Economical Synthesis of High Surface Area γ-Al<sub>2</sub>O<sub>3</sub> for the Adsorption of Organic Pollutant from Wastewater

A series of γ-Al2O3 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-Al2O3, and the largest surface area of γ-Al2O3 (416.65 m2/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-Al2O3 obey the Langmuir model. The maximum CR adsorption capacity of 831.7 mg/g was provided on the γ-Al2O3 having the largest surface area, verifying the importance of material surface area for achieving superior adsorption performance. The CR adsorption behaviors onto various γ-Al2O3 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-Al2O3 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.