Synthesis and characterization of mesoporous alumina and their performances for removing arsenic(V)

Mesoporous alumina, synthesized by combining the three-block copolymer Pluronic P123 as a template with aluminum hydroxide sal at room temperature followed by isolation and calcining, was employed as an effective adsorbent for removing arsenic(V) in the pH region of 2.5-7.0. Arsenic adsorption data of MA((400)) are well fitted by the Langmuir isotherm model and the maximum adsorption capacity is 36.6 mg/g at near neutral (pH = 6.6 +/- 0.1). Calcination temperature plays an important role in determining the performance of MA((400)), MA((600)) and MA((800)) for removing arsenic(V), and the corresponding As(V) removal is in the order of MA((400)) >> MA((800)) > MA((800)). The kinetics data were well fitted to pseudo-second-order, which implies that "surface reaction" might be the rate limiting step. Thermodynamic parameters illustrated that As(V) adsorption over MA((400)) was a spontaneous and endothermic process. Adsorption energy (2.61 kJ/mol) is less than 8 kJ/mol, indicating the adsorption process may be dominated by physisorption. The influence of coexisting anions on As(V) removal demonstrated that the removal was slightly affected by the presence of NO3- and SO42-, while the presence of SiO4-, PO43- and F-caused a sharp fall in removal effectiveness, especially when the ratio of coexisting anion concentration to As(V) was larger than 1.12. (C) 2012 Elsevier B.V. All rights reserved.