Removals of Cr(VI) and Cd(II) by a novel nanoscale zero valent iron/peroxydisulfate process and its Fenton-like oxidation of pesticide atrazine: Coexisting effect, products and mechanism

Nowadays, inorganic and organic pollutants always coexist in the environment, thus an economic and efficient treatment is urgently required. In this paper, a novel nanoscale zero valent iron (AMD-nZVI) produced from the reaction of acid mine drainage (AMD) with NaBH₄ was combined with peroxydisulfate (PDS) for the simultaneous removals of Cr(VI), Cd(II) and atrazine (ATZ) in water. Results demonstrate that the reactivity of AMD-nZVI/PDS process toward Cr(VI) removal was superior to that of AMD-nZVI/HCl or AMD-nZVI/H₂O₂ process. The coexisting species inculding PO₄ ^3-, HCO₃ ⁻, NO₃ and humic acid exhibited obvious suppression on the Cr(VI) removal. The simultaneous removal efficiencies of Cr(VI), Cd(II) and ATZ by AMD-nZVI/PDS process were high up to 90% within 40 min. Most of Cr(VI) species were converted to Cr₂O₃ and Cr(OH)₃, whereas both Cd(OH)₂ and CdO were main Cd(II) species. The radical quenching tests affirmed that SO₄ ^[rad]− was the primary radical species for ATZ degradation. A total of five intermediate products of ATZ were sucessfully identified, and the degradation of ATZ was achieved through dealkylation, dechlorinatione and hydroxylation processes. A possible reaction mechanism involving in Cr(VI) reduction, Cd(II) precipitation and ATZ Fenton-like oxidation by AMD-nZVI/PDS process therefore was proposed.