Iron oxidation kinetics and phosphate immobilization along the flow-path from groundwater into surface water
Grift, B. van der; Rozemeijer, J.C. ; Griffioen, J. ; Velde, Y. van der - \ 2014
Hydrology and Earth System Sciences 18 (2014)11. - ISSN 1027-5606 - p. 4687 - 4702.
suspended sediment - ferrous iron - fresh-water - phosphorus limitation - nutrient dynamics - fe(ii) oxidation - arsenic removal - natural-waters - riparian zone - river
The retention of phosphorus in surface waters through co-precipitation of phosphate with Fe-oxyhydroxides during exfiltration of anaerobic Fe(II) rich groundwater is not well understood. We developed an experimental field set-up to study Fe(II) oxidation and P immobilization along the flow-path from groundwater into surface water in an agricultural experimental catchment of a small lowland river. We physically separated tube drain effluent from groundwater discharge before it entered a ditch in an agricultural field. Through continuous discharge measurements and weekly water quality sampling of groundwater, tube drain water, exfiltrated groundwater, and surface water, we investigated Fe(II) oxidation kinetics and P immobilization processes. The oxidation rate inferred from our field measurements closely agreed with the general rate law for abiotic oxidation of Fe(II) by O-2. Seasonal changes in climatic conditions affected the Fe(II) oxidation process. Lower pH and lower temperatures in winter (compared to summer) resulted in low Fe oxidation rates. After exfiltration to the surface water, it took a couple of days to more than a week before complete oxidation of Fe(II) is reached. In summer time, Fe oxidation rates were much higher. The Fe concentrations in the exfiltrated groundwater were low, indicating that dissolved Fe(II) is completely oxidized prior to inflow into a ditch. While the Fe oxidation rates reduce drastically from summer to winter, P concentrations remained high in the groundwater and an order of magnitude lower in the surface water throughout the year. This study shows very fast immobilization of dissolved P during the initial stage of the Fe(II) oxidation process which results in P-depleted water before Fe(II) is completely depleted. This cannot be explained by surface complexation of phosphate to freshly formed Fe-oxyhydroxides but indicates the formation of Fe(III)-phosphate precipitates. The formation of Fe(III)-phosphates at redox gradients seems an important geochemical mechanism in the transformation of dissolved phosphate to structural phosphate and, therefore, a major control on the P retention in natural waters that drain anaerobic aquifers.
Quantifying microorganisms during biooxidation of arsenite and bioleaching of zinc sulfide
Dinkla, I.J.T. ; Gonzalez Contreras, P.A. ; Gahan, C.S. ; Weijma, J. ; Buisman, C.J.N. ; Henssen, M.J.C. ; Sandström, A. - \ 2013
Minerals Engineering 48 (2013). - ISSN 0892-6875 - p. 25 - 30.
acidithiobacillus-ferrooxidans - iron oxidation - ferrous iron - ferric iron - leptospirillum - bacteria - cultures - thiobacillus - chalcopyrite - arsenate
The development of molecular tools for the detection and quantification of both species as well as functional traits, aids in a better understanding and control of microbial processes. Presently, these methods can also be used to assess the activity of these organisms or functions, even in complex ecosystems and difficult matrices such as ores and low pH samples. In this paper we present the versatility of one of these tools, Q-PCR, to allow accurate and fast insight in changes in two types of microbial processes representing two ways in which microbes can interact with metals, bioleaching and bioprecipitation. Using the Q-PCR technique it was possible to identify and quantify the thermoacidophilic archaeon Acidianus sp. to be the main microbial strain responsible for biooxidation of arsenite in a low pH reactor. The method was also used to study the dynamics between the iron oxidizing and sulfur oxidizing acidophiles during bioleaching of a zinc concentrate in a batch reactor system and showed that the iron oxidizer Leptospirillum ferriphilum that dominated the starting culture disappeared upon addition of the concentrate. Gradually, bacterial activity was regained starting with growth of sulfur oxidizers and at later stage iron oxidizers started to grow. Molecular analysis can be used to direct research to the relevant organisms involved and concentrate on improving their application (in the arsenite case Acidianus sp.) or in understanding appearances and disappearances of microorganisms (during leaching of zinc concentrate the disappearance of Leptospirillum after high inoculation levels) in order to allow optimization of leaching efficiencies at the lowest (oxygen) costs.
Homogeneous, heterogeneous and biological oxidation of iron(II) in rapid sand filtration
Beek, C.G.E.M. van; Hiemstra, T. ; Hofs, B. ; Nederlof, M.M. ; Paassen, J.A.M. van; Reijnen, G.K. - \ 2012
Journal of Water Services Research and Technology-Aqua 61 (2012)1. - ISSN 0003-7214 - p. 1 - 13.
ferrous iron - fe(ii) oxidation - gallionella-ferruginea - isotope fractionation - metal (hydr)oxides - aqueous systems - organic-matter - atom exchange - ground-water - kinetics
Homogeneous, heterogeneous and biological oxidation may precipitate iron(II) as iron(III) hydroxides. In this paper we evaluate the conditions under which each of these processes is dominant in rapid sand filtration (RSF). It is demonstrated that in the presence of iron(III) hydroxide precipitates homogeneous oxidation is negligible compared with heterogeneous oxidation. As soon as iron oxidizing bacteria (IOB) are present, biological oxidation may contribute substantially, in particular under conditions of slight acidity and low oxygen concentration. As the oxidation step is preceded by an adsorption/uptake step, the competition between heterogeneous and biological oxidation is not determined by the oxidation rate, but by the adsorption or uptake rate. Extracellular polymeric substance (EPS), excreted by all kinds of bacteria, may serve as an initial adsorbent for dissolved iron(II) and iron(III) hydroxides. Because adsorption and oxidation of iron (II) either on biofilms (or EPS) or on mineral surfaces, are chemical processes, 'EPS iron oxidation' is not considered as a biological process. The so-called 'biological iron oxidation' actually refers to a treatment method characterized by high filtration rates and limited oxygen supply, where iron(II) is removed mainly by heterogeneous oxidation. The contribution of oxidation of iron(II) by IOB in this method is variable and may even be absent.
Adsorption and surface oxidation of Fe(II) on metal (hydr)oxides.
Hiemstra, T. ; Riemsdijk, W.H. van - \ 2007
Geochimica et Cosmochimica Acta 71 (2007)24. - ISSN 0016-7037 - p. 5913 - 5933.
oxide-water interface - lepidocrocite gamma-feooh - ray-absorption-spectroscopy - aqueous-solution interface - intrinsic proton affinity - solid-solution interface - electrical double-layer - charge-distribution - ferrous iron - ion adsorption
The Fe(II) adsorption by non-ferric and ferric (hydr)oxides has been analyzed with surface complexation modeling. The CD model has been used to derive the interfacial distribution of charge. The fitted CD coefficients have been linked to the mechanism of adsorption. The Fe(II) adsorption is discussed for TiO2, ¿-AlOOH (boehmite), ¿-FeOOH (lepidocrocite), ¿-FeOOH (goethite) and HFO (ferrihydrite) in relation to the surface structure and surface sites. One type of surface complex is formed at TiO2 and ¿-AlOOH, i.e. a surface-coordinated Fe2+ ion. At the TiO2 (Degussa) surface, the Fe2+ ion is probably bound as a quattro-dentate surface complex. The CD value of Fe2+ adsorbed to ¿-AlOOH points to the formation of a tridentate complex, which might be a double edge surface complex. The adsorption of Fe(II) to ferric (hydr)oxides differs. The charge distribution points to the transfer of electron charge from the adsorbed Fe(II) to the solid and the subsequent hydrolysis of the ligands that coordinate to the adsorbed ion, formerly present as Fe(II). Analysis shows that the hydrolysis corresponds to the hydrolysis of adsorbed Al(III) for ¿-FeOOH and ¿-FeOOH. In both cases, an adsorbed M(III) is found in agreement with structural considerations. For lepidocrocite, the experimental data point to a process with a complete surface oxidation while for goethite and also HFO, data can be explained assuming a combination of Fe(II) adsorption with and without electron transfer. Surface oxidation (electron transfer), leading to adsorbed Fe(III)(OH)2, is favored at high pH (pH > 7.5) promoting the deprotonation of two FeIII-OH2 ligands. For goethite, the interaction of Fe(II) with As(III) and vice versa has been modeled too. To explain Fe(II)¿As(III) dual-sorbate systems, formation of a ternary type of surface complex is included, which is supposed to be a monodentate As(III) surface complex that interacts with an Fe(II) ion, resulting in a binuclear bidentate As(III) surface complex.
A bipolar membrane combined with ferric iron reduction as an efficient cathode system in microbial fuel cells
Heijne, A. ter; Hamelers, H.V.M. ; Wilde, V. de; Rozendal, R.A. ; Buisman, C.J.N. - \ 2006
Environmental Science and Technology 40 (2006)17. - ISSN 0013-936X - p. 5200 - 5205.
electricity-generation - ferrous iron - thiobacillus-ferrooxidans - oxygen reduction - mediator-less - biofuel cell - oxidation - biofilm - reactor - water
There is a need for alternative catalysts for oxygen reduction in the cathodic compartment of a microbial fuel cell (MFC). In this study, we show that a bipolar membrane combined with ferric iron reduction on a graphite electrode is an efficient cathode system in MFCs. A flat plate MFC with graphite felt electrodes, a volume of 1.2 L and a projected surface area of 290 cm2 was operated in continuous mode. Ferric iron was reduced to ferrous iron in the cathodic compartment according to Fe3+ + e- Fe2+ (E0 = +0.77 V vs NHE, normal hydrogen electrode). This reversible electron transfer reaction considerably reduced the cathode overpotential. The low catholyte pH required to keep ferric iron soluble was maintained by using a bipolar membrane instead of the commonly used cation exchange membrane. For the MFC with cathodic ferric iron reduction, the maximum power density was 0.86 W/m2 at a current density of 4.5 A/m2. The Coulombic efficiency and energy recovery were 80-95% and 18-29% respectively
Denitrification in aqueos FeEDTA solutions
Maas, P.M.F. van der; Fassotte-Harmsen, L. ; Weelink, S.A.B. ; Klapwijk, A. ; Lens, P.N.L. - \ 2004
Journal of Chemical Technology and Biotechnology 79 (2004)8. - ISSN 0268-2575 - p. 835 - 841.
nitric-oxide - ferrous iron - pseudomonas-aeruginosa - bacteria - nitrate - oxidation - reduction - sediments - aquifer - cations
The biological reduction of nitric oxide (NO) in aqueous solutions of FeEDTA is an important key reaction within the BioDeNOx process, a combined physico-chemical and biological technique for the removal of NO, from industrial flue gasses. To explore the reduction of nitrogen oxide analogues, this study investigated the full denitrification pathway in aqueous FeEDTA solutions, ie the reduction of NO3-, NO2-, NO via N2O to N-2 in this unusual medium. This was done in batch experiments at 30degreesC with 25 mmol dm(-3) FeEDTA solutions (pH 7.2 +/- 0.2). Also Ca2+ (2 and 10 mmol dm(-3)) and Mg2+ (2 mmol dm(-3)) were added in excess to prevent free, uncomplexed EDTA. Nitrate reduction in aqueous solutions of Fe(III)EDTA is accompanied by the biological reduction of Fe(III) to Fe(II), for which ethanol, methanol and also acetate are suitable electron donors. Fe(II)EDTA can serve as electron donor for the biological reduction of nitrate to nitrite, with the concomitant oxidation of Fe(II)EDTA to Fe(III)EDTA. Moreover, Fe(II)EDTA can also serve as electron donor for the chemical reduction of nitrite to NO, with the concomitant formation of the nitrosyl-complex Fe(II)EDTA-NO. The reduction of NO in Fe(II)EDTA was found to be catalysed biologically and occurred about three times faster at 55 degreesC than NO reduction at 30 degreesC. This study showed that the nitrogen and iron cycles are strongly coupled and that FeEDTA has an electron-mediating role during the subsequent reduction of nitrate, nitrite, nitric oxide and nitrous oxide to dinitrogen gas. (C) 2004 Society of Chemical Industry.
Reduction of nitrogen oxides in aquous Fe-EDTA solutions
Maas, P.M.F. van der; Sandt, T. van de; Klapwijk, A. ; Lens, P.N.L. - \ 2003
Biotechnology Progress 19 (2003)4. - ISSN 8756-7938 - p. 1323 - 1328.
dissimilatory fe(iii) - activated-sludge - ferrous iron - nitrate - oxidation - denitrification - biodegradation - degradation - bacteria - removal
The reduction of nitric oxide (NO) in aqueous solutions of Fe(II)EDTA is one of the core processes in BioDeNOx, an integrated physicochemical and biological technique for NO, removal from industrial flue gases. NO reduction in aqueous solutions of Fe(II)EDTA (20-25 mM, pH 7.2 +/- 0.2) was investigated in batch experiments at 55 degreesC. Reduction of NO to N-2 was found to be biologically catalyzed with nitrous oxide (N2O) as an intermediate. Various sludges from full-scale denitrifying and anaerobic reactors were capable to catalyze NO reduction under thermophilic conditions. The NO reduction rate was not affected by the presence of ethanol or acetate. EDTA-chelated Fe(II) was found to be a suitable electron donor for the biological reduction of nitric oxide to N2, with the concomitant formation of Fe(III)EDTA. In the presence of ethanol, EDTA-chelated Fe(III) was reduced to Fe(II)EDTA. This study strongly indicates that redox cycling of FeEDTA plays an important role in the biological denitrification process within the BioDeNOx concept.