Formation and stability of iron(II) oxidation products under natural concentrations of dissolved silica

Mayer, T.; Jarrell, W. M.

doi:10.1016/0043-1354(95)00265-0

Cited by 73 publications

(58 citation statements)

References 20 publications

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“…Several researchers have observed that the presence of dissolved silica species can inhibit or promote the formation of different mineral phases (Anderson and Benjamin, 1985;Hansen et al, 1994;Mayer and Jarrell, 1996). We therefore expect to see qualitative disparities in the precipitates formed in Columns 1 and 3 compared to the silica-fed Columns 2 and 4.…”

Section: Precipitate Characterizationmentioning

confidence: 97%

“…(Klausen et al, 1995;Sivavec and Horney, 1997;Erbs et al, 1999;Williams and Scherer, 2001;Lee and Batchelor, 2002a,b;O'Loughlin et al, 2003). The presence of dissolved silica species has been shown (Anderson and Benjamin, 1985;Hansen et al, 1994;Mayer and Jarrell, 1996) to alter the types of iron (hydr)oxide phases that may form. A shift in precipitate identity to less redox active phases or phases with fewer sorption sites could potentially reduce PRB efficacy.…”

Section: Introductionmentioning

confidence: 99%

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The effect of silica on the degradation of organohalides in granular iron columns

Kohn

Roberts

2006

Journal of Contaminant Hydrology

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Dissolved silica species are naturally occurring, ubiquitous groundwater constituents with corrosioninhibiting properties. Their influence on the performance and longevity of iron-based permeable reactive barriers for treatment of organohalides was investigated through long-term column studies using Connelly iron as the reactive medium. Addition of dissolved silica (0.5 mM) to the column feed solution led to a reduction in iron reactivity of 65% for trichloroethylene (TCE), 74% for 1,1,2-trichloroethane (1,1,2-TCA), and 93% for 1,1,1-trichloroethane (1,1,1-TCA), compared to columns operated under silica-free conditions. Even though silica adsorption was a gradual process, the inhibitory effect was evident within the first week, with subsequent decreases in reactivity over 288 days being relatively minor. Lower concentrations of dissolved silica species (0.2 mM) led to a lesser decrease (70%) in iron reactivity toward 1,1,1-TCA. The presence of dissolved silica species produced a shift in TCE product distribution toward the more highly chlorinated product cis-dichloroethylene (cis-DCE), although it did not appear to alter products originating from the trichloroethanes. The major corrosion products identified were magnetite (Fe 3 O 4 ) ) was only found in the silica-free column, indicating that silica may hinder its formation. A comparison with columns operated under the same conditions, but using Master Builder iron as the reactive matrix, showed that Connelly iron is initially less reactive, but performs better than Master Builder iron over 288 days. D

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Section: Precipitate Characterizationmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

The effect of silica on the degradation of organohalides in granular iron columns

Kohn

Roberts

2006

Journal of Contaminant Hydrology

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“…As the Si concentration at the surface increases, the isoelectric point (IEP) and point zero charge (PZC) decrease. As anion adsorption decreases above the IEP, Si adsorption could decrease the adsorption of other oxyanions such as P. Ferrihydrite is usually slowly transformed into more crystalline Fe oxides, but ferrihydrite formed in the presence of Si is a stable oxidation product (Schwertmann and Thalmann 1976;Mayer and Jarrell 1996) which can actually act as a sink for P (Mayer and Jarrell 2000). The reactions of Si under changing redox conditions are thus also important in the cycling of P, although the processes work both ways.…”

Section: Anoxia and Si Resorptionmentioning

confidence: 97%

The effects of anoxia on Si dynamics in sediments

2015

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Purpose This study explored the effects of anoxia on adsorbed Si dynamics in surface sediments. While the effects of anoxia on the adsorption and release of phosphorus (P) have been studied frequently, its effects on adsorbed silicon (Si) are commonly ignored, despite the similarities between the elements. The study addresses the theory that as both Si and P produce anionic ligands, processes that affect adsorbed P and its release could also affect Si and its release. Materials and methods Two main procedures were conducted: A sequential extraction procedure composed of (1) water, (2) 0.46 M sodium chloride, (3) 0.11 M sodium dithionite, (4) 0.1 M sodium hydroxide and (5) 0.5 M hydrochloric acid extractions, and a long-term release dynamics experiment (RDE) lasting 28 days. Both were conducted using seven sediment samples of different composition. Results and discussion Silicon behaved differently than P under anoxic conditions. Although anoxia generally causes increased release of Fe-bound P due to Fe 3+ reduction, the release of Si decreased under anoxic conditions in the loosely sorbed and redox-sensitive fractions of the sediments. The long-term experiment (RDE) showed that Si release was time-dependent and slower under anoxic than oxic conditions. Resorption to Al oxides and the formation of colloidal mixed Fe-Si oxides are possible reasons for these results. There were, however, also some indications that anoxic conditions enhanced biogenic Si (BSi) and mineral Si dissolution. Conclusions Anoxia clearly affects Si sorption processes, but it may have both negative (e.g. increased resorption preventing P adsorption) and positive (e.g. enhanced BSi dissolution, increasing dissolved Si concentration in water) effects on the release of Si. More investigations dealing with the subject are needed.

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“…Transport of colloids is collectively influenced by the stability of colloidal material (tendency to stay suspended), the hydrodynamics of porous media, and the tendency for retention to occur in the soil or rock medium. Colloid stability is affected by elemental composition (Mayer and Jarrell, 1996), aqueous phase pH, ionic strength , and electrolyte speciation . At least two mechanisms for retention occur: attachment and straining.…”

Section: Introductionmentioning

confidence: 99%