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Contributions of Nanomaterials in Biohydrogen Production
Published in Madan L. Verma, Nanobiotechnology for Sustainable Bioenergy and Biofuel Production, 2020
Santosh Kumar, Rekha Kushwaha, Madan L. Verma
Engliman et al. (2017) investigated the impact of initial pH, metal oxide and concentration of nanoparticles on biohydrogen production in batch assays. For this study, they used glucose-fed anaerobic mixed bacteria in the thermophilic condition of 60ºC and also used the metal oxide nanoparticles of iron (II) oxide and nickel oxide. These two-metal oxide nanoparticles were able to enhance the hydrogen yield by 34.38% and 5.47% than the control. They optimized pH 5.5 for higher production of hydrogen without nanoparticles. In combination experiment, nanoparticles (either iron(II) oxide or nickel oxide) as well and pH 5.5 of maximum hydrogen yield 1.92 mol H2/mol glucose and 51% hydrogen content were obtained with optimal iron(II) oxide concentration of 50 mg/L. In this study, the researchers were able to recover nanoparticles without any loss after the experiment. Besides hydrogen production, Engliman et al. (2017) also studied the characteristic of the fermentation operations, such as metabolites distribution, sugar consumption and cell growth (Table 2).
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Published in Zbigniew Galazka, Transparent Semiconducting Oxides, 2020
Often “inert“ gases such as N2 or Ar are used for crystal growth. One can show that the term “inert“ must be used with care. If one heats, e.g., iron(II) oxide FeO in argon gas with 5N (99.999%) purity above its melting point Tf = 1644 K, it is gradually oxidized to Fe3O4 [45]. This means that this gas cannot be considered inert under these experimental conditions. The explanation is given easily by a predominance diagram of the Fe-O2 system where the FeO phase field is almost triangular with oxygen fugacities between p02 = 2.4 × 10-6 bar (T≈1700 K) and 7.5 × 10-26 bar (T 850 K). For higher p02, Fe3O4 is formed. A purity of 99.999% means that the gas contains 0.001% impurities, and typically air with 21% oxygen will be the main impurity. From this, one can conclude that a 5N gas has a constant background oxygen fugacity in the order of 2 × 10-6 bar.
Inorganic Chemistry
Published in Steven L. Hoenig, Basic Chemical Concepts and Tables, 2019
Ruby is an example of a crystal with a chemical impurity. The crystal is mainly colorless aluminum oxide, Al2O3, but occasional aluminum ions, Al3+, are replaced by chromium(III) ions, Cr3+, which give a red color. Various lattice defects occur during crystallization. Crystal planes may be misaligned, or sites in the crystal lattice may remain vacant. For example, there might be an equal number of sodium ion vacancies and chloride ion vacancies in a sodium chloride crystal. It is also possible to have an unequal number of cation and anion vacancies in an ionic crystal. For example, iron(II) oxide, FeO, usually crystallizes with some iron(II) sites left unoccupied. Enough of the remaining iron atoms have 3+ charges to give an electrically balanced crystal. As a result, there are more oxygen atoms than iron atoms in the crystal. Moreover, the exact composition of the crystal can vary, so the formula FeO is only approximate. Such a compound whose composition varies slightly from its idealized formula is said to be nonstoichiometric.
Inhibition effect of apium graveolens, punica granatum, and camellia sinensis extracts on plain carbon steel
Published in Cogent Engineering, 2020
Roland Tolulope Loto, Cleophas Akintoye Loto
Optical representations of PCS surface prior to corrosion test, and after corrosion in 0.5 M H2SO4 solution with and without the addition of plant extracts are displayed from Figure 5(a) to Figure 7 at mag. ×25. Figure 5(a) exhibits the morphology of PCS before corrosion. The serrated morphology is due to machining of the steel surface. The morphology in Figure 5(b) is due to the oxidation effect of SO42- anion reactions, which is the causative factor for the degradation of the steel surface. The corroded morphology results from general corrosion in addition to the growth of macro-pits. The oxidation of the steel surface caused the release of iron (II) oxide into the acid solution. Figures 6(a-b) and 7 displays the morphology of PCS after corrosion test in the presence of APG, CPG, and CLS inhibitor. The improved morphologies are due to the inhibiting action of the plant extracts. The mild surface deterioration is due to the gradual inhibitive action of the plant extracts. Further analysis from potentiodynamic polarization, which will be discussed later showed the plant extracts displayed dominant cathodic inhibition. Hence the inhibition mode of the plant extracts results from the modification of the corrosive media, whereby the molecules of the plant extracts reacts with the anions of the corrosive solution, hence limiting the cathodic reaction mechanism.
Effect of nitric acid contamination on mild steel corrosion in hydrofluoric acid at 25°C
Published in Corrosion Engineering, Science and Technology, 2020
R. van der Merwe, J. W. van der Merwe, L. A. Cornish
The addition of only 0.1% HNO3 to the 70% HF corrosion solution significantly affected the colour of the scales (Figure 4: Row (a)), as well as the steel substrate exposed after cleaning (Figure 4: Row (b)). In HF corrosion solutions with HNO3 (0.1, 0.5 and 1%), black scales with red-brown mottling were visible over the surfaces of all the coupons (Figures 4–6: Row (a)). Dilute HNO3 reacted with iron to produce iron nitrate, although iron nitrate is violet in colour and is readily soluble in water [22]. Thus, the red scale was most likely to be iron (III) oxide (red-brown Fe2O3 crystals), which formed when the black iron (II) oxide was further oxidised by HNO3.
Simultaneous removal of Cu (II) and Cr (VI) ions from petroleum refinery wastewater using ZnO/Fe3O4 nanocomposite
Published in Journal of Environmental Science and Health, Part A, 2022
E. Y. Shaba, J. O. Tijani, J. O. Jacob, M. A. T. Suleiman
The Fe0 reacts (redox) with ( and oxygen (O2) to form iron (II) oxide (Fe2+) in solution (see Eqs. 13 and 14). This reaction is faster in the presence of water. The Fe2+ oxide further reacts with O2 and formed of Fe2O3 (see Eq. 15). The Fe3+ in the solution that was not completely reduced by the further react with H2O to form magnetite under hydrothermal conditions (see Eq. 16). The Fe2O3 form could also react with iron metal (Fe) through the hydrothermal process to form Fe3O4.