Adsorption of aromatic organoarsenic compounds by ferric and manganese binary oxide and description of the associated mechanism

Abstract

The aromatic organoarsenic compounds including p-arsanilic acid (p-ASA) and roxarsone (ROX) used as feed additives in the poultry appear to be excreted with no chemical structural change, tending to environmental release of inorganic arsenic. Thus, effective removal and understanding the mechanism of organoarsenic compounds are of significant urgency. We herein investigated the interactions of organoarsenic compounds with ferric and manganese binary oxide (FMBO) to investigate their adsorption efficiency and mechanism, whereas ferric oxide (FeOOH), and manganese oxide (MnO2) were also studied for the comparison. The maximum adsorption capacities (Qmax) of FMBO towards p-ASA and ROX were determined to be 0.52 and 0.25mmolg−1 (pH=7.5). FeOOH and MnO2 showed lower adsorption capability, the corresponsive Qmax, p-ASA were 0.40 and 0.33mmolg−1 and Qmax, ROX were 0.08 and 0.07mmolg−1, respectively. The elevated pH inhibited the adsorption onto the adsorbents owing to the increased repulsive forces; the Qmax, p-ASA and Qmax, ROX onto FMBO increased to 0.79 and 0.51mmolg−1 at pH 4.0. Based on results of UV–vis spectra, UPLC-ICP-MS, FTIR, and XPS, the synergistic effect of heterogeneous oxidation and adsorption was the core for efficient aqueous removal of p-ASA by FMBO. Manganese oxide showed significant oxidation of p-ASA, while adsorption process was observed in ferric oxide and this effect also involves in the adsorption of ROX. Results herein extended the knowledgebase on organoarsenic species adsorption to Fe/Mn oxides, are important for potential engineering treatment application and help us to understand reactions at the interfacial level.