Uptake and degradation of Orange II by zinc aluminum layered double oxides

Abstract

In this work ZnAl-layered double oxide composites (LDO) were developed to remove organic dyes in wastewater by adsorption and photocatalysis. Various LDO composites were synthesized by adjusting synthetic parameters including the molar ratio of Zn to Al, and calcination temperature. LDO adsorption and photocatalytic properties for decomposition of organic dyes were also investigated. Orange II sodium salt (OrgII), an azo dye and water contaminant, was chosen as the model to investigate the properties of LDOs compared with commercial ZnO, TiO2 (P25) and ZnO-LDH. The adsorption and photocatalytic performance results showed that LDO composites significantly enhanced adsorption-photocatalytic performance for OrgII degradation. LDO at the Zn/Al molar ratio of 2 (2)LDO has the best adsorption capacity (800.8 mg/g of OrgII for (2)LDO), and improved photocatalytic activity (74.3% of OrgII decomposition for (2)LDO). It is believed that the better adsorption properties of LDO are due to the adsorption and intercalation of dyes in the interlayer during LDO's rehydration process. ZnO/ZnAl-rehydrated layered double hydroxide composites (ZnO-rLDH) after rehydration of LDOs in aqueous solution was also obtained. After restoration in water, the structure and morphology of ZnO-rLDHs were characterized by XRD, FTIR, SEM/TEM, N2 adsorption/desorption and UV-vis-DRS. Finally, the relations between the structural features of the ZnO-rLDH composites and the adsorption properties and photocatalytic activity of LDO was studied.

ZnO-Layered Double Hydroxide@Graphitic Carbon Nitride Composite for Consecutive Adsorption and Photodegradation of Dyes under UV and Visible Lights

“…(The change patterns of FT-IR spectra along with the adsorption time were given in Figure S9.) The successful intercalation of OrgII into LDH was also demonstrated by the shifting XRD pattern in our previous report [6]. …”

“…The (100) peak of g-C 3 N 4 represents the heptazine unit with an interplanar separation of 0.66 nm and (002) peak represents the graphitic-like layer with an interlayer distance of 0.31 nm [25]. The XRD pattern of ZnO-LDH showed the presence of both ZnAl-LDH and ZnO [6]. The strong peaks at 31.2°, 33.8°, and 35.6° two theta found in ZnO-LDH sample are indexed to the diffraction of the (100), (002) and (101) planes of ZnO (JCPDS No.…”

“…Recently, layered double hydroxides (LDHs), a family of anionic clay, have attracted much attention in the removal of organic dyes from wastewater due to their unique properties such as high ionic exchange capacity, tunable particle size, large surface area and various composition as well as good stability [2,3,4]. LDHs and the layered double oxide (LDO) by thermal treatment of LDH have displayed high adsorption capacity for organic dyes such as Orange II (Org II) [5,6,7]. Removal of the adsorbed organic dyes in the solid adsorbent is an essential step if the technology is to be used in practice.…”

“…Photocatalytic degradation is a sustainable and green approach to removing the adsorbed dyes. However, these LDHs and their derivatives are only photocatalytically active under UV light [6]. In addition, these LDH-based materials showed little adsorption towards cationic dyes and did not show good photocatalytic performance under visible lights.…”

Preparation of Salen–Metal Complexes (Metal = Co or Ni) Intercalated ZnCr-LDHs and Their Photocatalytic Degradation of Rhodamine B

“…The behavior of the materials in the UV-Vis diffuse reflectance indicates the photo-absorption ability. Previous studies showed that the narrowed-down band gap may lead to the enhancement of the responsiveness to visible light, as well as charge transfer and separation [36,37]. According to the literature, the band gap of the material can be calculated using the simplified Kubelka-Munk formula E g = 1240/λ (nm) [38], where λ is the wavelength corresponding to the absorption onset.…”