A spectroscopic and Monte Carlo study of the unexpected promotion of interfacial H4SiO4 polymerization on an iron oxide in the presence of arsenate

Swedlund, Peter J.; Din, Salah Ud; Airey, Margaux; Kuo, Cheng‐Yu; Weg, A.C.van de; Vella, Joseph; Akhtar, Naeem

doi:10.1016/j.colsurfa.2015.08.042

Cited by 3 publications

(2 citation statements)

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“…4 , Table 2 ). Considering that arsenate has been reported to inhibit silicate polymerization on goethite at elevated loadings [ 46 ], we speculate that the effect of P on the dissolution kinetics of the Si-containing precipitates could be due to inhibited silicate sorption and polymerization (see next paragraph) in the presence of elevated levels of phosphate, which in turn could facilitate the access of ascorbate.…”

Section: Discussionmentioning

confidence: 97%

“…Previous work indicated a ~ 2–3 times slower reductive dissolution of silicate-containing natural ferrihydrite (water treatment residues) [ 34 ] than of synthetic 2-line ferrihydrite in 10 mM ascorbic acid at pH 3.0 [ 27 , 32 ], which has been attributed to a stabilizing effect of sorbed silicate [ 34 ]. We speculate that the pronounced inhibiting effect of silicate on reductive dissolution kinetics could be due to silicate binding and polymerization on the Fe(III)-precipitate surface [ 46 – 50 ] that might limit surface accessibility for ascorbate.…”

Section: Discussionmentioning

confidence: 99%

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Reductive dissolution of As(V)-bearing Fe(III)-precipitates formed by Fe(II) oxidation in aqueous solutions

et al. 2019

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Iron(III)-precipitates formed by the oxidation of dissolved Fe(II) are important sorbents for major and trace elements in aquatic and terrestrial systems. Their reductive dissolution in turn may result in the release of associated elements. We examined the reductive dissolution kinetics of an environmentally relevant set of Fe(II)-derived arsenate-containing Fe(III)-precipitates whose structure as function of phosphate (P) and silicate (Si) content varied between poorly-crystalline lepidocrocite, amorphous Fe(III)-phosphate, and Si-containing ferrihydrite. The experiments were performed with 0.2–0.5 mM precipitate-Fe(III) using 10 mM Na-ascorbate as reductant, 5 mM bipyridine as Fe(II)-complexing ligand, and 10 mM MOPS/5 mM NaOH as pH 7.0 buffer. Times required for the dissolution of half of the precipitate (t50%) ranged from 1.5 to 39 h; spanning a factor 25 range. At loadings up to ~ 0.2 P/Fe (molar ratio), phosphate decreased the t50% of Si-free precipitates, probably by reducing the crystallinity of lepidocrocite. The reductive dissolution of Fe(III)-phosphates formed at higher P/Fe ratios was again slower, possibly due to P-inhibited ascorbate binding to precipitate-Fe(III). The slowest reductive dissolution was observed for P-free Si-ferrihydrite with ~ 0.1 Si/Fe, suggesting that silicate binding and polymerization may reduce surface accessibility. The inhibiting effect of Si was reduced by phosphate. Dried-resuspended precipitates dissolved 1.0 to 1.8-times more slowly than precipitates that were kept wet after synthesis, most probably because drying enhanced nanoparticle aggregation. Variations in the reductive dissolution kinetics of Fe(II) oxidation products as reported from this study should be taken into account when addressing the impact of such precipitates on the environmental cycling of co-transformed nutrients and contaminants.Electronic supplementary materialThe online version of this article (10.1186/s12932-019-0062-2) contains supplementary material, which is available to authorized users.

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Section: Discussionmentioning

confidence: 97%