a reducing concentration of 3% w / v for 3 hours. Dry samples were characterized using SEM, XRD, and FTIR. Based on SEM results, the surface morphological analysis of recycled NCA cathode scrap was successfully obtained. As obtained NCA XRD patterns were well indexed according to JCPDS Card # 87-1562. The electrochemical performance or charge-discharge capacity measurement was analyzed in an 18650-type cell and graphite was selected as the anode. The specific capacity of the material obtained from this study is 90 mAh / g. 

Adrian Nur

Papers

Recovery of lithium nickel cobalt aluminum oxide cathode material from battery scrap waste via sol-gel method