Characteristics and mechanisms of arsenate adsorption onto manganese oxide-doped aluminum oxide

This study focused on the characteristics and mechanisms of arsenate [As(V)] adsorption onto manganese oxide-doped aluminum oxide. The adsorbent surface was characterized via the Brunauer-Emmett-Teller method, scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. The characterization results indicated a rough and Al-enriched surface, a surface area of 91.2 m(2)/g, and an amorphous structure for manganese oxide-doped aluminum oxide. Most of the As(V) was adsorbed within 1.5 h, and the kinetics data were described well by the pseudo-second-order model. Meanwhile, the adsorption process was controlled by more than one rate-limiting step. The Langmuir model fitted the isotherm data better compared with the Freundlich model, and the maximum adsorption amount was 114.5 mg/g at T=298 K. The As(V) adsorption was an endothermic and spontaneous process. The optimal As(V) removal was achieved at a pH range of 4.0-6.0. Furthermore, the results of Fourier transform infrared spectroscopy and X-ray photoemission spectroscopy suggested that As(V) adsorption was primarily through the adhesion to the surface hydroxyl groups and ligand exchange with the sulfate. (c) 2015 American Institute of Chemical Engineers Environ Prog, 34: 1009-1018, 2015