Evaluation of the Adsorptive Performance of Rambutan-shaped γ-Al2O3 Micro-nanostructure against Wastewater Containing the Azo Dye: Methyl Orange

Aim: The aim of this study is to explore and evaluate the possibility of rambutan-shaped micro-nanostructured γ-Al2O3 material's usage as an adsorbent in industrial wastewater processing.Background: Every year, more than 7 million tons of dyestuff-containing wastewater are produced in the industry. Although there are many adsorbents like fly ash and clays, the shortages limit their actual applications. It is still necessary to find a new cheaper adsorbent.Objective: The paper aimed to investigate the adsorption capacity and decolorization ability of rambutan- shaped γ-A2O3 material synthesized via a composite soft template method.Methods: The rambutan-shaped γ-Al2O3 material was prepared and characterized via XRD, TEM, FE-SEM, and FT-IR (See our group's published article in "Ming Shen*, et al., Acta Phys.-Chim. Sin. 2013, 29 (10), 2286-2294"). The methyl orange aqueous solution was selected as the model of industrial wastewater. The methyl orange solution (15.0 mg·L^-1) with different pH (2∼9) was exposed to a series of amounts of γ-Al2O3 powder ranging from 10.0 to 70.0 mg. Different concentrations of methyl orange solution, ranging from 5.0 to 200.0 mg·L^-1 were also tested with the same amount of γ-Al2O3 powder (50.0 mg). The adsorption-calcination cycle analysis was performed with methyl orange solution (50.0 mg·L^-1) and 500.0 mg of γ-Al2O3 powder at pH=3.Results: The γ-Al2O3 material exhibits excellent adsorption capacity (114.10 mg·g^-1) towards acidic methyl orange aqueous solution. At the same time, the decolorization rate of the γ-Al2O3 material reaches about 88%. This material still keeps a 50% decolorization rate after 6 repeats of the adsorption- calcination cycle. Moreover, the excellent self-sedimentation ability of this material also provides an easy separation for future industrial applications.Conclusion: The γ-Al2O3 material with rambutan-like micro-nanostructure presents excellent adsorption capacity/decolorization ability and self-sedimentation ability. It can be used as a new type of adsorbent for wastewater processing. The rambutan-shaped micro-nanostructure plays an important role in maintaining the adsorption ability of the γ-Al2O3 material.