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 sol 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 36.6mg/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(600)>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 (2.61kJ/mol) is less than 8kJ/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. © 2012 Elsevier B.V.