Bioelectrochemical Chain Elongation of Short-Chain Fatty Acids Creates Steering Opportunities for Selective Formation of n-Butyrate, n-Valerate or n-Caproate
Raes, Sanne M.T. ; Jourdin, Ludovic ; Buisman, Cees J.N. ; Strik, David P.B.T.B. - \ 2020
ChemistrySelect 5 (2020)29. - ISSN 2365-6549 - p. 9127 - 9133.
biocatalysis - bioelectrochemical chain elongation - electrochemistry - electron acceptor - microbial electrosynthesis
Valorization of organic residual streams that produce short-chain fatty acids (SCFA) require an energetic electron donor to form more valuable elongated products. By microbial electrosynthesis such electrons donor is supplied by an electrode. Here we show that bioelectrochemical chain elongation (BCE) of SCFA was steered to high selective product formation efficiencies depending on the supplied fatty acid. n-Butyrate, n-valerate, n-caproate were in different experimental conditions formed at respectively 94.1, 95.4 and 83.4% carbon-based selectivity. The reactor microbiomes adapted to the new feeding conditions within a few days. Remarkably, propionate elongation appeared to be preferred over acetate elongation. Propionate elongation resulted in highly selective formation of the odd-chain fatty acid n-valerate; this seems contradictory to ethanol chain elongation studies in which acetate is concurrently formed leading to straight fatty acids as by products.
Microbial Fuel Cells for Organic-Contaminated Soil Remedial Applications : A Review
Li, Xiaojing ; Wang, Xin ; Weng, Liping ; Zhou, Qixing ; Li, Yongtao - \ 2017
Energy Technology 5 (2017)8. - ISSN 2194-4288 - p. 1156 - 1164.
biocatalysis - electrochemistry - environmental chemistry - microbial fuel cells - soil remediation
Efficient noninvasive techniques are desired for repairing organic-contaminated soils. Bioelectrochemical technology, especially microbial fuel cells (MFCs), has been widely used to promote a polluted environmental remediation approach, and applications include wastewater, sludge, sediment, and soil remediation. Soil MFC remediation has been of significant concern in recent years, and thus, several aspects, including reactor configuration, electrode materials, soil conductivity, mass transfer, and microbial activity, are reviewed. Recent studies and key issues of soil MFCs and perspectives of organic-contamination remedial application are summarized, with the aim of assisting environmental scholars and engineers to gain a comprehensive understanding of MFC remediation. Insights are also offered on how to extend applications to help soil MFC remediation technology to advance and be applied in the future on a large scale.
Bioelectrochemical methane production from CO2
Eerten-Jansen, M.C.A.A. van - \ 2014
Wageningen University. Promotor(en): Cees Buisman, co-promotor(en): Annemiek ter Heijne. - Wageningen : Wageningen University - ISBN 9789462570061 - 189
methaanproductie - hernieuwbare energie - kooldioxide - elektrochemie - technieken - methane production - renewable energy - carbon dioxide - electrochemistry - techniques
Nowadays, most of our energy and fuels are produced from fossil resources. Fossil resources are, however, finite and their use results in emissions that affect the environment and human health. For reasons of energy security and environmental sustainability, there is therefore a need to produce energy and fuels from renewable resources. However, currently several challenges need to be overcome before renewable resources can be implemented on a large scale for the production of renewable energy and fuels. At the moment, all the renewable resources can be converted into electricity. However, renewable electricity is often produced intermittently. Therefore, excess renewable electricity, when supply does not meet demand, needs to be stored not to get lost. On the other hand, fuels can currently only be produced directly from biomass. There are, however, discussions about whether sufficient biomass can be produced in a sustainable way to cover the global demand.
A methane-producing Bioelectrochemical system (BES) is a novel technology to store excess renewable electricity in the form of methane, independent of biomass. Key principle of the methane-producing BES is the use of microorganisms as catalysts for the reduction of CO2 and electricity into methane. At the start of this thesis, the methane-producing BES was at its infancy, and for implementation of the technology a more thorough understanding of the technology was needed. Therefore, the aim of this thesis was to investigate the principles and perspectives of bioelectrochemical methane production from CO2. Focus was on the main bottlenecks limiting system’s performance.
In Chapter 2, the performance of a flat-plate methane-producing BES that was operated for 188 days was studied. The methane production rate and energy efficiency were investigated with time to elucidate the main bottlenecks limiting system’s performance. Using water as electron donor at the anode, methane production rate was 0.12 mL CH4/m2 cathode per day and overall energy efficiency was 3.1% at -0.55 V vs. Normal Hydrogen Electrode (NHE) cathode potential during continuous operation. Analysis of the internal resistance showed that in the short term, cathode and anode losses were dominant, but with time also pH gradient and transport losses became important.
Since the cathode energy losses were dominant, in Chapter 3, the microbial community that catalyses the reduction of CO2 into methane was studied. The microbial community was dominated by three phylotypes of methanogenic archaea, being closely related to Methanobacterium palustre and Methanobacterium aarhusense, and six phylotypes of bacteria. Besides methanogenic archaea, the bacteria seemed to be associated with methane production, producing hydrogen as intermediate. Biomass density varied greatly with part of the electrode being covered by a thick biofilm, whereas only clusters of biomass were found on other parts of the electrode.
Based on the microbial community it seemed that methane was produced indirectly using hydrogen as electron donor. Therefore, the electron transfer mechanisms of bioelectrochemical methane production were investigated in Chapter 4. Understanding the electron transfer mechanisms could give insight in methods to steer the process towards higher rate. A mixed culture methane-producing biocathode was developed that produced 5.2 L methane/m2 cathode per day at -0.7 V vs. NHE cathode potential. To elucidate the formation of intermediates, methanogenic archaea in the biocathode were inhibited with 2-bromethanesulfonate. Methane was primarily produced indirectly using hydrogen and acetate as electron donor, whereas methane production via direct electron transfer hardly occurred.
Besides producing methane, a BES could also be used to produce higher value organics, such as medium chain fatty acids. Currently, medium chain fatty acids are produced by fermenting (low-grade) organic biomass using an external electron donor, such as hydrogen and/or ethanol. A BES could provide the electrons in-situ, either as the electrode directly or indirectly via hydrogen. In Chapter 5, medium chain fatty acids production in a BES at -0.9 V vs. NHE cathode potential was demonstrated, without addition of an external electron mediator. Caproate (six carbon atoms), butyrate (four carbon atoms), and smaller fractions of caprylate (eight carbon atoms) were the main products formed from acetate (two carbon atoms). In-situ produced hydrogen was likely electron donor for the reduction of acetate. Electron and carbon balances revealed that 45% of the electrons in electric current and acetate, and 31% of the carbon in acetate were recovered in the formed products.
In Chapter 6, the present performance of methane-producing BESs was evaluated. Analysis of the performances reported in literature did not reveal an increase with time. Based on the main bottlenecks that limit system’s performance as found in this thesis, methods to increase performance were discussed. Besides, we showed that our envisioned first application is to upgrade CO2 in biogas of anaerobic digestion to additional methane. Finally, the feasibility of production of higher-value organics, such as medium chain fatty acids, in BES was discussed.
Role of protein-protein interactions on protein aggregation and emulsion flocculation
Delahaije, R.J.B.M. - \ 2014
Wageningen University. Promotor(en): Harry Gruppen, co-promotor(en): Peter Wierenga. - Wageningen : Wageningen University - ISBN 9789462570054 - 158
methaanproductie - elektrochemie - kooldioxide - elektrolyse - microbiële brandstofcellen - duurzame energie - methane production - electrochemistry - carbon dioxide - electrolysis - microbial fuel cells - sustainable energy
In this thesis, the effect of molecular properties on the aggregation and flocculation behaviour is studied. The aggregation behaviour was thought to be mainly affected by the structural stability of the protein. A decreased structural stability results in unfolded proteins which are more prone to aggregation. The flocculation behaviour was shown to be affected by the adsorbed amount at saturation and the adsorption rate. These parameters have been combined in a surface coverage model, which describes the stabilization of emulsions away from the iso‑electric point (pI) to be affected by excess protein in the continuous phase. In addition, a model was proposed for the prediction of the adsorbed amount at saturation. This is influenced by the protein charge and radius and system conditions (i.e. pH and ionic strength). The adsorption rate, which is a measure for the affinity of the protein towards the adsorption to the interface, was shown to increase with increasing relative exposed hydrophobicity and a decrease of the electrostatic repulsion (i.e. decrease of ionic strength or the protein charge). Close to the pI, the applicability of protein-stabilized emulsions is limited. Hence, a steric interaction was introduced to stabilize the emulsion. It was shown that glycation of the protein with a trisaccharide was sufficient to sterically stabilize the emulsions against pH-induced flocculation.
Joint development of insight into colloid stability and surface conduction
Lyklema, J. - \ 2014
Colloids and Surfaces. A: Physicochemical and Engineering Aspects 440 (2014). - ISSN 0927-7757 - p. 161 - 169.
electrical double-layer - silver-iodide - streaming potentials - particles - electrolytes - electrochemistry - interface - emulsions - capacity - mercury
This paper presents a historical overview of the parallels between the developments of colloid stability and surface conductivity. Starting from the situation during the Second World War, the interaction between the developments of these two branches of science appeared mutually beneficial. In particular, the properties of the non-diffuse parts of the double layers drew much attention. Implementations in the direction of future developments are given.
Energy consumption in membrane capacitive deionization for different water recoveries and flow rates, and comparison with reverse osmosis
Zhao, R. ; Porada, S. ; Biesheuvel, P.M. ; Wal, A. van der - \ 2013
Desalination 330 (2013)2. - ISSN 0011-9164 - p. 35 - 41.
ion-exchange membranes - brackish-water - porous-electrodes - desalination - carbon - plant - optimization - performance - electrochemistry - experience
Membrane capacitive deionization (MCDI) is a non-faradaic, capacitive technique for desalinating brackish water by adsorbing ions in charged porous electrodes. To compete with reverse osmosis, the specific energy consumption of MCDI needs to be reduced to less than 1 kWh per m3 of freshwater produced. In order to investigate the energy consumption of MCDI, we present here the energy consumption, and the fraction of energy that can be recovered during the ion desorption step of MCDI, as a function of influent concentration, water flow rate and water recovery. Furthermore, the energy consumption of MCDI based on experimental data of our lab-scale system is compared with literature data of reverse osmosis. Comparing with literature data for energy consumption in reverse osmosis, we find that for feed water with salinity lower than 60 mM, to obtain freshwater of ~ 1 g TDS/L, MCDI can be more energy efficient.
Optimization of salt adsorption rate in membrane capacitive deionization
Zhao, R. ; Satpradit, O.A. ; Rijnaarts, H. ; Biesheuvel, P.M. ; Wal, A. van der - \ 2013
Water Research 47 (2013)5. - ISSN 0043-1354 - p. 1941 - 1952.
waterkwaliteit - water - terugwinning - ontzilting - ionisatie - ionenuitwisselingsbehandeling - membranen - water quality - water - recovery - desalination - ionization - ion exchange treatment - membranes - ion-exchange membranes - porous-electrodes - water desalination - brackish-water - transport-properties - carbon - electrochemistry - performance - efficiency - anions
Membrane capacitive deionization (MCDI) is a water desalination technique based on applying a cell voltage between two oppositely placed porous electrodes sandwiching a spacer channel that transports the water to be desalinated. In MCDI, ion-exchange membranes are positioned in front of each porous electrode to prevent co-ions from leaving the electrode region during ion adsorption, thereby enhancing the salt adsorption capacity. MCDI can be operated at constant cell voltage (CV), or at a constant electrical current (CC). In this paper, we present both experimental and theoretical results for desalination capacity and rate in MCDI (both in the CV- and the CC-mode) as function of adsorption/desorption time, salt feed concentration, electrical current, and cell voltage. We demonstrate how by varying each parameter individually, it is possible to systematically optimize the parameter settings of a given system to achieve the highest average salt adsorption rate and water recovery.
Variable Charge and Electrical Double Layer of Mineral-Water Interfaces: Silver Halides versus Metal (Hydr)Oxides
Hiemstra, T. - \ 2012
Langmuir 28 (2012)44. - ISSN 0743-7463 - p. 15614 - 15623.
surface structural approach - chloride aqueous interface - bond-valence parameters - x-ray-scattering - molecular-dynamics - ion adsorption - equilibrium-constants - potential data - iodide - electrochemistry
Classically, silver (Ag) halides have been used to understand thermodynamic principles of the charging process and the corresponding development of the electrical double layer (EDL). A mechanistic approach to the processes on the molecular level has not yet been carried out using advanced surface complexation modeling (SCM) as applied to metal (hydr)oxide interfaces. Ag halides and metal (hydr)oxides behave quite differently in some respect. The location of charge in the interface of Ag halides is not a priori obvious. For AgI(s), SCM indicates the separation of interfacial charge in which the smaller silver ions are apparently farther away from the surface than iodide. This charge separation can be understood from the surface structure of the relevant crystal faces. Charge separation with positive charge above the surface is due to monodentate surface complex formation of Ag+ ions binding to I sites located at the surface. Negative surface charge is due to the desorption of Ag+ ions out of the lattice. These processes can be described with the charge distribution (CD) model. The MO/DFT optimized geometry of the complex is used to estimate the value of the CD. SCM reveals the EDL structure of AgI(s), having two Stern layers in series. The inner Stern layer has a very low capacitance (C-1 = 0.15 +/- 0.01 F/m(2)) in comparison to that of metal (hydr)oxides, and this can be attributed to the strong orientation of the (primary) water molecules on the local electrostatic field of the Ag+ and I- ions of the surface (relative dielectric constant epsilon(r) approximate to 6). Depending on the extent of water ordering, mineral surfaces may in principle develop a second Stern layer. The corresponding capacitance (C-2) will depend on the degree of water ordering that may decrease in the series AgI (C-2 = 0.57 F/m(2)), goethite (C-2 = 0.74 F/m(2)), and rutile (C-2 = infinity), as discussed. The charging principles of AgI minerals iodargyrite and miersite may also be applied to minerals with the same surface structure (e.g., sphalerite and wurtzite (ZnS)).
Energy consumption and constant current operation in membrane capacitive deionization
Zhao, R. ; Biesheuvel, P.M. ; Wal, A. van der - \ 2012
Energy & Environmental Science 5 (2012). - ISSN 1754-5692 - p. 9520 - 9527.
water desalination - porous-electrodes - seawater desalination - carbon electrodes - charge efficiency - brackish-water - technology - electrochemistry - electrosorption - improvement
Membrane capacitive deionization (MCDI) is a water desalination technology based on applying a cell voltage between two oppositely placed porous electrodes sandwiching a spacer channel that transports the water to be desalinated. In the salt removal step, ions are adsorbed at the carbon–water interface within the micropores inside the porous electrodes. After the electrodes reach a certain adsorption capacity, the cell voltage is reduced or even reversed, which leads to ion release from the electrodes and a concentrated salt solution in the spacer channel, which is flushed out, after which the cycle can start over again. Ion-exchange membranes are positioned in front of each porous electrode, which has the advantage of preventing the co-ions from leaving the electrode region during ion adsorption, while also allowing for ion desorption at reversed voltage. Both effects significantly increase the salt removal capacity of the system per cycle. The classical operational mode of MCDI at a constant cell voltage results in an effluent stream of desalinated water of which the salt concentration varies with time. In this paper, we propose a different operational mode for MCDI, whereby desalination is driven by a constant electrical current, which leads to a constant salt concentration in the desalinated stream over long periods of time. Furthermore, we show how the salt concentration of the desalinated stream can be accurately adjusted to a certain setpoint, by either varying the electrical current level and/or the water flow rate. Finally, we present an extensive dataset for the energy requirements of MCDI, both for operation at constant voltage and at constant current, and in both cases also for the related technology in which membranes are not included (CDI). We find consistently that in MCDI the energy consumption per mole of salt removed is lower than that in CDI. Within the range 10–200 mM ionic strength of the water to be treated, we find for MCDI a constant energy consumption of 22 kT per ion removed. Results in this work are an essential tool to evaluate the economic viability of MCDI for the treatment of saltwater.
ECA-water een mogelijk alternatief voor fungiciden : sector ontwikkelt kennis en kijkt naar mogelijkheden van toelating(interview met Jantineke Hofland-Zijlstra)
Arkesteijn, M. ; Hofland-Zijlstra, J.D. - \ 2012
Onder Glas 2012 (2012)2. - p. 5 - 7.
sierteelt - ziektepreventie - gewasbescherming - elektrochemie - waterzuivering - desinfecteren - gebruikswaarde - groenten - snijbloemen - ornamental horticulture - disease prevention - plant protection - electrochemistry - water treatment - disinfestation - use value - vegetables - cut flowers
Het gebruik van fungiciden vormt een knelpunt. Daardoor stijgt de belangstelling voor alternatieven als elektrochemisch geactiveerd water in de teelt en na-oogst. De actieve stoffen onderchlorig zuur en hypochloriet doden schimmels, bacteriën, algen en virussen in water, lucht of gewas. Dit geactiveerde water is als biocide wel toegestaan, maar een gewasbehandeling via vernevelen en spuiten niet.
|Elektrochemisch geactiveerd water in elf vragen (onderzoek van Wageningen UR Glastuinbouw geleid door J. Hofland-Zijlstra)
Sleegers, J. ; Wageningen UR Glastuinbouw, ; Hofland-Zijlstra, J.D. - \ 2011
Vakblad voor de Bloemisterij 66 (2011)20. - ISSN 0042-2223 - p. 34 - 35.
sierteelt - gewasbescherming - biociden - elektrochemie - elektrische energie - waterzuivering - irrigatie - cultuurmethoden - ornamental horticulture - plant protection - biocides - electrochemistry - electrical energy - water treatment - irrigation - cultural methods
Telers hebben de laatste tijd veel interesse in elektronisch geactiveerd water. Dit wordt door diverse leveranciers op de markt gebracht. Wat doet het en wat zijn de verschillen tussen de producten?
Stand van zaken geactiveerd water
Hofland-Zijlstra, Jantineke - \ 2011
plant protection - disinfestation - electrochemistry - greenhouse horticulture - agricultural research
Bestrijding van Botrytis in gerbera met UV-C en geactiveerd water
Hofland-Zijlstra, J.D. ; Os, E.A. van; Hamelink, R. ; Leeuwen, G.J.L. van; Marcelis, L.F.M. - \ 2011
ultraviolette straling - elektrochemie - botrytis - gerbera - plantenziektebestrijding - snijbloemen - desinfecteren - glastuinbouw - uv-lampen - ultraviolet radiation - electrochemistry - botrytis - gerbera - plant disease control - cut flowers - disinfestation - greenhouse horticulture - uv lamps
Poster met onderzoeksinformatie.
Toepassing electrochemisch geactiveerd water in de glastuinbouw
Hofland-Zijlstra, J.D. ; Hamelink, R. ; Vries, R.S.M. de; Bruning, H. - \ 2011
gewasbescherming - elektrochemie - desinfecteren - landbouwkundig onderzoek - glastuinbouw - plant protection - electrochemistry - disinfestation - agricultural research - greenhouse horticulture
Poster met onderzoeksinformatie.
|Veel interesse voor ECA-water (onderzoek door Jantine Hofland-Zijlstra)
Sleegers, J. ; Hofland-Zijlstra, J.D. - \ 2011
Vakblad voor de Bloemisterij 66 (2011)49. - ISSN 0042-2223 - p. 33 - 33.
sierteelt - gewasbescherming - elektrochemie - waterzuivering - chemische behandeling - desinfectie - ornamental horticulture - plant protection - electrochemistry - water treatment - chemical treatment - disinfection
De belangstelling voor elektrochemisch geactiveerd water is groot. Dat bleek uit een grote opkomst bij de Arenasessie over dit onderwerp, vorige week donderdag in het GreenQ Improvement Center. Meer dan 80 toehoorders zaten schouder aan schouder te zweten in de luchtdicht afgesloten presentatieruimte.
Performance of metal alloys as hydrogen evolution reaction catalysts in a microbial electrolysis cell
Jeremiasse, A.W. ; Bergsma, J. ; Kleijn, J.M. ; Saakes, M. ; Buisman, C.J.N. ; Cohen Stuart, M.A. ; Hamelers, H.V.M. - \ 2011
International Journal of Hydrogen Energy 36 (2011)17. - ISSN 0360-3199 - p. 10482 - 10489.
cobalt-molybdenum electrodeposition - exchange membranes - stainless-steel - cathodes - ph - electrochemistry - transport - tungsten - model - water
H2 can be produced from organic matter with a microbial electrolysis cell (MEC). To decrease the energy input and increase the H2 production rate of an MEC, a catalyst is used at the cathode. Platinum is an effective catalyst, but its high costs stimulate searching for alternatives, such as non-noble metal alloys. This study demonstrates that copper sheet coated with nickel-molybdenum, nickel-iron-molybdenum or cobalt-molybdenum alloys have a higher catalytic activity for the hydrogen evolution reaction than nickel cathodes, measured near neutral pH. However, the catalytic activity cannot be fully exploited near neutral pH because of mass transport limitation. The catalytic activity is best exploited at alkaline pH where mass transport is not limiting. This was demonstrated in an MEC with a cobalt-molybdenum coated cathode and anion exchange membrane, which produced 50 m3 H2 m-3 MEC d-1 (at standard temperature and pressure) at an electricity input of 2.5 kWh m-3 H2.
Kennisinventarisatie naar de achtergronden en toepassingen van electrochemisch geactiveerd water in de agrarische sector
Hofland-Zijlstra, J.D. ; Vries, R.S.M. de; Bruning, H. - \ 2011
Bleiswijk : Wageningen UR Glastuinbouw (Rapporten GTB 1087) - 38
elektrochemie - water - toepassingen - landbouw - tuinbouw - ultrasone behandeling - verneveling - teelt onder bescherming - ziektebestrijdende teeltmaatregelen - elektrolyse - electrochemistry - water - applications - agriculture - horticulture - ultrasonic treatment - nebulization - protected cultivation - cultural control - electrolysis
Wageningen UR Greenhouse Horticulture, with funding of Dutch Horticultural Board, has described the history and background of electrochemically activated water and explored possibilities for applications within the agricultural sector. In the Netherlands, the use of activated water as a biocide is allowed since 2009. Active ingredients of activated water are chlorine gas, hypochlorous acid and hypochlorite. Together with a high oxidation-reduction potential (ORP 750-1100 mV) there is a broad activity against bacteria, fungi, viruses, algae, protozoa and nematodes. Agricultural applications of activated water are described for seed disinfection, cleaning equipment and packing materials, removal of biofilms from pipes, disinfection of flowers, fruits and vegetables. The recent development of ultrasonic atomization of activated water created new possibilities to treat crops and harvested products against pathogens without excessive volumes of water and disinfect air from pathogens. For applications in protected crops it is desirable that the corrosive properties of the activated water should be minimized and capacities of dispensing equipment must be enlarged.
Site-Specific Immobilization of DNA in Glass Microchannels via Photolithography
Vong, T. ; Maat, J. ter; Beek, T.A. van; Lagen, B. van; Giesbers, M. ; Hest, J.C.M. van; Zuilhof, H. - \ 2009
Langmuir 25 (2009)24. - ISSN 0743-7463 - p. 13952 - 13958.
organic monolayers - covalent attachment - silicon surfaces - micrometer-scale - alkyl monolayers - electrochemistry - lithography - microarrays - strategies - h-si(111)
For the first time, it microchannel was photochemically patterned with it functional linker. This simple method was developed for the site-specific attachment of DNA via this linker onto silicon oxide surfaces (e.g., fused silica and borosilicate glass), both onto a flat surface and onto the inside of a fused silica microchannel. Sharp boundaries in the micrometer range between modified and unmodified zones were demonstrated by the attachment Of fluorescently labeled DNA oligomers. Studies of repeated hybridization-deliybridization cycles revealed selective and reversible binding of cDNA strands at the explicit locations. On average, similar to 7 x 10(11) fluorescently labeled DNA molecules were hybridized per square centimeter. The modified surfaces were characterized with X-ray photoelectron spectroscopy, infrared microscopy, static contact angle measurements, confocal laser scanning microscopy, and fluorescence detection (to quantify the attachment of the fluorescently labeled DNA).
Electrical double layer on silver iodide and overcharging in the presence of hydrolyzable cations
Lyklema, J. ; Golub, T.P. - \ 2007
Croatica Chemica Acta 80 (2007)3-4. - ISSN 0011-1643 - p. 303 - 311.
water interface - metal-ions - adsorption - iron - oxides - electrochemistry - coprecipitation - hydrolysis - chromium
Previous studies on the surface charge and electrokinetic charge on silver iodide as a function of the pAg in the presence of some monovalent and trivalent cations as the counterions were extended to include the influence of pH. The main reason for this study was to investigate the possible propensity of overcharging by adsorption of hydrolyzed counterions. It was found that for K+ as the counterion the double layer properties could be well represented in terms of a simple Gouy-Stern model, without accounting for hydrolysis. However, with Al3+ or La3+ as the counterions, adsorption of hydrolyzed species takes place when the pH is high enough, leading to electrokinetic charge reversal.
Electronic structure of transition metal-isocorrole complexes: a first quantum chemical study
Oort, B.F. van; Tangen, E. ; Ghosh, A. - \ 2004
European Journal of Inorganic Chemistry 2004 (2004)12. - ISSN 1434-1948 - p. 2442 - 2445.
peroxidase compound-i - pi-cation radicals - noninnocent ligands - porphyrins - corroles - centers - iron(iv) - electrochemistry - absorption - insights
DFT calculations indicate that the broad electronic-structural features of metalloisocorroles are rather similar to those of analogous metallocorroles. Thus, like their corrole analogues, many metalloisocorroles feature substantially non-innocent ligands. Another key point is that both corroles and isocorroles can exhibit at least two kinds of radical character, a2 and b1. However, corrole and isocorrole derivatives also differ significantly in a few ways: for example, the S = 1/2 CoPh complexes of corrole and isocorrole exhibit ground states of different symmetries (2A and 2A, respectively, in Cs notation), reflecting different interplays of metal(d)-ligand(p) interactions in corrole versus isocorrole derivatives. The ligand non-innocence phenomena encountered in this study are broadly reminiscent of similar phenomena in peroxidase compound I intermediates and their synthetic models. It seems reasonable, therefore, to adopt the view that this study, along with related studies on corrole derivatives, provides a broader chemical context for appreciating the electronic structures of high-valent heme protein intermediates.