Determination of standard Gibbs free energy of formation of green rusts and its application to the Fe(II–III) hydroxy-oxalate

Denitrification of overlying water by microbial electrochemical snorkel

“…The surface coatings of the iron rod in both Fe-MES and Fe-Felt contain lepidocrocite (2h = 14.14°, 27.05°, 46.91°) and magnetite (2h = 29.56°, 36.30°, 43.31°, 52.74°). However, the surface coating on the iron rod in Fe-MES showed the diffraction peaks of goethite (2h = 21.19°, 36.11°) and hematite (2h = 23.18°, 39.57°, 48.71°, 57.72°) (Bourdoiseau et al, 2012;Liou et al, 2009;Wang et al, 2015). It has been reported that goethite and green rust can be interconverted into each other under a certain redox condition (Antony et al, 2004;Etique et al, 2014).…”

Oxidation of chukanovite (Fe 2 (OH) 2 CO 3 ): Influence of the concentration ratios of reactants

“…In previous studies of the oxidation of Fe(OH) 2 precipitates [15][16][17], the presence of a potential plateau on the E vs time curves recorded during the oxidation of Fe(OH) 2 into another solid phase was attributed to the equilibrium state between Fe(OH) 2 and its oxidation product. To check whether this approach could be applicable in the present case with chukanovite, the redox potential values measured at point P, E(P), were plotted vs the pH values measured at point P, pH(P).…”

“…It was recently shown that this contribution may be negligible for low oxygen flows, i.e. for low stirring speed, but not for large oxygen flows [17]. For this reason, before to discuss the possible thermodynamic meaning of the relation (3) between E(P) and pH(P), it was necessary to study the influence of oxygen on the redox potential measured at point P. Fig.…”

“…In particular, it must be recalled that green rust compounds are readily obtained from Fe(OH) 2 when Fe(II) dissolved species are in excess [14][15][16][17]. This is not the case with chukanovite.…”

“…The reaction was monitored by measuring the redox potential and the pH of the suspensions, a method that points out the various reaction stages involved in the oxidation process [12,14,15]. Moreover, the redox potential and pH values measured during a reaction stage involving two solid phases may in some cases correspond to the equilibrium conditions between these phases [15][16][17]. A thermodynamic approach was then used to interpret the variations of the measured redox potential with the pH of the suspension.…”