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A complex electrochemical technology for treating wastewater from a meat processing plant is described. During the water treatment process, sequential treatment occurs in an electrochemical module with a graphite anode and an electrochemical module with an iron anode, as well as holding in a maturation and averaging chamber. It has been proven that in the module with an iron anode, ferrates are generated, which simultaneously perform the functions of a soft oxidizer, coagulant, and steel corrosion inhibitor. [ABSTRACT FROM AUTHOR]

The ultra‐alkaline conditions of a hydroflux offer the possibility of redox chemistry far from the electrochemical standard potentials. We explored the possibilities of synthesizing tellurium(VI) compounds, using both tellurium(VI) and tellurium(IV) as starting materials. Colorless, block‐shaped crystals of the oxohydroxotellurate(VI) K2[TeO2(OH)4] were synthesized from (NH4)2TeO4 in a KOH hydroflux at 200 °C. In the triclinic crystal structure, [TeO2(OH)4]2− octahedra are connected via hydrogen bonds to form layers, which are separated from each other by potassium cations. Yellow‐colored platelets of the ferrate(III) tellurate(VI) K2[Fe2TeO6(OH)2] ⋅ 2H2O were obtained by oxidation of TeO2 with H2O2 followed by reaction with Fe(NO3)3 ⋅ 9H2O in a KOH hydroflux. In the monoclinic crystal structure, strongly corrugated anionic layers ∞2[ ${{}_{\infty }{}^{2}[}$ Fe2TeO6(OH)2]2− are covered with water molecules and separated from each other by potassium cations. The octahedrally coordinated iron(III) atoms form a distorted honeycomb network, in which they are antiferromagnetically coupled at room temperature and in external fields up to at least 7 T. [ABSTRACT FROM AUTHOR]

Cultivation of microalgae or/and cyanobacteria in nutrient-rich wastewaters offers an opportunity for enhancing sustainability of tertiary wastewater treatment processes via resources/energy recovery/production, mitigation of emitted GHGs and provision of added value products. However, maintaining a monoculture in wastewater-media constitutes a significant challenge to be addressed. In this regard, the present work assesses the efficiency of the low-cost wastewater substrate disinfection techniques of filtration, use of NaClO, H2O2 or Fe(VI), as a preliminary treatment stage upstream a cyanobacteria cultivation photobioreactor. The growth rate of cyanobacterium Synechococcus elongatus PCC 7942, and nitrate and phosphate removal rates, were experimentally assessed in cultivation setups with biologically treated dairy wastewater that had been subjected to a single or a synergetic couple of disinfection techniques. The results showed that filter thickness has a greater effect on disinfection efficiency than filter pore size. Furthermore, the disinfection efficiency of Fe(VI), which was produced on-site by electrosynthesis via a Fe0/Fe0 cell, was greater than that of NaClO and H2O2. Filtration at ≤ 1.2-μm pore size coupled with chemical disinfection led to unhindered Synechococcus elongatus PCC 7942 growth and efficient nitrate and phosphate removal rates, at dosages, in terms of Concentreation-Time (CT) product, of CT ≥ 270 mg min L−1 for NaClO and CT ≥ 157 mg min L−1 for Fe(VI). The coagulation action of Fe(III) species that result from Fe(VI) reduction and the oxidation action of Fe(VI) can assist in turbidity, organic compounds and phosphorous removal from wastewater media. Moreover, the residual iron species can assist in Synechococcus elongatus PCC 7942 harvesting and may enhance photosynthesis rate by increasing light transfer efficiency. Thus, a filtration configuration coupled with chemical disinfection, preferably using ferrates, downstream of sedimentation tank of a secondary biological wastewater treatment stage is proposed as a necessary, efficient and low-cost disinfection technique for full-scale scale implementation of cyanobacteria cultivation as tertiary wastewater processes. [ABSTRACT FROM AUTHOR]

Exploiting chemical cooperation between Na and Fe(II) within the bimetallic base [dioxane ⋅ NaFe(HMDS)3] (I), (dioxane=1,4‐dioxane, HMDS=N(SiMe3)2) the selective ferration of fluorobenzene, 1‐fluoronaphthalene, 1,4‐difluorobenzene, 1,2,4‐trifluorobenzene, 1,3,5‐trifluorobenzene, 1‐bromo‐3,5‐difluorobenzene, 3‐fluoroanisole and 3,5‐difluoroanisole has been realized, affording sodium ferrates [dioxane ⋅ Na(HMDS)(2‐F‐C6H4)Fe(HMDS)]∞ (1), [dioxane ⋅ Na(HMDS)(2‐F‐C10H6)Fe(HMDS)]∞ (2), [dioxane ⋅ {Na(HMDS)(2,5‐F2‐C6H3)Fe(HMDS)}2]∞ (3), [dioxane ⋅ {Na(HMDS)(2,3,6‐F3‐C6H2)Fe(HMDS)}2]∞ (4), [(dioxane)1.5 ⋅ Na(HMDS)(2,4,6‐F3‐C6H2)Fe(HMDS)]2 (5), [(dioxane)1.5 ⋅ {Na(HMDS)(4‐Br‐2,6‐F2‐C6H2)Fe(HMDS)2] (6), [{(dioxane)2 ⋅ Na2Fe(HMDS)2(2‐methoxy‐6‐F‐C6H3)}+{Fe(HMDS)3}−]∞ (7) and [dioxane ⋅ {Na(HMDS)(4‐methoxy‐2,6‐F2‐C6H2)Fe(HMDS)}2]∞ (8), respectively. Reactions take place under mild reaction conditions, with excellent control of the selectivity and no competing C−F bond activation is observed. Showcasing complex polymeric arrangements in some cases, the structures of compounds 1–8 have been determined by X‐ray crystallographic studies. In all cases, the Fe(II) centers occupy the position in the relevant fluoroarene that was previously filled by a proton, confirming that these metallations are actually ferration processes whereas the Na atoms prefer to form Na⋅⋅⋅F dative interactions. Compounds 1–8 are thermally stable and do not undergo benzyne formation (through NaF elimination) and their formation contrasts with the inertness of Fe(HMDS)2 which fails to act as a base to metallate fluoroarenes. [ABSTRACT FROM AUTHOR]

Alkali‐metal ferrates containing amide groups have emerged as regioselective bases capable of promoting Fe−H exchanges of aromatic substrates. Advancing this area of heterobimetallic chemistry, a new series of sodium ferrates is introduced incorporating the bulky arylsilyl amido ligand N(SiMe3)(Dipp) (Dipp=2,6‐iPr2‐C6H3). Influenced by the large steric demands imposed by this amide, transamination of [NaFe(HMDS)3] (HMDS=N(SiMe3)2) with an excess of HN(SiMe3)(Dipp) led to the isolation of heteroleptic [Na(HMDS)2Fe{N(SiMe3)Dipp}]∞ (1) resulting from the exchange of just one HMDS group. An alternative co‐complexation approach, combining the homometallic metal amides [NaN(SiMe3)Dipp] and [Fe{N(SiMe3)Dipp}2] induces lateral metallation of one Me arm from the SiMe3 group in the iron amide furnishing tetrameric [NaFe{N(SiCH2Me2)Dipp}{N(SiMe3)Dipp}]4 (2). Reactivity studies support that this deprotonation is driven by the steric incompatibility of the single metal amides rather than the basic capability of the sodium reagent. Displaying synergistic reactivity, heteroleptic sodium ferrate 1 can selectively promote ferration of pentafluorobenzene using one of its HMDS arms to give heterotrileptic [Na{N(SiMe3)Dipp}(HMDS)Fe(C6F5)]∞ (4). Attempts to deprotonate less activated pyridine led to the isolation of NaHMDS and heteroleptic Fe(II) amide [(py)Fe{N(SiMe3)Dipp}(HMDS)] (5), resulting from an alternative redistribution process which is favoured by the Lewis donor ability of this substrate. [ABSTRACT FROM AUTHOR]

In the paper, the isomorphous SO42− doped K2FeO4, aimed at the remediation of the discharge and stability of the super-iron battery, was first synthesized for doping and reforming the K2FeO4 crystalline structure via a facile co-precipitation and mechanochemistry. Afterwards, the compared cathodes were assembled by the undoped and doped K2FeO4 for an evaluation of the discharge and stability in the AAA super-iron battery system. The results show that the small amounts of K2SO4 were doped into the K2FeO4 in the calculated form of K2Fe1−xSxO4 by the isomorphous substitution. The doped K2FeO4 cathodes/batteries exhibited an excellent discharge with a normal discharge profile. The cathodes doped by two techniques had significantly enhanced the discharge capacity of the super-iron battery with an increase of 10–30% compared to the undoped K2FeO4. Moreover, the stability of the K2FeO4 cathodes was obviously remediated by the isomorphous SO42− doping. The shelf time of the doped K2FeO4 cathodes was prolonged by an increase of about 10% in comparison of the undoped K2FeO4 cathode. The desirable enhancements could be attributed to doping and reforming the similar building block and isomorphous SO42− into the FeO42− tetrahedral and crystalline in the form of the isomorphous substitution and filling vacancies.

Ferrate [Fe(VI)] is increasingly used for the treatment of several contaminants in drinking water and municipal/industrial waste water. Recent findings also show that Fe(VI) is a promising alternative for the treatment of gold mine effluents contaminated by cyanides (CN − ), thiocyanates (SCN − ), and ammonia nitrogen (NH 3 -N). However, the ferric [Fe(III)] salt used in Fe(VI) synthesis could affect this alternative’s efficiency and costs, as well as residual contaminants in the treated effluent. The objective of this study was to evaluate the influence of three Fe(III) salts on the performance of Fe(VI) in the treatment of gold mine effluents and the residual contaminants produced in the process. To do so, the performance of wet Fe(VI) synthesized with ferric nitrate [Fe(NO 3 ) 3 ], ferric chloride (FeCl 3 ), or ferric sulfate [Fe 2 (SO 4 ) 3 ] was evaluated for the treatment of a real gold mine effluent, with final adjustment of pH at ∼7. The results showed that for the effluents treated with Fe(VI) synthesized in the presence of Fe(NO 3 ) 3 , the final NO 3 − concentrations were 4 times higher relative to those in the treated effluents with Fe(VI) synthesized from either FeCl 3 or Fe 2 (SO 4 ) 3 . The use of Fe 2 (SO 4 ) 3 in the wet Fe(VI) preparation did not entail a significant increase of the final SO 4 2− concentrations, which were very similar to initial ones (1220 vs. 1012 mg/L). At the same time, Fe(VI) synthesized from Fe 2 (SO 4 ) 3 was the only one to remove the CN − and NH 3 -N almost totally (∼99%). Finally, the production yield of Fe(VI) with FeCl 3 was lower than Fe 2 (SO 4 ) 3 or Fe(NO 3 ) 3 (3400 vs. 5500 and 5635 mg/L, respectively). This low yield production of Fe(VI) from FeCl 3 entails more costly production costs. Thus, Fe 2 (SO 4 ) 3 is potentially the most appropriate Fe(III) salt source for Fe(VI) synthesis for use in the treatment of contaminated mine effluents. [ABSTRACT FROM AUTHOR]

Abstract: We report on the electrochemical generation of ferrate species in a batch reactor at neutral conditions (pH ∼7) using boron‐doped diamond (BDD) electrodes and Fe (III) salts for applications in drinking water treatment. The impact of several relevant variables, including current density (5–55 mA cm−2), pH (5–8), and type and concentration of the dissolved iron salts on the production of ferrates were examined. In addition, linear sweep voltammetry (LSV) studies were conducted using buffered electrolytes with and without the presence of iron (III) to decouple the parasitic oxygen evolution reaction. The LSV measurements in the presence of iron (III) and with a neutral electrolyte exhibit oxidation peaks centered ∼2.0 V (versus SHE), indicating the production of ferrates at this pH. The rate of ferrate generation is not strongly affected by the pH condition (≤ 20 %); however, current density and the source of iron were found to have a higher impact on the production rate of ferrates. The efficacy of the process was higher using FeCl3 instead of other sources of iron such as Fe2O3 and FeO(OH). The batch reactor results were successfully interpreted by a simple model that considered the kinetics of the ferrate generation and degradation reactions. [ABSTRACT FROM AUTHOR]

Three new ‘reduced’ Fe II containing sodium chalcogenido ferrates were obtained applying a reductive synthetic route. The mixed-valent sulfido ferrate Na 7 [ Fe 2 S 6 ] , which forms bar-shaped crystals with metallic greenish luster, was synthesized in pure phase from natural pyrite and elemental sodium at a maximum temperature of 800 °C. Its centrosymmetric triclinic structure (SG P 1 ¯ , a = 764.15(2), b = 1153.70(2), c = 1272.58(3) pm, α = 62.3325 ( 7 ) , β = 72.8345 ( 8 ) , γ = 84.6394 ( 8 ) ° , Z = 3, R 1 = 0.0185) exhibits two crystallographically different [ Fe 2 S 6 ] 7 − dimers of edge-sharing [ FeS 4 ] tetrahedra, with somewhat larger Fe-S distances than in the fully oxidized Fe III dimers of e.g. Na 6 [ Fe 2 III S 6 ] . In contrast to the localized AFM ordered pure di-ferrates(III), the Curie-Weiss behavior of the magnetic susceptibility proves the rarely observed valence-delocalized S = 9 2 state of the mixed-valent Fe III / Fe II dimer. The nearly spin-only value of the magnetic moment combined with the chemical bonding not generally differing from that in pure ferrates(II) and (III), provides a striking argument, that the reduction of the local Fe spin moments observed in all condensed sulfido ferrate moieties is connected with the AFM spin ordering. The two isotypic ferrates(II) Na 2 [ FeS 2 ] and Na 2 [ FeSe 2 ] with chain-like structural units (SG Ibam , a = 643.54(8)/ 660.81(1), b = 1140.2(2)/1190.30(2) c = 562.90(6)/585.59(1) pm, Z = 4, R 1 = 0.0372/0.0466) crystallize in the K 2 [ ZnO 2 ] -type structure. Although representing merely further members of the common series of chalcogenido metallates(II) Na 2 [ M II Q 2 ] , these two new phases, together with Na 6 [ FeS 4 ] and Li 2 [ FeS 2 ] , are the only examples of pure Fe II alkali chalcogenido ferrates. The new compounds allow for a general comparison of di- and chain ferrates(II) and (III) and mixed-valent analogs concerning the electronic and magnetic properties (including Heisenberg super-exchange and double-exchange interactions) based on the comprehensive literature and own DFT band structure calculations. [ABSTRACT FROM AUTHOR]