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Thiol-functionalized magnetite/graphene oxide hybrid as a reusable adsorbent for Hg2+ removal.

Bao J, Fu Y, Bao Z - Nanoscale Res Lett (2013)

Bottom Line: A thiol-functionalized magnetite/graphene oxide (MGO) hybrid as an adsorbent of Hg2+ was successfully synthesized by a two-step reaction.Its capacity reached 289.9 mg g-1 in a solution with an initial Hg2+ concentration of 100 mg l-1.After being exchanged with H+, the adsorbent could be reused.

View Article: PubMed Central - HTML - PubMed

Affiliation: Jiangsu Provincial Academy of Environmental Science, 241 Fenghuang West Street, Nanjing, Jiangsu 210036, China. jbaonj@gmail.com.

ABSTRACT
A thiol-functionalized magnetite/graphene oxide (MGO) hybrid as an adsorbent of Hg2+ was successfully synthesized by a two-step reaction. It exhibited a higher adsorption capacity compared to the bare graphene oxide and MGO due to the combined adsorption of thiol groups and magnetite nanocrystals. Its capacity reached 289.9 mg g-1 in a solution with an initial Hg2+ concentration of 100 mg l-1. After being exchanged with H+, the adsorbent could be reused. The adsorption of Hg2+ by the thiol-functionalized MGO fits well with the Freundlich isotherm model and followed pseudo-second-order kinetics.

No MeSH data available.


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Hysteresis loop and extraction of the thiol-functionalized MGO. (a) Hysteresis curve of thiol-functionalized MGO (inset, close view of hysteresis loops) and (b) the water solution dispersed with thiol-functionalized MGO and magnetic separation.
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Figure 3: Hysteresis loop and extraction of the thiol-functionalized MGO. (a) Hysteresis curve of thiol-functionalized MGO (inset, close view of hysteresis loops) and (b) the water solution dispersed with thiol-functionalized MGO and magnetic separation.

Mentions: GO was prepared from natural graphite using modified Hummer's method[16,17]. Fe3O4 nanoparticles were deposited on graphene oxide by decomposition of Fe(acac)3 in NMP solution (Figure 1, step A) at 190°C[18]. Figure 2a shows the XRD pattern of the product. The peaks at 30.2°, 35.5°, 43.1°, 53.5°, 57.0°, 62.4° in the pattern could be ascribed to diffraction of (220), (311), (400), (422), (511), and (440) crystal planes of Fe3O4 (magnetite, JCPDS no. 75–0033). Based on the Scherrer analysis of the pattern, the crystallite size of Fe3O4 was estimated to be 13.0 nm. The appearance of the magnetite phase was consistent with the electron diffraction pattern (inset in Figure 2b). The TEM image (Figure 2b) of the product showed that GO was decorated with magnetite aggregates with a size of several tens of nanometers. In the synthesis process, carbon monoxide was generated at a relatively high temperature and partially reduced Fe3+ to Fe2+. Then, the magnetite nanocrystals nucleated and grew at the oxygen-containing defects sites such as carboxyl, hydroxyl, and epoxy groups[14]. Finally, MGO was obtained. Thiol functional groups were grafted on the MGO by the reaction between MEA and carboxyl groups on GO activated by EDC (Figure 1, step B). Energy-dispersive X-ray spectroscopy (EDAX) analysis (Figure 2c) indicated the appearance of the sulfur element, indicating that the thiol groups were successfully grafted on MGO. Thus, the thiol-functionalized MGO was obtained after the reaction. The magnetic properties of the thiol-functionalized MGO were investigated using a superconducting quantum interference device (SQUID) magnetometer. Figure 3 shows the hysteresis loop of the thiol-functionalized MGO hybrids at room temperature (300 K). The saturation magnetization was 22.0 emu g-1, which was much smaller than 92.0 emu g-1, the saturation magnetization of bulk Fe3O4[19]. The reduction in the value of saturation magnetization could be attributed to the rather small size of magnetite and GO in the hybrids[20,21]. The remnant magnetization and coercivity for thiol-functionalized MGO were 0.74 emu g-1 and 11.89 Oe, respectively, which were ascribed to the superparamagnetic state of magnetite nanocrystals due to the size effect. Such superparamagnetic state of the adsorbent with small remnant magnetization and coercivity at room temperature could enable the adsorbent to be readily attracted and separated by even a small external magnetic field[22]. In fact, the thiol-functionalized MGO dispersed in water solution was easily extracted from water with a magnet (Figure 3b).


Thiol-functionalized magnetite/graphene oxide hybrid as a reusable adsorbent for Hg2+ removal.

Bao J, Fu Y, Bao Z - Nanoscale Res Lett (2013)

Hysteresis loop and extraction of the thiol-functionalized MGO. (a) Hysteresis curve of thiol-functionalized MGO (inset, close view of hysteresis loops) and (b) the water solution dispersed with thiol-functionalized MGO and magnetic separation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3842736&req=5

Figure 3: Hysteresis loop and extraction of the thiol-functionalized MGO. (a) Hysteresis curve of thiol-functionalized MGO (inset, close view of hysteresis loops) and (b) the water solution dispersed with thiol-functionalized MGO and magnetic separation.
Mentions: GO was prepared from natural graphite using modified Hummer's method[16,17]. Fe3O4 nanoparticles were deposited on graphene oxide by decomposition of Fe(acac)3 in NMP solution (Figure 1, step A) at 190°C[18]. Figure 2a shows the XRD pattern of the product. The peaks at 30.2°, 35.5°, 43.1°, 53.5°, 57.0°, 62.4° in the pattern could be ascribed to diffraction of (220), (311), (400), (422), (511), and (440) crystal planes of Fe3O4 (magnetite, JCPDS no. 75–0033). Based on the Scherrer analysis of the pattern, the crystallite size of Fe3O4 was estimated to be 13.0 nm. The appearance of the magnetite phase was consistent with the electron diffraction pattern (inset in Figure 2b). The TEM image (Figure 2b) of the product showed that GO was decorated with magnetite aggregates with a size of several tens of nanometers. In the synthesis process, carbon monoxide was generated at a relatively high temperature and partially reduced Fe3+ to Fe2+. Then, the magnetite nanocrystals nucleated and grew at the oxygen-containing defects sites such as carboxyl, hydroxyl, and epoxy groups[14]. Finally, MGO was obtained. Thiol functional groups were grafted on the MGO by the reaction between MEA and carboxyl groups on GO activated by EDC (Figure 1, step B). Energy-dispersive X-ray spectroscopy (EDAX) analysis (Figure 2c) indicated the appearance of the sulfur element, indicating that the thiol groups were successfully grafted on MGO. Thus, the thiol-functionalized MGO was obtained after the reaction. The magnetic properties of the thiol-functionalized MGO were investigated using a superconducting quantum interference device (SQUID) magnetometer. Figure 3 shows the hysteresis loop of the thiol-functionalized MGO hybrids at room temperature (300 K). The saturation magnetization was 22.0 emu g-1, which was much smaller than 92.0 emu g-1, the saturation magnetization of bulk Fe3O4[19]. The reduction in the value of saturation magnetization could be attributed to the rather small size of magnetite and GO in the hybrids[20,21]. The remnant magnetization and coercivity for thiol-functionalized MGO were 0.74 emu g-1 and 11.89 Oe, respectively, which were ascribed to the superparamagnetic state of magnetite nanocrystals due to the size effect. Such superparamagnetic state of the adsorbent with small remnant magnetization and coercivity at room temperature could enable the adsorbent to be readily attracted and separated by even a small external magnetic field[22]. In fact, the thiol-functionalized MGO dispersed in water solution was easily extracted from water with a magnet (Figure 3b).

Bottom Line: A thiol-functionalized magnetite/graphene oxide (MGO) hybrid as an adsorbent of Hg2+ was successfully synthesized by a two-step reaction.Its capacity reached 289.9 mg g-1 in a solution with an initial Hg2+ concentration of 100 mg l-1.After being exchanged with H+, the adsorbent could be reused.

View Article: PubMed Central - HTML - PubMed

Affiliation: Jiangsu Provincial Academy of Environmental Science, 241 Fenghuang West Street, Nanjing, Jiangsu 210036, China. jbaonj@gmail.com.

ABSTRACT
A thiol-functionalized magnetite/graphene oxide (MGO) hybrid as an adsorbent of Hg2+ was successfully synthesized by a two-step reaction. It exhibited a higher adsorption capacity compared to the bare graphene oxide and MGO due to the combined adsorption of thiol groups and magnetite nanocrystals. Its capacity reached 289.9 mg g-1 in a solution with an initial Hg2+ concentration of 100 mg l-1. After being exchanged with H+, the adsorbent could be reused. The adsorption of Hg2+ by the thiol-functionalized MGO fits well with the Freundlich isotherm model and followed pseudo-second-order kinetics.

No MeSH data available.


Related in: MedlinePlus