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.

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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.

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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.

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

Thermal stability of silica-coated magnetite nanoparticles prepared by an electrochemical method

An approach for a fast recycling process for Lithium Nickel Cobalt Aluminum Oxide (NCA) cathode scrap material without the presence of a reducing agent was proposed. The combination of metal leaching using strong acids (HCl, H2SO4, HNO3) and mixed metal hydroxide co-precipitation followed by heat treatment was investigated to resynthesize NCA. The most efficient leaching with a high solid loading rate (100 g/L) was obtained using HCl, resulting in Ni, Co, and Al leaching efficiencies of 99.8%, 95.6%, and 99.5%, respectively. The recycled NCA (RNCA) was successfully synthesized and in good agreement with JCPDS Card #87-1562. The highly crystalline RNCA presents the highest specific discharge capacity of a full cell (RNCA vs. Graphite) of 124.2 mAh/g with capacity retention of 96% after 40 cycles. This result is comparable with commercial NCA. Overall, this approach is faster than that in the previous study, resulting in more efficient and facile treatment of the recycling process for NCA waste and providing 35 times faster processing.

A Fast Metals Recovery Method for the Synthesis of Lithium Nickel Cobalt Aluminum Oxide Material from Cathode Waste

Electrochemical synthesis of hydroxyapatite particles was performed from a homogeneous solution of Na2H2EDTA.2H2O, KH2PO4 and CaCl2 without stirring to investigate the mechanism of hydroxyapa-tite formation. We found that OH- ions generated by water reduction at the cathode play an important role in the formation of hydroxyapatite particles. The OH- ions induce the liberation of Ca2+ ions and the dissociation of phosphoric acid, which serve as the reactants for the formation of hydroxyapatite particles. Two layers with a clear boundary were formed during electrolysis. The upper layer comprises the produced particles and the lower layer is a homogeneous solution. The produced particles were held in the region between the electrodes mainly due to the electrostatic interactions of charged particles in an electric field. The hydroxyapatite particles are agglomerates consisting of spherical particles. Aging the suspension for 24 h after electrolysis leads to the transformation of hydroxyapatite to brushite. Thus, if producing hydroxyapatite is desired, the particles should be continuously removed from the system. This method appears to be promising as a continuous process to produce hydroxyapatite parti-cles using an electrochemical method. © 2014 BCREC UNDIP. All rights reserved Received: 10th April 2014; Revised: 25th May 2014; Accepted: 27th June 2014 How to Cite : Nur, A., Setyawan, H., Widjaja, A., Lenggoro, I.W. (2014). Electrochemical Processes for the Formation of Hydroxyapatite Powders. Bulletin of Chemical Reaction Engineering & Catalysis , 9 (3): 168-175. (doi:10.9767/bcrec.9.3.6686.168-175) Permalink/DOI : http://dx.doi.org/10.9767/bcrec.9.3.6686.168-175

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Electrochemical Processes for the Formation of Hydroxyapatite Powders

An Experimental and Theoretical Investigation of the Formation of Hydroxyapatite Particles Prepared by an Electrochemical Method

https://iopscience.iop.org/article/10.1088/1757-899X/515/1/012049/pdf

Adrian Nur

Papers

Thermal stability of silica-coated magnetite nanoparticles prepared by an electrochemical method

A Fast Metals Recovery Method for the Synthesis of Lithium Nickel Cobalt Aluminum Oxide Material from Cathode Waste

Electrochemical Processes for the Formation of Hydroxyapatite Powders

An Experimental and Theoretical Investigation of the Formation of Hydroxyapatite Particles Prepared by an Electrochemical Method

Synthesis of ZnFe2O4 Nanoparticles with PEG 6000 and Their Potential Application for Adsorbent