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Direct Synthesis of Novel and Reactive Sulfide-modified Nano Iron through Nanoparticle Seeding for Improved Cadmium-Contaminated Water Treatment.

Su Y, Adeleye AS, Huang Y, Zhou X, Keller AA, Zhang Y - Sci Rep (2016)

Bottom Line: Syntheses monitoring experiments show that seeding accelerates the reduction rate from Fe(2+) to Fe(0) by 19%.Both X-ray diffraction and Mössbauer analyses further confirm that increased nanoparticle seeding results in formation of more Fe(0) crystals.The synthesized nanohybrid has high cadmium removal capacity and holds promising prospects for treatment of metal-contaminated water.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China.

ABSTRACT
Magnetic sulfide-modified nanoscale zerovalent iron (S-nZVI) is of great technical and scientific interest because of its promising application in groundwater remediation, although its synthesis is still a challenge. We develop a new nanoparticle seeding method to obtain a novel and reactive nanohybrid, which contains an Fe(0) core covered by a highly sulfidized layer under high extent of sulfidation. Syntheses monitoring experiments show that seeding accelerates the reduction rate from Fe(2+) to Fe(0) by 19%. X-ray adsorption near edge structure (XANES) spectroscopy and extended X-ray absorption fine structure analyses demonstrate the hexahedral Fe-Fe bond (2.45 and 2.83 Å) formation through breaking down of the 1.99 Å Fe-O bond both in crystalline and amorphous iron oxide. The XANES analysis also shows 24.2% (wt%) of FeS with bond length of 2.4 Å in final nanohybrid. Both X-ray diffraction and Mössbauer analyses further confirm that increased nanoparticle seeding results in formation of more Fe(0) crystals. Nano-SiO2 seeding brings down the size of single Fe(0) grain from 32.4 nm to 18.7 nm, enhances final Fe(0) content from 5.9% to 55.6%, and increases magnetization from 4.7 to 65.5 emu/g. The synthesized nanohybrid has high cadmium removal capacity and holds promising prospects for treatment of metal-contaminated water.

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Room-temperature Mössbauer spectra of (A) S-nZVI (in glass), (B) FeSSi-0.012 g nano-SiO2, (C) FeSSi-0.048 g nano-SiO2, (D) S-nZVI-0.064 g nano-TiO2, and (E) S-nZVI-0.082 g nano-Al2O3. (- -, original line; , total fitting line; , Fe0; , Fe2+; , Fe3+;).
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f6: Room-temperature Mössbauer spectra of (A) S-nZVI (in glass), (B) FeSSi-0.012 g nano-SiO2, (C) FeSSi-0.048 g nano-SiO2, (D) S-nZVI-0.064 g nano-TiO2, and (E) S-nZVI-0.082 g nano-Al2O3. (- -, original line; , total fitting line; , Fe0; , Fe2+; , Fe3+;).

Mentions: To further investigate the iron composition in the synthesized nanomaterials, Mössbauer spectroscopy was employed in this study (Fig. 6 and Table 4). A magnetic field or hyperfine field provides information on the electron spin density of a 57Fe nucleus in a magnetically ordered compound, and the isomer shift provides information on the oxidation state of Fe ions52. Every spectrum is composed of a sextet and two quadrupole doublets (Fig. 6). The sextet has a hyperfine field of about 33 T but no isomer shift, corresponding to zerovalent iron53. Among the two doublets, the one for Fe2+ is characterized by the large isomer shift, which is mainly due to the asymmetry of outer electrons; the other one is Fe3+, which has a smaller isomer shift due to the symmetric distribution of electrons on the d shell. As shown in Table 3, Fe0 accounts for 5.9% of total Fe in S-nZVI, 35.2% in FeSSi with 0.012 g nano-SiO2, 55.6% in FeSSi with 0.048 g nano-SiO2, 54.8% in S-nZVI with nano-TiO2, and 40.9% in S-nZVI with nano-Al2O3. Given the high Fe0 content in nZVI (~80%, shown by XANES), this result also corroborates our hypothesis that improved sulfidation suppresses Fe0 crystallization whereas nano-seeding can facilitate Fe0 formation in sulfidized systems. The accompanied change of ferrous and ferric ion content indicates the increased Fe0 content is due to the reduction of Fe2+ ions. Additionally, sulfidation can lead to the rise of isomer shift of Fe2+/Fe3+ ions, which may result from the decrease of shielding effect caused by p, d, and f shell on electrons in the s shell.


Direct Synthesis of Novel and Reactive Sulfide-modified Nano Iron through Nanoparticle Seeding for Improved Cadmium-Contaminated Water Treatment.

Su Y, Adeleye AS, Huang Y, Zhou X, Keller AA, Zhang Y - Sci Rep (2016)

Room-temperature Mössbauer spectra of (A) S-nZVI (in glass), (B) FeSSi-0.012 g nano-SiO2, (C) FeSSi-0.048 g nano-SiO2, (D) S-nZVI-0.064 g nano-TiO2, and (E) S-nZVI-0.082 g nano-Al2O3. (- -, original line; , total fitting line; , Fe0; , Fe2+; , Fe3+;).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837343&req=5

f6: Room-temperature Mössbauer spectra of (A) S-nZVI (in glass), (B) FeSSi-0.012 g nano-SiO2, (C) FeSSi-0.048 g nano-SiO2, (D) S-nZVI-0.064 g nano-TiO2, and (E) S-nZVI-0.082 g nano-Al2O3. (- -, original line; , total fitting line; , Fe0; , Fe2+; , Fe3+;).
Mentions: To further investigate the iron composition in the synthesized nanomaterials, Mössbauer spectroscopy was employed in this study (Fig. 6 and Table 4). A magnetic field or hyperfine field provides information on the electron spin density of a 57Fe nucleus in a magnetically ordered compound, and the isomer shift provides information on the oxidation state of Fe ions52. Every spectrum is composed of a sextet and two quadrupole doublets (Fig. 6). The sextet has a hyperfine field of about 33 T but no isomer shift, corresponding to zerovalent iron53. Among the two doublets, the one for Fe2+ is characterized by the large isomer shift, which is mainly due to the asymmetry of outer electrons; the other one is Fe3+, which has a smaller isomer shift due to the symmetric distribution of electrons on the d shell. As shown in Table 3, Fe0 accounts for 5.9% of total Fe in S-nZVI, 35.2% in FeSSi with 0.012 g nano-SiO2, 55.6% in FeSSi with 0.048 g nano-SiO2, 54.8% in S-nZVI with nano-TiO2, and 40.9% in S-nZVI with nano-Al2O3. Given the high Fe0 content in nZVI (~80%, shown by XANES), this result also corroborates our hypothesis that improved sulfidation suppresses Fe0 crystallization whereas nano-seeding can facilitate Fe0 formation in sulfidized systems. The accompanied change of ferrous and ferric ion content indicates the increased Fe0 content is due to the reduction of Fe2+ ions. Additionally, sulfidation can lead to the rise of isomer shift of Fe2+/Fe3+ ions, which may result from the decrease of shielding effect caused by p, d, and f shell on electrons in the s shell.

Bottom Line: Syntheses monitoring experiments show that seeding accelerates the reduction rate from Fe(2+) to Fe(0) by 19%.Both X-ray diffraction and Mössbauer analyses further confirm that increased nanoparticle seeding results in formation of more Fe(0) crystals.The synthesized nanohybrid has high cadmium removal capacity and holds promising prospects for treatment of metal-contaminated water.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China.

ABSTRACT
Magnetic sulfide-modified nanoscale zerovalent iron (S-nZVI) is of great technical and scientific interest because of its promising application in groundwater remediation, although its synthesis is still a challenge. We develop a new nanoparticle seeding method to obtain a novel and reactive nanohybrid, which contains an Fe(0) core covered by a highly sulfidized layer under high extent of sulfidation. Syntheses monitoring experiments show that seeding accelerates the reduction rate from Fe(2+) to Fe(0) by 19%. X-ray adsorption near edge structure (XANES) spectroscopy and extended X-ray absorption fine structure analyses demonstrate the hexahedral Fe-Fe bond (2.45 and 2.83 Å) formation through breaking down of the 1.99 Å Fe-O bond both in crystalline and amorphous iron oxide. The XANES analysis also shows 24.2% (wt%) of FeS with bond length of 2.4 Å in final nanohybrid. Both X-ray diffraction and Mössbauer analyses further confirm that increased nanoparticle seeding results in formation of more Fe(0) crystals. Nano-SiO2 seeding brings down the size of single Fe(0) grain from 32.4 nm to 18.7 nm, enhances final Fe(0) content from 5.9% to 55.6%, and increases magnetization from 4.7 to 65.5 emu/g. The synthesized nanohybrid has high cadmium removal capacity and holds promising prospects for treatment of metal-contaminated water.

No MeSH data available.


Related in: MedlinePlus