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Hierarchically porous silicon-carbon-nitrogen hybrid materials towards highly efficient and selective adsorption of organic dyes.

Meng L, Zhang X, Tang Y, Su K, Kong J - Sci Rep (2015)

Bottom Line: The hybrid material was conveniently generated by the pyrolysis of commercial polysilazane precursors using polydivinylbenzene microspheres as sacrificial templates.On the contrary, the hybrid materials do not adsorb the dyes with azo benzene structures, such as methyl orange, methyl red and congro red.Thus, the hierarchically porous Si-C-N hybrid material from a facile and low cost polymer-derived strategy provides a new perspective and possesses a significant potential in the treatment of wastewater with complex organic pollutants.

View Article: PubMed Central - PubMed

Affiliation: MOE Key Laboratory of Space Applied Physics and Chemistry, Shaanxi Key Laboratory of Macromolecular Science and Technology, School of Science, Northwestern Polytechnical University, Xi'an, 710072, P. R. China.

ABSTRACT
The hierarchically macro/micro-porous silicon-carbon-nitrogen (Si-C-N) hybrid material was presented with novel functionalities of totally selective and highly efficient adsorption for organic dyes. The hybrid material was conveniently generated by the pyrolysis of commercial polysilazane precursors using polydivinylbenzene microspheres as sacrificial templates. Owing to the Van der Waals force between sp-hybridized carbon domains and triphenyl structure of dyes, and electrostatic interaction between dyes and Si-C-N matrix, it exhibites high adsorption capacity and good regeneration and recycling ability for the dyes with triphenyl structure, such as methyl blue (MB), acid fuchsin (AF), basic fuchsin and malachite green. The adsorption process is determined by both surface adsorption and intraparticle diffusion. According to the Langmuir model, the adsorption capacity is 1327.7 mg·g(-1) and 1084.5 mg·g(-1) for MB and AF, respectively, which is much higher than that of many other adsorbents. On the contrary, the hybrid materials do not adsorb the dyes with azo benzene structures, such as methyl orange, methyl red and congro red. Thus, the hierarchically porous Si-C-N hybrid material from a facile and low cost polymer-derived strategy provides a new perspective and possesses a significant potential in the treatment of wastewater with complex organic pollutants.

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The MAS Solid-state 13C NMR spectra of MB, C1 and C1-MB (a), and the sp2-hybridization carbon atoms peaks fitted using Gaussian peaks (b).
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f19: The MAS Solid-state 13C NMR spectra of MB, C1 and C1-MB (a), and the sp2-hybridization carbon atoms peaks fitted using Gaussian peaks (b).

Mentions: Especially, the MAS Solid-state NMR was employed to give an experimental evidence for the adsorption mechanism. From the 13C NMR spectra (Figure 19a), there is an intense peak in the range of 120-150 ppm for C1, which is assigned to sp2-hybridized carbon atoms of Si-C-N materials7170. In addition, the peak at δ 1 ppm is ascribed to sp3-hybridized carbon atoms. For the pure MB, in addition to the broad signal in the range of δ 77–160 ppm assigned to the carbon atoms on the aromatic rings, a small peak at δ 178 ppm may be due to the carbonyl groups caused by air environment. For the C1 after adsorption of MB (C1-MB), the peak of sp2-hybridized carbon atoms at δ 120–150 ppm is significantly higher than that of sp3-hybridized carbon atoms at δ 1 ppm, indicating that numerous MB molecules have been adsorbed to the surface of porous C1. In order to have a clear study on the interaction of sp2-hybridized carbons between C1 and MB, the sp2-hybridization carbon atoms peaks of three samples were fitted using Gaussian peaks as shown in Figure 19b. Compared with pure C1 and MB, although no obvious chemical shift in the range of 120–150 ppm changes can be observed for C1-MB, the peak at δ 153.5 ppm derived from the central carbon atoms attached to triphenyl structure of MB was disappeared. It demonstrates that the chemical environmental of the carbon atoms attached to triphenyl structure of MB is changed because of the stack of MB molecules on surface of porous C1. Therefore, the chemical shift those carbons atoms changes towards high-field after adsorption. So the FTIR, XPS and MAS Solid-state NMR measurements mentioned above demonstrate that Van der Waals force between sp2-hybridized carbon atoms and electrostatic interaction might be the main reason for the highly effective and totally selective adsorption functionality of Si–C–N hybrid materials.


Hierarchically porous silicon-carbon-nitrogen hybrid materials towards highly efficient and selective adsorption of organic dyes.

Meng L, Zhang X, Tang Y, Su K, Kong J - Sci Rep (2015)

The MAS Solid-state 13C NMR spectra of MB, C1 and C1-MB (a), and the sp2-hybridization carbon atoms peaks fitted using Gaussian peaks (b).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4300473&req=5

f19: The MAS Solid-state 13C NMR spectra of MB, C1 and C1-MB (a), and the sp2-hybridization carbon atoms peaks fitted using Gaussian peaks (b).
Mentions: Especially, the MAS Solid-state NMR was employed to give an experimental evidence for the adsorption mechanism. From the 13C NMR spectra (Figure 19a), there is an intense peak in the range of 120-150 ppm for C1, which is assigned to sp2-hybridized carbon atoms of Si-C-N materials7170. In addition, the peak at δ 1 ppm is ascribed to sp3-hybridized carbon atoms. For the pure MB, in addition to the broad signal in the range of δ 77–160 ppm assigned to the carbon atoms on the aromatic rings, a small peak at δ 178 ppm may be due to the carbonyl groups caused by air environment. For the C1 after adsorption of MB (C1-MB), the peak of sp2-hybridized carbon atoms at δ 120–150 ppm is significantly higher than that of sp3-hybridized carbon atoms at δ 1 ppm, indicating that numerous MB molecules have been adsorbed to the surface of porous C1. In order to have a clear study on the interaction of sp2-hybridized carbons between C1 and MB, the sp2-hybridization carbon atoms peaks of three samples were fitted using Gaussian peaks as shown in Figure 19b. Compared with pure C1 and MB, although no obvious chemical shift in the range of 120–150 ppm changes can be observed for C1-MB, the peak at δ 153.5 ppm derived from the central carbon atoms attached to triphenyl structure of MB was disappeared. It demonstrates that the chemical environmental of the carbon atoms attached to triphenyl structure of MB is changed because of the stack of MB molecules on surface of porous C1. Therefore, the chemical shift those carbons atoms changes towards high-field after adsorption. So the FTIR, XPS and MAS Solid-state NMR measurements mentioned above demonstrate that Van der Waals force between sp2-hybridized carbon atoms and electrostatic interaction might be the main reason for the highly effective and totally selective adsorption functionality of Si–C–N hybrid materials.

Bottom Line: The hybrid material was conveniently generated by the pyrolysis of commercial polysilazane precursors using polydivinylbenzene microspheres as sacrificial templates.On the contrary, the hybrid materials do not adsorb the dyes with azo benzene structures, such as methyl orange, methyl red and congro red.Thus, the hierarchically porous Si-C-N hybrid material from a facile and low cost polymer-derived strategy provides a new perspective and possesses a significant potential in the treatment of wastewater with complex organic pollutants.

View Article: PubMed Central - PubMed

Affiliation: MOE Key Laboratory of Space Applied Physics and Chemistry, Shaanxi Key Laboratory of Macromolecular Science and Technology, School of Science, Northwestern Polytechnical University, Xi'an, 710072, P. R. China.

ABSTRACT
The hierarchically macro/micro-porous silicon-carbon-nitrogen (Si-C-N) hybrid material was presented with novel functionalities of totally selective and highly efficient adsorption for organic dyes. The hybrid material was conveniently generated by the pyrolysis of commercial polysilazane precursors using polydivinylbenzene microspheres as sacrificial templates. Owing to the Van der Waals force between sp-hybridized carbon domains and triphenyl structure of dyes, and electrostatic interaction between dyes and Si-C-N matrix, it exhibites high adsorption capacity and good regeneration and recycling ability for the dyes with triphenyl structure, such as methyl blue (MB), acid fuchsin (AF), basic fuchsin and malachite green. The adsorption process is determined by both surface adsorption and intraparticle diffusion. According to the Langmuir model, the adsorption capacity is 1327.7 mg·g(-1) and 1084.5 mg·g(-1) for MB and AF, respectively, which is much higher than that of many other adsorbents. On the contrary, the hybrid materials do not adsorb the dyes with azo benzene structures, such as methyl orange, methyl red and congro red. Thus, the hierarchically porous Si-C-N hybrid material from a facile and low cost polymer-derived strategy provides a new perspective and possesses a significant potential in the treatment of wastewater with complex organic pollutants.

Show MeSH