Simultaneous adsorption and oxidation of para arsanilic acid by a highly efficient nanostructured Fe-Ti-Mn composite oxide

The para arsanilic acid (p-ASA) used as feed additive in the poultry and swine industries tends to transform into more toxic inorganic arsenic (As(V) and As(III)), leading to a greater risk to human health and environmental system. In this study, simultaneous adsorption and oxidation of p-ASA was achieved by a synthesized highly efficient nanostructured Fe-Ti-Mn composite oxide (FTMO), with a high specific surface area of 424.7 m²/g. The maximum adsorption capacity for p-ASA could be as high as 45.6 mg/g, meanwhile the combined oxidation/photo-oxidation processes led to the formation of intermediate containing hydrazine group, however, without release of toxic inorganic As(III) and As(V). The p-ASA adsorption by FTMO was verified as the chemisorption process with the formation of inner-sphere complexes at the solid/water interface, which was prominently influenced by solution pH, coexisting ions and humic acid, however relatively insensitive to ionic strength. The systematic characterization by FTIR, XPS, EPR and XANES revealed that Fe phase of FTMO played the dominant role for p-ASA adsorption, while Mn and Ti phases were responsible for the oxidation and photo-oxidation of p-ASA, respectively.