The study evaluated the leaching of cobalt (Co) in soils fertilized with sewage sludge (SS) and composts depending on the extractant used. SS came from rural, mechanical–biological treatment plant in ...Dobrzeń, Lower Silesia region. In addition, those SS were processed by composting. Sludges and composts were used to fertilise the energy plants during lysimeter experiment conducted during 2008–2013. The overall, as well as extracted by H
O, 0.1M HCl and 1M HCl, 0.05M Na
EDTA and 0.1M Na
EDTA, content of Co in samples were analysed. Additionally, the impact of pH and organic matter (OM) content on the leachability of Co were researched. It was found that the soil samples were rich in Co. Its share slightly depended on fertilisation with SS and compost. Co leaching depends on the type and concentration of extractant. The highest content of Co were leched with 0.1 M Na
EDTA, and the lowest content with 0.1M HCl. Co concentration in H
O extracts was not determined as its content was below the limit of quantification. Leachability of Co in the analysed samples was influenced by the overall Co content as well as pH and OM content.
Cobalt catalysts are tested in methane decomposition reaction at 475–600°C and pressure ∼1
bar to evaluate their catalytic properties in non-oxidative methane conversion via an accumulation of ...carbon. Catalyst preparation method, a nature of a support and temperature regimes are found to strongly influence this process. The best performances are found with the coprecipitated 60–75
wt% Co–alumina catalysts at 500°C. XRD, EXAFS and TEM investigations indicate a close similarity between the Co and Ni catalysts previously studied. However, in contrast to nickel, the carbon filaments with a hollow-like core morphology are produced on the Co catalysts. Data further point that an accumulation of the filamentous carbon is a promising route to utilize methane as a main component of the natural gas.
SYMMETRY FACTOR FOR ELECTRONIC CONFIGURATION IN Ca3Co4O9 SYSTEM Karaman, Nazlı; Adiyaman University, Faculty of Science and Art, Physics Department, 02040, Adiyaman, TURKEY; Bayri, Ali; Inonu University, Faculty of Science and Art, Physics Department, 44280, Malatya, TURKEY
Journal of the Turkish Chemical Society, Section A, Chemistry,
01/2015
Journal Article
Recenzirano
Bu çalısma, Ca3Co4O9 sisteminde yüksek sıcaklıklardaki Co iyonlarının elektronikkonfigürasyonlarıyla ilgilenir. Bu sistemin manyetik davranısı 700 K civarında bir anomali gösterir. Bu anomalinin ...sistemdeki Co2+, Co3+ ve Co4+ iyonlarının spin durum geçislerinden kaynaklandığı düsünülmektedir. Octahedral bir alandaki Co iyonlarının dalga fonksiyonlarının simetri özellikleri; Co4+ iyonlarının, Co3+ iyonlarından daha önce yüksek spin konfigürasyonunu tercih edeceğini göstermektedir. Ancak octahedral alandaki d orbitallerinin ligand alan yarılma enerjileri; Co3+ iyonlarının yüksek spin konfigürasyonlarının, Co4+ iyonlarının yüksek spin konfigürasyonlarından daha önce gerçekleseceğini göstermektedir.
This study deals with the electronic configuration of Co ions in misfit Ca3Co4O9 system at high temperature. The magnetic behaviour of this system shows an anomaly around 700 K. It is believed that this anomaly is caused by spin state transitions of Co2+, Co3+ and Co4+ ions in the system. A detailed study of the symmetry properties of the wave functions of Co ions in an octahedral environment indicates that Co4+ ion prefers high spin configuration earlier than Co3+ ions. On the other hand the ligand field splitting of d orbitals in an octahedral environment shows that high spin configuration of Co3+ ions should be populated earlier than the high spin state of Co4+ ions.
Starting from the idea of Fischer–Tropsch (FT) synthesis as an ideal polymerisation reaction it is easily realised, that product olefins undergo secondary reactions and thereby modify the product ...distribution. This generally leads to chain length dependencies of certain olefin reaction possibilities, which are again suited to serve as a characteristic feature for the kind of olefin conversion. By extending an existing model and accounting for olefin readsorption, incorporation, hydrogenation and isomerisation via double bond shift and the chain length dependence of product solubilities, typical deviations from ideal distributions can be simulated and experimentally observed data with cobalt and iron catalysts can be satisfactorily described, suggesting the correctness of the assumptions made. Furthermore, other existing models dealing with the same issue are briefly discussed in this paper.
The activity and the selectivity of cobalt catalysts supported on a crystallised and on an amorphous zirconia were compared with cobalt supported on a γ-alumina catalyst. The catalysts supported on ...zirconium dioxide were found to present a better reducibility of the active phase and also to be capable of hydrogen adsorption via a spillover mechanism. It is proposed that these properties could account for a better catalytic activity and an increase of the chain growth probability (
α). At the same time, the estimated quantity of crystallised Co
3O
4 obtained after airflow calcination (for the same total cobalt loading) is related with the surface area of the support.
To study whether trace element limitations are present in methanogenic granular sludge from full-scale anaerobic bioreactors, four different anaerobic granular sludges (Nedalco, Eerbeek, Hoogeveen ...and Heineken) were screened for their metal content and their response to the addition of a metal cocktail and more specifically to cobalt. Three different methanogenic substrates (methanol, acetate and H
2/CO
2) were used and the response to trace metal addition was monitored by on-line measurement of the changes in the specific methanogenic activity (SMA) of the sludge. A significant increase of the SMA due to trace metal addition was observed only with the substrate methanol, especially addition of only cobalt had a great effect: the SMA with methanol of the Nedalco and Hoogeveen sludge increased from, respectively, 306 and 155
mg CH
4-COD
g
VSS
−1
d
−1 to 535 and 334
mg CH
4-COD
g
VSS
−1
d
−1 upon the addition of solely 5
μM cobalt. In the Heineken sludge, a limitation for another element was present as well. The cobalt concentrations in the sludges were low compared to the other trace elements and could not be directly related to the response of the SMA. With acetate as the substrate and in the presence of cobalt (5
μM) a reduction of the lag-phase was observed for the Nedalco, and more pronounced for the Heineken sludge. This indicates that cobalt is also important for the onset of the activity/growth of the acetotrophic methanogenic population. Screening of the trace metal content of anaerobic granular sludge in combination with the response of the SMA to trace metal addition is therefore a valuable tool to prevent and foresee trace metal limitation in anaerobic bioreactors.
Cobalt(II) complex nanoparticles of 14aneN
4: 1,5,8,12-tetraaza-2,9-dioxo-4,11-diphenylcyclotetradecane; 16aneN
4: 1,5,9,13-tetraaza-2,10-dioxo-4,12-diphenylcyclohexadecane; Bzo
214aneN
4: ...dibenzo-1,5,8,12-tetraaza-2,9-dioxo-4,11-diphenylcyclotetradecane and Bzo
216aneN
4: dibenzo-1,5,9,13-tetraaza-2,10-dioxo-4,12-diphenylcyclohexadecane have been encapsulated in the nanopores of zeolite-Y. The new complex nanoparticles entrapped in the nanoreactor of zeolite-Y were characterized by deferent techniques. These complexes (neat and encapsulated) were used for epoxidation of styrene with O
2 as oxidant in different solvents.
Cobalt(II) complex nanoparticles of 14aneN
4: 1,5,8,12-tetraaza-2,9-dioxo-4,11-diphenylcyclotetradecane; 16aneN
4: 1,5,9,13-tetraaza-2,10-dioxo-4,12-diphenylcyclohexadecane; Bzo
214aneN
4: dibenzo-1,5,8,12-tetraaza-2,9-dioxo-4,11-diphenylcyclotetradecane and Bzo
216aneN
4: dibenzo-1,5,9,13-tetraaza-2,10-dioxo-4,12-diphenylcyclohexadecane have been encapsulated in the nanopores of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of bis(diamine)cobalt(II) (diamine
=
1,2-diaminoethane, 1,3-diaminopropane, 1,2-diaminobenzene, 1,3-diaminobenzene); Co(N–N)
2
2+–NaY; in the nanopores of the zeolite-Y, and (ii) in situ condensation of the cobalt(II) precursor complex with ethylcinnamate. The new complex nanoparticles entrapped in the nanoreactor of zeolite-Y were characterized by several techniques: BET, chemical analysis and spectroscopic methods (FT-IR, UV–vis, XRD, and DRS). These complexes (neat and encapsulated) were used for epoxidation of styrene with O
2 as oxidant in different solvents. Electronic spectra of the reaction mixture indicated that the oxidation proceeds through a free radical mechanism.
Aus der Literatur ist bekannt, dass anaerobe, Essigsäure umsetzende und methanbildende Bakterien ein verstärktes Kobaltbedürfnis haben. Deshalb kann die Leistungsfähigkeit einer Vergärungsanlage ...durch einen Mangel an Kobalt limitiert sein. Die Untersuchungen bestätigen, dass im vorliegenden Fall die Vergärung einer Mischung aus kommunalen und gewerblichen Bioabfällen einer Limitierung durch Mangel an Kobalt unterlag und erbrachten somit erstmalig den Nachweis, dass auch bei einer Bioabfallvergärung ein Kobaltmangel auftreten kann. Ferner zeigten sie, dass Batch‐Gärtests, die gemäß der VDI‐Richtlinie 4630 mit ungewaschenem Klärschlamm durchgeführt wurden, auf einen Spurenelementmangel keinen sicheren Hinweis lieferten. Eine Kobaltdosierung erhöhte die Durchsatzleistung der Faulung und steigerte gleichzeitig die Biogasrate um fast 17 %. Trotz Verkürzen der hydraulischen Verweilzeit von 17 auf 12 Tage konnte die Biogasausbeute gesteigert werden (+3 %). Dabei können die zusätzlichen Chemikalienkosten durch die höheren Erlöse aus der Einspeisung des aus dem Biogas erzeugten elektrischen Stroms kompensiert werden.
Untersuchungen zur Vergärung von einer Mischung aus kommunalen und gewerblichen Bioabfällen bestätigen eine Limitierung der Biogasausbeute durch Kobalt‐Mangel. Eine entsprechende Kobalt‐Dosierung kann die Durchsatzleistung der Faulung erhöhen und gleichzeitig die Biogasausbeute steigern.
PDF
