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 36.6 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(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 (2.61 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.

► Arsenic is a toxic and carcinogenic element, and adsorption has attracted much attention.
► Mesoporous alumina was used as an effective adsorbent for removing arsenic(V).
► Arsenic species, pH and adsorption mechanism were investigated and illustrated.
► Calcination temperature plays a crucial role in determining the performance of adsorbent.
► The presence of SiO4-, PO43- and F- caused the sharp reduce on arsenic(V) removal.