Study of adsorption capacity and mechanism of nano-alumina for arsenic ion by isothermal adsorption model simulations

Amorphous nanometer alumina (nano-Al2O3) was prepared by inverse microemulsion method in the presence of aluminum sulfate octadecahydrate as the aluminum source, poly(ethylene glycol) octyl-phenyl ether and cetyl trimethyl ammonium bromide as the emulsifiers, and n-butanol as the co-surfactant. The optimal condition for preparing nano-Al2O3 was investigated in relation to the effect of stirring rate on the morphology and adsorption performance of the product; and the adsorption capacity and mechanism of nano-Al2O3 for AsO43- ion in aqueous solution were explored based on simulations with conventional isothermal adsorption models. Findings indicate that nano-Al2O3 prepared in the absence of emulsifiers and co-surfactant exhibits a high adsorption capacity of 149.76 mg center dot g(-1) towards AsO43- ion, higher than the adsorption capacity reported in the literature. The adsorption capacity of nano-Al2O3 for AsO43- is dependent on the pH value and temperature of the solution as well as coexisting ions; and the maximum adsorption capacity occurs at a solution pH of 6. Moreover, the adsorption of AsO43- ion by nano-Al2O3 in aqueous solution obeys Langmuir model and pseudo-second-order kinetic equation, referring to monolayer adsorption and chemical adsorption. The adsorption process is governed by both membrane diffusion and internal diffusion; and the adsorption rate is dominated by membrane diffusion. In summary, nano-Al2O3 has strong adsorption capacity and stability for AsO43- ion in aqueous solution and could be a promising nano-adsorbent for removing heavy metal like AsO43- ion therefrom.