Abstract
A series of γ-Al<sub>2</sub>O<sub>3</sub> with high surface area applied for removal of Congo red (CR) from aqueous solution was prepared from cheap inorganic aluminum precursor using simple precipitation method in presence of an inexpensive anionic surfactant (sodium dodecyl sulfate, SDS). The material characterization by several techniques revealed that SDS plays an important role on the morphology and textural properties of the resultant γ-Al<sub>2</sub>O<sub>3</sub>, and the largest surface area of γ-Al<sub>2</sub>O<sub>3</sub> (416.65 m<sup>2</sup>/g) was obtained by varying molar ratio of SDS to aluminum precursor to be 0.375. The CR adsorption experiments identified that the adsorption isotherms on the as-synthesized γ-Al<sub>2</sub>O<sub>3</sub> obey the Langmuir model. The maximum CR adsorption capacity of 831.7 mg/g was provided on the γ-Al<sub>2</sub>O<sub>3</sub> having the largest surface area, verifying the importance of material surface area for achieving superior adsorption performance. The CR adsorption behaviors onto various γ-Al<sub>2</sub>O<sub>3</sub> materials were analyzed using different kinetic models, and the results suggest a multistep adsorption mechanism. Besides, the equilibrium adsorption data well fitted the pseudo-second-order kinetic model, manifesting that the chemical adsorption process is the rate-limiting step. Moreover, the γ-Al<sub>2</sub>O<sub>3</sub> synthesized showed good recyclability for CR removal, and thus could be a very effective and cost-saving adsorbent for the treatment of industrial wastewater containing organic pollutants.
Highlights
Synthetic dyestuffs are used in various manufactories for the production of rubber, paper, textile, plastics, cosmetics, etc., where a large amount of water is expended for cleaning purpose, resulting in dye-containing waste effluents [1, 2]
Different types of adsorbents have been utilized for dye removal from aqueous solutions [6, 7]. γ-Al2O3 is one of the most commonly used adsorbents owing to their large surface area, high chemical stability, nontoxicity, abundant sources, and so on [8, 9]
The pseudo boehmite and γ-Al2O3 materials synthesized in the present work and the sample of Com-Al2O3 as well were identified by means of XRD technique, as shown in Figure 2, confirming the deserved crystal structure of each material
Summary
Synthetic dyestuffs are used in various manufactories for the production of rubber, paper, textile, plastics, cosmetics, etc., where a large amount of water is expended for cleaning purpose, resulting in dye-containing waste effluents [1, 2]. What’s more, CR is resistant to biodegradation because of its complex and stable aromatic structure. It must be removed from wastewater before being discharged into natural water bodies. Different types of adsorbents have been utilized for dye removal from aqueous solutions [6, 7]. Γ-Al2O3 is one of the most commonly used adsorbents owing to their large surface area, high chemical stability, nontoxicity, abundant sources, and so on [8, 9]. In addition to adsorbing dyes, γ-Al2O3 is adaptable for the purification of other aqueous pollutants such as heavy metals [10], nitrates [11], fluorides [12], etc
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