Zero-valent manganese nanoparticles coupled with different strong oxidants for thallium removal from wastewater

Nano zero-valent manganese (nZVMn, Mn-0) was prepared through a borohydride reduction method and coupled with different oxidants (persulfate (S2O82-), hypochlorite (ClO-), or hydrogen peroxide (H2O2)) to remove thallium (Tl) from wastewater. The surface of Mn-0 was readily oxidized to form a core-shell composite (MnOx@Mn-0), which consists of Mn-0 as the inner core and MnOx (MnO, Mn2O3, and Mn3O4) as the outer layer. When Mn-0 was added alone, effective Tl(I) removal was achieved at high pH levels (>12). The Mn-0-H2O2 system was only effective in Tl(I) removal at high pH (>12), while the Mn-0-S2O82- or Mn-0-ClO-system had excellent Tl(I) removal (>96%) over a broad pH range (4-12). The Mn-0-S2O82- oxidation system provided the best resistance to interference from an external organic matrix. The isotherm of Tl(I) removal through the Mn-0-S2O82- system followed the Freundlich model. The Mn-0 nanomaterials can activate persulfate to produce sulfate radicals and hydroxyl radicals. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy suggested that oxidation-induced precipitation, surface adsorption, and electrostatic attraction are the main mechanisms for Tl(I) removal resulting from the combination of Mn-0 and oxidants. Mn-0 coupled with S2O82-/ClO- is a novel and effective technique for Tl(I) removal, and its application in other fields is worthy of further investigation.