Implementing conversion of Sb(III) to Sb(V) and their sequestration by iron shavings simultaneously: Synergistic role of hydroxyl radical and iron (hydr)oxides

Trivalent antimonite (Sb(III)) and pentavalent antimonate (Sb(V)) prevail in printing and dyeing wastewater (PDW). Conventional iron -based materials such as iron flocculant and nanoscale zerovalent iron (NZVI) suffer from lack of oxidative capability and agglomerative deactivation for Sb removal, respectively. Herein, this study proposed a dual -function iron shavings coupling aeration system (iron shavings/O2) for the "oxidation -sequestration" of Sb(III) and the direct sequestration of Sb(V). Results collectively demonstrated that iron shavings/O2 system performed effectively in a broad solution chemistry environment, including wide pH range, co -existing inorganic ions, organic compounds and even practical water matrices. Fe(0), the primary constituent of iron shavings, activated dissolved oxygen (DO) to center dot OH through electron transfer (O2 -> O2 center dot -> H2O2 -> center dot OH), while it was oxidized to Fe(II) and Fe(III). The generated center dot OH and Fe(III) synergistically oxidized Sb(III) to less toxic Sb (V), which was then sequestered by iron (hydr)oxides and newly formed iron muds via inner sphere complexation and co -precipitation. Furthermore, the proposed system exhibited stable and efficient Sb removal in a continuous flow reactor. Overall, this work illustrates iron shavings/O2 is a promising alternative for mainstream iron -based materials towards Sb removal and offers enormous potential for practical PDW treatment.