Fast Degradation of Green Pollutants Through Nanonets and Nanofibers of the Al-Doped Zinc Oxide

doi:10.1007/s40195-017-0682-4

Abstract

Abstract:

In this study, series of nanolayered structures of Zn-Al LDHs were prepared by urea hydrolysis. Nanofibers and nanonets of the Al-doped ZnO were formed via the decomposition of the nanolayers under high pressure and temperature. Nanospheres were also prepared for comparison. The different morphologies of the prepared nanomaterials were confirmed by several techniques. An improvement for the optical properties of the doped zinc oxides was observed through narrowing of their band gap energies because of transforming the nanolayers to nanonets and nanofibers. The photocatalytic activities of the prepared nanomaterials were studied through photocatalytic degradation of the pollutants of acid green dyes. Complete decolorization and mineralization of green dyes happened in the presence of the nanolayers and nanospheres within 4-6 h, while the nanonets and the nanofibers achieved the complete decolorization and degradation of the dyes at shorter time 1.3 h. These results could be explained though the kinetic study of the photocatalytic degradation of dyes. It was concluded that the nanonets and the nanofibers were very effective for the photocatalytic degradation of pollutants.

Key words: Al-doped ZnO nanolayers, Nanofibers, Nanonets, Band gap energy, Photocatalytic degradation, Acid green dyes pollutants

Osama Saber, Haifa Alomair, Mohamed Abu-Abdeen, Abdullah Aljaafari. Fast Degradation of Green Pollutants Through Nanonets and Nanofibers of the Al-Doped Zinc Oxide[J]. Acta Metallurgica Sinica (English Letters), 2018, 31(5): 533-546.

Figures/Tables 14

Scheme 1 Scheme 1 Chemical formula of acid green 1 and photocatalytic reactor

Fig. 1 XRD patterns of: a ZnAl-30, b ZnAl-15, c ZnAl-05

Fig. 2 FTIR spectra of: a ZnAl-30, b ZnAl-15, c ZnAl-05

Fig. 3 Thermal analyses (TG and DSC) of: a ZnAl-30, b ZnAl-15, c ZnAl-05

Fig. 4 TEM images a and EDX analysis b of ZnAl-30

Fig. 5 XRD patterns of: a ZnAl-30-TP, b ZnAl-15-TP, c ZnAl-05-TP

Table 1 Average crystallite size calculated from X-ray patterns of the treated nanolayered structures

Samples	2θ (deg.)	Area	Cry. size (nm)	Av. size (nm)
ZnAl-30-TP	31.7	100	7.8	6
	34.4	291	3
	36.2	164	6.4
ZnAl-15-TP	31.7	194	11.4	11
	34.4	136	10.8
	36.2	305	9.6
ZnAl-05-TP	31.7	192	16.2	16
	34.4	140	16.2
	36.2	317	14.5

Fig. 6 TEM images and EDX analysis of ZnAl-30-TP

Fig. 7 TEM images and EDX analysis of ZnAl-15-TP

Fig. 8 TEM images and EDX analysis of ZnAl-05-TP The chemical composition of the ZnAl-30-TP, ZnAl-15-TP, and ZnAl-05-TP was analyzed by energy-dispersive X-ray analysis (EDX) as shown in Figs. 6c, 7d, and 8e. The zinc, aluminum, and oxygen peaks were clearly shown. The EDX analysis and XRD results indicated that the aluminum was successfully immobilized onto the zinc oxide nanoparticles.

Fig. 9 UV-Vis spectra and band gaps of: a, f ZnAl-30, b, d ZnAl-15, c, e ZnAl-05

Fig. 10 UV-Vis spectra and band gaps of: a, f ZnAl-30-TP, b, e ZnAl-15-TP, c, d ZnAl-05-TP

Fig. 11 Absorbance spectra of AG1 with different irradiation times in UV light in the presence of a ZnAl-05 LDH, b ZnAl-15 LDH, c ZnAl-30 LDH (inset—typical kinetics obtained for the mineralization of AG1)

Fig. 12 Absorbance spectra of AG1 with different irradiation times in UV light in the presence of a ZnAl-05-TP, b ZnAl-15-TP, c ZnAl-30-TP (inset—typical kinetics obtained for the mineralization of AG1)

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