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Schwertmannite Synthesis through Ferrous Ion Chemical Oxidation under Different H2O2 Supply Rates and Its Removal Efficiency for Arsenic from Contaminated Groundwater.

Liu F, Zhou J, Zhang S, Liu L, Zhou L, Fan W - PLoS ONE (2015)

Bottom Line: Results showed that pH decreased from ~3.48 to ~1.96, ~2.06, ~2.12, ~2.14, or ~2.17 after 60 h reaction when the ferrous ions solution received the following corresponding amounts of H2O2: 1.80 mL at 2 h (treatment 1); 0.90 mL at 2 h and 14 h (treatment 2); 0.60 mL at 2, 14, and 26 h (treatment 3); 0.45 mL at 2, 14, 26, and 38 h (treatment 4), or 0.36 mL at 2, 14, 26, 38, and 50 h (treatment 5).Slow H2O2 supply significantly inhibited the total iron precipitation efficiency but improved the specific surface area or arsenic (III) removal capacity of schwertmannite.However, the above parameters correspondingly changed to 17.3%, 16.30 m2/g, and 96.5%, respectively, in treatment 5.

View Article: PubMed Central - PubMed

Affiliation: Environmental Engineering Laboratory, College of Resource and Environment, Shanxi Agricultural University, Taigu, China.

ABSTRACT
Schwertmannite-mediated removal of arsenic from contaminated water has attracted increasing attention. However, schwertmannite chemical synthesis behavior under different H2O2 supply rates for ferrous ions oxidation is unclear. This study investigated pH, ferrous ions oxidation efficiency, and total iron precipitation efficiency during schwertmannite synthesis by adding H2O2 into FeSO4 · 7H2O solution at different supply rates. Specific surface area and arsenic (III) removal capacity of schwertmannite have also been studied. Results showed that pH decreased from ~3.48 to ~1.96, ~2.06, ~2.12, ~2.14, or ~2.17 after 60 h reaction when the ferrous ions solution received the following corresponding amounts of H2O2: 1.80 mL at 2 h (treatment 1); 0.90 mL at 2 h and 14 h (treatment 2); 0.60 mL at 2, 14, and 26 h (treatment 3); 0.45 mL at 2, 14, 26, and 38 h (treatment 4), or 0.36 mL at 2, 14, 26, 38, and 50 h (treatment 5). Slow H2O2 supply significantly inhibited the total iron precipitation efficiency but improved the specific surface area or arsenic (III) removal capacity of schwertmannite. For the initial 50.0 μg/L arsenic (III)-contaminated water under pH ~7.0 and using 0.25 g/L schwertmannite as an adsorbent, the total iron precipitation efficiency, specific surface area of the harvested schwertmannite, and schwertmannite arsenic(III) removal efficiency were 29.3%, 2.06 m2/g, and 81.1%, respectively, in treatment 1. However, the above parameters correspondingly changed to 17.3%, 16.30 m2/g, and 96.5%, respectively, in treatment 5.

No MeSH data available.


Scanning electron microscopy images and specific surface area of precipitates harvested from different schwertmannite synthesis systems.150 mL of FeSO4·7H2O solution with addition of a: 1.80 mL of H2O2 at 2 h (treatment 1); b: 0.90 mL of H2O2 at 2 and 14 h (treatment 2); c: 0.60 mL of H2O2 at 2, 14, and 26 h (treatment 3); d: 0.45 mL of H2O2 at 2, 14, 26, and 38 h (treatment 4); e: 0.36 mL of H2O2 at 2, 14, 26, 38, and 50 h (treatment 5); and f: Acidithiobacillus ferrooxidans; volume concentration of H2O2: 30%; molar concentration of FeSO4·7H2O: 160 mmol/L
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pone.0138891.g005: Scanning electron microscopy images and specific surface area of precipitates harvested from different schwertmannite synthesis systems.150 mL of FeSO4·7H2O solution with addition of a: 1.80 mL of H2O2 at 2 h (treatment 1); b: 0.90 mL of H2O2 at 2 and 14 h (treatment 2); c: 0.60 mL of H2O2 at 2, 14, and 26 h (treatment 3); d: 0.45 mL of H2O2 at 2, 14, 26, and 38 h (treatment 4); e: 0.36 mL of H2O2 at 2, 14, 26, 38, and 50 h (treatment 5); and f: Acidithiobacillus ferrooxidans; volume concentration of H2O2: 30%; molar concentration of FeSO4·7H2O: 160 mmol/L

Mentions: The morphology of schwertmannite was investigated through scanning electron microscopy (SEM) method, and the SEM images of the synthesized schwertmannite in this work are shown in Fig 5. Schwertmannite particles were small spheroids with a diameter of 0.68 μm (Fig 5A) and a specific surface area of 2.06 m2/g when formed in the fastest ferrous ions oxidation system, i.e., treatment 1. The size and specific surface area of these spherical particles were relatively smaller than that of schwertmannite formed under systems with slow H2O2 addition. For example, in treatment 2, the diameter and specific surface area of schwertmannite particles increased to 1.37 μm and 2.40 m2/g, and the particles surface evidently generated some spikes (Fig 5B). When the H2O2 supply rate was further reduced, the diameter or specific surface area of the schwertmannite particles further increased to 1.56~1.81 μm or 9.50~16.30 m2/g, and long needle-like structures grown on the particle surface formed the characteristic “hedge-hog” structure of schwertmannite (Fig 5C–5E). In general, small solid particle diameters indicate large specific surface area [43]. On the contrary, the results of the present study showed that the specific surface area of schwertmannite was increased with the increasing particle diameter. Therefore, the “spike” “needles”, and “hedge-hog” structures resulted in existence of more cavities on the schwertmannite surface, which may play a vital role in improving the specific surface area of schwertmannite. This finding had not been reported in previous studies. Consistent with the present study, schwertmannite “spherical” or “hedge-hog” structure had also been revealed in a number of previous studies [27, 28].


Schwertmannite Synthesis through Ferrous Ion Chemical Oxidation under Different H2O2 Supply Rates and Its Removal Efficiency for Arsenic from Contaminated Groundwater.

Liu F, Zhou J, Zhang S, Liu L, Zhou L, Fan W - PLoS ONE (2015)

Scanning electron microscopy images and specific surface area of precipitates harvested from different schwertmannite synthesis systems.150 mL of FeSO4·7H2O solution with addition of a: 1.80 mL of H2O2 at 2 h (treatment 1); b: 0.90 mL of H2O2 at 2 and 14 h (treatment 2); c: 0.60 mL of H2O2 at 2, 14, and 26 h (treatment 3); d: 0.45 mL of H2O2 at 2, 14, 26, and 38 h (treatment 4); e: 0.36 mL of H2O2 at 2, 14, 26, 38, and 50 h (treatment 5); and f: Acidithiobacillus ferrooxidans; volume concentration of H2O2: 30%; molar concentration of FeSO4·7H2O: 160 mmol/L
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4580644&req=5

pone.0138891.g005: Scanning electron microscopy images and specific surface area of precipitates harvested from different schwertmannite synthesis systems.150 mL of FeSO4·7H2O solution with addition of a: 1.80 mL of H2O2 at 2 h (treatment 1); b: 0.90 mL of H2O2 at 2 and 14 h (treatment 2); c: 0.60 mL of H2O2 at 2, 14, and 26 h (treatment 3); d: 0.45 mL of H2O2 at 2, 14, 26, and 38 h (treatment 4); e: 0.36 mL of H2O2 at 2, 14, 26, 38, and 50 h (treatment 5); and f: Acidithiobacillus ferrooxidans; volume concentration of H2O2: 30%; molar concentration of FeSO4·7H2O: 160 mmol/L
Mentions: The morphology of schwertmannite was investigated through scanning electron microscopy (SEM) method, and the SEM images of the synthesized schwertmannite in this work are shown in Fig 5. Schwertmannite particles were small spheroids with a diameter of 0.68 μm (Fig 5A) and a specific surface area of 2.06 m2/g when formed in the fastest ferrous ions oxidation system, i.e., treatment 1. The size and specific surface area of these spherical particles were relatively smaller than that of schwertmannite formed under systems with slow H2O2 addition. For example, in treatment 2, the diameter and specific surface area of schwertmannite particles increased to 1.37 μm and 2.40 m2/g, and the particles surface evidently generated some spikes (Fig 5B). When the H2O2 supply rate was further reduced, the diameter or specific surface area of the schwertmannite particles further increased to 1.56~1.81 μm or 9.50~16.30 m2/g, and long needle-like structures grown on the particle surface formed the characteristic “hedge-hog” structure of schwertmannite (Fig 5C–5E). In general, small solid particle diameters indicate large specific surface area [43]. On the contrary, the results of the present study showed that the specific surface area of schwertmannite was increased with the increasing particle diameter. Therefore, the “spike” “needles”, and “hedge-hog” structures resulted in existence of more cavities on the schwertmannite surface, which may play a vital role in improving the specific surface area of schwertmannite. This finding had not been reported in previous studies. Consistent with the present study, schwertmannite “spherical” or “hedge-hog” structure had also been revealed in a number of previous studies [27, 28].

Bottom Line: Results showed that pH decreased from ~3.48 to ~1.96, ~2.06, ~2.12, ~2.14, or ~2.17 after 60 h reaction when the ferrous ions solution received the following corresponding amounts of H2O2: 1.80 mL at 2 h (treatment 1); 0.90 mL at 2 h and 14 h (treatment 2); 0.60 mL at 2, 14, and 26 h (treatment 3); 0.45 mL at 2, 14, 26, and 38 h (treatment 4), or 0.36 mL at 2, 14, 26, 38, and 50 h (treatment 5).Slow H2O2 supply significantly inhibited the total iron precipitation efficiency but improved the specific surface area or arsenic (III) removal capacity of schwertmannite.However, the above parameters correspondingly changed to 17.3%, 16.30 m2/g, and 96.5%, respectively, in treatment 5.

View Article: PubMed Central - PubMed

Affiliation: Environmental Engineering Laboratory, College of Resource and Environment, Shanxi Agricultural University, Taigu, China.

ABSTRACT
Schwertmannite-mediated removal of arsenic from contaminated water has attracted increasing attention. However, schwertmannite chemical synthesis behavior under different H2O2 supply rates for ferrous ions oxidation is unclear. This study investigated pH, ferrous ions oxidation efficiency, and total iron precipitation efficiency during schwertmannite synthesis by adding H2O2 into FeSO4 · 7H2O solution at different supply rates. Specific surface area and arsenic (III) removal capacity of schwertmannite have also been studied. Results showed that pH decreased from ~3.48 to ~1.96, ~2.06, ~2.12, ~2.14, or ~2.17 after 60 h reaction when the ferrous ions solution received the following corresponding amounts of H2O2: 1.80 mL at 2 h (treatment 1); 0.90 mL at 2 h and 14 h (treatment 2); 0.60 mL at 2, 14, and 26 h (treatment 3); 0.45 mL at 2, 14, 26, and 38 h (treatment 4), or 0.36 mL at 2, 14, 26, 38, and 50 h (treatment 5). Slow H2O2 supply significantly inhibited the total iron precipitation efficiency but improved the specific surface area or arsenic (III) removal capacity of schwertmannite. For the initial 50.0 μg/L arsenic (III)-contaminated water under pH ~7.0 and using 0.25 g/L schwertmannite as an adsorbent, the total iron precipitation efficiency, specific surface area of the harvested schwertmannite, and schwertmannite arsenic(III) removal efficiency were 29.3%, 2.06 m2/g, and 81.1%, respectively, in treatment 1. However, the above parameters correspondingly changed to 17.3%, 16.30 m2/g, and 96.5%, respectively, in treatment 5.

No MeSH data available.