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Advances in electrochemically active bacteria: Physiology and ecology
Published in Maximilian Lackner, Philipp Stadler, Wilhelm Grabow, Handbook of Online and Near-real-time Methods in Microbiology, 2017
A.C. Marques, L. Santos, J.M. Dantas, A. Gonçalves, S. Casaleiro, R. Martins, C.A. Salgueiro, E. Fortunato
EET also plays an important role in the anaerobic corrosion of steel where Fe(0) acts as electron donor for different types of respiration, including sulfate reduction and methanogenesis (Stams et al. 2006). Anaerobic corrosion of steel is caused either indirectly by an hydrogen sulfide attack yielding hydrogen and iron sulfide or directly by bacterial hydrogen consumption affecting the equilibrium of the chemical reaction: Fe(0) + 2H+ → Fe(II) + H2 (Stams et al. 2006). Additionally, evidence for the hypothesis that sulfate-reducing bacteria obtain electrons directly from metallic iron rather than via H2 were also presented (Dinh et al. 2004). Anaerobic corrosion is an important environmental problem, with very high costs associated in off-shore industrial processes, for example.
Differential and mechanism analysis of sulfate influence on the degradation of 1,1,2- trichloroethane by nano- and micron-size zero-valent iron
Published in Environmental Technology, 2023
Yi Li, Naijin Wu, Jiuhao Song, Zhenxia Wang, Peizhong Li, Yun Song
In this study, we investigated the effect of different concentrations of SO42− on the removal of 1,1,2-TCA by ZVI. The effect of SO42− on the degradation of 1,1,2-TCA varied for different types of ZVI, and the degree of the effect varied. For mZVI, the removal efficiency of 1,1,2-TCA gradually increased with increasing SO42− concentration, and Kobs increased by 0.6 (2 mM), 0.5 (4 mM), 1.1 (8 mM), and 1.6 times (80 mM). For nZVI, the removal efficiency of 1,1,2-TCA decreased with increasing SO42− concentration; however, the inhibition weakened when it increased to 80 mM, with Kobs decreasing by 32% (2 mM), 39% (4 mM), 45% (8 mM), and 9% (80 mM). For mZVI, DO, and ORP declined. The presence of SO42− promoted the anaerobic corrosion of Fe0, resulting in a simultaneous increase in pH and dissolved iron concentrations. For nZVI, compared with mZVI, the change of DO was similar, but ORP declined more rapidly. However, as the SO42− concentration increased, the trend of dissolved iron concentration was opposite that of the mZVI group and decreased greatly compared to the N0 group, indicating that the presence of SO42− inhibited the ZVI corrosion process. the effect on pH was the same as in the mZVI group, except that the onset of pH increase occurred slightly later than in the mZVI group.
Corrosion of the interior steel surfaces of offshore monopiles
Published in Ships and Offshore Structures, 2022
I.A. Chaves, R. Petersen, R.E. Melchers, R. Jeffrey
The trends in the data for corrosion loss with increased exposure period shown in Figures 6 and 7 are all interpreted as showing bi-modal behaviour after making allowances, as noted, for some degree of variability in experimental data. This applies for all zones and for both sites. Although for the low corrosion loss data other trends could be fitted, those shown have consistency with what has been found earlier, and repeatedly, for the development of corrosion of steels and various other alloys over several years of exposure (Melchers 2018). This type of non-linear trending is consistent with the recognition that the corrosion process changes from initially being driven by aerobic corrosion processes, that is, by the oxygen reduction reaction (although rate controlled by oxygen diffusion), to eventually changing to predominantly anaerobic corrosion in the form of the hydrogen evolution cathodic reaction (Melchers and Jeffrey 2022). In the plots shown in Figures 6 and 7, this change occurs at around 24–30 months exposure. This compares to about 12 months for immersion corrosion in seawaters at similar average water temperatures (Melchers 2014). Apart from any theoretical aspects, from a practical point of view, these trends show that short-term (instantaneous, or 6–12 month) observations of corrosion loss are inadequate for estimating the longer-term corrosion losses, in particular for exposure more than just a few years.
Removal of heavy metals from landfill leachate using zero valent iron and granular activated carbon
Published in Environmental Technology, 2020
Stefania Bilardi, Paolo Salvatore Calabrò, Rosa Greco, Nicola Moraci
The pH increased by flowing through the reactive medium from the initial value to 7 for the entire duration of the test. Regarding redox potential, Eh values, determined at the outlet of the column, were slightly positive and ranged from 6 to 36 mV. In Figure 11 the hydraulic behaviour of the granular mixture is shown. A sudden reduction of the hydraulic conductivity was observed after 2000 h of test duration. More specifically, after 2500 h a value equal to 1.44·10−4 cm/s was reached and the test was interrupted. A visual observation has shown the presence of gas bubbles and of filamentous mucilage at the inlet and outlet of the column. Since during the disassembly of the column, a cementation phenomenon was not observed, clogging could be due to the presence of gas bubbles (likely hydrogen developed during the anaerobic corrosion of ZVI) and to a biofilm formation.